anyone have the jeff mod for volume balance?

guys i have a sd 18 II dose anyone have the jeff b. approved mod tech sheets to do the volume balance .
when im on the gain channel and switch to the clean it jumps in volume i have seen some talk about a Jeff B. approved mod to volume balance the channels thanks

Yes, it is VERY easy to do this mod. Here is the "offical" mod:

"Superdrive 18
Normal / Drive volume balance mod.

OK, here’s the disclaimer: Due to the fact that in certain instances the potential for death or bodily harm could exist, we are recommending that a qualified service technician perform the following work. Budda Amplification will not be responsible for the death or injury of anyone performing this work, and substandard workmanship could also lead to the product warranty becoming null and void.

In the center row of components (yeah, the ones all in a row like little soldiers), count 18 components in from the input jack side of the board (total of 10 resistors and 8 capacitors). It should be a 1M resistor (brn,blk,grn). Parallel another 1M across it thereby reducing the total resistance to 500K. This should bring up the Drive volume with respect to the Normal volume. If it doesn't bring it up enough, go to a lower value resistor like a 680K or a 470K.

And now for the adventurous:
For variable control of the Drive Channel level, substitute a 100Kohm resistor and a 1Mohm potentiometer, wired in series, in place of the 1Mohm resistor. If you’re going to mount the pot somewhere on the chassis, more than likely the rear panel, it’s probably best to use a dual-conductor co-ax cable with the shield connected to ground on the board end only."

now...just to be sure. This is dead simple. I did this mod and it took about 20 minutes total.
All you have to do is take off the backplate, then undo the 4 screws holding the amp to the cabinet, take out the cab, you count 18 component in from the left (and double check that it is a 1 Mohm resistor there) take another 1 Mohm resistor that you bought, and make little hooks on the resitor ends...solder it in parallel with the existing 1Mohm resistor, which will halve the resistance at that point, and put it all together again.

I did the mod, and felt no need for a pot in there instead of a resistor. The 1Mohm parallel resistor did the trick totally for me on my SD-18. I take no responsibility for your safety on this though, you have to know what you are doing and how to bleed the power caps, to safely work on the amp...but it is dead simple...

Good luck!

The mod is pretty good for the sd 80 can post this if needed..

Does it matter what wattage the 1M resistor is? I went to the Shack and they have several different 1M resistors...

Thanks!

StompBoxBlues wrote:

Yes, it is VERY easy to do this mod. Here is the "offical" mod:

"Superdrive 18
Normal / Drive volume balance mod.

OK, here’s the disclaimer: Due to the fact that in certain instances the potential for death or bodily harm could exist, we are recommending that a qualified service technician perform the following work. Budda Amplification will not be responsible for the death or injury of anyone performing this work, and substandard workmanship could also lead to the product warranty becoming null and void.

In the center row of components (yeah, the ones all in a row like little soldiers), count 18 components in from the input jack side of the board (total of 10 resistors and 8 capacitors). It should be a 1M resistor (brn,blk,grn). Parallel another 1M across it thereby reducing the total resistance to 500K. This should bring up the Drive volume with respect to the Normal volume. If it doesn't bring it up enough, go to a lower value resistor like a 680K or a 470K.

And now for the adventurous:
For variable control of the Drive Channel level, substitute a 100Kohm resistor and a 1Mohm potentiometer, wired in series, in place of the 1Mohm resistor. If you’re going to mount the pot somewhere on the chassis, more than likely the rear panel, it’s probably best to use a dual-conductor co-ax cable with the shield connected to ground on the board end only."

now...just to be sure. This is dead simple. I did this mod and it took about 20 minutes total.
All you have to do is take off the backplate, then undo the 4 screws holding the amp to the cabinet, take out the cab, you count 18 component in from the left (and double check that it is a 1 Mohm resistor there) take another 1 Mohm resistor that you bought, and make little hooks on the resitor ends...solder it in parallel with the existing 1Mohm resistor, which will halve the resistance at that point, and put it all together again.

I did the mod, and felt no need for a pot in there instead of a resistor. The 1Mohm parallel resistor did the trick totally for me on my SD-18. I take no responsibility for your safety on this though, you have to know what you are doing and how to bleed the power caps, to safely work on the amp...but it is dead simple...

Good luck!

Hi every one, new to this forum. I was following this instructions and counted the components as described above but the 1m resistor on the SD landed on the 17th not 18th. I tried paralleling another 1M resistor but it didn't notice any difference. Other note, I bought the 1M resistor from radio shack but why is it way smaller than the resisters in the Budda, I'm using the right resistor? Please help if you can.

jimmi V wrote:

Hi every one, new to this forum. I was following this instructions and counted the components as described above but the 1m resistor on the SD landed on the 17th not 18th. I tried paralleling another 1M resistor but it didn't notice any difference. Other note, I bought the 1M resistor from radio shack but why is it way smaller than the resisters in the Budda, I'm using the right resistor? Please help if you can.

No, in both my SD's (a 18 and a 45) it is most definitely the 18th component in from the left side (component meaning cap, or resistor). It is right after a capacitor, and the bottom of it, the trace goes directly to the one side of the adjacent cap, where the other side of the restistor trace goes from resistor over to the top of the resistor to the right I believe. It is definitely the 18th though.

Also, that resistor you describe, I wouldn't use it even if it probably works. It is a 1/4 or even 1/8 watt resistor you have, where I think the one in the Budda is a 1/2 watt.
When you do the mod, half of the current will end up going through each resistor, so probably a 1/4 watt is okay, but I'd stil want overkill, and go with a 1/2 watt.

But that you aren't seeing it as the 18th would worry me.