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Available Pot Evaluation

From mike–(at)–n-tune.com Thu Apr 20 18:45:20 CDT 2000
From: “Mike Suchoff”
Newsgroups: rec.music.makers.builders
Subject: Results of my potentiometer evaluation
Date: Thu, 20 Apr 2000 20:58:26 GMT
Xref: geraldo.cc.utexas.edu rec.music.makers.builders:44257

By profession I’m an electronics engineer and know something about resistive
devices (resistors and pots)
for audio applications (in the 70s I was chief engineer at Arp Instruments
(designed analog music synthesizers)).

For fun, I’ve been into building bass guitars.

I’ve been frustrated at trying to get decent off the shelf potentiometers.

Ideally, we’d like to use pots that have conductive plastic or cermet
elements, NOT carbon composition.
I.E. nobody uses carbon comp. resistors in audio circuits (well maybe in
tube amps) we all use metal film
(or at least carbon film) because they are tighter tolerance and less noisy.

Good luck trying to find them in the values and types (dual linear,
push-pull) that we need. I couldn’t.

So now that we’re left with carbon comp., I tried getting a stocking
supplier of CTS, the so called, high
quality musical instrument potentiometer (thats a laugh). Well can’t find a
stocking supplier for them. CTS builds
to order. For fun, I told local rep I needed 1000/year and got CTS to send
me samples. Shafts wouldn’t fit
any common knob I wanted to use and they didn’t feel good anyway – not
viscous damped.

So, I bit the bullet and bought 4-6 samples of the different potentiometers
available from Digikey and Mouser.

Here’s how I evaluated.

1. Only tested brands that had linear, audio, duals, and linear with center
detent. Yes you can find the occasional
Clarostat cermet pot – but I was interested in finding a family.

2. Noise & grit test. Grounded both ends. Connected wiper to mike preamp –
turned up gain and listened through
headphones while rotating control over full range.
Compared each manufacturer’s pots for pot-2-pot consistency, then
compared equal value pots
from different manufacturers.

3. Feel. I like a nice viscous damped feel – but not too viscous because I
want to be able to quickly rotate a knob with
the edge of my hand while playing.

4. Construction. I.E. are they sealed, does shaft wobble, will leads dink
off, metal/plastic body.

Results:

1. Mouser’s Xicor 16mm minaiture carbon comp. They are dead quit.
Rotation feel is silky smooth. Have big
solder lugs for their size. Center detent feels good. Note. Was able
to detect some scratchy noise on one
push-pull control – but it went away after a little use.

Note: The Xicors are the “Alpha” pots that have been posted here before.
I did a Web search on Xicor and
see that they import for Alps. I think these are Alps pots which
would explain their quality. Anyone out
there that would like to do further research on this can contact me.

Knobs. Only comes with a solid round shaft. You need a knob with a set
screw.

2. Mouser Xicor 24mm potentiometers. The 16mm don’t come in dual versions I
needed so I bought the 24mm
versions. Same quality as 16mm.

Knobs. Only comes witha sold round shaft. You need a knob with a set
screw.

3. Mouser Xicor 17mm miniature. These feel OK, but some had scratchy noise
when rotated. Solder lugs are
too small and will dink off unless wires are dressed carefully. Can’t
get duals. Can’t get audio taper without switch.

4. Digikey’s Panasonic 9mm & 12mm potentiometers. Noise was OK for all but
units with detent. In detent units,
when you “go over” the detent you can hear the wiper pull away from
element. Only come in PC mount version.
Plastic shaft wobbles from side to side. Not viscous damped. Shaft has
a flat side so you can use the soft plastic
knobs (if thats what you’re into).

My final selection for volume, blend, active cut/boost treble, mid & bass
was…..

Volume. Xicor 24mm audio with switch. Switch wired in series with stereo
jack so can turn off circuit either by pulling
out plug or via switch (during break between sets).

Blend. Xicor 24mm dual linear.

treble, mid & bass. Xicor 16mm linear with center detent.

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