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There is a 100uf electrolyte cathode bypass capacitor in the input section of my amp. I am thinking to add a small film capacitor to bypass it. Is it a good idea?
Follow Ups:
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"There is a 100uf electrolyte cathode bypass capacitor in the input section of my amp. I am thinking to add a small film capacitor to bypass it. Is it a good idea?"
It is doubtful that you will hear any difference in subjective result without proper high efficiency transducers.
Altec or something on a similar level of quality.
DT667
More specific of my previous question: with my limited knowledge, the high value electrolytic cathode bypass capacitor allows only bass frequency to passthrough. If I add a small value film cap to that position, it will also allow the high frequency passthrough, will it creates ill effect?
"More specific of my previous question: with my limited knowledge, the high value electrolytic cathode bypass capacitor allows only bass frequency to passthrough. If I add a small value film cap to that position, it will also allow the high frequency passthrough, will it creates ill effect?"
No, that's not how it works. What a cathode bypass capacitor does is to remove a source of negative feedback, the cathode resistor, thus increasing the gain of the stage. So all frequencies pass through the cathode bypass. It's very much in the signal path in that sense.
With cathode bypass capacitors, you want them to be large enough to bypass the entire frequency range you want to amplify. The actual math to figure out exactly how large it needs to be is complicated, but one major parameter is the value of the cathode resistor.
Some people misunderstand how they work and think that using bigger and bigger bypass caps will magically produce more bass, but that doesn't happen. There is a definite point of diminishing returns.
When working with guitar amps rather than HiFi, we sometimes use a smaller value of bypass (or "incomplete bypass") on purpose to limit the bandwidth and create a high-pass filter around 80Hz to eliminate un-musical strumming noises.
So if you only use a small film bypass, it will bypass any ESR/DF from the electrolytic capacitor in the higher frequency range affected by the small film bypass. But it will be hard for you to calculate exactly how much of the frequency range will be covered by your bypass.
You can always experiment and see how you like the results. It would be hard to hurt anything with a film bypass unless you don't know what you're doing and connect the bypass in the wrong place.
In practice, I suspect that many cathode bypass values are determined somewhat by trial and error or by copying other circuits.
Dear Thermionic 27609,
I enjoyed reading your post. Nice job.
You state "the actual math is complicated."
Here is my favorite go-to resource on Rs and Cs in combo, a useful site to bookmark and use :
http://www.sengpielaudio.com/calculator-RCpad.htm
Jeff
The cathode resistor (RK) is in parallel with the impedance of the tube's cathode (rk).
The formula is, bypass cap value in uf = 1000000/ 6.28 * F3 * r
r = (RK * rk) / (RK + rk)
rk = (RL + RP) / (mu + 1)
RK = value of cathode resistor
RP = plate resistance of tube
RL = value of plate resistor (or load that the plate is seeing)
Mu = Mu of tube
F3 = the 3db down point of the filter
So let's say you have a 2a3, 800 ohms plate resistance with a 2.5k primary impedance output transformer using a 750 ohm cathode resistor, with a mu of 4.2
If you wanted to bypass the cathode resistor alone all the way down to 5hz it would only take a 42.44uf cap (just like your link).
But the cathode of the tube has it's own impedance of 634.6 ohms and the cathode resistor is in parallel with that so the cathode bypass cap needs to bypass 343.75 ohms. To do that all the way down to 5Hz it takes a 92.6uf cap.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Those are standard engineering formulas used to design a conventional 2A3 amplifier.
Don't think that will help us come up with the main 2A3 cathode bypass cap value that DF would recommend.
The max value was about 15uF, but perhaps it has changed in 2022.
DT667
At 15uf (as a cathode bypass cap value for the 2a3 output tube) there will be current feedback applied to the output tube at the lower frequencies but not at the higher frequencies.That current feedback will increase the plate resistance of the 2a3 output tube at the lower frequencies and lower the damping factor of the amplifier (it will increase the output impedance of the amplifier).
Lowering the damping factor lowers the amplifiers ability to control the movement of the woofer cone. "Damping Factor (DF) is the amplifier's ability to control speaker motion once a signal has stopped."
Do you know why he does that?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 02/03/22 02/07/22 02/07/22
If you use a bypass capacitor on the input/voltage amplifier stage of an amplifier that is insufficient in value to bypass all audio frequencies, would that in fact effect the output impedance of the amplifier as measured at the output transformer secondaries? (I ask because it seems to me the output transformer would not be affected by the value of the cathode bypass capacitor used at the input stage.) I am sure it could affect tonal balance of the amplifier but maybe not the output impedance. Or maybe it would if you use global NFB as well as the local NFB at the cathode.
It would effect the output impedance and FR of the input stage but it would not effect the output stage (other than by effecting what the output stage is receiving in terms of an input signal and how it's being driven).If there is global negative feedback then yes because the input stage would be non-phase linear and within the FB loop. I'm not sure just what the effect would be but it can't be good.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 02/04/22
But thanks for the clarification.
If it affects them plate impedance of the output tube, then yes, it would affect the output impedance of an amplifier. The significance of this practice is multi factorial.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Yes, but how would the choice to bypass or not to bypass the cathode R of the input tube affect the plate impedance of the output tube, assuming the circuit is conventional? As mentioned, I suppose the output impedance of the amplifier, measured at the transformer secondaries, could be affected if there is global NFB.
"Do you know why he does that?"
Quote from DF published 3/9/2018
"So, the cap-banks on the cathodes of all tubes, and plate supplies of driver stages become a BIG DEAL. Both require extensive capacitor bypassing in order to even approach the response and bandwidth of a good push/pull amp. And those big uF caps never work in SE-- use a MAX. of 15uF or so..."
This was taken from archived posts on AA.
DT667
OK, Tre was kind en0ugh to show the math and theory to back up his claims.How about we do the same for yours or rather Dennis's theory?
Edits: 02/03/22
"How about we do the same for yours or rather Dennis's theory?"
DT667's SE DC 7C5 breadboard amp uses a 15uF as the main cathode bypass cap value for the finals.
With the "wideband bypass cap bank" added to the 15uF, the -3dB roll off is about 5Hz.
Not sure if there is any significant subjective effect due to phase shifts above the -3dB roll off point.
