DOD FX55 Distortion mods?

[toddebner]

concerning FX55C:
Distortion section is similar, but the gain poti is in the feedback loop like a tubescreamer. Its like a tubescreamer and Distortion+ together.
Tone-control is completely different to the other units we are talking about.
It´s like a Fender tone-stack with fixed bass and mid.  After that a FET- buffer-stage
analogguru

CD's suggestions above end up modding the 55b to have the gain pot like your description of the 55c (just remove the 3.9M R and put the jumper in on the pcb next to where the 3.9M R was.  Replacing the 470 ohm gives a more reasonable gain.  (was 8,000, but replaced with a 1k resistor, now is closer to 400/500)

Regarding the tone stage, Where can I get the fx55c schematic ?  I'd like to see what is different.

Todd

[Quackzed]

the fx53 is almst exactly the same schem . i removed the diodes in the feedback loop for more distortion + sound. or you could cut the diodes to ground for more ts style distortion. sounds much more open without the fb loop cllipping diodes

[diy213]

Would like to have the schematics too.  I have the two knob version and took some pics of the inside.  Anyone who can help out would be greatly appreciated.  It is great sounding when distortion is all the way down, it gives a tube breakup type of sound through my twin reverb and pignose g40v.  But would like to see what I can change to give it more bottom end.  I have posted 4 pics on photobucket.  Here is the lnk to the first pic and you can get the rest from the site or do a search for dod fx55 on photobucket.
Thanks in advance
http://i666.photobucket.com/albums/vv23/socaldeals4u/dod%20fx55/983_1026.jpg

[zombiwoof]

I have read several glowing reviews for the fx50 preamp/overdrive pedal.

Upon looking at my fx55b, the circuit board is marked fx50b-ht.

Anyone have a schematic for the fx50 ?

Perhaps we can find someone who has modded a fx50 and then we can find a way to improve this pedal.

The FX50 (no "B") is the preamp/overdrive pedal.  It seems to be a step up in evolution from the 250 OD, with a different opamp and electronic switching.  I have one, and it is a very nice sounding overdrive.  The FX50-B added an extra gain stage and a bunch more components (and an extra control) that turns it into more of a distortion at higher settings.  I also have one of those, and the problem with it IMO is that it gets very noisy in the higher settings.  The FX55 is basically an FX50 with added gain (still two knobs). The other DOD distortions seem to be similar, just with changes in circuitry.  Here's the story on the FX55B, which adds a tone knob to the FX55 (this site also details all of the other DOD pedals, so you can see the changes as they went along):

http://www.americaspedal.net/fx55b/

Also, with the DOD pedals, the "B" doesn't mean bass, it just means a change in the circuit, for the bass versions they just used a different model number.  I think the "C" versions are the ones that were made after the production changed to China.

Al

[diy213]

Here is the link to the schematics, hope this helps.
http://files.effectsdatabase.com/docs/schematics/dod_%20fx55_schem.gif

Just a little info on what I've done to my pedal to try to make it better.  I replaced the input resistor with a 4.7k ohm resistor and the input cap with a .1uf cap.  I did this to match the ts808 which has a 4.7K ohm resistor with a .047uf cap in the input.  I changed the input cap to .1uf because I read that changing to this value would give it more bass.  I also swapped out all the 1M resistors with metal film resistors to help decrease some of the noise and added an extra diode in series with one of the diodes in the clipping section closest to the distortion pot.  This was supposed to help with the distortion sound, and it did.  I will be swapping out all the non polarized caps with lower noise caps and all the electrolytic as well. 

So far with the few parts I have swapped out it has made a significant difference.  It definately has more bass now and the distortion sounds a bit smoother.  When I compare it to my fulltone ocd the dod tends to target more of the highs while the fulltone has more of a low end chunk.  The distortion is not as harmonically balanced as the ocd but its also not as expensive as the ocd and wil definatel serve a purpose on my pedal board.  I was thinking of selling this pedal but not anymore. 

If anyone else has any ideas on how to turn this pedal from zero to hero, please let us know.

[Quackzed]

with 2 spst switches, it could be made more versitile.

-one switch between the first pair of diodes in the feedback loop and their connection piont. this will take them in/out of the circuit, with them out of the circuit, tone is dist + like, good marshall type distortion.

-one switch between the second pair of diodes to ground and ground. this will take them in/out of the circuit, with them out of the circuit, tone is tubescreamer like, good smooth tubey sound.

with both on and in the circuit it acts as normal. with both off and out of the circuit, you should get a decent clean to slightly dirty boost.

[Joe Kramer]

Anyway - the TL06x series is a low noise variant of the TL07x series.

I think you meant to say "the TL06x series is a low voltage variant of the TL07x series."  It's also much noisier, though it depends on how much gain you ask from it.  If it's in the signal path and providing lots of gain, it's likely replacing it with almost anything else will be quieter.

As for mods, FWIW, I'd try a 1458 op amp.  Not a hi-fi chip to be sure, but has a certain guitar-friendly sound. 

[zombiwoof]

Here's a couple of schematics, for the FX55 and FX55B.  The FX55C supposedly is very similar to the FX55B, except for the chip (according to the "DOD - America's Pedal" website).

http://files.effectsdatabase.com/docs/schematics/dod_%20fx55_schem.gif

http://www.schematicheaven.com/effects/dodfx55b_dist.pdf

Al