John Curl's Blowtorch preamplifier

[Sigurd Ruschkow]

John,
yes, PMA seems to be an EMI expert, and I do not want to
discredit him in any way. That was not my intent.
Me, working as a project manager sometimes, I tried to see the whole picture and cannot focus on details (too much).
For me it is impossible to agree with PMA that EMI is THAT important.

I have worked as an SMPS designer in the mid 80s so I do know how important EMI is, and I remember all the looong hours I spent in the EMI chamber we had at RIFA Power Division.
All those standards to fulfill....




Sigurd

"

Right you are, Sig. However, each of us likes to address what we are best at. For one, it might be EMI; for me, circuit topology, someone else, nice case; yet another, ultra low measured distortion. Everything is important, but sometimes, one thing might be more important than usual.

 

[PMA]

The fact that you have reached different conclusions than John or me can only be resolved if we do our listening tests together, in the same room with the same system. Then we can point out to each other exactly which part of the sound quality we are focused on, and how it affects the musical presentation.

Charles,

that is exactly what I think about when I read here about listening impressions and experience. That is why I spoke about a long distance barrier, when it is impossible to get mutual experience, and find possible reasons of different approach.

 

[scott wurcer]

Charles, one point: Scott did not say that the sorting was done as a result of a listening panel. I doubt that it was, and in my first conversation about it some years ago, he expressed doubt that it was.

To be honest, doing a proper listening test of more, uhhh, outre speculations requires a LOT of time and effort. Which is, of course, why no-one does it, including the fans of such, uhhh, technologies. I do a lot of listening tests, but they focus more on topologies, speakers, and room acoustics, where I think the payoff is a lot more tangible.

The experiment would really need to be repeated with proper protocol observed. The parts left 'apparently' without anyway of separating them and the 'cryo' was probably being dropped into LN and dumped back out. Bob Adams related the story and there was at least some evidence to him that the customer was able to separate the groups honestly.

A better story was actually the time Bob Gendron drew spokes on a CD and using a fancy telecom data analyser saw the spurs in the jitter spectrum. This was verifyably repeatable and reported in the AES journal (I think). Got them thrashing.

 

[hermanv]

Herman, clearly you are simply a victim of mass delusion. Are you sure that Obi-wan wasn't in the room with you?

Ah, ha. That explains the guy with the hood.

 

[SY]

the 'cryo' was probably being dropped into LN and dumped back out.

Ouch. In that case, I can absolutely believe that the thermal shock would have significant electrical and possibly audible consequences. Did the good Dr. Adams pursue this any further?

 

[PMA]

For me it is impossible to agree with PMA that EMI is THAT important.

I have made a LOT of listening tests on this issue, supported by measurements of interference and output in time and frequency domain. Also, we have made a LOT of measurements with and without mains purifiers, pure DC supply and compared to listening results. That is why I dare to speak about it. My conclusion is that RF content, no matter if it comes through supply or as D/A residuals, has SIGNIFICANT influence to resulting sound, and that it is one of the main reasons why different cables sound different.

 

[jacco vermeulen]

in New Mexico

Arliss Loveless's next script line would likely be that you'd have to be called a New Mexican't for the remainder.
(i'll settle for Sam McLoud)

 

[MikeBettinger]

I think more to the point, the question should concern the magnitude of these effects.

If it's being said that one cannot build highly resolving, accurate, musically involving examples of this art if they are not applying any or all of the various topics of discussion here, then I disagree.

 

[Jakob2]

Hi Scott,

Originally posted by Scott Wurcer,

the 'cryo' was probably being dropped into LN and dumped back out.

Wasn´t Ed Meitner involved in these early cryogenic trials?
If so maybe he could supply some information about the cryogenic treatment choosen.

Jakob2

 

[scott wurcer]

I have made a LOT of listening tests on this issue, supported by measurements of interference and output in time and frequency domain. Also, we have made a LOT of measurements with and without mains purifiers, pure DC supply and compared to listening results. That is why I dare to speak about it. My conclusion is that RF content, no matter if it comes through supply or as D/A residuals, has SIGNIFICANT influence to resulting sound, and that it is one of the main reasons why different cables sound different.

Last weekend I had my hand on a cable and for an instant heard a sound sort of like the president calling in "In Like Flint". In a meeting Friday someone's computer did the same thing, but he knew it was a cell phone. I still agree RFI especially with the high DSP content in most AV equipment these days is way up on scale of things to look out for.

 

[scott wurcer]

Hi Scott,

Wasn´t Ed Meitner involved in these early cryogenic trials?
If so maybe he could supply some information about the cryogenic treatment choosen.

Jakob2

I don't think anyone followed up after these early experiments, I know our listening room ended up with his amps and if he actually did the cryo it might have been more controlled. I think only Bob is still around from those days.

