[sdiy] Audio taper pots - shunt resistors and contact resistance

[Neil Johnson]

David G Dixon wrote:
> V2164 in quantities is about $1 per chip, and you get four high-quality VCAs
> per, about 25 cents per VCA.  With this, the pot doesn't need to be anything
> special, since it's just going to be sending DC to the control circuit.
> THAT Corp. dual VCAs are a bit more, but still, it's cheaper than buying
> fancy pots, and you avoid bringing audio to the panel.

Certainly cheaper than fancy pots, to be sure.  The pots used in the 
MOTM modules would fall into the "fancy" category, being sealed Spectrol 
IIRC.

The nice thing about using the 2164 is its "audio" response to CV, so 
you can use a linear pot (and filter the resulting CV) and not have to 
worry about conformance to true audio attenuation.  Even better for 
stereo, where the channel-to-channel matching of the 2164 is far better 
than the matching you'll get on a low-cost dual log pot.

But then you are paying more.  If we consider commercial volumes (since 
you mention "quantities"), a cheap Chinese carbon track log pot in 
volume is going to be cents (think Behringer quality).  Compare that to 
a 2164, of which you still need a pot, plus the RC network on the input, 
and a share of the supply decoupling caps, and additional PCB area, and 
higher power consumption, and increased assembly time, and higher 
unreliability (more components, more MTBFs, do the stats), so... yes... 
there is a cost.

Neil
-- 
Modules and more :: www.cesyg.com
Homepage :: www.njohnson.co.uk ::