Eldartford - you should check out Lynn Olson's article "Ultrapath, Parallel Feed and Western Electric" in VTV #16. Of interst here is the section titled 'Audibility of Power Supplies'. |
John_tracy...But it doesn't pass through it. |
This is a forum where people will argue that different types of "wire" will each have their own sonic signature. Yes a large PS cap will look like a short circuit to an audio signal. Will it also impart it's "sonic signature" to that audio signal when it passes through? You bet'cha. |
Aball...Yep. I don't know what I was thinking. I guess that the point I was making is that the PS capacitors are such huge values, compared with coupling capacitors, that they would look like a short circuit to an audio signal. |
Yes, you are correct - I meant coupling caps and not decoupling. The input coupling cap is generally the one in the signal path.
Decoupling caps are from power to ground (parallel to the power supply reservoir caps) to remove radio frequency components - hence cleaning up the sound. the power supply caps, being much larger in size, remove the ripple to clean the sound of those frequencies. |
"There is some confusion: "in the signal path" means in series."
I agree; that's the definition I always understood.
"Decoupling capacitors are in the signal path."
'Decoupling' usually means a relatively small cap from DC power to ground that isolates one part of the powersuppply 'line' from the next. Decouplers are NOT in series so are not in the signal path. Did you mean COUPLERS?
"Parallel caps are fine and necessary - cleans up the signal which everyone likes."
You'll have to be more specific for me to understand what you mean.
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Actually, if the power supply caps were in the signal path (in series), you would have a highpass filter so it would be an LF rolloff. There would be no bass.
There is some confusion: "in the signal path" means in series. Decoupling capacitors are in the signal path. Parallel caps are fine and necessary - cleans up the signal which everyone likes. |
John_tracy...Get real! If power supply capacitors were in the signal path the amp's HF rolloff would be about 0.0001 Hz! |
Look carefully at the design of all amps that claim "no caps in the signal path" and you will find lurking in the shadows the power supply caps. They are in the "signal path". The only designs that I am aware of where this is not the case are topologies like the parafeed and ultrapath and like designs which use a high quality film type to get around the caps in the power supply. |
My SS amp has Output transformers and it sounds swell. Caps? Who knows and who cares? Listen for the music, not how you get there. "I have 6 large for a new amp, what, oh what, should I buy?" Gee whiz Wally, listen to a NAD first, perhaps blindly, Then commit if you Must. Just my .02, I could be wrong. |
A DC-coupled amp is really a DC power supply with analog command input, and a high slew rate. In fact, many years ago a power supply manufacturer demonstrated his product at a trade show by playing music through it. Subsequently, some audio amp manufacturers took this approach.
I have a couple of old Kenwood L07M amps that are direct coupled, and they do sound really good dispite their age (or should I say "vintage"). |
Parasound JC-1 monoblocks. They are DC-coupled. |
Just FYI, an amplifier without COUPLING capacitors (ie without capacitors in the signal path) is called direct-coupled. All the direct-coupled amps I know of (but I don't get around much) are solidstate. All tubed amps I'm aware of have at least one coupling cap per channel in the signal path.
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wavac amps don't have caps in the signal path.
btw, they sound wonderful.
rhyno |
I think what he meant is that no caps in the signal path. I think Arcam Diva series do not have caps in the signal path either. They use some kind of servo circuits on the output to remove any DC residual.
But for the power section of the amp, there must be caps there. |
SimAudio claims that their amps have no caps in the signal path. I believe that they do put caps in the power supply, though. |
Vecteur, YBA and REDesigns all make amps with no Caps in the signal path.
They are all very natural sounding amps and quite stunning in the right system. This is no accident. |
All amplifiers have capacitors. I suppose theoretically one could be run off humongous batteries, but converting AC to DC will require capacitors. Many companies tout having no capacitors in the signal path. This requires an extra level of care as speakers will detonate if significant DC is present on the output. There are numerous design techniques to eliminate the DC without caps. |
Yes.
It is also possible to make a crossover for the speaker where the tweeter has no capacitor in series with it. It uses an inductor across the tweeter. The drawback is that such a crossover wastes a lot of power in a resistor needed to avoid a short circuit on the amp at low frequency. |
