From: dam@dcs.glasgow.ac.uk (David Morning)
Newsgroups: alt.guitar
Subject: Fuzz Box From Hell (corrected version)
Date: 30 Sep 92 09:24:37 GMT
Organization: Glasgow University Computing Science Dept.


I knew I shouldn't have posted something which had been collecting dust
for years in my files. Oh well. My original version used 2 batteries to
provide a split rail supply. In my rush to post it, I bodged the battery
supply splitter. I wasn't convinced I'd got it right after I'd posted it
so a built it from scratch at the week-end. There are 2 connection errors
in the original, both the input resistor and the 680 ohm feedback resistor
should go to the V/2 rail and NOT the battery -ve.

Sorry folks. This one does the trick. Oh..and it's a 9 volt battery (small type)



Battery is 9 volts.
Op-amp is anything. 741 is noisy, TLO71/72 is less noisy, NE5534 is least
noisy but drains the battery.

                             
                       ---  Op-Amp                           
                      |    \                                          
                      |     \                                                  
Inputo----||----------| +    \                                 
        0.47u |       |       \                 0.47uF        
              |       |        >-----------------||------     
              |       |       /       |       |          |    
              |    ---| -    /        |      ---\        -
              -   |   |     /         -      / \  ZD1   | |
             | |  |   |    /         | |      -         | |100k
        68k  | |  |   |   /      330k| |      |          -
              -   |    ---            -       -          |-------o Output
              |   |                   |      \ / ZD2     |
              |   |                   |      ---/        -
              |   |                   |       |         | |
              |    -------------------|-------          | |2k2**
              |                       |                  -
              |                       -                  |
              |                      | |                 |
              |               680ohm | |                 |
              |                       -                  |
              |                       |                  |
               ------------------------------> V/2*      |
                                                         |
Input                                                    |          Output
Gnd o----------------------------------------------------------------o Gnd


Battery rail splitter
=====================

Batt +ve-----------------------------------------> To Op-Amp +Vs
                                   |
                                   |
                                   - 
                                  | |220k
                                  | |
                                   -
                                   |
                            -------|------------> To V/2*
                           |       |
                          --- ++   -
                   100uF  ---     | | 200k
                           |      | |
                           |       -
                           |       |
                           |       |
Batt -ve -----o\o-------------------------------> To op-amp -Vs
             Jack socket switch           |
                                          |
                                           ------> To Gnd






Jack socket switch wiring:-
=========================

                   -------------------
                  | Sleeve  Ring  Tip |
   Jack plug ---> |   -     -     -   |
   goes in here   |  | |   | |   | |  |
                  |  | |   | |   | |  |
                   --| |---| |---| |--
   From battery -----| |   | |   | |
   -ve terminal       -     -     -
                            |
                             -------------> To battery rail splitter

Inserting mono plug shorts sleeve and ring together and activates the
battery.


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