MXR Dist.+/DOD250/YJM308/etc. Mods

[WGTP]

I got a YJM308 on sale for $30 with the intention of comparing and modding.  I worked with it quit a bit on the breadboard and got some pretty good sounds, but still wasn't happy.  So, I added a ROG Mosfet stage "Booster" to the end of it and  Whomp there it is.

Mosfets seem to have more SWIRL and BLAZE to them than other distortion types.  When I move my wang bar with chords, it almost sounds like a flanger or chorus, or at least this does.

Check out Aron's Shaka pedals for the original idea.  I guess that is a pretty extreme mod, but it sounds nice and has a Blazing Mosfet  sound to it.  So it's the Blaze mods.  Other mods are shown as well.  I used the Blaziest BS170 I had.  I haven't mounted it in the box yet, but don't anticipate any problems.  Should go on a small piece of perf and insert between the end of the circuit and the output pot.  Attaching the +9v and Ground should do it.  The questionable part is whether to leave in the diode clippers, or just drive the Mosfet with the op amp.  May need a switch, try it both ways.  With the diodes it's more compressed has 3 stages of distortion and the Mosfet gets less signal.  Without the diodes, the Mosfet gets lots more signal and contributes more to the distortion. 

I tried subbing in LED's for the diodes, and that has a very nice sound.  Also might try the diodes in the feedback loop to keep the op amp from going over the top, but then again, you may prefer that.

The 4.7K/.047uF circuit on the end does a nice job of "boosting" the bass and works well with open back SS combo amps.  If your going to use this to boost tube amps, you might not want it.

Let me know if you see any problems.   

http://aronnelson.com/gallery/WGTP/MXR_YJM_DOD250Mods?full=1

[tungngruv]

Very cool. I tried Jacks mini booster in front and behind the DOD 250. Two different and usefull sounds. Before adds saturation and behind adds volume. BTW, have you done anything lately with your "Angel Duty, Booty, etc......". They seem pretty interesting but I haven't heard any sound samples.

[WGTP]

I haven't messed with those much lately and I haven't figured out how to do sound samples.  It's interesting mixing the different stages and breadboards are great for that.  I was thinking today about the percentage of each stage you hear when you mix them.  33% first stage, 67% seconds stage???  The only one I boxed up was the one with the Blackfire/Mu-Amp.  It has a throatier sound than 2 Mu-Amps and is a little smoother than a Blackfire.  There is probably a way to use a switch and reverse the order for 2 different sounds, but I haven't figured that out either.   

[John Lyons]

Those tweaks look like some good ones. I'll have to get around to trying those.

Thanks for posting them.
Is the black fire muamp mosfets instead of Jfets configured as a mu amp?


John

[Sam]

Funny. I always found that placing my Zvex SHO after my RAT made the distortion fuller and crunchier - even at unity gain.

[WGTP]

No, the Blackfire was a different circuit Joe Davidson did with 2N5089's, but he did also have a Mosfet version posted for a while.  Do a search, it is really a cool distortion either way.  You can make a Mu-amp with Mosfets, but the biasing is different.   

[John Lyons]

Oh, ok...I knew that...for some reason I was thinking Mu-amp like the BSIAB and when you said blackfire/mu-amp I put them together as a mu-amp with Mosfets in my mind.
What would you say is the main sound difference between the 2n5089 and Mosftet versions of the Blackfire?

John

[WGTP]

IIRC, it has been several years, the difference wasn't as much as you might think.  Joe has continued to post the BlackFire with the 2N5089s, although I don't see it now, and the Mosfet one didn't stick around too long.