MXR/ROSS/YJM/Whatever Mods

[WGTP]

OK, the thing about these type distortions, is that the gain control also rolls off the bass when maxed out because it changes the resistance to ground of the RC network coming off the negative feedback loop.  Modding that RC network isn't going to effect things with the gain at 1/2.  As you approach the max gain setting, it begins to act as a treble boost.  The thing I like about the YJM308 is that it has a small input cap that keeps it from getting too woolly even with the gain at 1/4.  So, here are some "solder on" mods I came up with that will allow easy modification by soldering parts on rather than replacing them, except for the diodes.

These mods will increase the output (depending on diode selection) and distortion generally Turboizing it.

Changing the diodes to LEDs will get you a lot more output, but less distoriton .  Using 2 GE's will give you lots of distortion, but the least output.  If your going into a solid state amp and are not trying to OD the input tubes, I would recommend a blend of 1 SI and 1 GE.  I like this sound the best  Just solder the GE to the existing SI and it will bypass it.  Of course switches can be used with good results for multiple pedals in one.

If your trying to OD a second pedal, or tube preamp, you will need to remove the existing diodes and replace with LED's.  You can also compromise by using 2 SI's for each direction, or 1 SI for one direction and 2 for the other.  This is another favorite, but with increased distortion and reduced output.  It keeps the crisp SI clipping sound but adds the thicker asymmetrical clipping tone to it.

As mentioned in another thread, the 10K resistor can be replaced with a 100 ohm, but that seems a little low to me, so solder a 1K resistor on to the 10K. 

Now to make up for the lose of distortion resulting from higher threshold clipping diodes, solder a 1K resistor to the 4.7K resistor that goes to the pot.  Also, solder a .1uf cap to the .047uf cap.  This will give you lots more drive at max gain with a slight bass roll off.  As the gain is reduced, it will have no effect, so stock setting will be the same.

The .001uf cap at the input works for me, but if you want more bass, double it to .002uf by soldering a .001uf cap to it.  The other models already have a larger cap there that you might try reducing if you have too much wool.

Also, you can double the .001uf cap parallel with the diodes for a little more treble roll off and less fizz by soldering on another .001uf cap.  If you reduce the 10K resistor at the op amp output to 1K you will need to increase the cap to .02uf and if you reduce it to 100ohm, you may need to increase the cap further.  I like to leave enough treble in that I can use my tone control on my guitar some at lower volume settings. 

Here are some other mods.  The Mosfet at the end really rocks.   

[MartyMart]

Good- useful stuff and nice to find it all within one post
Cheers for that, I'm sure many people will find it very handy.
Personal "best" of these is the Liquid drive and the '77 Dist+ but my recent Ross with volume mod
is also a little cracker - still not sure that reducing that 10k to 1k or lower is a "good" way to do it though !
I used the other half of the opamp and added 6 components - no biggie ..
MM.