John Curl's Blowtorch preamplifier

[serengetiplains]

I understand what you mean by charge retention. It's the out-of-time charge release I'm concerned about, for audio purposes.

 

[poobah]

Right,

I'm saying that the return effect is sorta DC-ish in nature. I'm just saying that I can't imagine shoving a bunch of AC through a DC biased cap, shorting it, and then expect to see AC (music) coming out in the discharge... what that DC is doing remains to characterised... methinks it does something though... even "disbelievers" (guys with $5 power cords) seems to say something about caps...

 

[serengetiplains]

I don't question your assumption that you don't see music coming out the discharge. What you will see is an AC voltage (declining or increasing DC = AC) the magnitude of which is correlated with the original voltage which in turn is determined in part by the AC the cap is coupling or some power supply variation caused by AC the amp is amplifying. The discharge *is* related to the AC signal in question, but not in the manner of an echo, which is a naive characterisation.

 

[poobah]

Right,

I gotta believe to one extent or the another that this would have some "smearing" effect on the audio signal.

 

[serengetiplains]

I gotta believe to one extent or the another that this would have some "smearing" effect on the audio signal.[/B]

IME I have no doubt it does. I often use the term "smearing" to describe the effect. The effect is subtle, but it's bothersome enough, to me at least, that I find it a good game expunging a circuit of it where I can.

 

[Steve Eddy]

How do you know what you assert? Not anything like ... ? Show me a picture or do your best to describe in words, then we can compare.

I'd be happy to oblige if you can tell me how to show you something which isn't there.

Here, how's this?

An externally hosted image should be here but it was not working when we last tested it.

DA, or something to which DA corresponds or correlates---for simplicity's sake, what I'll call DA---smears and/or ghosts and/or adds to and/or subtracts from an audio signal. I hear DA's effects as a form of veiling and grunge, among other descriptions I could throw at it; veiling because DA disrupts my ability to hear clearly into instruments, spaces and dynamics, and grunge because I feel a sense of subtle relaxation or relief when DA is removed as if an irritation has been removed.

Ok, so you've been making objective claims based not on any sort of objective proof or evidence, but on sighted, subjective listening? I'm afraid that won't really get us anywhere if what we're after is what is "*actually*" going on.

se

 

[serengetiplains]

Steve, here's a subjective claim: almost no one can have a meaningful discussion in this forum with you. I'm sure this is not, in one form or another, news to you. I'm back to ignoring you.

 

[Steve Eddy]

Steve, here's a subjective claim: almost no one can have a meaningful discussion in this forum with you. I'm sure this is not, in one form or another, news to you. I'm back to ignoring you.

Ciao.

se

 

[lineup]

Test 2 examined a number of higher value aluminum and tantalum electrolytics. Comparison of units 1 and 2 shows that a higher voltage rated unit of the same value will tend to have a lower relative DA.
This is an interesting point, as this same consideration for selection criteria is also true with regard to DF.
It means that wherever possible,
if you must use an electrolytic, use the highest practical voltage rating.
This applies to either aluminum or tantalum units. Units like number 1 should be avoided at all costs!
Unit three is a 50- u F non-polar aluminum electrolytic of a type often seen in solid-state audio circuits. As can be noted it has a somewhat lower DA. Apparently, a back-to-back connection tends to reduce the DA of a single unit. For example, unit 4, actually a series pair of two units like number 1, shows less DA than a single. This tends to say that nonpolar units or non-polar connected conventional electrolytics will be better in DA relative to a conventional polar cap.
However, this difference is largely academic we feel,
since if you want really high-quality sound,
you cannot tolerate more than a small fraction of a percent DA.
Obviously this rules out all but the best of the film dielectrics.
Unit 6 is an example of one of the better quality aluminum electrolytics (see also Fig. 7).
While studying the DA problem in tantalum and aluminum electrolytics, we also bench-tested .......

-------------------------------------

Acknowledgements
The authors would like to acknowledge private discussions with
John Curl and J. Peter Moncrieff
on the subject of capacitors in audio circuits and how they might influence subjective testing.

