Tone stack comparison ?

[tubenit]

The tone stack on the Tweed BluezMeister seems to give a nice warm full "clean" tone.  I like the clean on it better than the Tweed Overdrive Special.

I am pondering an idea.  I am noticing that I tend to turn the treble pot to about "5" and the mid pot to about "5" without PAB on. AND that with the PAB on that the mid pot really doesn't do much but the treble does.

The TOS has a one pot tone stack (5E3 type).  IF these two schematics functionally are the same IF the bass pot is dialed to "zero" .......... then I am thinking about an idea.

I can take a 250k dual pot.  Put a resistor across one pot to make it around 25k
and leave the other alone at 250k .  I'd essentially have a 250k treble and a 25k mid pot on one knob.  Then I could wire it up like the schematic on the right and recreate the BluezMeister with one knob.  Since I don't change tone pot settings much (and use my guitar switch instead), this could be workable for me, I think.

I'd have to measure the BluezMeister 25k mid pot at "5"  and then figure a resistor across to recreate that value.  Does this make sense?

IF this won't work, then I could still recreate the BluezMeister with two pots IF I eliminate a 500k bass pot dialed to zero.

What do you guys think?   I'd be kind of cool to get the BluezMeister clean channel with the TOS overdrive (which I like alot).

With respect, Tubenit

[jjasilli]

The resulting slope of the pot may be hard to use, due the wide mismatch of a 25K resistor across a 250K pot.  E.g. : @ 1/4 turn, the pot is at 63K; 63K in parallel with a 25K resistor = 18K or 3/4 full up.  The rotation of the pot is so magnified that it might be hard to control.  OTOH, if there are particular settings that you like, you might be able to select them with fixed resistors and switch(es).

[tubenit]

OK, if I punt on the dual gang idea and go with two pots ............

(again presuming bass is on zero)

Does the schematic on the right equal the one on the left?? (1st post)  I'm thinking with the bass pot out that you've got two .01 caps being paralleled for a .04 value?  IF so, I think I'll call this the BluezMeister Lite tone stack

With respect, Tubenit

[jjasilli]

No I think they are not equal.  There's a good discussion on this in the ax84 theory statement paper.  Anyway, the bass pot is never at -0- resistance with respect to BOTH caps; instead it's mixing them.  At full rotation one way its blocking the top .02 cap.  At full rotation the other way its blocking the bottom .02 cap.  The blocking may not be 100%.  The 500K bass pot is treating ea cap equally only when it's at 250K.  But even that treatment doesn't ultimately come out equal if the mid pot (and/or raw resistor) comes into play. The mid pot will push signal back up to the the treble pot. In summary, the FMV tone stack knobs are very interactive.

You can try the design.  I suspect there will be more insertion loss, and less overall control of tone.

[tubenit]

Please be patient with me. I've had no training in electronics and I know you've got a great deal of knowledge in this area. I am likely missing something?

Since the wiper is connected to the side terminal ............ why is there still resistance?  I can understand that if it were not connected.

If the pot dialed to "zero" shows no resistance across the outside lugs ............ wouldn't that mean the .02 caps are simply paralleled?

With respect, Tubenit

[sluckey]

If the pot dialed to "zero" shows no resistance across the outside lugs ............ wouldn't that mean the .02 caps are simply paralleled?

yes

[jjasilli]

If the pot dialed to "zero" shows no resistance across the outside lugs ............ wouldn't that mean the .02 caps are simply paralleled?

yes

Whoops I stand corrected; and apparently was confused by the bass pot being used as a variable resistor.  Generally, a pot is never at -0- resistance across the outside lugs.  Across the outside lugs, the pot is always at the full resistance for which it is named -- in this case 500K.  The resistance only changes through the middle, wiper, lug.  But, here, as a variable resisitor the wiper is externally attached to the top lug. 

(Still, with the bass pot at -0- in an FMV tonestack, there will be more insertion loss, and less tone control.)

[tubenit]

there will be more insertion loss, and less tone control.)

Good point. Your response helped me think thru the whole idea better anyhow.

Thanks, Tubenit

[Geezer]

there will be more insertion loss, and less tone control.)

Good point. Your response helped me think thru the whole idea better anyhow.

Thanks, Tubenit

But that's basically what you have now, right? Since you always run the bass pot on -0-?

I do the same.....this circuit (Bluesmaster/TweedMaster) is loaded with bass....someone over at the TAG board commented "It should be called a BassMaster".

If I was limited on space, that's what I would do (eliminate the pot & parallel the caps, or simulate it with a .04).

G

[tubenit]

OK guys,

I like the warmth of the TBM clean channel, so I am going to lose the 5E3 tone stack on the TOS and experiment with this  one knob "TBM ultra-lite" tone stack.

Will post over the wkend how it goes. IF I can make this work, then all I will have to change on the amp is two switches and one pot out.
 

With respect, Tubenit

[tubenit]

OK, this is what I tried.  I like it!  I installed it in the Tweed Overdrive Special in place of the 5E3 tone stack and two useless switches (that I wasn't using).  Gives the amp a little warmer feel and the two switches add more tonal possibilities to the TOS.

The center off SPDT in the center position lifts the tone stack out of the circuit altogether and gives a pretty decent boost. Would be a nice feature to have on a ft.switch relay switching.

With respect, Tubenit

[67polara]

Good stuff tubenit,  I notice you have a 220k resistor after the OD volume, that wasn't on the original TOS was it?  What does it do?

I notice that when I have the clean channel on maybe 5 when I go to the OD channel I have it set to like 2 and it is still really loud, does this help with that problem.  I am talking about the OD master and the Clean Master V.

Tony

[tubenit]

Tony,

Don't remember why I did that?  Honestly, Geezer and I were experimenting like crazy, trading notes, tweaking, trying new stuff, undoing new stuff and putting the original back .......... etc........ 

Kind of lost track why that was there?    

Could've been one of those arbitrary "Let's see what this does?" or maybe I was thinking it would help in some fashion. Who knows ...... I might have actually have some reason and logic behind it.
 

I know little to nothing about electronics ........ just persistent at tweaking and trying stuff.   

With respect, Tubenit

[JN]

Have you tried the "bigmuff" tone stack... If you play around with the values (try big changes using the tone stack calculator first) you can get a great fender three-knob tone out of one knob, with significantly less loss in the circuit...

[jjasilli]

Maybe not a bad idea, though tubenit probably already has holes in his front panel for tone controls.  The big muff idea prompted me to play with the Duncan Tonestack calc.  By changing the value of the top 20K resistor before the bigg muff pot, the amount of the mid dip varies.  If that resistor is broke down into 2 series resistors, a sw could be used to short-out one resistor and cause a mid boost.