Recommendation and source for quality volume potentiometers

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MagnetoSound said:
ruffrecords said:
The way to work this out is to think about what you want the pot to do at the half way point. With a linear 10K pot, for example, you get 5K above and 5K below the wiper giving 6dB of attenuation. For a log pot you typically want 20dB attenuation at the mid point which needs 9K above and 1K below. To get the same from a 10K linear pot you need it to be 5K above and  555 ohms below. So you slug the 5K from the wiper to ground with about 620 ohms to get the required 555 ohms. For the antilog equivalent you just connect the 620 from the wiper to the top.

You can now see why I made the point before about load variation. The 10K slugged log pot looks like 10K when fully I off and like 555 ohms when fully up.


Not to be awkward, but I've most commonly seen the 10k LIN pots in Neve switching units slugged with 5k1 resistors.

These look like 3k4 when fully up, and 10k when fully down. Not so bad.

Clearly, these are designed not so much for a specific mid-point value, as for reasonable load variation in use. After all, there are usually a few of these in parallel as Aux Send pots - off/pre-fade/post-fade switchable too, so they are not always in the same circuit.

That's right. That's the AUX pots I was referring to in another reply. The 5K1 gives a mid point at about -10dB. I have also seen 1K pots slugged with 620 or 560 ohms used as monitor level controls on 600 ohm outputs.

Cheers

Ian
 
Gold said:
MagnetoSound said:
I've most commonly seen the 10k LIN pots in Neve switching units slugged with 5k1 resistors.

These look like 3k4 when fully up, and 10k when fully down. Not so bad.

Is that looking forward from the source? Looking back from the load wouldn't a 555Ω source impedance be better? Or does the 555Ω look like 0Ω at the fully up position to the load?

Yes, I mean the load seen from the source. The driven load (after the pot) is a bus resistor, typically of around 15k IIRC, so the pot impedance looks enough smaller for the bus resistor to not mind the variation either. Given that the actual bus impedance after the resistor is much lower, the variations are pretty negligible there.

 

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