Selmer Buzztone Build Report

[jmusser]

I just heard of this circuit a couple weeks ago  http://britamps.mysite.wanadoo-members.co.uk/selmer/schematic/buzz.html  I believe Brian Wenz may have unvailed it, because one post with his name, is about all the info I could come up with. He got his to work, so that's why I was trying to get his attention on the forum. I like trying to bring thes ancien circuits to life. The circuit is drawn backwards from the way we're all used to seeing it, with the input on the right and output on the left of the schematic. The schematic is real fuzzy also, and the component values are hard to make out. If that's not enough drawbacks, the thing runs off negative 3 Volts! The transistors are all 2N2613s, which crosses to a NTE102A germanium. I tried 3 Russian GT309Bs in there, and it was deader than a hammer. I got hold of Gez, and his thoughts were that I needed to adjust the collector resistors to get somewhere around half supply voltage on Q2 and Q3. I tried that with the germaniums, but it was still no go. I pulled those out and subbed in 2N3906 Si transistors, and started adjusting the 5K pots I had put in place of Q2s 1K, and Q3s 1.5K, and she jumped to life! The 2N3906 transistors were noisy, so I went with 2N5087s. That cleared up most of it, and focused the sound a lot more. Q2 collector voltage can be adjusted all over the place, depending on what tone you like. If you want the BUZZTONE that this thing is named after, adjust the Q2 collector voltage to around 1 Volt. It's as buzzy as any square wave fuzz you've ever heard. I believe it's as close to the "Incense and Pepperments" tone, as anything I've built. With Q2 collector voltage adjusted to .7 Volts, gives you a full and bassy tone, and up to around 2 Volts gives a nice grind. I'd leave that pot on top of the enclosure. The 25K Depth pot, seems to do nothing at all, and needs to be turned completely off to make the circuit work. This thing is loud, and has a gob of sustain. The sustain goes into "American Woman" land, with the gain dimed out on the little Epi Tube amp. The last thing I tried, was a higher gain Russian germanium GT308B in Q2. I like it's tone in there, but if you want the intense buzz, you won't get it with the germanium. It sounds good, but different and of course, less harsh. Q3 collector voltage was set and left at around 1.6 Volts. I will probably put the 2n5087 back in Q2 position and set it's collector to Buzzzzzzz!!!!

[gez]

The 25K Depth pot, seems to do nothing at all, and needs to be turned completely off to make the circuit work.

My preference would have been to leave the collector resistors in tact and try different values for the base resistors of 2nd and 3rd trannies. 

Anyway, glad you got it working!

[jmusser]

Well, I could certainly do that. I have it working, and sounding pretty good, but then again, I had the 60s Style Fuzz sounding pretty good with Q2 turned totally backwards! I'm guessing that we're talking about the 22k for Q2, and the 15K for Q3? To me, it looks like the Depth Pot's job was to adjust the voltage to Q2 base, but I sure don't know what all these resistors are supposed to do.  Should I substitute a pot for each of the resistors, and see if I can adjust them to get the circuit working that way? I'd really rather have the circuit to sound more like it was intended. BTW, I don't know why the original germaniums didn't work, but I plugged them into the Sola Sound Tone Bender afterwards, and they worked fine. I have found this whole thing interesting, that I have been able to bastardize the original designs on these two circuits, and have them not only work, but have totally different tones! I'm sure if I finally get this working like you're talking about, it will have to sound different than it does now, especially with 3 germaniums. This would be a good circuit for me to learn on, because it's about as basic a 3 transistor circuit as I've ever seen.

[MartyMart]

I'd love to have a proper look at it, just can't read that schem picture at all !!
Is there a clearer one around ?
Well done getting a decent tone out of it !

Marty.

[gez]

I'm guessing that we're talking about the 22k for Q2, and the 15K for Q3? To me, it looks like the Depth Pot's job was to adjust the voltage to Q2 base,

By the look of things, with the wiper fully counter-clockwise the pot forms a divider with the input resistance seen at the base of the transistor and divides down the output from the buffer/input stage, so you get less fuzz.  With it fully shorted you get the full voltage applied to the input of Q2 and so more fuzz. 

With stock values you'd probably get Q2 and Q3 biasing towards saturation, so making the base resistors (22K and 15K) larger would help bias the collectors where you want them.  Would also provide more fuzz I should think.  You’d need to post voltages with the stock values in place to decide what would be best though.

The voltage measurements you gave me with the Ge trannies in place made no sense.  There was virtually no voltage drop across the base-emitter junctions of all three transistors, suggesting shorts with all three or they’re damaged.

[jmusser]

Gez, sometime this evening, I'll put the stock resistors back in the circuit, and let you know what I get with germaniums, and see what has changed, since I know how to put the thing back and make it work again. Marty, I have a hand drawn schematic that I built from, that I drew up from the original. I put the original in paint and blew it up so it would be some what easier to make out the values. I can draw one back up and send it to you, sense the one I have is highlighted now.

[gez]

By the look of things, with the wiper fully counter-clockwise the pot forms a divider with the input resistance seen at the base of the transistor and divides down the output from the buffer/input stage, so you get less fuzz.  With it fully shorted you get the full voltage applied to the input of Q2 and so more fuzz. 

