John Curl's Blowtorch preamplifier part II - Page 2815 - diyAudio
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Old 12th October 2012, 05:18 PM   #28141
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I have made direct listening comparisons between FR-4 and Polyamide. I'm pretty sure that I heard the difference. I don't use Teflon for Parasound, it is too expensive, and the power supply boards are all made of FR-4. I haven't left it behind, just tried something better.
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Old 12th October 2012, 08:54 PM   #28142
wayne is offline wayne  United States
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It is about getting better. The bleeding edge of audio is like drag racing, shave a little time spend lots of money. Perception is a big part of it also for the audio consumer. I don't think doctors worry about the PCB's in the EKG machine.
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Old 12th October 2012, 09:32 PM   #28143
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Of course it is, Wayne. The vast majority of test instrumentation does NOT need Teflon boards. I used to design laser control circuitry. It did not require special board material.
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Old 12th October 2012, 10:10 PM   #28144
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Quote:
Originally Posted by RNMarsh View Post
The film itself isnt microphonic. However, how it is made will determine if it will be microphonic .... As far as harmonic distortion is concerned the npo et al are very good. Ditto the ps type.

I feel confident to recommend Rel Cap out of so calif for the most reliable and well made parts - they are a specialty cap maker for communications industry and military... where high reliability and long operating life is foremost.
Mr. Marsh, you are right that it is the construction and mounting of most polystyrenes that give their microphonic behaviour.

But polystyrenes I've used in the past, even in packages that allow tight mounting to the PCB, show this.

The polystyrenes that the unwashed masses and Golden Pinnae brigade normally worship, are unfortunately prone to this fault.

From this, I gather that Rel Caps, if glued to your "hand carved from solid teflon by virgins" PCB, with Unobtainium epoxy (without nasty dielectric factors), will be as good as NPO/COG ceramics.

I'd still like to see some evidence that polystyrenes are better practical caps than NPO/COG ceramics.

We'll ignore trivial issues like soldering and reliability.
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Old 12th October 2012, 10:30 PM   #28145
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The Relcap 3 uf polystyrene with 0.01 Polystyrene caps that feed the R2 Raven Ribbons i use have noticably more refined detail and harmonic structure over the Film and foil Polypropelenes they replaced. The upgraded fully RelCap Film and foil crossovers i installed in the Martin Logan CLX'x all have 0.33/600v polystyrene bypasses were a big improvement over the stock metalized Solen polypropylenes. Try a nice Hi Def download or Hi res release of Stevie Ray Vaughn's Tin Pan Alley, Patron Anejo tequila, and a box of Qtips. ( one or more them will fix what ails you or your system)
I usually suffer from liquor absorption rather than dielectric absorption in my system

Last edited by ticknpop; 12th October 2012 at 10:41 PM.
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Old 12th October 2012, 10:57 PM   #28146
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Originally Posted by john curl View Post
..........
Also, I would like to point out that the Vendetta Research and the CTC Blowtorch preamps use double ground planes tightly spaced.
..........
Yes, it works, BUT it allows much more surface area to be seen by the circuit as parasitic capacitance to ground.
..........
Bingo! That should be it.
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Old 12th October 2012, 11:30 PM   #28147
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Quote:
Originally Posted by kgrlee View Post
We'll ignore trivial issues like soldering and reliability.
Well; ceramics are may be reliable, but when they die they go deadly short. Sometimes such a chance is unacceptable.
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The Devil is not so terrible as his math model is!
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Old 13th October 2012, 12:46 AM   #28148
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Originally Posted by ticknpop View Post
The Relcap 3 uf polystyrene with 0.01 Polystyrene caps that feed the R2 Raven Ribbons i use have noticably more refined detail and harmonic structure over the Film and foil Polypropelenes they replaced .... and a box of Qtips. ( one or more them will fix what ails you or your system)
I can well imagine using microphonic capacitors in speaker crossovers may lead to "more refined detail and harmonic structure, huge soundstage bla bla."

But I have never tried Relcaps so it would be inappropriate for me to pontificate on their performance in speakers.

My love for NPO/COG ceramics is in very specific applications like capacitor mikes at the critical gate/grid. They are Unobtainium in the sizes required for speaker crossovers.

However, as a Blind Listening Test guru ala Lipshitz & Vanderkooy bla bla in my previous life, I seriously recommend you get your ears syringed out at outpatients rather than use a Qtip. Qtips are dangerous in inexperienced (or even experienced) ears and hands.

Quote:
I usually suffer from liquor absorption rather than dielectric absorption in my system
I actually have some reliable results on the effects of alcohol on Blind Listening Test performance but they belong to another thread.

Quote:
Well; ceramics are may be reliable, but when they die they go deadly short. Sometimes such a chance is unacceptable.
Err..rh! Could you tell us how polystyrenes go when they die?

Last edited by kgrlee; 13th October 2012 at 12:48 AM.
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Old 13th October 2012, 12:54 AM   #28149
RNMarsh is offline RNMarsh  United States
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John -- The dual ground plane I suggested to you all those many years ago, I still use. However, stray c is higher and important in specialized high Z circuits (like mic preamps). Never-the-less, I use it to great satisfaction when under distributed power traces to keep the Pwr Supply Z low and stable at high freqs. making the traces wide as possible and under the that trace put the pwr supply ground trace of same width. The signal ground plane should never cross the pwr ground planes. generally, if you make the pcb signal and power traces the same way you draw the schematic, all is well. I also put all signal traces on the TOP side of the pcb; Easier to repair, trouble-shoot and modify without tearing the thing apart. -RNM
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Old 13th October 2012, 12:54 AM   #28150
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Rel RT polystyrene caps are one of the best audio caps in the world. I use them in in the CTC Blowtorch, Vendetta Research, and Parasound products as a first preference. Ayre uses them too! They are DAMPED, and do not ring.
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