50K or 100K pot?

[2Bak]

Since I'm really happy with the sound of my gainclone, I'm going to build another one.
My first gainclone was a four-channel power amp version using the attached circuit, except for a fixed 100K resistor to ground at input.
For the new one, which will have a volume control, I wonder if can I use a 50K linear pot instead of a 100K pot? What are the drawbacks?

Thanks /Jan

[li_gangyi]

try not to use a linear pot...unless you really have to or you are just experimenting...I guess 50K will work too...

[soundNERD]

What really is the difference with using linear tapers? For all of my amps, I always use a 25K 10% tolerance linear made by Allen Bradley (at least thats what the box says, I didn't buy them, I was given them).

Do the audio ones made a large difference?

[2Bak]

Originally posted by li_gangyi
try not to use a linear pot...unless you really have to or you are just experimenting...I guess 50K will work too...

OK, then I have a 100K log. pot I could use.
Does "linear taper" on the circuit not refer to a linear pot...?

[soundNERD]

Taper/Pot, same thing

[li_gangyi]

hmmm...wonder why they would want you to use a linear one though...

[Upupa Epops]

I am again and again wondering that people use pots with high resistance in semiconductor circuity. It is relict of " tube age ", where gain stages had great output impedance, which must had only little " load ". Today, when typical output impedance of any semiconductor machine is 100 Ohm or lower, is it nonsens. In this case optimal resistance of pot should be approximately 1 kOhm, but it is very hard to made ( in logaritmical version ). So use 10 Kohm pot - you get lower noise and much more independet frequency charakteristic in every positions of pot.

[Pedja]

Originally posted by Upupa Epops
I am again and again wondering that people use pots with high resistance in semiconductor circuity. It is relict of " tube age ", where gain stages had great output impedance, which must had only little " load ". Today, when typical output impedance of any semiconductor machine is 100 Ohm or lower, is it nonsens.

The reason of usage 100k is here more related to the goal of obtaining logarithmic curve with linear potentiometer since its wiper is always loaded with 10k resistor. This is the relict of the theory that the linear pot sounds better than logarithmic. (The theory has technical merits but I must say that my listening experience did not confirm this theory.) However, with logarithmic pot (and wiper loaded with 10k), the resulting curve might appear “overcompensated”.

But, more important: the circuit’s output impedance is not necessarily related to the circuit’s driving ability. Only a minor part of the transistor circuits around wouldn’t mind if you load them (even) with 10k.

Originally posted by 2Bak
For the new one, which will have a volume control, I wonder if can I use a 50K linear pot instead of a 100K pot? What are the drawbacks?

With 220k in the feedback I'd rather use 50k than 100k pot.

Pedja

[Peter Daniel]

It is also my experience that 50k pot works better than 100k. And log taper works more realistic in IGC than a linear (by that I mean more uniform control range). It all depends on a split, but most common Japanese pots are usually 10/40 and not 10/90.

I'm using old production Nobel pots, 31 detented positions, mono. I match them before installing and it is not that hard to actually match them to 0.2dB or better accuracy. They also sound pretty good, very claean and not romantic.

[Upupa Epops]

Pedja, I certainly know that this concrete circuit will have approximate logaritmic curve, but I say, that his impedance is too high, what is wrong in " noise look ". My note was general, not concrete to this circuit.