DIYstompboxes.com

DIY Stompboxes => Building your own stompbox => Topic started by: DiscoVlad on January 05, 2011, 05:05:31 PM

Title: Yet another Opamp Big Muff
Post by: DiscoVlad on January 05, 2011, 05:05:31 PM
This is my first build of 2011, and it worked first time... here's to a continued 100% success rate  :icon_mrgreen:

This is basically the same as the V4/V5 opamp Big Muffs from 1977/78 and has the tone bypass circuit onboard, instead of christmas tree style like the originals. I've also added polarity protection (in the form of a Mosfet/Zener) which the original didn't have.

Outside:

(http://cabbages.orconhosting.net.nz/graphics/joes_rubbish/fx/BMP/OABMP-1_tn.jpg) (http://cabbages.orconhosting.net.nz/graphics/joes_rubbish/fx/BMP/OABMP-1.jpg)

Insides:

(http://cabbages.orconhosting.net.nz/graphics/joes_rubbish/fx/BMP/OABMP-2_tn.jpg) (http://cabbages.orconhosting.net.nz/graphics/joes_rubbish/fx/BMP/OABMP-2.jpg)

It fits into a 1590bb, but is a pretty tight fit. Resistors are all 0.25W Metal film, Opamps are just whatever 741/4558 were cheapest.
Wires have been hot-glued for strain relief, and there's nomex paper (offcuts from work) underneath the board for insulation. so hopefully it should be robust.

Schematic Here (http://cabbages.orconhosting.net.nz/graphics/joes_rubbish/fx/BMP/BMP.pdf)
Eagle files and Board transfers here (http://cabbages.orconhosting.net.nz/graphics/joes_rubbish/fx/BMP/Opamp-BMP.zip) these are a newer revision than from what I built, and have a couple of components resized (all resistors and diodes are 0.3" pad spacing now).

This thing absolutely nails the Smashing Pumpkins - Siamese Dream guitar tone, and the first comment from my local music shop's guitar guy was that it sounds like a Guild Foxey Lady ??? I don't know either... It does sound great for fuzzed out bluesy solos, and thick grungy riffs though.
Title: Re: Yet another Opamp Big Muff
Post by: John Lyons on January 05, 2011, 08:39:00 PM
Looks great!