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neazoi 14th October 2007 07:54 PM

Multi-turn pot?
 
Is a multi-turn precision pot good for audio?
Better than the ladder types, or not?
If not good, why is that?

rdf 14th October 2007 10:29 PM

I've used one in a passive for a dozen years. If it has a sound, it's slightly subtractive in nature. Downsides are they're linear so most of the control is in the first turn. With efficient speakers and a marginally sensitive amp late night listening is often around the 2 mark on a scale of 1000. It's possible to bridge the output of a high value WW with a resistor for a 'fake law' curve, at the expense of either a lower value pot at high volume settings or a higher output impedance. The latter is of little consequence driving a tube.
I like them.

neazoi 15th October 2007 12:35 AM

So it is not prohibited as I thought...
what do you mean with: late night listening is often around the 2 mark on a scale of 1000? This refers on dound performance or turns to volume ratio?
what about inductance?

rdf 15th October 2007 02:43 AM

Sorry, didn't occur this might not be universally true. I use vernier dials calibrated from 1-1000 on my passive's pots. Since we hear intensity on a logarithic scale most of the change in volume occurs in the first turn of the pot. Coupled to an amp with high gain and efficient speakers I commonly find turning the volume up to 2/1000 is loud enough.
Inductance is a good point but it'll be in series with the kilo ohms of resistance so likely a non factor. Certainly it won't come within orders of magnitude of the inductance common with very well received magnetic volume controls.

neazoi 15th October 2007 06:05 AM

I have found a dual (stereo) 100kohm linear pontentiometer and I am thinking of using it. Well now, the pontentiometer is 100K and it is 10 turn. i.e. for about 10k, that is used on most preamps, it will be 1-2 turns. I think the inductance in that point will be quite low and maby less than the ladder type, as some film resistors may have quite high inductance because of the many turns of carbon around the resistor body...
I do not know, what you think about it?

soundbrigade 15th October 2007 06:20 AM

You can "logaritmize" a linear pot:
A Better Volume Control

unclejed613 15th October 2007 09:27 PM

multiturn pots are better used in situations where fine adjustment is required, such as bias adjustments or hum balancing, or at the input of a diff amp when you are trying to adjust for a null to make a measurement. the only logical reason to use it in a volume control would be to make it more difficult for somebody to "crank" the amp instinctively.

anatech 15th October 2007 09:42 PM

Hi Unclejed613,
Quote:

multiturn pots are better used in situations where fine adjustment is required, such as bias adjustments or hum balancing,
No. Proper circuit design and the proper control will do. Multiturn controls are used in some test equipment (were anyway) where that much precision was required. They are not suited to bias control duty at all.

Hi neazoi,
Why don't you simply use the correct part? Other than the issues pointed out already, there is nothing wrong with a linear control. I suspect that you will put the right one in after you get tired of turning the control so much. :devilr:

-Chris

rdf 15th October 2007 11:41 PM

Quote:

Originally posted by anatech
I suspect that you will put the right one in after you get tired of turning the control so much. :devilr:

15+ years and still spinning. :spin:

anatech 15th October 2007 11:51 PM

Hi rdf,
LOL!

I'm counting on human nature to straighten him out. :D

-Chris


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