Build report (pics & mp3): Opamp BMP!

[Sam]

While bread-boarding I changed a few caps and did some work on the tone circuit. I'm not sure exactly what I manage to do electronically speaking since I can't use Duncan TSC (Mac user) at the moment. I threw in some trimmers at adjusted R15 by ear while swapping caps back and forth. The tone pot seems to be focused somewhere in the upper mids (both HP caps in the filter are roughly in the same size - 0.1u and 0.22u) and mainly determines the power of that region in the spectrum. Personally I feel all settings are usable. I used some luxury caps just for fun.


PBC layout: http://topopiccione.atspace.com/PJ14EHBigMuff1977.html - Thanks btw!

Schematic (with my mods):

I didn't find any 62k resistors so I used 68k for R7, figuring the change in gain wouldn't be that significant. Oh, and I used a 100k log volume pot for the same reason and will probably change to it standard value when i order a new batch of pots. 

Oh, and yes, a SOUND CLIP!
Gain is at max throughout the clip and Tone at mid, min and max. Signal chain: Tokai Silver Star ('70s Strat) and SF Deluxe Reverb, Sennheiser MD 421 (slightly off-axis), Joe Meek VC1Qcs pre-amp (no compression or EQ) and Logic Express on an iMac. http://download.yousendit.com/C8DD29EC5F1E644D

My questions:
1. (In Seinfeld-voice) What's up with that tone control?
2. What real difference will the 25k volume pot make?
3. Does it sound "right" or simply dull? 

[jimbob]

It sounds great to me. Im thinking about having a 3 in 1 box w a triangle muff, russian, and this opamp 1977.

[sfr]

If you've got access to an Intel-based Mac, I was able to get the Duncan Tone Stack calculator to run using the free beta of Codeweavers CrossOver Mac.  FWIW.

[Sam]

If you've got access to an Intel-based Mac, I was able to get the Duncan Tone Stack calculator to run using the free beta of Codeweavers CrossOver Mac.  FWIW.

Yes, I've got an Intel-based iMac. Thanks! I'll definitely try that - can't live without the DTSC.

[mydementia]

jimbob - I just finished a multibox with the following path:
BMP --> toggle switchable Rangemaster/Brain May Treble Booster --> Triangle BMP --> Rat
I wanted to be able to push the booster with a BMP or push a BMP with a booster - awesome sounds both ways.  I think my favorite is the Rangemaster into the Triangle BMP - fun stuff.
Mike

[Sam]

New sound sample link: http://media.putfile.com/Opamp-BMP

[Sam]

If you've got access to an Intel-based Mac, I was able to get the Duncan Tone Stack calculator to run using the free beta of Codeweavers CrossOver Mac.  FWIW.

Thanks again! It worked nicely.

[mcasey1]

The Op-amp you made sounds different than the 4 transistor triangle knob I made.  I think it sounds great.

[Doug_H]

Sounds good!

[Sam]

Well, thank you. Next up is building a qouple of the transistor version voiced in different ways.