Tonestack 124

[vatch23]

Hi, im a Dumble newbie who is trying to (very slowly) to build an 124 ODS. So far the first triode is there but I do have a problem with the tonestack. Or maybe it's not a problem that's what I dont know:
When the treble pot is on max the mid and bass pots don't do anything anymore. They work fine at lower treble settings. Is this the way it should be? My Fuchs isn't like that.

[pompeiisneaks]

First, I'm unsure how you have a working first stage without the rest of the amp built? Power supply that can output 300VDC and a breadboard type setup? Photos of the amp would help. Also if you implemented the rock/jazz switch, it could have something to do with that. The Rock/Jazz changes the interaction of the tone stack significantly, and that may be what you're seeing.

~Phil

[talbany]

Hi, im a Dumble newbie who is trying to (very slowly) to build an 124 ODS. So far the first triode is there but I do have a problem with the tonestack. Or maybe it's not a problem that's what I dont know:
When the treble pot is on max the mid and bass pots don't do anything anymore. They work fine at lower treble settings. Is this the way it should be? My Fuchs isn't like that.

The Treble pot basically mixes both the bass frequencies (from the bass pot) and treble frequencies (from the treble cap) through the top and bottom of the pot, then exits out through the wiper back to the input volume pot then off to the tonestack recovery grid(V1B) to be amplified.
Either you have the wrong value treble pot or something else is not wired correctly??..Dumble used a 250K Audio taper pot there
Maybe a picture or 2
Tony

[vatch23]

I have built the powersupply and the first stage stage with briteswitch, no deep or jazz/rock switch yet. Also no FET or PAB. After that I have a 1Meg pot bridged with a 68pF as masterout. Into a MosValve it is really a 3dimensional sounding depending on which caps and resistors I use, cause this is the problem; I have rebuilt it very many times to try different components and values, but the treblecontrol allways behaves like this, so I figured maybe it should be like that. The building goes on point to point in an old chassis but it's too messy to show you right now. Looking at 102 and 124 it has the input to the basspot connected to the wiper and 183 doesnt, weird. Well thanks for your answer. I'll rebuild it again and check all values.

[txbluesboy]

Do you have the bass pot wiper jumpered to the input side of the pot?

[vatch23]

Hi guys, personal matters made it hard to follow through in the thread. That build is long gone too Im afraid.