DT667
I wouldn't get too anal about a given cathode
bypass value for SE.Remember, what counts the most is the final
sound quality VS total reliability. Both are
accomplished in the SAME DESIGN.This double-requirement must change with what
ONE CAN BUY in order to get it accomplished.WIMA made it practical to use values larger than
15UF on a 2A3 cathode, and still get speed, detail, and
wide bandwidth. Those caps are designed as a
stack-up of flat plates, and DO NOT behave like
cylindrical capacitors, which tend to "tune" at
certain frequencies, according to their length VS
diameter ratios, far worse than flat-plates do..Flat plates are far more linear in Frequency
response, and the best WIMA's are as good as
Dynamicaps or Mundorf Silver-Oils, in overall
transparency, bandwidth and speed. What this means
is that now, you can go up to 50UF instead of 15UF,
if you want to or need to.Somebody is going to wonder-- why not use the
same Wima in a 20UF or, maybe a 35UF? (for some
purpose or other). It's a good question-- it deserves an
answer: The answer is all cap manufacturers make caps
that sound like junk, and some that really perform.
You won't know what they are until you've used a given
one in a variety of uses. In this case, the 20UF and the
35UF-- by comparison to the stellar 15UF-- the 20 and the
30 or 35 just don't cut it-- oh, they're OK, but so are
lots of others. The moral is-- when a company turns out
something that is really good, then find a way to use THAT!Let's say both GOOD quality values are WIMAS-- with like
construction. Both will require the usual bypassing.
Sonically, the 15UF is still superior to the 50UF, but
not by enough to scare you out of the 50UF.OK, now we have a new world! Put in the 50UF, and
work-out a whole new set of bypasses for IT.This has been done over the last 5 years or so, on all
our newer amps. Any that land here for a check-up get
upgraded automatically for no extra charge.What is the advantage? NONE, sonically-- they're both great.
But if you want bigger bottom-end (if your speaker sensitivity
is a bit marginal), now you have it. If your speaker is both
superb and very sensitive, then stick with the tried and true
15UF-- one of WIMA's best sounding caps-- ever.-Dennis-
Edits: 02/04/22 02/04/22
Wima makes a nice 400uF @ 400V now. I wish it was @500 or 600V.
That is a beam power tube in a circuit with loop feedback. A whole different set of rules apply.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
"That is a beam power tube in a circuit with loop feedback. A whole different set of rules apply."
Measurements are enough to see if there are early roll offs on either end of the bandwidth spectrum. In the case of the SE DC 7C5 breadboard amp, there was no early roll offs, so it is OK.
DT667
Correcting a design with FB is less-than-ideal.
Keep in mind, I have no use for cathode bypass, or SE, but it should be obvious that the NFB is responsible for your measured performance, and that you are not measuring all the impacts of the inadequate bypass cap.
Going after a linear design in the first place, and understanding its behaviour w/o NFB might just be useful.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"Going after a linear design in the first place, and understanding its behaviour w/o NFB might just be useful."
Building a standard SE console amp circuit, like the Magnavox DG-SE1 or similar, linear biasing of driver stage and finals for lowest THD% before working out the FBK network make sense because it is a traditional approach to circuit design.
DG promotes the idea of running SE finals at MAX. plate dissipation and with symmetrical clipping of the output waveforms. There is no attempt to extend tube life by reducing standing bias currents.
In the minds of the MLP designers, linear biasing and lowest possible THD% seems not to be the primary concern.
DT667
Idle current is only a slice of the equal clipping process. It is of course the lowest fruit and as you note, not without cost.
Tube life is a worry-free item for me; don't care about it at all. It is not like I see you building with a real tube like an HY51B that could be for some available in very limited quantity.
It is all about the honest reproduction. Turning them down makes it easier to build an effects box...but waaaiiiit, you already said that... :)
As to DG, why not go present this idea of yours to him happybear?
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"It is all about the honest reproduction. Turning them down makes it easier to build an effects box...but waaaiiiit, you already said that... :)"
DT667 never said that "reducing standing bias currents" creates an effects box.
People might want to associate a schematic or measurement data with how an amplifier will sound subjectively.
Without listening to a tube amplifier on high efficiency transducers of good quality, a complete understanding of circuit performance is not possible.
Realism in audio will mean a different subjective result to each person who builds a tube audio amplifier.
This goes beyond the technical aspects of circuit design and goes into the realms of audiophile psychology.
The 6V6 family are very popular tubes and readily available tubes - certainly considered REAL tubes by those that use them.
DT667
6V6GTA make a very fine voltage amp. So does the 6AQ5. Indistinguishable actually.
High eff speakers are useful for many reasons. I have been listening to such beasties(high eff of *excellent* quality, not just 'good' ), for a loooong time. Would not have it any other way. I give you Official permission to stop reminding me of this... :)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Any opinion of the KLIPSCH Forte IV? Klipsch calls 'em 99db but stereophile makes 'em closer to 96.....
I'm considering, but need to do an hours worth of listening before pulling the trigger.....even THAN?
Too much is never enough
!
The Mind has No Firewall~ U.S. Army War College.
Sort of, I guess. IF I believe Stereophile, and I tend to, the trend is to be optimistic.
But some are within 'tenths' whichI consider below the ability to distinguish while Klipsch seems to fit your rule of about 3db.
One speaker manufacturer even listed Anachoic and 'in room' which WERE 3db apart.
the reason I sort of defer to stereophile? ONE organzation with one method which means I should theoretically be able to compare across speakers and time.
IF they keep the measurment equipment calibrated....another can of worms altogether.
Too much is never enough
You will have to make your own opinion. I doubt you'll hate them.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Any thought as to how well these speakers would get along with some of the VTA amps?
They can be had with nearly any output tube from EL34 to up in the KT line.....with stops at 6550 and who knows where else?
VTA kits are an extremely attractive propostion which both get good reviews for performance but for completeness of kits AND the instruction manual....
Too much is never enough
I'm considering a BIG change....including selling my Maggies and a pair of amps.....
Than build a pair of VTA monos of 125 each.....which should be enough power to get me evicted from the STATE.
I just need to go hear those KLIPSCH.....which I can't do near where I live bur rather must migrate up to Los Angeles which has a couple places for a listen....
Too much is never enough
The criteria for subjective design of an amplifier is not how an amplifier measures on a scope, or distortion equipment, but rather, subjectively, how it plays back all the musical instruments....... to the listener's ears.
For example, when listening to a drum solo, do the various drum heads maintain their own distinct sound, such that you can sense the drum head's size, and after-reverberation, as IF you were hearing it the room , live?
Do the cymbals sound real - have a metallic sound, with proper high-frequency extension, detail and harmonic structures ? Very important, are the dynamic shadings, of each and every instrument, portrayed in a life-like manner?
Does the music's timing both thrill and fool you, at the same time?? OR, does the music's playback timing seem to be slightly out-of-synch with hearing the " real thing " ( feedback amps ). Does music come to you as though you were hearing multiple music / acoustic events, happening distinctly, and IN both the instrument's and musician's own time frame? NOT in the time frame of ANY sort of audio amplifier ??
