MS wrote:
(ThePaulThomas) wrote in message . com...
...try selecting your electrolytic by ESR instead of by
cutoff frequency in low level blocking/coupling applications...

OK. But how is that done? -Paul

Scott has good suggestions and following up on those ideas, you can
get a general trend by looking at some of Illinois Capacitors product
lines. Their site is good in that it lists the nominal (120Hz) ESR
for all values of a given model in a table, here's an example:


http://www.illcap.com/RadialExtLife.asp?Alum7_Action=Find('SERIESID','10 ')&Alum7_Position=FIL%3AORD%3AABS%3A1KEY%3A10PAR%3 A

I tend to pick caps with
1. low ESR
2. good high frequency performance
3. 105'C temperature rating.

You can see real quick that small electrolytics pretty much suck, they
have a pile of ESR. And though you don't see this in the tables, that
ESR isn't linear, it reduces as frequency increases but on a curve
particular to that device. The larger caps do the same thing, but if
you have .95 ohm nominal ESR and scale down to point-0-something ohm
over frequency, it's alot different than starting at 1K or so and
scaling down... I ESR sized the blocking caps of an INA103 based pre
and it sounded great.

Yup. So you can sometimes gain a lot by going to larger value caps
(or sometimes higher voltage caps... just make sure peak voltage is
at least half the voltage rating of the cap so it doesn't deform).

But you can also decide to select a tantalum or a film cap for smaller
values in some of these cases.

...Since I'm sharing some sound and tone preservation things I've come
across for low level stuff, another is hookup wire. More specifically
the insulation thereof. I actually found this on the "audiophool"
boards. Those guys are always singing the virtues of silver wire and
one person said they found it wasn't the silver, but it was the teflon
insulation doing the deed. They contended that you could use copper
with teflon insulation and actually get warmer yet "silver clear"
sound than with silver/teflon.

I like teflon wire. On very high-Z circuits, I could believe you could
hear a difference because of the improved dielectric quality. But that's
much less of an issue than the fact that teflon wire is very easy to work
with; you can't melt the insulation with an iron so you can get very small
joints built with it. On top of that, it lasts forever and never becomes
brittle or sticky decades later.

So, I took an Oktava MK319 with some Scott Dorsey mods (and a few of
my own), that sounded alot better than stock but still not great, and
rewired from the capsule to the board (all hand wiring inside). I
used standard Belden 24ga tin clad copper/teflon and 4% silver solder
for the entire signal path to the JFET. All I can say is "you got to
be freaking kidding me that wire insulation can make that kind of
difference" after hearing the results (it's actually a great mic
now)... Of course if it ever will, it's going to be in this
application, there's just not very many electrons carrying the signal
from the capsule to the JFET...

Hand wired a 319? THAT sounds silly to me. Next thing you're going to
be ordering teflon PC boards. (The Teflon stuff is a lot nicer than FP4,
but you don't even want to think what the board houses charge for it).
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."