Great Jumpin Germaniums! (Ge Diode and Transistor Reviews & Discussion)

[Travis]

Looking forward to your build Zach :)

I used MP20A for Q1 and Q2 and an AC125 for Q3. Sounds great!

[rocket88]

nice. i have all of those .

any suggestion on hfe and leakage for q3?

[Travis]

I'm not sure of the leakage in mine, and I left it at my studio so I can't check right now

You can take a transistor type that you know to generally be pretty leaky and kinda play around with the ones that are in the right hfe range, which is something like 130-150

And of course the frequency response of whatever trannies you use will also impact the sound

[Travis]

I meant to also say that I think anywhere around 300ma leakage should be fine. Not too strict on numbers

[rocket88]

haven't finished the built yet, as i spent most of my afternoon shoveling, and had to run to help my folks, so i got both boards done, but not wired up, which i intend to do over the next couple days.

i spend some time searching for a good transistor for Q3 for the greasebox, and since it should be leaky i started testing the tungsram AC125Fz's and AC128z VI bought specificy because they're known to be leaky and you know what? i did 150 of each and the leakiest AC125Fz i had was 120uA, and the leakiest AC128z VI i got had 250uA, with the vast majority having leakage under 100uA.

i haven't tested them in any circuit yet, but i can tell you the breakdown:

AC125Fz gain spread 40-110hfe, with the vast majority in the 60-80hfe range, 1 in the 100's, 2 in the 40's, with a nice chunk in the 90's. now i've only tested 1 bag of 150 so it could be i got luck or they really are good transistors. the gains are not "the best" for a fuzzface, but given my experiences with lower gain russians, these should still be great fuzz transistors and will go nicely in a rangemaster. most of the leakages were 100uA-80uA, a few as high as 150uA. i noticed that as the gain went up the leakage increased as well. so all the 60-70hfe transistors are on the lower end, and the 80-100hfe had higher.

AC128z VI gain spread of 50-110hfe, with the vast majority in the 70-90hfe range, 2 in the 100's, and 2 in the 50's, and a good chunk in the 60's too. also, i only tested 1 bag 150, so again it could be luck or it could be these are really good as well. same deal with the leakage as the AC125Fz, the higher the gain the higher the leakage, but these were on the leakier end of the spectrum with a vast majority havnign leakage of 100uA-150uA. i've heard the tungsram AC128's were notoriously leaky and that you get a lot of junk, but all of mine from that bag are usable. i haven't tested them in a circuit, but as with the AC125Fz, these should be great in a fuzzface, rangemaster, etc. from what i can tell from audio clips of effects that have them these have a little more treble, or bite to them.

also, i should note that all 4 bags i have are unopened NOS transistors, and i got them from minifx on ebay, as i have had nothing but good experiences with him, even though i know a lot have not from his auctions of sets of 10 and such. according to the data sheet the gains should be between 75-150hfe, the lower hfe readings may be due to the weather, since even though i've got the heat on, it is a little nippy due to the weather. i can't believe i'm going to say this, but i can't believe that i bought transistors specifically to be leaky and so far all the ones i tested are not.

 i'll post up my sound review as soon as i use them. i'll probably sort through the rest first, but i have to fix my DCA55, as the damn wires are shit and break off at clips every so often, i have to resolder it so i can continue testing and sorting.

[Travis]

Yo Rocket! How's your Greaser coming?

[rocket88]

hehehe, i finally got her done on Friday, sounds great, a little more overdrivey then i thought she would be. it could be because i was testing it in the lab and its fucking cold, even with a space heater it was like 61F. sounds good, i ended up increasing the input cap to 100nF, and now she's really thick sounding, with the 15nF input cap i felt it was a little thin for my taste. for Q1 & Q2 i used 2 MP20a's with hfe in the 60's, and Q3 is a random Ge, i think its 1T2332 or something, that i got from our favorite bulgarian seller in a set of gifts awhile ago that tested as 145hfe and 500uA leakage.

surprisingly on bass there's just a hint of distortion, even when i increased the input and caps to 1uF and still nothing, so i'll have to look over the schematic and see if there's a high pass filter or something in there. but, this is one of my favorites. next up is the FR-69, which sounds like a monster in the videos online. it's based on the ge FuzzRite, with a few tweaks. i've done a bunch of research about transistors to use since it's listed as Q1 is high gain and Q2 is low gain. i would build it this weekend, but i have to head to Pennsylvanian in the Lancaster area for a friends birthday, so if anyones in that area i'll be around and maybe .

i've been meaning to add about the AC125's and AC128's i got too. i finished sorting them all, and they are lower hfe then expected, but low leakage. i won an auction for AC12125uZ VI to compare it to the ones i won before. theoretically these should also be in the 75-150hfe range, so we'll see. still can't believe i'm complaining that i only get low leakage transistors, and that i actually want leaky ones. mostly for more tonebenders, zonk machine, etc.

[Travis]

Did you try some different trannies? What amp did you test with?

It shouldn't sound thin with the 15n. It will have a real midrange peak but definitely not thin.