 

[myhrrhleine]

Hi Chuck,

Thanks for these insights. The whole thing about the use of magnetic materials is fascinating. There is certainly a theoretical cause-effect regarding excitation of the magnetic domains, but it is unclear if anyone has ever been able to measure its effect on a signal under short-distance situations like component leads and end-caps. I agree with the conservative approach of assuming that there may be something audible here, and perhaps lumping it into the pile of things we just perhaps don't understand. At the same time, it would be fascinating to come up with some kind of a measurement that produced different results for magnetic and non-magnetic versions of the same component that could have some relevance to sonics.

Cheers,
Bob

It may be a broad generalisation too.
Every time i've tried a magnetic component, it sounds bad.
Therefore magnetism is the culprit.

Rather than well designed/built components [coincidentally] are also non-magnetic.

 

[gl]

This is the best definition of audiophile related burn-in and burn-out I've seen. Thank you Nelson.

Graeme

 

[mlloyd1]

john, charles, and others:
keep rolling those pearls out on the floor. you can rest assured that not everyone is ignoring and disputing them.

as for the rest, oh well ....

mlloyd1

 

[john curl]

Finially, someone brought up a real potential problem to address: OUTPUT IMPEDANCE


If I had my way, I would have an output impedance near the characteristic impedance of the output cable.
How come I use 1K ohm, because it is a compromise between 120 ohms (or so) and 2000 ohms that I know many audio systems can tolerate. Maybe, there are cables out there that really hate 1000 ohms. Well, we made our OWN output cables and you could buy them, and we knew that they worked pretty good. We just could not please EVERYBODY, but we offered an internal fet follower buffer, like those discussed around here, for an extra price. Why should EVERYBODY pay extra, if they didn't need it? Maybe Charles knows something that will make my next design (if any) output buffered from the get-go.
I invented the complementary J-fet output buffer, in 1970, I'll have you know, just ask Erno Borbely, if you don't believe me. Now why do I have to point this out? Because many here have NO IDEA where new designs come from and who did them first. If I had worked at Bell Labs, it would have been called the CURL buffer, and they would have patented it, just like the Darlington.

 

[Nelson Pass]

If I had worked at Bell Labs, it would have been called the CURL buffer

Thanks for that. I am still writing my buffer article, and now I
can include the CURL buffer, and your name will be duly enshrined
in the annals of this backwater planet.

BTW, I found a cute trick for it.

Back to the subject of magnetic materials, I have measured
distortion caused by magnetic material in proximity to electron
flow, so it is only a matter of whether you can hear it, not
whether it's there.

 

[fizzard]

Could you not shoot for a low output impedance, and use a series resistor to isolate it from the cable capacitance and match the cable impedance?

Back to the subject of magnetic materials, I have measured
distortion caused by magnetic material in proximity to electron
flow, so it is only a matter of whether you can hear it, not
whether it's there.

Yes, I've measured something similar too.

 

[SY]

Nelson, that makes sense and is a pretty well-established phenomenon (especially if the material is going in and out of saturation), but... can you/have you measured distortion due to copperweld or similar leads? Or ferromagnetic resistor endcaps? I can't, but that doesn't mean that no-one can.

 

[Sigurd Ruschkow]

PMA;
with significant I can agree in some cases. I say that the importance of EMI depends on what noise one has around an amp and what comes in into an amp. How noisy an environemnt is varies a lot depending on your location and surrounding equipment and how clean your AC mans is.

I cannot agree that in ALL cases EMI is xy% important.

I do use AC mains filters for some amps, and use special shielding when I find it necessary, and have the PS in separate box(es),
and use input filter etc.

EMI and EMC is always in the back of my head like a background process in a computer system.


Sigurd

I have made a LOT of listening tests on this issue, supported by measurements of interference and output in time and frequency domain. Also, we have made a LOT of measurements with and without mains purifiers, pure DC supply and compared to listening results. That is why I dare to speak about it. My conclusion is that RF content, no matter if it comes through supply or as D/A residuals, has SIGNIFICANT influence to resulting sound, and that it is one of the main reasons why different cables sound different.

 

[Sigurd Ruschkow]

Nelson,
that is interesting! Both the article and the dist you measured.

Was that measurement made under normal audio listening conditions? or did you have to "force" the dist to appear by using non normal magnetic fields (currents)?

(Not to accuse you of anything but to emphasis that this is a REAL phenomena that appears under normal listening conditions.)



Sigurd

Thanks for that. I am still writing my buffer article, and now I
can include the CURL buffer, and your name will be duly enshrined
in the annals of this backwater planet.

BTW, I found a cute trick for it.

Back to the subject of magnetic materials, I have measured
distortion caused by magnetic material in proximity to electron
flow, so it is only a matter of whether you can hear it, not
whether it's there.