Avoid caps where possible. Choose the best design.
Where not choose a decent cheap cap to do the job.
However that doesn't change the basic essential fact that every single component choice has an impact on the final sound, and this is doubly so with amps that don't resort to large amounts of gNFB to smooth the differences out.
Shoog
Where not choose a decent cheap cap to do the job.
However that doesn't change the basic essential fact that every single component choice has an impact on the final sound, and this is doubly so with amps that don't resort to large amounts of gNFB to smooth the differences out.
Shoog
from my modest experience , i can say that every change of component change the sound, you change the coupling caps type , power supply filtering, rectifier, load or cathode resistor, choke, ..
second you keep the same components but only change the values it change the sound even more...
you change the schematic, battery bias, led bias, RC coupled , DC coupled, choke load, CCS load, etc... you change the sound to another level.
now make a mix of this 3 kind of changes all together and your wife will end up with the neighbor 😀
second you keep the same components but only change the values it change the sound even more...
you change the schematic, battery bias, led bias, RC coupled , DC coupled, choke load, CCS load, etc... you change the sound to another level.
now make a mix of this 3 kind of changes all together and your wife will end up with the neighbor 😀
In a power output stage - burning up 200-400V and probably 20-30W's in a cathode resistor - reducing efficiency to 10% or less, seems like a very wasteful and bad design to me. There's also the little problem of output stage explosion in a fault situation.
Shoog
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my 6C33 set amp eats 220 watts of power at turn-on for a mere 20watts output.....what a waste.....
I have never been a fan of SET amps due to the extreme behavior it engenders in many of its advocates.
Still I am willing to be proven wrong and will be testing how well they stack up against a good Class A PP amp in my next project.
Shoog
Still I am willing to be proven wrong and will be testing how well they stack up against a good Class A PP amp in my next project.
Shoog
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This illustrates the basic principle.
The versions I have tried are both PP, one using a Triode output, the other a pentode.
Both are self adjusting and intrinsically safe in operation due to the two CCS which maintain bias and prevent current runaway.
Shoog
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Interesting. If you have an idea for a DC coupled 2 stage cathode bypass-less concept do share. I can run simulations. What I have seen in the past adds so much complexity as to make the amp too big and complex.
It looks like you killed the voltage amplification in the first stage by adding a CCS in the cathode?
Indeed you are right in this case and I missed it - but think of it as a PP with a LTP to see how it should work in the builds I have implemented.
You would have to put the bypass cap in to make it work, but at least there are other advantages it brings to the table.
I think it would probably still work fine if you replaced the bottom CCS with a resistor - but initial setup would be must more difficult and critical.
Shoog
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In 1929 Loftin and White had limited technology at their disposal. They did the best they could with what they had. Their compromises do not have to be our compromises; I'm sure they would find it amusing/perplexing that anyone today might put them or their designs on a pedestal.regal said:
See here for a description of what they did and why.
So... we've got rid of that pesky coupling capacitor and replaced it with a coupling transformer. Progress at last! Wait..what?
I'd far prefer an interstage transformer to a coupling cap for all kinds of reasons, not least of which is that a good one sounds better even than a teflon cap (and much better than everything inferior to that...).
Here's my simple solution - the amp I use everyday. No cathode bypasses. No high voltages, total cost of all tubes less than $25. It's better than all the 300b SETs I built even with really good parts and circuits - but which had cathode bypasses in the output.... You could hear the difference with filament bias and no cap quite clearly.
Well as long as it sounds better and isn't, you know, more linear or anything.
I maintain that the fashion for chokes and transformers rather than capacitors is further proof that many audiophiles only claim they are in search of better linearity, when what they really want (consciously or unconsciously) is the right kind of effects box. Hence why we still use valves.
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As almost any capacitor is going to be closer to being an ideal component than any transformer I think there is a good case for eliminating transformers wherever possible and replacing them with caps.
Early amplifiers (e.g. in the 1920s) used interstage transformers because early valves had such low mu that a bit of transformer voltage step-up reduced the number of stages. We don't need to copy them.
Early amplifiers (e.g. in the 1920s) used interstage transformers because early valves had such low mu that a bit of transformer voltage step-up reduced the number of stages. We don't need to copy them.
That's dangerous talk. A reading of this thread will provide plenty of examples of people who clearly want effects boxes, give one supporting example after another, then get quite angry when that term is used. Linear amplification is "boring," "lifeless," "sterile," or somesuch, regardless of whether it is provided by transistors or tubes.
I love coupling transformers. Personally I think that the OT is the main reason why people like the sound of Valve amps.
Others may not agree.
The strange thing is that coupling transformers are ubiquitous in recording studio's - go figure.
If you disagree Gary Pimm shows you how to achieve the same thing with stacked power supplies and no coupling caps or transformers.
Shoog
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Indeed, that may well be why people like the sound of valve amplifiers. The transformer(s) give a colouration to the sound that is appealing to the ear. It is, in effect, giving an effects box. Nothing wrong with that, but it's good to recognise it for what it is, I think.
Chris
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