Modifications on Green Russian Muff

[azrael]

Recently rehoused an old Green Russian Muff to a more pedalboard friendly 1590BB.

Anyway, to get to near unity gain, it needs the volume to be cranked to about 3 o'clock to max! I'd like to change this, with minimal modifications or change to the overall tone. Would the best way to do this be to change the last stage's resistor values? Perhaps an emitter resistor of 1K? I believe that would increase volume with minimal tonal variation. Is this right? And if so, will this be enough gain?

Second, I modified an NYC Muff for my bassist once, and put an LPB in front of it (inside the box of course) to give it more "grunt", similar to what I read is going on under the hood of the Blackout Effectors Musket Fuzz. Worked great! I thought that any cleanish boost would have similar results.
However, I tried the same idea with this Muff mod, this time using a SHO, and did not have the same results. What's wrong here?
I may have decreased the input resistor in the NYC to 3.3K, decreasing the input impedance. Can't remember, unfortunately, been a while! Is this the key factor here? I'm almost positive it has something to do with impedance. Is it due to the difference in input/output impedance of the SHO/LPBs?

[Barcode80]

2 things:

1) I can't believe you rehoused a green muff. They are worth quite a bit of money in original condition.

2) there should be plenty of volume on tap with a muff, so you may have something wrong on the board. post transistor voltages and we may be able to spot the issue.

[azrael]

1) It was actually not in working condition when I received it. It's for a friend, and he wanted it thus. Have mercy! It's actually one of the later 90s ones, right before they converted to black Russians, though. He also owns another Green Russian, and older one, and that one is staying stock, if that makes you feel any better!

2) He says he keeps his other Russian around 1-2 o'clock. The collector-emitter resistor choices for Q1-3 result in a much lower gain circuit than say, an NYC or something, I believe. 15K/390 = 38x, whereas as Ram's head has 15k/150 = 100x?

I'm at school right now, but I'll post some voltages when I get home.

Any idea on the booster situation?

[azrael]

Finally got it in my hands, here's the voltages:

fresh battery at 9.56V

Q1: C > B > E
4.85
0.76
0.14

Q2:
5.02
0.74
0.13

Q3:
4.87
0.74
0.12

Q4:
5.83
1.59
0.99

I believe that Q1-3 are operating fine, but Q4's voltages look a bit off?

[Barcode80]

Q2 and Q4 look pretty high. They should float around 4.5 to 4.8 for good gain. try tuning the collector resistors, raise the values a bit.

[azrael]

Okay, not surprised about that. I remember measuring some values and finding some to be as far as 10-20% from their written value.

[azrael]

I ended up increasing Q2's collector resistor to 15K, and Q4's collector resistor to about 13K. Got them both to about 4.7V.

Gain got better, with unity gain around 1-2 o'clock. Thanks, Barcode.


If anyone has a better idea about the "Musket Fuzz" like idea, and why the LPB works better than the SHO, I'd love to know.

[Barcode80]

What do you mean "works better?" Better for what?

[azrael]

In a previous Muff build, I stuck an LPB in front of the Muff to get more grunt out of the circuit. Sounded very much like a Blackout Effectors Musket Fuzz (which i heard is a modified Civil War Muff + some sort of boost in front).

I put the SHO before this muff, but it does not seem to do the same thing. Just seems to boost the volume.

[Barcode80]

You're probably getting the LPB to overdrive some. the SHO can have a bit more headroom. FYI, the LPB is just a single drive stage of the muff with no clipping diodes. It's a good for more gain.

[azrael]

Oh, I looked into it more, and it definitely has to do with the input impedance. The LPB's is much lower than the SHO, so it doesn't preserve as much high end, and as a result, can "sound fatter".

But I also believe your theory, as the LPB isn't as clean as the SHO.


BTW, the Green Muff is coming back to me once again, it doesn't quite match the sound of his slightly older (and all original ) Green Muff. So I'm getting my hands on both of them, and modifying the rehoused one to sound more like the old one. Needs more gain/distortion, and not necessarily output this time.

I'm thinking of decreasing one of the resistors in front of Q2 or Q3 a bit to accomplish this. What do you think?