Bass pot ground resistor?

[Normster]

When eliminating the rock/jazz switch, it appears that the bass pot functions strictly as a variable resistor. That being the case, does the 10k resistor on the ground leg of the bass pot serve any useful function?

[Normster]

Anybody?

[heisthl]

You could try it and see but it should really affect the adjustment range(onset of bass feel) of the pot(assuming your going to ground the pot). If you're intent on eliminating the 10K I would think you would want to connect it like a more conventional tone stack (probably using a smaller value mid pot).

[Bob-I]

When eliminating the rock/jazz switch, it appears that the bass pot functions strictly as a variable resistor. That being the case, does the 10k resistor on the ground leg of the bass pot serve any useful function?

I always thought it was there to lift the entire tone stack above ground, and reduce the load it places on the first gain stage.... but what do I know

[Normster]

I guess the only way to find out is going to be to run a jumper over the resistor and see what difference it makes. I've just been blindly putting it in all my builds, but since Gil pointed out that the bass pot is wired as a variable resistor, I'm wondering how much difference a 10k resistor really makes as a tail on a 500k pot.

[swt]

to me it makes a lot to the character of the tone stack. It also adds mids, and works like a loudness control. If you simulate it you'll see. try a jumper or a pot in there and report the results...

[skeezbo]

I experimented with this and reported in on the all clean dumble thread a week or so ago. I removed the 9.8k and wired up a 25k pot just like I was adding a midrange in place of a 6.8k on the bass pot of a blackface Fender. The new pot functions as a low midrange control, but is easily swamped by the bass control as it approaches 4. It seems that HAD preset the amount of low mid with this resistor. The real mid, at least on the skylinerish stack I built, comes down the .01 separate from the other stuff to a 250k pot. It works very well for guitar. and is just terrific for bass (I put this mod in a Bassman 100 that will be my gig amp for bass if it is loud enough.)
After messing with the 25k low mid pot, for guitar anyway, I found that I always leave it somewhere in the middle, at 6 for my tele. HAD's 10k is probably lower in value; did he voice his amps for Gibsons? His value would be slightly less thick, I guess, than my 25K pot set a 6.
I'm going to try a lower value bass pot (100k linear) to see if I can get a better balance and use the 4 control stack for bass; If it doesn't work, I'll put the 10K back in for simplicity.
The low mid cut that makes this stack sound so good clean does seem to be a gain extractor, although the large amount of negative feedback in the Bassman 100 probably doesn't allow a true test of this stacks's OD potential.

Skeezbo

[dogears]

The only 2 effect sof the resistor are to lift the .001 cap above ground and to set a minimum amount of bass with the pot on zero. That's it I believe. Changing it won't effect the tone other than the interaction of the .001. I think I'll experiment with sending the .001 to ground using different values.

[Normster]

Crap, I forgot about the .001uF. That would be the reason for leaving it in...unless I get rid of the.001.

[Tonegeek]

Crap, I forgot about the .001uF. That would be the reason for leaving it in...unless I get rid of the.001.

I did an A/B with the .001 and cannot hear any difference. This is with no Rock/Jazz switch and the Deep switch disabled. I may not have tested with the bass pot in more than one postion, which could make a difference as the pot is turn up.

[Bob-I]

I did an A/B with the .001 and cannot hear any difference. This is with no Rock/Jazz switch and the Deep switch disabled. I may not have tested with the bass pot in more than one postion, which could make a difference as the pot is turn up.

I think the true test would be to remove both the 10K and the .001uF at the same time. My guess is that these 2 components interact smoothing out the low mids.

[dogears]

That is very odd as the cap has a very very noticeable effect....

Crap, I forgot about the .001uF. That would be the reason for leaving it in...unless I get rid of the.001.

I did an A/B with the .001 and cannot hear any difference. This is with no Rock/Jazz switch and the Deep switch disabled. I may not have tested with the bass pot in more than one postion, which could make a difference as the pot is turn up.

[skeezbo]

I had it wrong; Dogears and Normster I think are on track. When I compare the frequency response of the bass control with that of the pot that I used to replace the 10k resistor on the Dumble stack I discovered I didn't have a four way tone stack after all. The bass control swamps out the new "low mid" because it is the same information, but it seems that the ultra lows are removed on the new pot, I guess by the .001 cap.
What was he thinking? The bass is preset so you can't turn it all the way off? Maybe this: because the preset (by the 10k resistor) part of the bass spectrum seems to have the ultra lows removed you can turn down the bass until you reach the preset level. If you turn down further you remove only the ultra low.
Strange but useful, I guess: less mud in OD?
Skeezbo

[skeezbo]

Further evidence of genius: if HAD's 10k was designed to work the way it seems to in my modded stack, there is a simpler way to explain the effect. The bass control is more linear if, at lower settings the preset (the frequency range sent to the 10k) prevents the bass control from removing the low mids, too, as is evident if you sweep the bass out in the tone stack calculator. Could you call it a bass control bright cap? I think heisthl and SWT had this idea scoped in earlier posts.
Skeezbo out.

[Tonegeek]

That is very odd as the cap has a very very noticeable effect....

Crap, I forgot about the .001uF. That would be the reason for leaving it in...unless I get rid of the.001.

I did an A/B with the .001 and cannot hear any difference. This is with no Rock/Jazz switch and the Deep switch disabled. I may not have tested with the bass pot in more than one postion, which could make a difference as the pot is turn up.

Got my curiosity aroused now. Next time my amp is apart I will do some more thorough tests by switching the cap in and out with the bass pot in different positions.