Bass pot ground resistor?

[ayan]

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.

I think if you play with the cap off and on while varying the tone control settings, you will hear that it has some effect on the tone. Try to think of it this way: in normal mode, which is the way most people use the amp, the cap parallels the bass pot to ground (via the 10K tail resistor). When the pot is set to zero, the cap is shorted out so there is no effect at all.

When you turn the bass control all the way up, however, while the lower frequencies see the full 500K + 10K path to ground, which allows the "bass content" to travel upwind through the circuit, the higher frequencies present at the input of the bass pot (which will not be the highest of all, since those will favor travelling forward through the treble cap) will see an easier path to ground thanks to the cap and will not travel upwind. The effect? Less " treble."

In between those extreme settings, the effect will be varied. As with all other controls on the Dumble, as opposed to say an old Boogie, where turning the treble knob half a notch could make or break the sound of the amp, the effect is subtle to me.

Cheers,

Gil

[skeezbo]

ayan-
Thanks for the explanation.
Skeezbo

[Tonegeek]

Did some more thorough A/B listening tests with the .001 cap switched in and out across the bass pot.

It seems to cut high mids slightly when in circuit. It is more pronounced as you turn the bass pot up past 25%. In circuit it makes the tone softer/rounder sounding. Out of circuit it sharpens up the tone a bit but is not harsh or even edgy, just a bit clearer. I actually like it better out of circuit. My amp/speaker combo wants a bit more attack/clarity on the clean channel which removing the .001 cap supplies. Don't think it warrants a switch, but both the sounds are useful. I was able to remove the cap and roll off the treble control a bit to get it to sound about the same as it did with the cap in circuit. I will play with it over the next few days at different volumes to see if I still like the change. I am curious to see if it gets edgy with the volume at club level.