If it measures bad, and sounds good, no worry at all - you are " there " !!!
If it measures good, and sounds bad, you are measuring the wrong thing !!
DT667 is correct, having good high efficiency speakers, with large radiating surfaces, goes a long way in designing amplifiers on a subjective basis. After a lifetime of inefficient speakers, both dynamic dynamic and electrostatic, I now run very mildly modded ALTEC Voice of the Theater A7-8s ( 515Bs and 802Ds ). I love what both driver's horn loads do during music playback. The amplifier you pair with such speakers has to be good - or you will notice minor anomalies in the electronics - easily.
All of this post refers to subjective testing. After all is said and done, while test equipment can be partially helpful, we have to listen to an amplifier and how it plays back music. Can it play back all of the musical instruments convincingly ???.
Jeff
It could be that measures bad, sounds good is acceptable.
It is more likely that a particular passage/song/set is going to sound good on such a machine. Care to bet that all music will be improved by the same defect?
I won't. But I'll be happy to take your $$ if you'd be so foolish as to think so... :)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Perceived sonics on play back depends largely on how good is the source, and particularly, the original recording.
If an amp can play all of the musical instruments on a good recording convincingly / subjectively to me,...... that is all that is required.
If said amplifier " hypothetically " also didn't measure well using conventional bench testing, I would be most hesitant of using your assumed and descriptive word " defect ".
( Unless, perhaps, if we were applying a word like " defect " to one's conventional bench testing. )
An amplifier that is able to subjectively play back all the musical instruments, very convincingly, is the goal, and the key IMHO, to our long-term audio satisfaction.
Jeff
Pak would need to change his "mental models" regarding the advanced SE tube amplifier design and construction methods that you have or will present on Tube DIY in the future.
There has been ZERO evidence to indicate that will happen or that other MLP "critics" will change their spots either.
Not everyone is ready for the "brave new world" of the MLP in 2022.
Only a select "elite" of SE tube amp builders will rise and answer the call of greatness.
DT667
Beliefs. Desires and expectations. Strategies. Motivated reasoning. Rhetoric. Nothing more or less.
A lot of people want to belong to an exclusive club and want to be or have a guru. People want to be special and valued and to support those who value them.
It plays out here every day, by all of us.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
DF & JDM founded their exclusive audio club, the MLP, DF being the guru.
Many builders of LOW DCR SE tube amplifiers look to the MLP for inspiration.
Absolutely nothing wrong with that in spite of the constant wailing and gnashing of teeth from MLP critics.
DT667
The wailing is from your side. As demonstrated by the post this one follows.
You make non-sensical claims about demonstrably effects box designs, and when met with, 'I don't think so there happybear...' responses, you accuse folks of wailing and gnashing teeth. Really?
Bandwidth/drive limited, plus frequency variable output Z equals effects box.
Where do you find hats BTW?
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"You make non-sensical claims about demonstrably effects box designs, and when met with, 'I don't think so there happybear...' responses, you accuse folks of wailing and gnashing teeth. Really?"
Still stalking people on internet audio forums?
You will end up on a neighborhood watchlist.
DT667
Expecting you to explain yourself is 'stalking'? Questioning your ridiculous claims about things like 'transfer efficiency' is stalking? How quaint... :)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Maybe we can simplify this.
Perhaps you just don't understand a SE
amplifier and how it has to operate in
order to work well musically.
-Dennis-
There is nothing magical, except for your sales pitch we have heard waaaaaaay too many times.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Why would you assume that?
It's not very complicated. The forces at work have been well understood for decades.
Maybe it's you who doesn't understand?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
To hell with answering the call to greatness...would be quite happy if questions regarding outlandish claims were answered with something other than nonsense.
oooohhh...transfer efficiency, that sounds plausible.
Ultimately there my dear happybear, until you discover how to put what you're doing into a format that can be reproduced, nobody is going to give your ideas any respect. Your 'only a master builder is capable of doing it', holds no water either.
given how difficult all that may sound to you, I expect you to continue to claim you're not building effects boxes.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"To hell with answering the call to greatness...would be quite happy if questions regarding outlandish claims were answered with something other than nonsense."
On Tube DIY is one of the greatest resources of SE tube amp knowledge in the history of this hobby, DF.
And now his devoted messenger has returned from years in exile.
You have all this esoteric knowledge at your disposal.
A great moment is history is unfolding, so take advantage.
As it was said before, brave new world or status quo.
DT667 wants to see you take the next step and reach self-actualization as a builder of tube amplifiers and become a better human being in the process.
Good luck, sir.
DT667
While I agree that low DCR chokes are 'almost' always advantageous, time constants being slowed down are indispensable ALSO. Doug's suggestions have merit for finding cause/effect/rationale of the Montana boys mantra.
The Mind has No Firewall~ U.S. Army War College.
Why would DF or the MLP care about establishing "credibility" with a group of inexpert Tube DIY hobby-level personnel?
DF proved himself for over a DECADE at RMAF, an industry leading audio trade show setting featuring "world class" brands.
Herb Reichert, legendary audiophile, knows DF and the SS brand for all their outstanding attributes.
Maybe a handful of people who post here like Paul Joppa are on a similar level of professionalism in this trade.
Why must we go over this well-worn ground so often when the truth is self-evident to anyone with a modest degree of common sense?
DT667
You are speaking and the point you are making remains on your head, because contempt prior to investigation will leave you in everlasting ignorance ; as you are unable to deduce without hearing other builds. I HAVE built an amp utilizing Jeff's criteria utilizing a choke you will never find (500 ma/5 Henry/19 ohm monster... you see... years ago before you came along Jeff was touting no choke above 20 ohms and therefore mine met the criteria... I also used substandard .32 Henry 10 ohm also with these experiments whereby the choke was improperly loaded... I did not indulge in the 12 gauge foray as I tried that many years ago with no experiential improvement. Sadly, I report there was no epiphany.
All my speakers are 104 to 108 db and weigh 140 lbs minimum.
I will leave you with the last word to assuage your meager self-esteem.
The Mind has No Firewall~ U.S. Army War College.
You build a tube amplifier circuit that was NOT an exact replica of a DF or JDM circuit and it failed to produce results.
Who's fault is that, sir?
You built it, you are accountable for its lack of performance.
DT667
In 2021, I posted on another DIY forum, that two ten Ohm Stancor 320 mA. C-2708s did not " cut it " for me. The amp was boring and uninspiring to hear.( If Cleartimestream used two of the ten ohm cheapies from Triad, as some people did, results would even be worse !!! Especially with no wire optimizations. )
I did share in a 2021 DIY thread how I went from two ten Ohm Stancor C-2708s ....... to two 6 Ohm chokes, Hammond 159ZAs. Using the usual L1/C1/L2/C2 filter topology. All became superb, listening wise. I posted before and after photos, page 1, maybe 2, of this choke swap, in that thread.