Maybe try a higher hfe for Q2, like 90 or something. And Q3 is the important one. Try the ac125 even if you don't think it's leaky enough. Once it gets warm again I bet those ac125s will look different..

[rocket88]

Hmmm, I will try higher gains in the 90's and see what happens. I tried it with my mesa m6 , I think that your description that it's was more midrangey then thin is better and mor accurate after playing it again, but with the 100nf cap it thickens it up a bit without becoming wooly. It's definitely a fuzz, especially whe you play cords, and I love the sound, it just seems a little smoother almost overdriven when playing single notes, and the higher strings didn't get much fuzz compared to the lower strings. The temperature could be the main cause, I mean there's all these stories about people putting their ge fuzzface into the freezer to smoother them out and get a certain tone......

In any event this is a great fuzz and an awesome suggestion. I think it's a must have.

[Travis]

Might even be cool to make the input cap switchable on your build so you could have guitar/bass settings!

Personally, my ac30 is pretty sensitive to low end. It doesn't like to be pushed with a lot of low end or it gets muddy, but when you feed it something like the grease box with the 15n input cap you don't really hear any low end loss. The sound comes through very thick and full but just without getting muddy

I bet your Mesa is a lot more "transparent" than my amp so you probably want that full bodied sound coming in the front end. At least that's how I figure the different values may work best for our gear

I do have high quality recording of my grease box but it's a little embarrassing since it's a rough track my band is working on. We're going to change a few things about the track, and it isn't mastered.

But if you wanna check it out I can forward you the track


Btw I saw your FR-69 layout nice! Lemme know how you get on with it. I remember reading David saying he built that with some "reissue" transistors. Like the OCxx you get from mammoth. He said they don't sound right for Benders but he liked using them for the FR-69

[rocket88]

Interesting about the fr-69 transistors, I didn't find that out, just that Q1 was high gain, Q2 was low gain. I'll let you know how it turns out, I'm going to have to verify my own layout, it should be good.

Trust me, my mesa isn't transparent at all. It's an m6 carbide bass amp. It's just a beast. Lol. Even with my guitar amp, which is a bugera v22, which I think is based on some vintage 22watt tube amp not sure which amp, but if sounds great with the 15nF and the 100nF. I might add the switch, one for stock mid the other for thickening the fuzz. It doesn't seem to like my basses at all, which is odd, but either way definitely an awesome fuzz stock or not.

Definitely would like to hear yours so I can compare it to mine. I'm also wondering if because I set mine up with an inverter so I can daisy chain it could also have an effect on how it sounds, even though it's not supposed to.

[Travis]

I think the inverter would likely affect the sound slightly if you changed the ripple cap.

The Grease Box has a ripple cap already (unlike the Fuzz Face, etc) so the inverter could possibly have no effect

I'm still confused why it sounds clean on bass. That's odd. I'll forward the track now

[rocket88]

Sounds good man. I found an error in my build, I think I switched the wires to the sustain pot, which may fuck everything up. What gains were the Mp20a's you used for Q1 & Q2? Also, what diode did you use? I stuck a D310 in, which looks like a little nuclear bomb. Not sure if that makes a difference too.

[Travis]

Since I've been using my build a lot I've just been leaving it at the studio. I can't check right now but I think it was like 70 for Q1, 90 for Q2, and about 135 for Q3. I used a 1n270 for the diode, for no particular reason other than I've used them a lot in the past for the reverse bias in MKIII style circuits

[SpaceCommandant]

Does anybody have any experience with the MP20?
Just wondering how it compares with the MP20a.

[rocket88]

MP20's are similar to MP20a, MP20b, etc. the difference seems to be that they aren't as sorted for gains, so you can end up with a wide range, and in my experience with some of the others that don't have a letter after the number seem to have lower gains more often then the others. Think of transistors like bc108's. All bc108's will be the same, but are unsorted, unlike bc108a (lower gain), bc108b (medium gain), bc108c (high gain).

The russian Ge's doing go in gain order by alphabet, you have to check the data sheets. The regular MP20's will sound good, btw.

[Silver Blues]

So I've got a box of 1T308V on the way. They're to try out a circuit design that I think will be very, very interesting for some of you lovers of gnarly fuzzes. Excited to try them out!

[Silver Blues]

Got my order from our Bulgarian friend... got to say I'm quite pleased. This is what I ordered:

And this is what I got in addition to that:


So that's

25 1T308V
2 2SA49 and a 2SA53
3 GT2307 and 2 GT2306
38 (actually they're SFD106, not D9D. My mistake)
13 D9I (or possibly 11 D9I and 2 D9G)
a random D18
40 capacitors of various values
a handful of what look to me like bead inductors (not super useful but hell if I'm complaining)

Haven't tested anything yet (just got it an hour ago) but it looks amazing. You can add me to the list of people who recommend this guy.

How long 'till I can join the Ge Deathstar development crew?

[rocket88]

Well you're a brother from the great white north, so I say you're in.

Btw, did you build the blueberry & did you read what I wrote about the difference between the BJFE and Bearfoot.

[Silver Blues]

Haha awesome

No, but I'm going to do it this weekend. I did, and I think I'll have to build the BJFE version as well.