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Brian Clark from www.sempremusica.com reported exellent results with one tube(6C45)amplifier.It is my next project, but with two 6C45 in parallel, becuase I need little more power.
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Using two tubes seems like it defeats the purpose of having a one tube amp, if you ask me. You're only getting 3db more output, and if that makes a difference, you need about 10db more headroom anyway, which means new speakers.Another solution is simply to drive the tube harder. Mine goes at 235V and 35mA, or about 1.5W. Maybe this will wear the tube out faster, but I've never heard of anyone actually burning one out. They seem to be very durable.
My amp runs directly from a DIY DAC that takes output directly from the DAC ICs with no gain stage. (tnt-audio Convertus type circuit.) So there's only one tube between DAC IC and speakers. However, most of the time a 1:4 stepup is necessary, which is not really ideal.
Hi nl,
I agree with you about using two tubes, but maybe (just maybe) 6C45's will surprise me :-). This tube is really unpredictable.My experience with 6C45 is only in amp driver stage, and my strongly recommendation for 6C45 is teflon socket. With teflon socket this tube work very quiet and sounds excellent.
Output toroidal transformer should be next good choice in combo with this tube, because toroidal transformers "want" high capacitive input ie. tubes with high internal capacitance such as 6c45 (or high capacitive power cable for mains toroidal transformers).
Your comment is on my paper. Thank you very much.
best
How about a dual dissimilar triode like 6FM7? That has a voltage amp and a powr amp in one bottle. Still one tube, and you can probably get a tad more power out of it, say a couple of watts.
I did it with ECL86 tubes - one per channel. 4 Watts out, too much gain. I should put in Tone Control section to drop some of that gain.Chris
Read Kurt Vonnegut, Tom Robbins, and Charles Bukowski.
... Im on "your way". I have 6 or 7 pcs unused 6C45PE tubes and must use them.
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there is a PSE design at http://digilander.libero.it/paeng/pae.htm look very interesting, i am deciding on a design to build, just got my 6c45 tubes. more suggestion are much appreciated either on pre or amp
PE stands also for a Special Quality Tube with 10.000 hours of
guaranteed operation!
...and the character that looks like pi is the Cyrillic P.Brian.
Hi,Not to dampen your enthusiasm, but I suspect two 6S45 in parallel will loose a lot of the magic. Low Mu Triodes have enough difference between valves to cause audible problems. With the medium mu and high gm 6S45 the effect will likely be much more pronouced.
How about using two 6S45 in push-pull, but with a little "trick"? What you do is to build the main forward path just like the "Semper Musica", but with a PP OPT of 10k nominal A-A impedance.
In fact, I could think of a few moderatley large (30VA...50VA) torroid mains transformers of the 115V+115V : 6V+6V (or 9V+9V) variety that will show very low leakage inductance. They would hence be suitable to give 12k (6V windings in parralel to 8 Ohm Voice Coil) or 5k (9V windings in parallel to 8 Ohm Voice coil) primary impedances.
Anyway, construct a complete second amplifier path using the second 6S45 and other halve of the primary but drive the grid via either a transformer tap or resistive divider from the previous triode. I think taking the drive to the second 6S45 with a 100 Ohm Pot and some resistors on either side to limit the adjustment from one of the two secondary windings should work okay.
You will need to have actually a small adjustment range in any case to match this, the second "driven" 6S45 should clip slightly before the one in the forward path. Of course, adjsuting the ratio of signal division between the two valves will give a chance to adjust the sound "to taste".
Hi,could you perhaps name these toroids ?
brand and supplier (UK) would be useful...
or would any surplus 60VA toroid be adequate ? surplus can be as low as a third of the usual retail price...do you think it would be worth attempting to remove a few secondary turns to achieve higher primary impedance (if one needed say, 25kOhm) ? from your experience, would that be likely to increase the leakage inductance significantly ?
what kind of power bandwidth are we talking here (roughly..) ? 20-20k?
thanks
This is something I simply MUST try. Could be a killer!Brian.
...a good idea but flawed . 6C45 vary enourmously , electrically matched pairs are a must as toroids do not like any DC across them . Toroids working at low HT work very well but any DC caused by imbalance and your circuit is buggered !
Koinichiwa,> ...a good idea but flawed . 6C45 vary enourmously ,
> electrically matched pairs are a must as toroids do
> not like any DC across them.Well, the "Semper Musica" 6S45-PE SE Ampliifer has a bias adjustment. If you build the the circuit twice and only derive the "out of phase" drive from the other anode you retain the individual adjustability and hence the amp will have balanced DC.
So I fail to see the flaw. BWTFDIK.
...so your telling me that it's ok to stuff any old 6C45 into a PP amp ? I wouldn't do it , these 6C45 things are all over the place out of the box , best to buy a bunch , burn in then retest and select before using . Same goes for just about any high gm valve . If this pot is between the cathodes , then degenerative feedback will occur anyway and increase Rout , better to select and reduce the value of the pot
Koinichiwa,HAVE YOU ACTUALLY LOOKED at the "Semper Musica" Amplifier circuit? Have you made the effort to draw out what I suggested?
Maybe you really want to have a look at what you are criticising before you criticise.
As for mismatches in PP Amplifiers, note that my proposed circuit has already some deliberate "mismatch" build in to reduce the 3rd harmonic content at the expense of more 2nd Harmonic and a little less power.
It sounds better that way. I would personally tune the Amp for minimised 3rd harmonic content. There is a distinct minima at around 30% Mismatch IIRC after wich 3rd harmonics rise again.
NO NEED TO SHOUT ! Jeez , no wonder you're not flavour of the month round here . I am familiar with the design , I still think this new design is flawed .
Koinichiwa,So, the design is flawed. Fine. If you say so, please explain how.
It is obviously NOT flawed when it comes to DC balance, as both Valves operating points are fully adjustable. So no flaw there, even IF using torroidal mains transformers as outputs. Also, the sub 3k differential drive impedance to the torridal mains transformer abused as output will give good bandwidth.
It is obviously NOT flawed where it comes to AC balance as it CAN be adjusted for optimum balance. Or IF we desire a better overload behaviour and a harmonic spectrum more akin to an SE Amplifier with lower levels of 3rd harmonics than a "theoretically ideal" amplifier we can deliberatly unbalance the Amplifier.
When it comes to noise rejection et al the circuit matches the original "semper musica". Again, no flaw I could note.
As it is in many ways NOT a push-pull amplifier, other than the way the transformer is driven, applying PP logic foes no-where.
So, where is the flaw. Please enlighten me.
Sayonara
PS, may I mention that similar circuits where in use in the 1920's and 1930's with Pentode PP Outputs. They worked then...
I have a decent stock from which to pick matched pairs Nic but it is good that you have pointed this out. When I get around to knocking up a pair of these Pushme-Pullyous I will put results up on my webpage.
Why not use a 350-400V HT supply and stack the things as SRPP cap coupling a mains toroid between the top 6C45 cathode and 0V ? Battery bias with a chunky NiCad or NimH on the cathode of the lower valve . A 230:6-0/6-0 mains toroid with the secondaries in series will provide about a 3k impedence into an 8r load . I suppose there are plenty of possibilities ! That reminds me , I must try building something with the 7788's !
;)
...ooops forgot to add : 6C45 in push pull driving via the cathodes would probably be the best application . Very good damping , should also have low distortion . I'm tempted to try this myself but too busy with sales and other projects at present .
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