Under 20 Ohms was Mr. Fulton, way way back in 1982. Today it is 6 Ohms maximum, and two L/C sections in series.
From about 2018 on, DF and I have been using 6 Ohms or less. DF had some lovely 4 Ohms chokes custom made, which he enjoyed. That is what it takes to boogie. about 12 Ohms TOTAL, or less, both chokes. We both determined the choke's lead outs are nice if made of 12 AWG Mil Spec, m22759/11, a wideband wire with silver content. YMMV.
These 159ZA 6 Ohm Hammonds need 75 hours to break in. Their midrange is recessed - just a bit, until broken in. L1 should equal L2 in SE amps, if you want to avoid audible, objectionable sonic skewing. That consistently has been the case on all A-Bing at home on VOTTs.
Have fun. I do !!!
Jeff
Edits: 02/08/22 02/08/22 02/08/22
They are 600 ma ... .32 @ 10 ohms and you were touting less than 20 ohms circa 2007, perhaps you have forgotten.
The Mind has No Firewall~ U.S. Army War College.
Correct- back then. We have evolved and learned things since 2006-08 I hope, all of us. Since about 2018, we regularly use the 6 Ohm Hammond 159ZAs, 1 A. rated chokes. Other than a 75 hour break in, they work and sound fine !! Preferable to Stancor c-2708s.In retrospect, I was mistaken to even mention on A.A. those cheapie Triads in 2006. Sorry. But now you know !!
However, 12 Ohms DCR total - to the output transformer for both Ls -is really a lot of fun to hear !!
Cleartimestream, I also LOVE what GTO caps do to the Finals filtering. About $50.00 each. One GTO 5 uF across ( bypassing ) a 30 uF WIMA 4 Pin C1 and a second 5 uF GTO across ( bypassing ) a 50 uF at 800 VDC 4 Pin WIMA C2.
Also, starting in 2019, I have gone to two 5U4GBs, each as a separate diode, for rectification.
Well, there you have my current favorite topology. YMMV. Contact me if you have any questions.
Jeff
Edits: 02/08/22
"We"
It doesn't need to be an exact replica of a DF or JDM circuit to preform badly like theirs do.
No amplifier using a driver stage that has too high an output impedance and too little current drive capability to properly drive the Miller capacitance of the output tube will work properly. The band width will suffer.
No amplifier using a power supply filter like DF and JM's will work properly. Because the input choke has less than critical inductance and the filter caps are relatively small in value, the supply has poor regulation and is unstable.
A 2a3 running low idle current (43ma. or so) can work just fine but will not be even close to optimal at the voltage and load impedance used by Dennis. HD will be higher at all power levels and that will be audible as having less clarity and detail than would otherwise be achieved if a proper plate voltage and a proper load impedance that matched up with the idle current chosen was used.
No amount of design tweaks can properly compensate for these deficiencies.
All three short comings would need to be fixed, then and only then would the amplifier work properly.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hello Tre,
You are a little bit behind the times in your understanding. WE do not stand still !!!
With tubes like the symmetrical 7B4, about three years ago, the current was modestly raised. For over a year now, my amp designs use a driver stage running at 7.5 times that to which you are referring. Dennis runs a driver stage in this same time period at 19.63 times the amount of current you are referring to.
For 2022, my new 6005 " triple ", Dennis inspired, will be running a driver stage at 33.33 times what you have been writing about.
These are the actual facts Tre, known to me. I am posting here just to inform you.
Take care, I appreciated your previous phone help, very much. That was nice of you.
Jeff
Well that is a move in the right direction.
Dennis also said that he has increased the cathode bypass cap for the 2a3 from 15uf to 50uf.
Another move in the right direction.
I guess if you two live long enough you will both come around to traditional thinking. Certainly these two changes are in that direction.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
the partially bypassed cathode. Does wonders for the tone... LOL
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I understand Dennis has increased the 2a3 cathode bypass cap from 15u (plus some smaller parallel caps) to 50u (with, I assume, some smaller parallel caps).
That is at least a step in the right direction.
Jeff just posted that the idle current in the driver tube has been in increases a bunch. So much so that I wonder how the 7b4 can handle it. Maybe I misunderstood and Dennis is using a different driver tube?
So I guess we can say that DF and JM are making progress and coming around to traditional thinking.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Hi Tre,
It was not a 7B4 driver tube being used for the newest build !
My " 33.3 TIMES the current " 2022 driver stage is to be operating at only 54% of it's maximum rating. Just a bit under the 62% Golden ratio figure.
It is reasonably linear also.
Jeff
2022 Power tube:
HY51A. Idling at 60/65ths of its plate rating. Class A PP, cathode drive...on a 10k a-a load. I anticipate its making enough power to push an S-265-Q to its limits when made with decent M4 steel.
Fortunately horn loading does wonderful things to the need for low output Z... :)
Near certainty to drive it with vert deflection pentodes...bent to something more linear than a 2A3 :)
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Re: RMAFs ,
Likely more than anyone else, other than Dennis or his brother, I attended about ten of 12 year's worth of RMAF shows that Dennis did.
Yep, either drove or flew, from Kansas City to Denver - and back, on my dime.
I was usually in the Serious Stereo room, when someone like Herbie visited. I spent most of my RMAF time - in that demo room.
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
**** I would like to report personally to all Forum Members, that the in-room results varied greatly, from year to year. ****
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
The factor involved was the set up time, that the two brothers had. They had to self-drive their vehicle from Montana to Denver, fully loaded by the two of them. They arrived, usually tired, with a limited " unload and show set-up time " available to them, before the event was to commence.
Another lesser factor sometimes, might possibly be their choice of program material played.
In some years it was very easy for me to tell the TOTAL excellence of Dennis' amps and his GPA 604 MLTL speakers. In other years, with less set up time, they could sound less - than what they really were ..... at least to me !!! Cuthroat must have caught an off year, as best as I can deduce.
I can report however, that in me attending TEN shows, I have a very good idea as to Dennis' capabilities.
Dennis is superb in audio amplifier building. He is THE Master - as far as what I personally have heard.
Herb Reichert attended and reported in a few of the better set up years !! Hoorah.
Unlike those decent people who usually belittle Dennis, I often wonder what they would say, IF they had my listening time, over ten differing RMAF shows, to Dennis' amps??
However, what I really think is ...... that many, ( if not all ) of the critical posters, have never even heard what they are critiquing. And certainly not his latest amps. Nor will they. " Zero " direct experience. Could this be the equivalent of a blind person publicly critiquing a Monet painting ??
