bad precision pot?

[Harry Bissell]

IHMO No: you can resolve a hell of a lot more than 128 steps with an analog
pot... it would only be useful if you were going to move it under electronic
control...i.e. computer control of op-amp offset etc....  :^) Harry

Rory McDonald wrote:

> What about a digital pot like the Analog Devices AD5220?
> Check out http://products.analog.com/products/info.asp?product=AD5220
> 10k, 50k, or 100k w/ increment/decrement count, 128 positions and powerup
> centering.
> Would this be an interesting chip to replace some pots?
> -Rory Mc Donald
> > -----Original Message-----
> > From: jhaible [SMTP:jhaible at debitel.net]
> > Sent: Tuesday, August 10, 1999 4:37 AM
> > To:   Martin Czech; synth-diy at mailhost.bpa.nl
> > Subject:      Re: bad precision pot?
> >
> > No other observations.
> > I don't like them on synths, nevertheless. With a coarse and fine pot,
> > you can make fast changes as well as small precise ones. With a 10-turn
> > you end up dialling like a madman - no you rather end up using the pot
> > less than you would otherwise.
> > There is one exception to this, and that's the use of special coarse /
> > fine
> > knobs that have some gear inside. But these are very expensive, and
> > not exactly tasteful looking.
> >
> > (Speaking of VCO frequency applications, I was. There would be other
> > applications where it might make more sense.)
> >
> > JH.
> >
> >
> > ----- Original Message -----
> > From: Martin Czech <martin.czech at intermetall.de>
> > To: <synth-diy at mailhost.bpa.nl>
> > Sent: Tuesday, August 10, 1999 8:58 AM
> > Subject: bad precision pot?
> >
> >
> > > I've read somewhere that precision 10 turn wirewound pots have problems.
> > > The slider seems to stick on the windings, that means problems with
> > > resolution.  And it was said that mechanical shock or vibration would
> > > change the value.  The author claimed that he would rather prefer
> > ordinary
> > > pots, maybe two, one for coarse and one for fine.
> > >
> > > I was sceptical.
> > >
> > > I took a 10 turn 10k Burns with 10 turn display/knob for my test
> > > oscillator.  I doubt that I get better resolution with a carbon or
> > > other type pot.  I tryed also reasonable shock and vibration (finger,
> > > pencil, screwdriver) and I couldn't find any change of value (even if
> > > the mechanical break was inactive).
> > >
> > > So, I came to the conclusion that these guys are expensive, but worth
> > > the money.  Especially for analog coefficents.
> > >
> > > As they are wire wound they should have high inductance, however.
> > > Won't harm for dc control voltages.
> > >
> > > Any other observations?
> > >
> > > m.c.
> > >
> > >
> > >
> >