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onboard midboost suggestions?

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3/30/2000 8:07 PM

onboard midboost suggestions?

Ive been trying to find a schematic for the 25dB onboard midboost preamp that's used by Buddy Guy (Fender sells these but I don't know if they actually make them), and I haven't had any luck. Does anybody know anything about it, or possibly have a schematic, spec sheet, patent #--Anything would be helpful at this point. If not, Im open to suggestions regarding a different midbooster design (I'd like at least 12dB boost, though).

Thanks
Jeff

3/30/2000 11:04 PM
Max	Hi Jeff! Have a look there!http://www.mimf.com/cgi-bin/WebX?13@^16421@.ee6f8f4 Best regards. Max.

3/31/2000 12:09 AM

Jeff:

There is a hand-drawn schematic of the one supposedly used in the EC strat on my schematics page, but errors have been noted so you are on your own...

http://www.ampage.org/blueguitar/

Steve Ahola

P.S. If your amp has plenty of gain a passive mid-boost (actually a high/low cut) can also be used but I guess you are looking for the boost, too... I have the one I use buried in the FrankenStrat drawing (p-p pot- down is mid-cut, up is mid-boost/cut). The mid-boost function works great to smooth out a too-bright strat bridge pickup, and at high gain settings you do not notice the cut in signal level at all... (well, if it is passive it only cuts and doesn't boost- which can be a problem if you are plugged into a wimpy amp).

3/31/2000 3:58 AM

Steve,

I found that schematic a few months ago, and it was a no go. I patiently etched a beutiful PCB, followed it to a T, checked, rechecked, pulled out some hair, rechecked some more, and so on--I got a real pretty looking hunk of silicon and solder to stare at in bewilderment, though. Any idea what the errors are--I'd definititly be willing to tinker with it some more if you have any ideas as to what the problem may be. If I could get it working I'd be more than happy to send you a nice corrected, computer-drawn schematic for your site.

I didn't know that was your website (well, how would I)--It's a great site. I got some really good ideas there when I was rewiring one of my guitars into a sci-fi Freinkenstein creation. 2 Duncan Humbuckers each with a series/parallel/split switch, going into a 6-way rotary switch for bridge only, neck only, both in series, both in parallel, both in parallel with a bass cut, and a standby. There's a Fishman piezo-under-the-saddle, running through a homebrew JFET buffer; then a Gibson-style 3-way switch to choose between piezo, magnetic, or both; seperate volumes for magnetic and piezo, and a master tone. Im working on a variable capacitance tone circuit for it, but I haven't gotten it quite right yet--it's too hard to control. Anyhow, I'm just rambling now, so I'll shut up.

You take it easy,
Jeff

3/31/2000 5:18 AM

Jeff -

What transistors did you use in your copy? I never got around to actually building one, but the simulations I ran in Electronics Workbench didn't work 'til I subbed in Motorola BC109C or 2N3904s for the MPSA18s. The two MPSA18s tied together should have their emitters going to the 82k resistor to ground as well. With these changes (the 2N5087 works as posted) the circuit works fine, with alot of mid boost, but I never got the tone control working.

If anyone wants my EWB file to play around with, send me an e-mail.

BTW - anyone know if this is the same circuit used in the Buddy Guy Strat, but with a different tone network for a full range boost?

3/31/2000 6:13 AM

Cole,

Thanks for that info. I've never tried a simulation program for debugging--it would probably save me alot of frustration. I usually just sit and stare at the board, poking around with a meter, and do a lot of bitching and moaning.

Anyhow, I have a bunch of 2N3904s sitting in my parts box (I just got them a few days ago to make up a batch of Jack Orman's Triple Bypass circuits), so Ill give that a try tomorrow, and post the results as soon as I'm done. If it works I'll draw up a new schematic, and send it over to Steve.

As for your question about the Buddy Guy Strat: Ive been wondering the same thing. Buddy Guy's tone is just unbelievable, there's something so undefinable about it--it also doesnt hurt that he's probably the best guitarist alive.

Take Care
Jeff

3/31/2000 7:07 PM
Reid Kneeland	There's a mid-boost circuit in Craig Anderdton's "DIY Projects For Guitarists" that's probably worth looking at. Reid

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