Since the fun and pivotal ( to me ) 2019 "MLP" get together in Livingston, Dennis ( and I ) have made great strides forward in amplifier performance. His latest amps, for many solid technical reasons, are super-high performing. He certainly is not standing still - at all .... and nor am I.
FYI : Dennis " amp and audio - mentors " me.
I usually simply follow his wise, highly experienced lead, and maybe put a few of my own ideas, into an amplifier's build " mix ". We two guys are very excited about what we are doing. Being on the same wavelength, we also have a LOT of fun discussing design, and doing it.
True story : One year on Interstate 70, going WEST in Colorado, I earned a $435 speeding ticket. Yep, in my Crown VIC Police Interceptor - on the way to Denver's RMAF show. 119 MPH, clocked.
Jeff
wow...
"However, what I really think is ...... that many, ( if not all ) of the critical posters, have never even heard what they are critiquing. And certainly not his latest amps. Nor will they. " Zero " direct experience. Could this be the equivalent of a blind person publicly critiquing a Monet painting ??"
what little self awareness to make this statement...
you verbally trashed many amp build(s) and builders for years having never heard those amps...
you did it on every forum you went... for example Klipsch tube forum is one for sure, until they like most, got tired of your condecending bs...
Hello !!
That is a great post you authored. Especially pointing out my lack of "self awareness", ...... that really hit me between the eyes.
Please let me explain to you, something that you, and perhaps many others, do not understand :
(1) I don't need to hear other people's amps, I have heard other people's manufactured and DIY SE amps, and P-P amps, conventionally designed and built, "all of my life, almost everywhere ". Only a handful impress me.
(2) I have been rude and condescending to others, mainly - NOT treating others with respect. THIS I PROMISE I will do my best to change, to exhibit a positive demeanor, henceforth !!
(3) These people who I trashed, likely have ZERO experience hearing Serious Stereo amps as I have, in a variety of systems, over a variety of occasions.
(4) Allow me ask you nicely, and without trying to raise a fuss, what is your personal experience, and the extent of you hearing Dennis' amps???
- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
Let me tell you MY experience hearing Dennis Fraker's Serious Stereo amps.
I read the following 6 Moons article from Stephaen, in 2005. It piqued my interest and I decided in 2006 to start to attend RMAF, to directly hear what was going on :
https://6moons.com/industryfeatures/rmaf05stephaen/rmaf05_2.html
From 2006 on, I went to about ten shows over twelve years. Spent most of my show time in the Serious Stereo room, listening. Each show attended required 1,317 miles of a round trip, usually driving. Ten shows means I traveled 13,170 miles, and spent ten weekends of my life, to listen to Dennis' two stage Directly Coupled, SE 2A3 amps.
Are you getting the picture ? This was all on my dime.
Furthermore, in 2019 I did a round trip, from my residence to Livingston, MT, with my new DIY 12BZ7-KT88 SE DC amp. A 4,022 miles drive. So, in all, I have traveled 17,000 plus miles, and spent much time, hearing Dennis' S.S. amps.
Not only that, I was actively DIY building clones of the basic circuit topology, from 2006 on, to this day.
In 2006, I was eager to share my positive listening experiences of this amplifier topology. I alone, started to introduce on this Tube DIY A.A. Forum. The concept of a L.S.E.S power supply.
To newer Forum Members : L.S.E.S. stands for " Low Stored Energy Supply ". Since the concepts presented were in opposition to what was taught conventionally ( for maybe 100 years in all E.E. textbooks ). My posts, and manner, received a lot of " pushback " from many conventionally trained individuals. None of these people, to my knowledge, had heard the Serious Stereo amps, as I had at that time.
Between 2006 and 2008, the highly capable E.E., Mr. Henry Pasternak, came up with his own version of the L.S.E.S. concept, which he dubbed " The Flywheel ". ( it started out with a Triad C-56U, 35 mHY, 2 A.-rated, 0.79 Ohm DCR choke ).
During this 2006-08 time period, only two audiophile E.E.s on A.A., took the time to run a series of posts, fully explaining what they HEARD and did, using the concepts of L.S.E.S. These were Messers John Swenson and John L. Hasquin, both quite talented individuals.
NOTE : I have saved a great compilation of all their posts, and any A.A. Forum Member in 2022 who would like to receive a copy, please simply contact me by the Forum Messaging system, with your email address. I will gratis, promptly send it off to you.
It is easy to deduce that both these DIYers, " got it " and were extremely pleased with the new approach's sonics.
My very first DIY tube amp build was for The Absolute Sound's Classical Record reviewer, Neil Levinson, in about 1979. It was his Audio Note 300B kit, which we converted to 2A3 Finals. Golly, that was 43 years ago.
In 1982, my audio mentor at the time, the late and great Robert W. Fulton ( FMI-80s, Fulton J-Modular, Fulton Premiere speakers ) told me " Jeffrey, amps are the turkeys, and we could build something much better than that kit". He laid out several amp building guidelines to me. Things like " hopefully NO negative feedback." A second guideline was " all triodes ". A third guideline was that " all the chokes have to be 20 Ohms or less ". He ably explained all the reasons for each guideline.
So my A.A. audio friends, I have been aware of the need for lower DCR for four decades. The average tube amp out there, Manufactured or DIY, will world-wide routinely use chokes with DCRs of from about 30 Ohms to 110 Ohms.
For the past several years, I use two Hammond 159ZAs in series, as L1/C1/L2/C2. Each choke being only 6 Ohms in DCR. So, the TOTAL DCR to the output transformer's primary is only 12 ohms.
My point to you, awsjr, is that I have been hearing what LOW DCR does in any decent audio amp, .....for forty years now. I really do not have to hear other's amps, using 30 to 110 Ohms DCR inductors as their FINALS stage filtering. But OTHERS, who have not experienced L.S.E.S., etc., need to do so !!!!!!!!!
Furthermore, I have spent time, paid my dues, listening to Dennis' amps, using his own L.S.E.S. supply. This is, to the large part, the opposite of all who ( technically and theoretically only ) have given Dennis pushback on AA, over the last two decades.
In most cases, these people who are critical of Dennis, have little ( or in most cases zero ) listening experience to his builds. Notice how, after posting what I did above, no one has immediately volunteered their " extensive listening experience ". I was going to give it a week's time, but your post " called my hand ".
We are all unique, and we each have unique experiences. I hope this post outlines mine in a logical and reasonable manner, and creates some new and positive understandings. Peace.
Best wishes,
Jeff
At the time, you were espousing one combination after another of various inductors. One after the other, each more perfect than the last.Then Henry dug into one of them and described how it worked. The Flywheel. At that point you disowned that particular combination claiming only your Low Inductive Energy Storage design could possibly work( what ever it happened to be that day ). Couple other folk went forward with that bit you stumbled upon and Henry investigated.
