John Curl's Blowtorch preamplifier

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john curl said:
I'll stick the Reliable polystyrene caps, at the very minimum.

John, there have been MIL spec NP0 ceramics for ages, so reliability is not a concern with legitimate vendors. Back in the Clinton administration, the COTS (commercial off-the-shelf) initiative was originated. This meant that new contracts going forward did not require MIL spec parts. This was a great cost-saving measure. But prior to that time, for decades, all MIL spec capacitor vendors had to go through "qual" (qualification) for their parts to be put on the QPL (qualified parts list) for the MIL spec in question. This meant all kinds of crazy tests they had to pass.

For me, the data of such tests means far more than anecdotal information from questionable sources. It's not tall tales about submarines or anything like that.
 
Hi Bratislav,
That was my point, and has been for many years now.

Hi Andy,
For some of his tests in which capacitor distortion was easily measurable, he was not able to measure changes in capacitance with voltage. So while conventional distortion measurements have been (rightly IMO) criticized for not relating to audibility, it seems they are very good for "sniffing out" very small nonlinearities.
The problem with trying to test these parts is that the problems are dynamic by nature. Their impact also varies with the circuit parameters. The very worst place to have a "bad capacitor" is in a high impedance circuit with large voltage swings. The high impedance allows the distortion mechanism to be excited without any ability to swamp it's effect. The large voltage swings exercise the full departure from a linear transfer characteristic as well. By definition, that would be the Vas in an amplifier and any other capacitor in a similar position across a transistor C-B junction. With a lower impedance location, the effect of dielectric non-linearity is very small compared to the total amount of electronics available. High impedance = lower current flow rate = fewer electrons = more of an effect. I know you that you understand these things, but for the benefit of some other members who are learning I drew it out.

I plan to use it in the configuration Renardson recommends for distortion measurement, so I hope it works out well.
I also have the same card intended for the same purpose. I haven't set it up yet, could you please give me a link or PM me with this information? I'd really appreciate it.

Hi John,
I'll stick the Reliable polystyrene caps, at the very minimum.
Heck, nothing wrong with that!

-Chris

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anatech said:
When someone trained in any branch of physics begins reading these works of art, their response is generally one of annoyance at best. These individuals typically do not get through the entire article. In fact, many freeze within the first paragraph, then read on as if watching a train wreck in slow motion.

That's funny, man! I am listening to Hugh Masakela's Hope on headphones while reading this, and laughing very hard, but I cannot tell how loud I am laughing. My neighbors probably think I am very weird - and they're right! :clown:
 
andy_c said:


Well, it's a nulling technique very similar to Bob's "distortion magnifier" - so I hope it works out well. My bench test equipment is quite modest, so any input one way or another on cheap distortion measurement is welcome.


Well I hope the technique is valid and works out well. I looked up his website a while ago for distortion measurement info, but stopped reading after I saw this and read that "the distortion is less than 0.001% up to 20kHz".

Cheers,
Glen
 
Please, I challenge ANYONE to make cost effective analog electronics that sounds as good or better than what we make in hi end, today.
Maybe it is already being done, I don't know.
I also challenge engineers to make autos either in GB, Canada, or the USA that exceeds the efforts of Mercedes, Porsche, and BMW, at the very least. at very low cost.
Also, let us make a CHEAP auto tire that does everything that is needed in a modern, fast car.
I would love to have a source of cheap, but drinkable Cognac that tastes at least as good as REMY Martin VSOP.
Go for it, fellow engineers.
 
Hi John,
No one (at least I'm not) saying they can exceed your performance level cheaply. Mind you, with the cost of the casework reduced it should be possible to clone your design at lower cost.

No one has stated that you don't know what you are doing either.

So in that light, why the challenge?

I also challenge engineers to make autos either in GB, Canada, or the USA that exceeds the efforts of Mercedes, Porsche, and BMW, at the very least. at very low cost.
They cost less in Germany. 😉
The maintenance cost of a BMW over 5 years is the same as a Honda and not much higher than a Ford Capri. The only difference is that the Ford will be worth zilch and the BMW will still look and handle close to new. That's given good competent service is performed on each. Getting good service tends to be the problem.

Also, let us make a CHEAP auto tire that does everything that is needed in a modern, fast car.
That will happen in China, just you wait ....

I would love to have a source of cheap, but drinkable Cognac that tastes at least as good as REMY Martin VSOP.
They all do ... after the first glass.

Honestly John, why try to compare the more expensive options with the bottom of the barrel options? There is no value in that at all.

I would love to hear one of your Blowtorch preamps some day. That way I could see what all the hub-bub was about.
 
Has someone related caps sound characteristics to the triboelectric effect between two materials…?

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