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In Reply to: RE: This long thread just tells me what commercial SETs aren't.... posted by tube wrangler on September 03, 2017 at 03:40:55
Filament bias isn't an "attempt to get more power" - that's fixed bias in the old-world sense where it was used for output tubes.
The modern usage is for DHTs, usually but not exclusively in the input section(s). The modern implementation uses sophisticated solid state circuits like Rod Coleman regs (now version 7) and choke input filament supplies. This is not trivial engineering - it's been very well thought out and has a LOT of users around the world.
I'm not particularly surprised you don't understand the sonic benefits since
1. You don't use DHTs in the input section
2. You believe that cathode bypass caps are an acceptable alternative. I don't, and I've tested plenty.
Since you can't do a direct comparison, it's pretty meaningless trying to compare the sonic results.
Follow Ups:
Honest observations, but cathode bias CAN be done right.
This does avoid installing chips designed by geniuses.
It's no longer a tube amplifier if solid state devices
are used in the amp, it's a hybrid.
Sonically, I prefer the sound of a vacuum tube acting
alone-- with no devices or control devices attached to
it, even if that's another vacuum tube.
The good thing about cathode bias is that you're using
only passive devices on the cathode. The "bad"
(as in expensive) thing about it is that it
requires multiples of expensive caps, no one cap
can even begin to work at the highest audio performance
levels. Also, the cathode resistor had better be the
world's best resistor. (Tiny audio currents thru the
resistor not withstanding).
I appreciate your comments and I always enjoy learning
from other worlds.
-Dennis-
"It's no longer a tube amplifier if solid state devices
are used in the amp, it's a hybrid."
That's not how a hybrid is defined.
If the solid state devices modify or directly influence the signal path, it's a hybrid. I'll add that the difference between a MOSFET that is obvious in its role of amplifying the signal and one that appears to reject the signal (such as occurs with a CCS) is illusion only.
--------------------------
Buy Chinese. Bury freedom.
so you can sensibly use SS stuff when you want to.
cheers,
Douglas
Friend, I would not hurt thee for the world...but thou art standing where I am about to shoot.
That would appear to be a definition that is only accepted/proposed here.
Cracks me up to look at AA for the first time in maybe a year, and still nothing has changed since 2010. Some poor guy asks for some advice on components and we see the thread deteriorate rapidly into a sort of audio theory acid trip.
To the OP, a rule of thumb that has been used to pretty good effect is you want to be able to hit roughly 102dB peaks. That's instantaneous peaks, not average listening level. The industry standard (recording industry, not audiophile jewelry industry) average listening level is around 82dB, the 102dB is a headroom allowance. Not everyone listens at that 82 dB average level, but it's a good starting point for most as much over 85dB average can cause hearing damage with extended exposure. This implies that you can do the job with a 93dB sensitivity speaker and an 8W 300B amp. Saying things like the falloff at a distance greater than 1M negates the utility of the 1M loudness level figure in a large room shows a lack of practical experience. The reverberant field in the room dominates at mid field listening distances and thus one can pretty much use the 1M distance loudness figure to determine required power at the listening distance unless your system is sitting on the top of a mountain. My experience has been that this approach works quite well.
All of this of course hinges upon how honest the loudspeaker manufacturer is about the sensitivity of their speaker. Suffice it to say I think it is worth questioning a lot of the published specs.
when working out whether my amp will have enough juice. PJ has shared it a few times times in the past.
Yes, an acid trip is right. I mostly stay out of it these days... Where else is there to go? DIYaudio is worse; other non-commercial forums are either not technical enough or just plain goofy.
I generally like it here, but I miss some of the old contributors and wish that threads stayed within a yell of being on topic (yes, I'm guilty as well).
Cheers,
91.
"Confusion of goals and perfection of means seems to characterise our age." Albert Einstein
Yes we need Steve Eddie and more of the old timers on here back :)
fun reading for sure
Lawrence
Yes, now if you use a tube rectifier with a high voltage mosfet amp, Audio Asylum declares that it's a hybrid!
I totally agree on parts quality in simple circuits like we use - everything counts. I do constant cathode resistor tests and sometimes get surprising results, like Russian ex-military parts. I don't use bypasses so no issues there.
I've come to value the solid state stuff I use. Regretfully I can't design it - I just know tube circuits. But I do know smart guys who can do all the clever stuff, and some of it is very clever indeed and quite innovative. For me DHTs and solid state are where it's at right now, though I confess that my input tube right now uses a plate choke. Whatever sounds best!
Solid state engineering has continued to progress,
and devices get better and better.
Most solid state amps sound different than most tube
amps, but nearly all of both can often leave you cheated
when it comes to listening to music.
One company that I never tire of is Berkeley Audio Design,
and Spectral. These guys often work together. The older
reference to these guys was Pacific Microsonics.
I continue to admire Bob and Phil at Lynx Studio Technology.
Bob is mostly engineer, Phil is mostly applications, but
both of them often wear both hats.
And Hats Off to both of them, them, I say!
-Dennis-
Again you are off topic and not helpful.
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