I am sure you meant well, but it could be that you will want to learn not everybody wants the same thing as you do. What you are doing is to put it bluntly, building your best personal favourite sounding amp you can. If you treat the process as anything different you may rediscover something else.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Edits: 02/08/22
I should start another thread - but this is easy enough.
Douglas - do you think a flywheel supply would be problematic with MV rectifiers? I know the general recommendation is to run them in to a L-critical choke. .035H seems like it might not do the trick and its typically followed by 10-20uF.
I've got these big beautiful heyboer transformers - but they give me about 350V with L-critical. I still like to experiment with diret coupling and like in the neighborhood of 475-500V and the flywheel gives me that - but I am nervous about the results with MV.
As you know - once you've built one MV supply it's addicting. :)
"do you think a flywheel supply would be problematic with MV rectifiers? I know the general recommendation is to run them in to a L-critical choke. .035H seems like it might not do the trick and its typically followed by 10-20uF."Tried a MV rectifier, Type 83, with a "flywheel" filter and it will work but the service life of the rectifier was not the best.
Got about 1 year of intermittent use before the MV stopped working properly.
You are better off not wasting a good MV rectifier.
The 5U4G or SS diodes + snubber is a better option.
DF was warning everyone about mercury from rectifiers somehow getting outside the glass bulb and creating a health hazard.
How this could happen, no idea.
DT667
Edits: 02/09/22
DT,I built two supplies recently. One I posted here with 816s and 5H @ 25 ohms choke input + 400uF Wima film. The second is dual 5u4GB, same 5H choke and 400uF Wima.
Both sound great. I like that blue glow. I had to use a 1uF cap in front of my 5H on the 5u4GB supply to get voltage up a touch and stop the choke from buzzing. My 816 supply uses .1uF Wima film and foil and never buzzed. Same model choke.
I take those old Stancor 2708s and use them as the second L in my supplies on the audio chassis and follow with a 50uF film or 68uF Panasonic electrolytic.
I don't worry much about DCR anymore... wouldn't mind a smaller 5H choke at 50 ohms or so... maybe like the higher DCR supplies better. They're quieter, less fuss.
pic shows with 5t4s instead of 5u4.
Edits: 02/09/22
It is a matter I think of the peak repetitive current. Think for a few minutes about breaking one when they are hot and hopefully induce some paranoia... :)
Am tempted to say, probably not a good idear to try the usual suspects on what is effectively a tuned up cap-input supply.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
thank you - a healthy fear and respect is warranted. I agree it is a tuned up cap input supply!
"Hello !!
That is a great post you authored. Especially pointing out my lack of "self awareness", ...... that really hit me between the eyes.
Please let me explain to you, something that you, and perhaps many others, do not understand :
(1) I don't need to hear other people's amps, I have heard other people's manufactured and DIY SE amps, and P-P amps, conventionally designed and built, "all of my life, almost everywhere ". Only a handful impress me.
(2) I have been rude and condescending to others, mainly - NOT treating others with respect. THIS I PROMISE I will do my best to change, to exhibit a positive demeanor, henceforth !!
(3) These people who I trashed, likely have ZERO experience hearing Serious Stereo amps as I have, in a variety of systems, over a variety of occasions.
(4) Allow me ask you nicely, and without trying to raise a fuss, what is your personal experience, and the extent of you hearing Dennis' amps???"
excuses and followed by a lot of mumbojumbo....
1 you know so much and have so much experience... you still don't get it
2 you should have stopped right there...
3 people should be trashed because they haven't heard an amp build by a niche amp builder?
really... you're going to go with that ?
4 I don't give a FF about "experience with SS amps"... I don't give a FF about telling you my experience with anything
the mumbo jumbo... same as it ever was... you have soooo much experience... you know sooo much... that means it must be the only way.... you justify the SS methods because of your experience etc... yet many others have much more formal technical education, as much or more diy knowledge yet for them that is not enough to have any idea how a ss amp may perform...
you don't get...you're still in the my way is the only and best way...too bad... with such a closed mind you never learn anything... obviously been the way for many years... thats why you been kicked off so many audio forums..
Bah! got ticketed at nearly that much over.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"On Tube DIY is one of the greatest resources of SE tube amp knowledge in the history of this hobby, DF."
errr...I am truly confused by this statement. I have yet to see him give any instruction on how to build a tube amp, or any part of one. If it comes to him writing any sort of instruction on the process, I will read it, and likely follow it( as long as it is not more of his effects box stuff ). No interest in that wee little niche. Not for me, IOW.
In case you think to argue that you are not idolizing an effects box purveyor, do please copy something he has written a description of that is not bandwidth limited, and possessed of widely frequency dependent output Z.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I was hoping to hear you had discovered some proof I was mistaken.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"I was hoping to hear you had discovered some proof I was mistaken."
DT667 learned that Pak is a creepy internet forum stalker.
We can add that to your long list of outstanding accomplishments in this hobby.
DT667
have fun wid that hb... :)
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
OK, sets of combined defects. For instance, inadequate cathode bypassing. Output Z varies with frequency, and even position on the waveform. That is audible. And, 'no thanks', not for me...
That some might consider it a useful sonic effect, who cares?
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
I don't do that-- to that extent.
Your observation would be correct if I did.
It's a balance of factors, as usual with me.
-Dennis-
don't forget the transfer efficiency.
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
"That's tuning by ear" If you like how a 15uf sounds, then that's the right number for you.If this is done on a product for sale the buyer must realize the amp is no longer a linear device* and hard tuned to a particular speaker design, listening room, and listener personal preference.
If all that's OK, then you found what you need. If not look elsewhere.
There is no science to this approach.
*Yes, no amplifier is a pure linear device. But we strive to reach that goal within the limits of current technology offerings.
Edits: 02/03/22 02/03/22
that sums it up pretty well.check out Dave's output Z plot. shows this happening. Would of course be neat to show the effect with a few different values of bypass cap.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
Edits: 02/03/22
Truly excellent, thanks !!
Jeff
It depends entirely upon how well it is executed. If done really well, it can be superb.
In Sound Practices magazine, 1994, we have a published example from Ciro Marzio and Christino Jelasi. They built an non-electrolytic power supply. They extensively used 0.22uF paper in oils, and a 0.022 uF silver micas, to bypass many of the caps in their SE circuit. Look at the C6 parts in their schematic, which is the Input tube's Rk bypassing caps.
Their 0.22uF value would enhance the midrange's music, and the 0.022uF silver micas, the highs.
http://www.ispra.net/audio/DCSingleEndedAmplifier/index.php
A decent amp design, for back then.
