Tone pot value on the Bluesbreaker

[mordechai]

I've seen some folks out here suggest changing the value of a tone pot on the Tubescreamer for "better" sweep/control (e.g., making it 10-5k).  Would this type of changed value work well for the Bluesbreaker as well, or is it such a different beast that this wouldn't apply?

[GGBB]

Totally different beasts.

[Mark Hammer]

Yep, Gord's right.  The TS pot has a "reciprocal" action, rolling off highs at one extreme, and applying gain to the mids and highs at the other extreme.  The Bluesbreaker tone control only rolls off highs.  Now, it may well be that a 10k pot produces exactly the sort of treble cut you want, but all the same, the two tone controls function in a different way.

[mordechai]

Well, actually, what I'd like to doing have less highs introduced as I increase the gain/drive.  But I suspect that this involves wiring a small cap across the lugs of the gain pot (lugs 2 and 3, I would think...yes?) rather Han changing the sweep range of the tone pot...

Cheer from lovely Cape Breton, btw!

[Mark Hammer]

Well, actually, what I'd like to doing have less highs introduced as I increase the gain/drive.  But I suspect that this involves wiring a small cap across the lugs of the gain pot (lugs 2 and 3, I would think...yes?)

Yes.  Raising the value of the 47pf cap up to 220pf, or maybe even 330pf would take some of the fizz away.  f that isn't enough, consider adding 100pf in parallel with the 220k resistor in stage 2.  That ought to round off any harsh edges nicely.

BTW, what are you doing in Cape Breton?  If you haven't yet visited, you owe it to yourself to visit Fort Louisbourg, a superb historical site that explains a great deal about the transition between a French and English North America.

[mordechai]

I already upped the first 47pf cap in the first op amp stage too 100 (as per Analogman's KOT), but I'll move it up a bit more and also put one across the 220k resistor in the second stage.  Is it advisable to try using a small cap in parallel with the diodes (like a 47pf) a la a TS?

I am thinking of a fairly small cap across lugs 2/3 of the drive pot...maybe just at 82pf, since there would noob several other "softening" caps in place as per the notes above.  Or would this be too small to really be worthwhile?  I do want **some** bite to come through when I have he drive up fairly high.

Finally, and a bit OT....I'm in Cape Breton for a second honemoon (the first one in January got rained out!).  Fort Louisburg was intriguing.  Though when the role-playing armed "guard" asked me if I was Anglais or Fracais, I was tempted to say "neither...in the mid18th century, Jews were denied citizenship in both." 

[Mark Hammer]

I already upped the first 47pf cap in the first op amp stage too 100 (as per Analogman's KOT), but I'll move it up a bit more and also put one across the 220k resistor in the second stage.  Is it advisable to try using a small cap in parallel with the diodes (like a 47pf) a la a TS?

No.  The suggested cap paralleled with the 220k resistor is already accomplishing what you want to do.   

I am thinking of a fairly small cap across lugs 2/3 of the drive pot...maybe just at 82pf, since there would noob several other "softening" caps in place as per the notes above.  Or would this be too small to really be worthwhile?  I do want **some** bite to come through when I have the drive up fairly high.

You already have what amounts to 4 poles of lowpass filtering in there with: the added feedback cap in stage 1, the suggested feedback cap in stage 2, the tone control, the 6k8/10nf network between the tone control and volume pot.

One potential strategy is to modify the circuit to have a variable passive 2-pole lowpass filter at the output, instead of the one tone control and fixed filter (6k8/10nf).  Take a dual-ganged 10k pot, and wire up each section as a variable resistance (that gets smaller as you go clockwise) in series with a 1k fixed resistor, like so:
-> existing 1k resistorA -> pot-sectionA -> 1k resistorB -> pot-sectionB -> volume pot.  Now, run a 15nf to 22nf cap to ground from the junction of pot-section a / resistor B, and the junction of pot-sectionB and volume pot input.  using 15nf caps will get you a cutoff range that goes from 965hz-10610hz.  Bump those caps up to 22nf, and the control range shifts from 658hz-7234hz.

Finally, and a bit OT....I'm in Cape Breton for a second honemoon (the first one in January got rained out!).  Fort Louisburg was intriguing.  Though when the role-playing armed "guard" asked me if I was Anglais or Français, I was tempted to say "neither...in the mid18th century, Jews were denied citizenship in both." 

Those folks do a great job of staying in character all the time.  I don't know if their training would have afforded them a suitable comeback, though.  I'm sure Parks Canada management and communications folks would have likely frowned on "Then what are you doing here?" 

BTW, a buddy from the Canadian Guitar Forum is based out that way, somewhere on Cape Breton, and makes a nice product: http://www.maritimeanalog.com/store/  Say Hi, if you get the chance.

[tubegeek]

Cheer from lovely Cape Breton, btw!

Lovely it is, thank you! Haven't been there in a long time and I miss it - what's the name of that beach with the waterfall at the end of it? Sweeeeeeeet place!