Civil War / Green Big Muff - which transistor HFE is ideal?

[Fuhgawz]

I have some KT3102 transistors and also some Russian silicon diodes with the colored stripes that you can see on the gut shots of Kit Rae's website. The issue is though, I measured the transistors and the hfe ranges from about 400 to 850, with most of them in the 450-550 range. Yeah, I know, "just try different configurations and see what you like" and "EHX/Sovtek probably just put in whatever they grabbed first".

I'm just wondering if someone actually tested this already so I can save myself some time. I'm also wondering if anyone here has disected a really good sounding Sovtek Green/CW Muff and measured its transistor gain. Maybe someone built a clone with specific hfe-values that made it sound like an excellent original? Perhaps someone can say something like "don't use hfe over/under xxx for Q1/4"? In other words: any info on actual Russian Muffs is appreciated!

[bluesdevil]

I plan on building up a Civil War Muff as well soon.
Give this a read:
http://www.diystompboxes.com/smfforum/index.php?topic=88048.0

I wouldn't get hung up on exact gains, other things shape the sound more.
Good luck on your build!!

[Tony Forestiere]

Give this a read:
http://www.diystompboxes.com/smfforum/index.php?topic=88048.0

Nice job of "dumpster diving". Your "search-fu" is impeccable.   

[bluesdevil]

Give this a read:
http://www.diystompboxes.com/smfforum/index.php?topic=88048.0

Nice job of "dumpster diving". Your "search-fu" is impeccable.  

Had a funny reply here, but jokes sometimes don't translate.
Thanks!!

[Tony Forestiere]

Give this a read:
http://www.diystompboxes.com/smfforum/index.php?topic=88048.0

Nice job of "dumpster diving". Your "search-fu" is impeccable.   

Sorry, I don't understand..... is that an insult or compliment?
Just trying to help OP.

It was absolutely a complement! I apologize if it appeared any other way. You uncovered a rather valuable piece of information that answered the OP's question perfectly. A great read resurfaced. Thank you for linking!

[bluesdevil]

 :icon_redface:No need to apologize..... I was trying to be funny, but didn't mean to come off as sarcastic. 

[LucifersTrip]

I'm just wondering if someone actually tested this already so I can save myself some time. I'm also wondering if anyone here has disected a really good sounding Sovtek Green/CW Muff and measured its transistor gain.

You don't actually have to rip it apart if you take the transistor voltages...here's a cool thread:
http://www.diystompboxes.com/smfforum/index.php?topic=98421.msg860294#msg860294

I own an original Green Muff that I really love.  Q1-3 collector voltages were in the 4.5 - 4.75 range and Q4 was a little over 5V.

You should be able to work backwards to get the estimated hfe's

[Fuhgawz]

Thanks guys! I'll go read and measure voltages.

[LucifersTrip]

you'll see that when you reach 100-150 hfe and higher, there's just a slow change (drop) in collector voltage as hfe increases. the faster change is when you're below 100....which is why most say there's little difference in what transistor you use, since most moderns are easily over 100 hfe.

edit: found my green russian voltages

[Fuhgawz]

Okay, so maybe I went a bit overboard with all this. Here are gain and voltage measurements between three sets of transistors:



As you can see there are only very slight differences between the voltage readings of the high, medium and low gain sets. All of them fall within the expected range. I used the Bubble Font Green Russian schematic btw, as found on Kit Rae's website, with the 470pF capacitors and 2k7 resistor at the emitter of the last transistor. If you change the 2k7 resistor to a 2k resistor, as found on GGG's Green Muff schematic, you get the following voltage readings for Q4: C: 4,57v, B: 1,36v and E: 0,85v ('low gain' transistor set). It appears after a quick switch that it sounds a bit more sharp/distortion-y with the 2k resistor and more fuzzy with the 2k7, but maybe I should put it on a switch and do a better comparison. Based on pictures and 'LucifersTrip' voltages it appears that 2k7 is the 'correct' resistor though. I don't really know where GGG's 2k came from, because I did not find it anywhere else. Does anyone know?

Moving on to the sound differences between the transistorsets. When changing one set out for the other, I did not notice a big difference. Changing out transistor sets takes time though, so I made simple recordings of a Mastodon riff and compared them:



As you can see from the end of the waveforms, the amount of sustain is nearly identical. I did notice a small difference in sound though when playing them back. As you go from low to high the sound gets slightly less boomy and more buzzy, or less bass and more treble, if you prefer. The difference is not that big though and you can make up for it with the use of the tone knob.

So my conclusion is the same as what has been said before, that hfe doesn't really matter in a Muff. I should compare these Russian KT3102's with some 2N5088's some time though. But that's for another day. Thanks for reading!


EDIT: I have since recorded and tested the 2N5088's vs the KT3102's with similar gains. There is a small difference in sound, but not very big. The 2N5088's seem to have more mids, where KT3102's are darker sounding with less mids. The Russians do seem a bit more balanced though, but as I said the difference is small and I think you could build a convincing Sovtek Muff with these modern transistors. I have also recorded and tested the 2k vs 2k7 resistor from the emitter of Q4. Like I found earlier, with the 2k it sounds sharper, which also comes through on the recordings, and as expected the waveform is slightly bigger / louder with the 2k. I prefer the 2k7.

I know, these are not very strange results and they are in line with what others found out. Like others said, the 2k will be slightly louder than 2k7 and there is only a very small difference in sound between transistors. I do prefer to test things myself though, because I have come to find out that I do not always with agree with 'some guy on some internet forum'.

Next up: Russian diodes!

[LucifersTrip]

very good job...yes, as expected when you use modern mid - high gain transistors.

but if you went through that trouble, why not try ones with hfe around 100  where you'll probably hear a bigger change?

[jrod]

Yo Fuhgawz! Thanks for posting your experiment!!! I think that's some good info!

[Fuhgawz]

very good job...yes, as expected when you use modern mid - high gain transistors.

but if you went through that trouble, why not try ones with hfe around 100  where you'll probably hear a bigger change?

Because that really isn't what this topic is about. It started when I purchased some KT3102 transistors. The ones with the white and green dots that are in Sovtek Big Muffs, from part of the Civil War era through to the big box black russians. The same vendor also had the diodes with the yellow, green, blue and black bands, that you can see on the gut shots at Kit Rae's website. All schematics I've seen call for either 1N914s or 1N4148s, but these clearly look different. Just look at the gut shot of your own Muff. Those aren't 1N914 or 1N4148.

The idea was, if I have all these original parts, I want to build a Sovtek Big Muff that comes as close as possible to a really good sounding original one. Since I read on several places that there seem to be good sounding and bad sounding Sovtek Muffs, some experimentation is required and that's what I'm trying to achieve here. To see where the difference can be and to find out what sounds best to my ears.

EDIT: I will say this about lower gain transistors in Big Muffs. A few years ago I built a Triangle circuit. Of course, original transistors cannot be found and the circuit differences where vast, so I tried different transistors myself and the ones that came out on top where regular old 2N3904s with hfe's of around 250. Sounded more clear and defined than higher gain transistors like 2N5088 or BC239C in that circuit. I didn't expect it, but it was a clear winner.