Taming the Bass

[talbany]

Tom
I assume you used an Allen Bradley for the bass pot.. Did you by chance check the taper of the pot before you installed it..
You might be experiencing the same issue (or similar) you had with the master pot..

Tony

[Structo]

Anything is possible at this point.

When I tried a smaller coupler at V1b (.02 from .047) it seemed to disable the bass pot where I didn't hear hardly any change.

Like I said, I need to devote a day where I can have it all set up and make quick changes so I can hear the difference between value changes.

The reason I tried the 1uf bypass on V1b is I saw that on a schematic I have.
Can't remember now if it was the Bluesmaster.
What I like about that is it didn't seem to affect the clean tone character much if at all but it did clean up the OD a bit.
The bass isn't as wooly and non distinct.

But really, I don't care how I achieve it, I just want better control of the tone stack.

[CHIP]

Tom, IMHO I think maybe just installing a high value 250k bass pot may do the trick.
Notice the #183 layout, the bass pot value is 311.7k.
I have a 500k in my #183 build, and with an open back 2x 12-65 I have to keep my bass pot at about 9 oclock, especially with humbuckers
If there's one thing I'm going to change it is finding a pot around 310k and installing that instead of the 500k.

Anyone out there have one to sell?

[bluesfendermanblues]

Tom, IMHO I think maybe just installing a high value 250k bass pot may do the trick.
Notice the #183 layout, the bass pot value is 311.7k.
I have a 500k in my #183 build, and with an open back 2x 12-65 I have to keep my bass pot at about 9 oclock, especially with humbuckers
If there's one thing I'm going to change it is finding a pot around 310k and installing that instead of the 500k.

Anyone out there have one to sell?

All you need is a 820K resistor, that you solder to the two outer pins on your 500k bass pot (parallel) and voila 311K instead of 500K.

[CHIP]

That's easy enough. Thanks. I'll try it when I pull the chassis.

[Structo]

Thanks for the update guys.

[hans-jörg]

Anything is possible at this point.

When I tried a smaller coupler at V1b (.02 from .047) it seemed to disable the bass pot where I didn't hear hardly any change.

Hi and sorry but is it not V1a? Input to V1 is V1b (Pin 6 to . I´m now a little confused about.

I follow this thread becaus I argue the same reason of fizzi OD.
I´ll try to discribe the tone:
Hit the high E string on 12th fret - nice overdrive. But when I hit a second single tone (let us say B string 12th fret) emidiatly after the first, so this second tone breaks into peaces (the viennise chain saw massacre). But the first still sounds well.
Understandable?

Is this the same problem of you Structo? is this the bass too which destroy my tone?

Hans-Jörg

[David Root]

Hans-jorg, I think we are using -a and -b to describe first and second stage circuit-wise, and not strictly as pins 123 are -a and pins 678 are-b. So if stage 1 is pin 678, then that is called V1a.

The break up tone you describe sounds like intermodulation distortion (IM distortion) but I think it is still "the fizzies".

[Structo]

No, I am talking about low end bass.

The noise you describe is probably the often described fizzies in the overdrive.

Sort of a high pitched buzziness that accompanies high frequencies.

There are a few ways to address that.

Are you familiar with smoothing caps?

This is where you take a ceramic cap with a value of say, 50-100pf and put it as a shunt to siphon away the high fizz.

This is why the "snubber" caps on V2 are there (The 250-330pf caps).

You can try putting a cap in parallel with a plate resistor, or between the plate resistors, or from the plate to ground or plate to cathode.
You just have to experiment with placement and value.

I also feel that perhaps the GNFB or Presence circuit may be part of the issue with the fizzies as well. But I'm still experimenting with that.

It can be aggravating.
I thought I had those all but eliminated but I fear they are back in my amp now......
Right now I am wondering if power tube rattle may be partly to blame.
I have some tube dampers on the way...

[hans-jörg]

Hans-jorg, I think we are using -a and -b to describe first and second stage circuit-wise, and not strictly as pins 123 are -a and pins 678 are-b. So if stage 1 is pin 678, then that is called V1a.

The break up tone you describe sounds like intermodulation distortion (IM distortion) but I think it is still "the fizzies".

Ups, ash on my haed!
Sorry, but now its clear (for me).

The smootthing caps is avery good injection to me. Today I´m going for smoothing!

Thanks al lot (again) and sorry for "fizzin" your thread, Structo.

Hans-Jörg

[bepone]

hello structo , to easy tame the bass in the OD channel- one more cap you should solder in the circuit .

2.2 nF/400-600V MKT film cap after the OD relay, just before , and in series with the 220 k resstor which goes to the OD trimmer.

so when you switch to the OD channel, V1b coupling cap 47nF and the new 2.2 nF OD cap are connected in series, making more efficient high pass filter with OD trim pot. you have more bass reduction.

that help in my case, i dont like too much bass in dumble OD circuit also, i'm pretty satisfied with this solution. drive is more "mid focused" and not so "fuzzy-loose"

[hitchcaster]

i always have craploads of pots on hand, all marked with actual values.. then i can pick out the tolerances i want out of my stash... alpha's i get from mouser can be way off, for example, but sometimes thats a good thing

[hans-jörg]

No, I am talking about low end bass.

The noise you describe is probably the often described fizzies in the overdrive.

Sort of a high pitched buzziness that accompanies high frequencies.

There are a few ways to address that.

Are you familiar with smoothing caps?

This is where you take a ceramic cap with a value of say, 50-100pf and put it as a shunt to siphon away the high fizz.

This is why the "snubber" caps on V2 are there (The 250-330pf caps).

You can try putting a cap in parallel with a plate resistor, or between the plate resistors, or from the plate to ground or plate to cathode.
You just have to experiment with placement and value.

I also feel that perhaps the GNFB or Presence circuit may be part of the issue with the fizzies as well. But I'm still experimenting with that.

It can be aggravating.
I thought I had those all but eliminated but I fear they are back in my amp now......
Right now I am wondering if power tube rattle may be partly to blame.
I have some tube dampers on the way...

Hello, and thank you very much. The smoothing cap was THE solution. I put 47p between the anode resistors of V2 AND between the anode resistors of V3! Greate singing now and greate sustain wich was`nt before. For the moment was there a Ge 5751 Jan at V2 and a Sovtec LPS at V3. But I´ll try other tubes further, because its always possible better. But for the first step I´m very glad becasue I see I´m on the right way.
There is rearly a big spectrum of tones in that amp.
I couldnt stop playing this morning and my neigbours had to stan up earlier (7-8 am)

Greatings

Hans-Jörg

[gary sanders]

Ok heres what I see here as solutions (my amp has the same super bass after 9 oclock)

820k to lug one and three of the bass pot?
or
.02 between relay and 220k resistor in OD circuit
or
47p cap on the plate resistors,where exactly does this go?from plate to what?

correct me if i am wrong on any of these cause im going to give it a try,guess you could say my amp needs neutered....

[Structo]

Yesterday I changed the mid cap from .01 to .05

I like this much better, it shifted the mid highs a little higher and changed the low bass so that it isn't so heavy.

I may experiment with that cap some more, like a .02