Whoops, scrub that.  It's just a bog-standard inverting amp with variable input resistor to control gain.  The way it's drawn up (back to front) confused me!

[MartyMart]

Thanks Jeff that would be great !
Is it just "drawn" in a wierd way ? it all looks backwards to me !!

Marty.

[jmusser]

OK Marty, you should have the new drawing in your E mail. OK Gez, I put everything back the way it was (stock resistor values, and Russian germanium PNPs), and all the voltages look about the same, but I'll post them again for anyone else that's following this thread. Note: these are negative voltages. Q1 c= 1.05, b=.831, e=.795. Q2 c=.314, b=.054 e= 0. Q3 c=.308, b=.047, e= 0. The transistors are OK, and were again subbed into the Sola Sound Tone Bender, and worked just fine. The Depth pot does nothing to change the voltage on Q2. it's probably not supposed to, but I thought I'd mention it anyway. I took that value to be 25K, although, it looks something like 26K. If you interpreted it a different way, let me know.

[jmusser]

Man.... I hate to write this.... Gez ole buddy, I had my germanium transistors upside down all this time! I went back to look at the Sola Sound, and I had plugged the transistors from the Buzztone in exactly like I took the other ones out, so that's why they worked. When I put them back in the Buzztone, I put them in the way I'd always had them. One thing in my defense, is that the Russian GT309b transistor has THE weirdess pinouts I've ever seen. The emitter is in the center with a dot, the collector is a pin welded to the case. I thought that was the base, until I looked at the spec sheet again. Anyway, when I finally found the error of my ways, and plugged them in right, guess what? The thing lit right off!!! I haven't had but a couple minutes to play around with it, but it has plenty of sustain, and pretty good buzz. I actually think the buzz is way more intense set up with Si transistors the way I had it. The 25K Depth takes it from a fuzz to no fuzz condition. I guess if there is a positive thing out of this, it's that I found another way to make it work, and get new tones out of it. If I hadn't had the transistors in upside down (or in the U.K. wrong way up), I would have never experimented like I did with the collector voltages. So, you have every reason to say "I told you so" when you said the transistors were either bad or in wrong. I'm going leave this confessional now, and go throw up!

[jmusser]

I've been running the old Buzztone through the mill. I found out, that the 5 K pots really didn't make that much difference, with the exception of the Q2 collector doing some tone changing.  I fiddled with several different gains of germanium and silicon transistors. Right now, I have to go with the 2N5087s in Q1 and Q3 positions, and a high gain GT308b Russian germanium in the Q2 spot. The fuzz is just way more intense that way, and the germanium takes the rawness out of the tone and gives better breakup. Another 2N5087 sounds great in the Q2 position also. All of this is just going to be a matter of personal taste anyway. I subbed the 25K pot with a 100 K pot for the Depth adjustment, but the fuzz is as intense with the 25K as it's going to get. This is a good sounding circuit, and goes to a nice OD with the change of the pickup from neck to bridge. The guitar volume needs to be maxed, and the Depth pot of the effect maxed too. I appologize to all the forumites who have been following this mess for having screwed up something as basic as transistor pinouts, but you get used to a certain package style and it's hard to change habits I guess. Anyway, enjoy. If anyone wants to build this thing after all this, I can E Mail you my hand drawn copy to go by.

[MartyMart]

Jeff was raving about this, so I quickly put one together in 1,1/4 hrs this morning
before work took over ...
My fastest and first 3 volt circuit too
His re-draw helped an awful lot, as the original was "right to left" as far as
input - output goes, Jeff's is "left to right" making much more sense to me  !
Using a 5k trim pot to Q2 gives you "HUGE" amounts of fuzz and is a serious
improvement, though it does make the 25k pot all but useless, replacing that
with a 10k - 22k resistor would possibly make more sense in this case.
I used some Si BC557's throughout and they work VERY well, giving a Fat
and Nasty Fuzz, very "Ge" sounding IMO
Guitar volume can clean things up quite a bit, so my only external pot will be
the 100k volume.
MODS : Adding a BM tone stack may be nice or the SWTC before output.
THis is "Nasty & LOUD"
Very good sounding circuit   
Thanks Jeff and anyone else who chipped in,

Marty.

EDIT:
I had a mistake on vero, tops of Q1/Q2 were directly connected !
However it still "worked" this way even if Q2 was removed !!
Now the 25k pot makes sense as an external "fuzz" pot 
Marty.

[jmusser]

Thanks Marty. I kind of ramled on and on about this as i was sorting it all out (and discovering Russian germanium pinouts), but it ended up being a pretty wicked circuit all the way around. As far as I know, Brian Wenz is the one that brought the circuit to the attention of the forum initially, but he didn't really elaborate much on it, and sort of left the country after he built it. With the sort of old and abscure circuits like this one, I think it's fun to wring them out, and see what they have to offer. After you build them, it makes you kind of wonder what the original would have sounded like. It looks like Selmer as a company was around a long time, and heavy into the amp business. The Buzztone was sort of a periphleral product for them. I believe they also have some sort of a fuzz wah too, but I can't remember for sure. I think this also may have been a UK company, and I have had never heard of them at all, up until Brian's post. Of course, what do those guys in the UK know about amps and effects!