Know any good mods for a Bluesbreaker distortion?

[Chris Goodson]

I just built one the other night and I like it a lot.  I just wish it would get a little more distortion. What I thought would be nice is if I could add a toggle switch to increase it when I want.
One thing I was concidering was adding a switch that would swap two of the existing diodes with Ge's.  Any thoughts as to whether this is a good/bad idea or what the end result might be?

[Russ]

Hi Chris, I've wanted to ask the same exact question about my DIY Bluesbreaker. Anyone have any ideas?
Thanks, Russ

[Ansil]

yes  

http://www.generalguitargadgets.com/v2/diagrams/bluesbreaker_sc2.gif

utilizing the above shcematic

u could also shunt two of the diodes to ground causeing hard clipping

or use a switch to make the feedback loop reistor bigger

my favorite kill r8 and c6 all toghetehr

[Chris Goodson]

What would be the result of "killing" r8 and c6?

[petemoore]

Tag an alligator clipped wire over those two and see what you think/
 By taking passive components out of the signal path, there will be less reduction of signal amplitude, frequency response may change also.

[petemoore]

Put a aligator clipped wire from a diode rail to the middles of the diodes, eliminating two from the feedback loop. Should clip a little harder and have reduced output.

[petemoore]

any values in the feedback loop can be messed with.
 The chain between the outputs and input of the OA, second one has the diodes, caps and resistors in it, see the mods page, AMZ has some clipping info.
 Ge's clip sooner. less output more clipping.
 Since I perf, I can put an 8 pin IC socket in the feedback loop, one column of pins for the output of OA2, [pin 7] th other for input [pin 6].
 The first OA's gain pot could be larger, and you'd still have the range you had with a 100k, but in a smaller portion of the shaft travel.
 And, for one of my favorites...Tailor a booster for the front end voiced for lead boost.

[Chris Goodson]

What is c6 doing?  Also, what direction should I go with it's value(up or down) if I tweak it?

[petemoore]

About the same thins as the next cap in the line there on the other side of the 4k7 resistor.
 clip a bypast C6 and the 4k7 right after it.
 larger cap differece of C6 will be cut by C7, smaller values there will roll bass off.
 Caps cut how much bass gets through. in the signal path this rolls off bass.
 a cap or cap and R connected between the signal path and ground determines how much of the bass content is Shunted TO Ground...more you shunt to ground, the less gets by...therefore a cap from signal to ground rolls off Highs.
 you only need one coupling cap there. I doubt Any difference could be detected by eliminating one from the signal path. The relatively small 4k7 resists, dropping the signal level down a bit there. Eliminating that, or bypassing it [elecricity chooses the path of least resistance...in this case a wire], will let more signal pass in through.
 Never tried that one, I don't think it'll make a huge difference, but youll have an extra cap!
  Good luck!!! Let me know how i'ts going...

[petemoore]

Try putting a simple buffer [AMZ] before or after the circuit...

[Gus]

The stock bluesbreaker seems to sound its best with a marshall tube amp at playing volume.  Its not a massive boost but it has a eq, boost, clipping that works well with a tube amp with distortion going on IMO.  When I traced the circuit a few years ago I noted it was a clever design.  Look at the gain control and how it affects both stages.  

 You could try a different fet input opamp.

  It might work well with a small tube amp under 10watts with a good 12" speaker.

[Chris Goodson]

I think this is a nice pedal, there's something I find really natural about the tone.  I'm playing through a 67 Blackface Bassman w/Andy Ruhl's mods.  I also modded the bass channel's tone stack to be somewhat like a Marshall and added a mid and presence control.

What I find interesting while using the Bluesbreaker is if I scoop the mids it really seems to reduce the disortion but if I really crank the mids up - bingo.  What I've done with it at this point is mounted it in a box w/ an 808(in the order of BB then the 808).

So far I like what I've got quite well. But a little more drive from the Bluesbreaker would be cool.  I'm gonna pop it open and experiment later today, I'll let you guys know what happens.

What I eventually want to build is a single pedal something like this-
compressor(Ross?) + Bluesbreaker + 808.  I think they would all fit in one of those large Hammond enclosures.  I might try to come up with a layout using a single board.

[Doug H]

The stock bluesbreaker seems to sound its best with a marshall tube amp at playing volume.  Its not a massive boost but it has a eq, boost, clipping that works well with a tube amp with distortion going on IMO.  When I traced the circuit a few years ago I noted it was a clever design.  Look at the gain control and how it affects both stages.  

 You could try a different fet input opamp.

  It might work well with a small tube amp under 10watts with a good 12" speaker.

I breadboarded one once and with my Firefly breaking up a little it sounded -really- nice. I was able to get Gary Moore tones out of it, esp when I cranked the output vol a little to drive the amp more.

One mod I liked was a small treble-leak cap from the gain pot wiper to the coupling cap going to the 2nd stg. This opened up the tone of it a little at lower gain levels. It sounded a little dull in low gain without it, to me.

Doug

[Gus]

I gave a hint but now I will type it out.  Remove c7 and r8 install  jumpers in place of the two parts.  stock is .11uf C and 9.4K R  now it will be .22uf and 4.7K same eq but X2 the gain at max.  keep in mind that you are still limited by the diodes for output the gain will come on faster maybe with less "touch" control.  I think at more than the x2 mod it becomes less of a bluesbreaker and more like a eqed fuzz.  I think the person(s) that did this petal design did a good job.

 You might like the eq with c6 a different value.

 In this circuit a TL072 might not like to drive under a 2.2k load so if you adjust the gain with  r7 keep this in mind.

[mrsage]

I gave a hint but now I will type it out.  Remove c7 and r8 install  jumpers in place of the two parts.  stock is .11uf C and 9.4K R  now it will be .22uf and 4.7K same eq but X2 the gain at max.  keep in mind that you are still limited by the diodes for output the gain will come on faster maybe with less "touch" control.  I think at more than the x2 mod it becomes less of a bluesbreaker and more like a eqed fuzz.  I think the person(s) that did this petal design did a good job.

How would this work using a switch to go from the original design to this mod?

Would you use a DPDT, or could you wire up an SPDT?

Any other opinions on this or other mods so you could toggle gain on the bluesbreaker?

[WGTP]

On Franks Clarks mod's he added a larger cap to the end of the ciruit comming off the first feedback loop, as a boost.  Lots of possible tweets to those 2 resistors and 2 caps for more gain and tonal contouring.

The one I have bread boarded, I replaced the 4 diodes and 6.8k resistor with 2 LED's.    

[mrsage]

Which 2 resistors and caps are you referring to?

I'm using the GGG layout:
http://www.generalguitargadgets.com/diagrams/bluesbreaker_lo2.gif

And does Frank Clark have a current website? The only links I can find point to a site that is clearly not FX related...

[WGTP]

Frank seems to have disappeared, hope he is doing OK.

There are 2 .01uf caps and 4.7 and 3.3k resistor.  He increased the .01uf that went to ground x 20 to a .2uf with a switch and called it a boost.  Works pretty good.  I replace the whole deal with a 1k resistor and .2uf cap.  

[mrsage]

Okay, that makes sense.

So that increases the gain? What would you compare the post-mod sound to?

I've got an original Bluesbreaker that I really like, and I'm building one for my brother in law as a christmas present...he likes higher gain stuff than I do, though, so I thought I'd add a toggle to give him that option.

[WGTP]

I guess it becomes a Blues Blaster.  It adds gain and more mids and lows.  If you really want to go off, connect 2 SI diodes to VREF at the input of the second op amp and change the 220k to 470k, it adds more sustain and distortion.