Testing Capacitor DA

 

[john curl]

'Smear' is a pretty good description of DA. I once used the term 'echo' for DA effects, more than 20 years ago in a LTE to 'Wireless World' or 'Hi Fi news'. I never heard the end of it from Doug Self, etc. , but 'echo' is a good first approximation. It is signal AFTER the original input has gone, and there should be only silence.

 

[serengetiplains]

The term "echo" communicates sufficiently to me, as does "ghosting." In case I'm being misinterpreted again, those terms should not be taken literally to imply that a smaller Mini-Me version of the originating AC signal pops out like the return of sound waves in the Grand Canyon. I personally wouldn't be surprised, as seemingly must be the case, that dielectric voltage absorption and release are non-linear in frequency and time domains, among others.

 

[Steve Eddy]

It is signal AFTER the original input has gone, and there should be only silence.

If that's what's actually happening, then it should be pretty darned easy to demonstrate it.

So has it been demonstrated in the more than 20 years since you wrote about it, using the term "echo"?

se

 

[john curl]

Of course.

 

[Steve Eddy]

Of course.

Oh, well then let's see it. I'd love to see these "echos" trailing the original signal after the original signal has ended.

se

 

[poobah]

Nothing that happens here, because of DA, can be nonlinear; at least on a discussion of second order (FORGET THIRD FOR NOW)effects. That is because the components and the best models of DA are linear. That is not to say that many linear effects can't cause audible stuff/flaws.

 

[Steve Eddy]

Nothing that happens here, because of DA, can be nonlinear; at least on a discussion of second order (FORGET THIRD FOR NOW)effects. That is because the components and the best models of DA are linear.

Quite so. And certainly nothing that will have an "echo" signal following behind the original signal.

That is not to say that many linear effects can't cause audible stuff/flaws.

True.

se

 

[poobah]

Give Serengeti a break,

I'll beat up cable guys all day long... just for fun... R = R. But this cap thing is not all hooey. Tom may choose words which don't suit you, but he has not implied, and in fact has spoken to the contrary, that there is no "echo" i.e. complex AC waveforms" stored" in DA.

I think he's out there sometimes, but unlike so many of us, he has taken the initiative to have prototype caps built. Except for his ears, he may not have the the toys to subject these prototypes to more "acceptable" methods of testing.

Study a DA model, then ponder what it does to an audio signal. Google "capacitor soakage" and read. And then don't tell me Bob Pease or serengeti is full of ****. I'm sitting on the fence here. I have a plan and things I want to learn for myself. There is one crucial measurement/aspect of DA that has been overlooked.

 

[lumanauw]

Hi, Mr. Curl,

I wanted to ask your opinion about Snubber.
People put snubber (1ohm+100nf, series) in parrarel with big bank capacitor (like 10.000uF). In what way this snubber affects or not affecting the sound of an audio amplifier?

 

[Steve Eddy]

Give Serengeti a break,

I did. Back when I said "Ciao."

I'll beat up cable guys all day long... just for fun... R = R. But this cap thing is not all hooey.

Never said it was.

Tom may choose words which don't suit you, but he has not implied, and in fact has spoken to the contrary, that there is no "echo" i.e. complex AC waveforms" stored" in DA.

But John, who I was actually referring to, did say as much:

It is signal AFTER the original input has gone, and there should be only silence.

If we're talking about audio here, then "signal" is indeed a complex AC waveform.

Study a DA model, then ponder what it does to an audio signal.

I have.

Google "capacitor soakage" and read.

Done that too.

And then don't tell me Bob Pease or serengeti is full of ****.

I won't tell you that Bob Pease is full of ****.

I will tell you that I have disucssed the issue with him.

I'm sitting on the fence here. I have a plan and things I want to learn for myself. There is one crucial measurement/aspect of DA that has been overlooked.

What measurement/aspect of DA is that?

se

 

[poobah]

I won't tell you about the "measurement", your very cranky right now, it's extraordinarily obvious, and might make me a buck or two.

In the case of "john", a slowly decaying DC potential may represent distortion... it's all about where you draw the line between DC and AC. that is not only about fundamentals, it is about spectral (harmonics) as well.

No one here has described caps as short term tape delays, although you have chosen to assume that for the sake of rudeness.

Oh, and next time you talk to Bob, tell him to call me, please... I lost his number and we were supposed to camping...

(jeeze!)