Fetzer Valve in a OD1 clone?

ChristoMephisto · Post by **ChristoMephisto** » 01 Dec 2010, 00:04

Instead of going through the bother of adding a 12AX7 tube to a Boss OD1 clone i have,
is it possible to add a Fetzer Valve to the mix?
Looked around and there's not too many sites that show where to add the tube expect this place
http://screamertube.blogspot.com/
Going with that and the Fetzer at ROG http://www.runoffgroove.com/fetzervalve.html
Would you add it right after the output of the first half of the opamp?
The OD1 only has a 10k resistor connecting the two halves of the opamp, so would I just replace that with the Fetzer and use the original Volume pot as the output?
Since it was a Boss SD1 there is a hole for a knob and was thinking of using the Fetzer Deluxe and using the Level pot shown, a 1meg, kinda much imho, and the Presence switch.
Would it have to run on the 4.5v rail so it still works in bypass?
Guess this could be done to any SD1/TS pedal...

jimbob_400 · Post by **jimbob_400** » 02 Dec 2010, 13:15

I'm not quite sure what you're saying in places. After the clipping section/feedback loop part of the circuit insert a 10uF DC block cap, insert your fetzer valve leaving out the volume control. From the 47n cap carry on the circuit to output buffer.

ChristoMephisto · Post by **ChristoMephisto** » 02 Dec 2010, 21:54

Here's a link to the OD1, pretty much like the SD1/TS
http://www.hobby-hour.com/electronics/s ... rdrive.php
So I can basically replace R7 on the OD1 with the Fetzer from the 33k input resistor to the 47n cap at the end?
I get the idea of the 10uf cap, at the input of the Fetzer part?

jimbob_400 · Post by **jimbob_400** » 02 Dec 2010, 23:10

ChristoMephisto wrote:Here's a link to the OD1, pretty much like the SD1/TS
http://www.hobby-hour.com/electronics/s ... rdrive.php
So I can basically replace R7 on the OD1 with the Fetzer from the 33k input resistor to the 47n cap at the end?
I get the idea of the 10uf cap, at the input of the Fetzer part?

Ahh okay, gottcha. from pin 7 of the opamp cut the part going to R7 and insert the fetzer valve in here. Omit the volume control from the fetzer valve and then take the output of the 47n cap to R7. So basically put the fetzer valve part between the output of the clipping section and R7

ChristoMephisto · Post by **ChristoMephisto** » 03 Dec 2010, 00:04

That's perfect!! Wasn't sure about leaving the 10k resistor in or not
Went to go dig out some J201s i thought i had, they were BS170, and found a couple 2N5457
Might try those and order a few J201s

jimbob_400 · Post by **jimbob_400** » 04 Dec 2010, 11:28

ChristoMephisto wrote:That's perfect!! Wasn't sure about leaving the 10k resistor in or not
Went to go dig out some J201s i thought i had, they were BS170, and found a couple 2N5457
Might try those and order a few J201s

2N5457s will work just fine! Good luck.

HTH · Post by **HTH** » 17 Dec 2010, 16:54

I've converted an SD-1 to be an OD-1 too. This just got me thinking - the spare hole where the tone control was could be used as a second 'gain' pot to control the gain of the second opamp stage. Might well give this a bash.

ChristoMephisto · Post by **ChristoMephisto** » 17 Dec 2010, 21:50

I tried spicing in the Fetzer and after two hours with a breadboard and wires sticking out
couldn't get it to work...

moving on to another mod...
already had multiple clipping, gain, bass...
also tried hard clipping with two Ge's

as a tip, if you do convert a SD1 to an OD1, change the caps and resistors to the 14 pin version
especially at C2/R4, make it .047/10k instead of .0047/100k
the .0047uf cap is too much of a choke, even at 338Hz