Jeff
If space is available, the DC link caps are the way to go, but they are large in size. If that is not an option, a bypass is worthwhile. In one of my amps, there is a 100mfd cathode bypass on the first stage. I bypassed it with a 5.0 mfd Multicap film and foil polypropylene. An audible improvement resulted.
I've replaced all my cathode bypass caps with DC Link caps. Mine are Kemet, but there's Vishay and others. Smooth and detailed. These caps are getting popular so many are on back order. You may not need 100uF - I use 30uF.
I don't hear a difference doing this. I want to, but I don't.
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Buy Chinese. Bury freedom.
You must be using a quality part. I don't like bypass caps. It can make things worse. Sometimes different. YMMV and all that.
You might enjoy the section of the link below titled "Power Supplies and Noise Spectra". Scroll down to almost the bottom of the page.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
There's a lot of interesting information in that article, and I took particular note of this:
"It also looks like folks who are stuck with bridge-capacitor supplies (the worst kind) for heater supplies and solid-state amplifiers might be wise to slow down the bridge with modest values of resistance, rather than leave the damping to the unpredictable value of ESR in the first filter cap."
I'm going to have to take another look at the SS rectified DC heaters in my 12AX7 phono/line stage.
Thanks
I hate to be the odd man out here, but I'll go on record as saying that much of what's posted in that article is a solution looking for a problem. I also find much of it to be so subjective and/or undefined as to be of extremely dubious value. I don't have time to pick it apart and focus on individual items right now, but I suggest you take most of it with a grain of salt until proven otherwise. And especially, if any part of that treatise causes you to consider spending a lot of cash for an improvement you didn't know you needed, by all means get a few more opinions before busting out the credit card. :)
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Buy Chinese. Bury freedom.
Keeping all this within the context of my 12AX7 based phono/line stage, I'm not looking to make a big investment. Building a large, expensive, brute force, choke input filament supply for that circuit certainly doesn't warrant the cost involved, or so I would imagine.
What I took note of in Olson's article was this suggestion: "...folks who are stuck with bridge-capacitor supplies (the worst kind) for heater supplies and solid-state amplifiers might be wise to slow down the bridge with modest values of resistance, rather than leave the damping to the unpredictable value of ESR in the first filter cap."
My preamp's DC filament voltage could probably use a bit of reduction anyway, so my idea was to add "modest values of resistance" since it would be cheap and increase tube life.
That brings up at least two questions though. Olsen says a "bridge" supply, but would this also apply to a full wave arrangement? The second question is, in this attempt to "slow down the bridge", would the resistance be applied prior to the rectification, or prior to the first cap after rectification?
I'd ask you what you think about SS filament regulation, as I did Tre', TK, but I think I already know the answer. [annoying smiley thing]
That paragraph is painful to read. If we're going for content here, this is substance abuse. "Slowing down" a bridge has zero engineering significance.
Anyway, it should be possible to mitigate hum issues in high gain 12AX7 stages by shielding the tubes and elevating the heaters. This assumes the layout is appropriate and that 60 Hz isn't being radiated into other components from the filament wiring. I would try applying +70V or so to the filament winding center tap before doing anything else. This might be all you need.
The biggest problem with DC filament supplies is removing the ripple. The second biggest is deciding how much has to be removed. We don't actually need DC here, because there's no direct connection to the circuit path unless the filament is the cathode in a DHT. This means it might be possible to create a decent filament supply without a regulator. It can be difficult to find the right combination of parts to produce the exact voltage. However, accepting a small amount of residual ripple can allow you to produce a supply that's much more efficient than absolute regulation. Remember that a 6.3VAC supply imparts nearly 18V pk-pk across the filaments. Transforming that to DC with one or two volts of ripple can make a big improvement.
The simplest "conventional" means for producing 6.3V of pure DC is to start with a significantly higher AC voltage, rectify it, filter it somewhat, then remove the remaining 120 Hz ripple with a regulator. The tradeoff with this method is that smaller filter caps require a higher initial AC voltage, and the regulator will waste more power stripping off the ripple. IOW, this becomes more efficient as the filter caps are increased in value, but then they take up much more space in the equipment.
You could also consider using inexpensive switchers for this. It's not difficult to modify the 5V modules to produce 6.3V. With this approach, the whole filament supply is smaller than just the filter caps that would otherwise be needed, and very little heat is generated. The downside is that these products may not be serviceable when they fail, so it might be necessary to keep a couple spares on the shelf, just in case. The upside is that they're vey inexpensive. :)
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Buy Chinese. Bury freedom.
IE Hexfred full wave bridge, small value first cap... CLCLC.But always sounds atrocious to a MV choke loaded supply, what's more, the MV/LC measures superb... even if we still have a long way to go in KNOWING what to measure.
The Mind has No Firewall~ U.S. Army War College.
Edits: 02/05/22
""Slowing down" a bridge has zero engineering significance."
But do you agree that....
"The first power-supply cap connected directly to the rectifier charges up very rapidly"?
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
"The first power-supply cap connected directly to the rectifier charges up very rapidly"?
That statement is dependent on the RC time constant and also what you mean by "rapidly." I'm not evading your question, I just don't know the context. Other aspects of the rectifier/filter relationship are usually more important than charge time.
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Buy Chinese. Bury freedom.
"That statement is dependent on the RC time constant "I thought it had more to do with the value of the first cap and the fact that the diodes can't turn on (conduction angle) until the voltage at the transformer is larger than the voltage across the cap (forward biasing the diode). And I thought the charging current peak is high because the diode will only be on for a short time but still needs to deliver the same power as it would if (they) were on for the entire half cycle (like they are when a critical inductance choke follows the rectifiers instead of the first cap).
I think Lynn is looking at the first half of this spike and calling that "fast" (.001 second from nothing to .59 amps) as the thing that needs to be "slowed down".
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 02/05/22
Sorry, I didn't realize you were referring to conduction angle. There's still a RC time constant involved, but not in the same way. Anyway, here's the thing. We know peak current is higher with a cap-input filter. We also know the peak current can be reduced with a series resistor (although that comes at the expense of power supply regulation). The question is, why would we bother to do that? Does the peak current matter, assuming all the components can withstand it? Is there some effect here that we need to mitigate, even though the voltage output from the supply is clean and relatively stable? If you're still questioning whether the truly awful voltage spikes at the input side of a choke-input filter are real, I'll have to insist that you make the measurement before continuing this discussion. Nothing that results from the potentially negative aspects of a cap-input filter even comes close to this.
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Buy Chinese. Bury freedom.
