What does this 1k R do?

[daz]

Some people put a 1k resistor in series with the presence pot in a marshall type circuit. Is this for tonal reasons or something else?

[Chuck H]

Well, I can't see the circuit and I'm not familiar with the practice, but... I fgure it's there to make the presence control 4/5ths effective. So you can't actually turn the presence control all the way up. This would make sense for some amps since, as you may have heard, some Marshalls are just plain annoying with the presence all the way up. The resistor would then eliminate the users ability to adjust the control into the nasty settings. So it doesn't actually make the presence control sound better. It eliminates the users ability to make it sound bad. It may also smooth out the taper for the coltrol.

[daz]

Well, I can't see the circuit and I'm not familiar with the practice, but... I fgure it's there to make the presence control 4/5ths effective. So you can't actually turn the presence control all the way up. This would make sense for some amps since, as you may have heard, some Marshalls are just plain annoying with the presence all the way up. The resistor would then eliminate the users ability to adjust the control into the nasty settings. So it doesn't actually make the presence control sound better. It eliminates the users ability to make it sound bad. It may also smooth out the taper for the coltrol.

I may be wrong, but i think there is another reason that i read of long ago but can't remember. But it wasn't about keeping it from being fully up. (tho that certainly DOES sound nasty)

[loudthud]

I've seen amps that have a tendency to oscillate when the Presence is all the way up. I just stick a resistor in series with the cap. Something like 470 ohms will limit the Presence control to 20dB boost. Is this what the CBS guys didn't like about Leo's designs?