Date: Tue, 10 Apr 1990 11:12:21 EDT
From: EBERGER@B.PSC.EDU
Subject: Re: Listening To More Polystyrene Capacitors

The circuit I use for evaluating these capacitors ~750pf & ~3000pf is a 
simple NE531 ic-opamp based phono preamp with regulated powersupply.

This circuit uses an active RIAA eq very similar to the Audio Research SP-6
series preamplifiers.  The circuit is built with 1% resista resistors and 
WonderCap power supply bypasses.  It uses an electrolytic (yuck!) in the 
feedback path to ground so that it can be direct coupled to the line in of
a modified SP-6 (exhaustive parts changes, India 12AX7s).  Speakers/Amps 
are modified Acoustat X electrostatics/servo-charge amps on stands.

Input source is a Supex SDX-1000 mc (modified& still running after 8yrs!)
pre-preamplified by a Thorens PPA-990 headamp (modified).

Cables are all Livewire DB-1 litz interconnect, which aren't made anymore,
but really should be, since they ARE my favorites :-)

Most of the products are very picky about ancillary components, so chances
are that nobody except for me and few friends will appreciat them, especially
the Dual 731q direct drive turntable (Anyone have one for sale?)

The SP-6 already has SIEMENS caps in the RIAA stage, so I made the test setup
to try other things like different ICs & eq caps.  I like the NE531 IC for its
dynamics & bass, but it is a quirky chip, and was used by Rappaport as
digging into a dead lump of epoxy & wires revealed...

-Ed Berger
eberger@b.psc.edu
 
Date: Tue, 10 Apr 90 17:21:35 EDT
From: eacj@tcgould.TN.CORNELL.EDU (Julian Vrieslander)
Subject: Re: Listening To More Polystyrene Capacitors

Thanks for the reply.

I have been out of the tweaking business for a few years now, but I
used to do a lot of playing with op-amps and passive components in modified
HiFi gear.  I did a heavily rebuilt Dyna PAT-5 back in about '76 that
used some teflon caps in the RIAA EQ network.  I got them as freebies
by begging for samples from some mil spec cap vendor (can't remember who).
I'm not sure if they would sound as good as the film caps favored by
audiophiles these days, but they sure looked sexy - little stainless steel and
hermetic glass tubes, with 1% tolerance markings and gold leads!  The PAT-5
sounded pretty good, too.  It embrassed quite a few SP-3a's, etc. before
I sold it to a friend.  The most effective A/B demo I ever did involved
drag racing the Dyna against a Crown IC-150A.  The Crown had better specs
than a PAT-5 (at least the stock PAT-5, I never measured the modified one).
For source material, I used a recording of Julian Bream and his consort.
I first played a selection through the Crown - what came out was a very nice,
smooth solo guitar sound.  When I played it on the Dyna, jaws would drop.
You could hear that there was a harpsichord playing in unison behind the
guitar - the Crown completely eliminated it.  I wish I could restage this
demo for the experts on the net who contune to claim that audible differences
between components exist only in the imaginations of audio fetishists.

I am currently thinking about doing some upgrade mods on my CD player (Philips
CD-680X).  Most likely I will go with most of the recommendations made by
Walt Jung in his "POOGE" series from Audio Amateur, and possibly an upgrade
to the IC voltage regulators.  Jung seems to recommend the Panasonic film
and electrolytics, probably because they are cheap and easily available from
places like DigiKey.  I'm not sure if your recommendations (Siemens, etc.)
are relevant to this application.  The Philips players seem to benefit from
better electrolytics in the power supply filters and local bypass locations,
and good film caps for bypassing the electrolytics and DAC taps, and for
the final output coupling caps.  But there is not much space on the board.
The DAC tap bypasses have to be really compact, since you are replacing
surface mount ceramic caps.  The kit from Audio Amateur/Old Colony provides
0.82 microfarad Panasonic stacked film caps for that application, but they
are still rather big.  For some Philips/Maggotbox decks you have to cut 
clearance holes in the bottom of the case (plastic) to clear the caps, since
they mount on the underside of the circuit board.

I have requested capacitor catalogs from Panasonic, Roederstein, and (at your
suggestion) Siemens.  I notice that a lot of high end audio products use
WIMA caps.  Do you know who makes or distributes these?  I can't find WIMA
in the EE Master.  And have you figured out who makes "WonderCaps?"  I suspect
that the markup on those puppies must be enormous.  There are several
other audiophile capacitors floating around (Solen, Sidereal, etc.) that I am
likewise suspicious of.  Maybe I'm too much the skeptic, but I find it hard
to believe that the tiny companies advertising in the back pages of Audio
are manufacturing their own components.

- Julian