265vdc supply. 5Hy choke, LC loaded with 3000 ohms so drawing about 88 ma.
Critical inductance would be about 3Hy.
Scope connected from the input of the choke to ground. 5 volts per division.
Scope connect across the choke. 5 volts per division.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Well, all I can say is that something in the supply or the measurement process is quenching the spikes. I have witnessed this phenomenon repeatedly through the years, just as the simulations predict. I don't have time right now to make the physical measurement again on the bench just to make a post, so let's say for a moment that choke-input filters don't behave this way. Let's say the input of the choke isn't a high impedance and that everything I know about this is wrong. Which EMI-related or current-related problem does the choke resolve? Which audible anomaly created by a cap-input filter does the choke prevent? The fact is, Olson's writings on electronic minutiae typically focus on non-existent problems for which he then cleverly creates potential "solutions." In this regard, his work is often the antithesis of audio's golden-era pioneers such as Hafler, Fisher, Crowhurst and the rest, engineers who analyzed real world problems and provided real world answers and caveats. Naturally, if you can demonstrate a sonic defect that's inherent to all cap-input supplies, I'm listening. Otherwise, we should both move on to something more productive.
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Buy Chinese. Bury freedom.
"Remember that a 6.3VAC supply imparts nearly 18V pk-pk across the filaments. Transforming that to DC with one or two volts of ripple can make a big improvement."
I have found that the shape of the ripple makes a big difference. Saw tooth is nasty to listen to and it doesn't take much to make it audible.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I've read of your success in using switchers, and admit that I've been conditioned to immediately balk at the idea of switching power supplies. 'Contempt prior to investigation' applies here.
At some point I'd like to try something instead of large amounts of capacitance on the DC filaments of this phono stage. I need to do some experimenting, and once I do, I'll post, seeking any necessary advice.
Thanks, as always, TK.
"The electro-magnetic interference (EMI) noise generated by bridge-capacitor and pi-filter power supplies is responsible for a significant amount of tonal coloration as well as low-level veiling."
Even if the EMI is not getting into the signal path I still don't want all of those large violent current swings going on in my preamp.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Tre', the ripple current in C1 is shielded by the circumferential construction of the capacitor. It doesn't radiate. More important in terms of EMI is the voltage at the positive output of the bridge . The first image below represents this point as it appears with the same cap-input filter you modeled. Ripple is approximately 4.7V pk-pk. The second image shows this same point with the choke-input filter. Ripple at the peak of the time constant is nearly 1.5KV pk-pk and is composed of huge spikes (HF ringing) of that same amplitude that become visible when I zoom in.
If you're looking for a supply that won't contaminate an audio system, I think the conclusion here is obvious.
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Buy Chinese. Bury freedom.
There is either something wrong with your sim or something wrong with my sim.
Here's the current at the bridge.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
PSUD is excellent for basic functionality, such as output voltage and ripple. It's limited though, and clearly not useful for this exercise. You only need to probe a choke-input filter with a scope to see this phenomenon. LOL, the guitar amp I built recently reminded me of this when I accidentally forgot to install the wire to the first filter cap of the CLC filter. The choke was only 0.5H, but it radiated into the amplifier and created a loud buzz. Power supply output was still clean, but the EMI was everywhere.EDIT: It should be obvious why this happens when it's considered that the rectifier is looking into a high impedance. Average DC flows through the choke, but the AC component is effectively unloaded, and it "kicks" the choke (and the power transformer) as the diodes turn on and off. I'll just add that the example above used a 5AR4 rectifier. There were no solid state diodes switching on and off.
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Buy Chinese. Bury freedom.
Edits: 02/05/22
It was there all along in PSUD and looking just like my scope.
What I don't understand is how can that voltage be so high when there is very little current? The impedance of the choke must be much, much higher than I think it is?
BTW You're guitar amp with C1 disconnected would, for sure, cause a lot of havoc. A non critical choke in the input position is a big no-no.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
Edits: 02/07/22
I don't know what causes this. I used to think it was due to the rapid switching of the SS diodes, but I've seen it with tube rectifiers too, like in the guitar amp. Why do you say that a smaller choke creates more of a problem in this regard? The effect doesn't go away in SPICE when the choke is made larger, and I'm pretty sure I've seen this on the bench with larger chokes. I really think a choke-input filter is simply a problem in audio gear unless precautions are taken.
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Buy Chinese. Bury freedom.
Here's the critical inductance input choke.
Here's the non-critical inductance input choke.
Be sure to also note the voltage levels of these wave forms.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
TK - I think most people are using a small C In front of their choke input supplies. It does seem to help.
thank you for that PSUD2 visual for cap vs choke input tre'!
Tre',
I don't know if you've ever looked at any of the early Hammond Organ Company amps, but they were big fans of choke-input power supplies. It's known that they designed with reliability in mind because they wanted to establish a reputation for electric organs as equipment that could be relied on and didn't need frequent service -- like tube replacement.
Many of their early amps use an L-C-L-C power supply.
Yes, I believe in the old days critical inductance choke input filters were considered the "proper" way of doing things and everything else was considered a compromise.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I use critical inductance choke input filters LCLCRC on my heater supplies for my preamp and driver tubes. The filament supplies for my direct heated output tubes also use critical inductance choke input filters LCRCL.
The definition of "critical inductance" is the inductance value that, in a given situation, keeps the diodes (each in turn) on for it's entire half cycle. This keeps the peak current no higher than the load current.
With a less than critical choke input filter (or a cap input supply) the diodes (all of them) are off most of the time so the current has to be high (multiple times the load current) when they are on.
The same amount of "power" still has to be delivered to the load but because the time when the diodes are on is short the supply has to "make hay while the sun shines" so the current has to be high. These current "Spikes" are the problem in terms of noise.
You can clearly see all of this with the Duncan power supply designer II modeling software. Or a scope.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I would imagine a choke input supply would be optimal on the filaments. Although in my case, a larger chassis would be required, and if I got that far, an entirely new phono circuit would probably be in order.
Have you ever tried regulating the filaments with a SS regulator?
No. Just a lot of Henrys and a lot of capacitance to get rid of the ripple.
I admit, regulators do take up a lot less room.
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
I've only gone the "a lot of capacitance" route. a ridiculous amount, as a matter of fact.
I've been curious about a regulator, but I suspect a cheap 78XX may not do the proper job. I've lived with an umbilical and two big 120,000 uF computer grade caps dangling off the back of my preamp for a long time. I'd love to eliminate them, if a bit of sand would do the trick.
His PP amps were the inspiration for mine.
Lynn, along with Gary Pimm and Gary Dalh are truly remarkable designers. Cutting edge!
Tre'
Have Fun and Enjoy the Music
"Still Working the Problem"
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