Bohm Trickverzerrer..er..er..er..er

[digi2t]

Found this circuit in my travels of late. Some D.D.R. Cold War (I think) era fuzz.



So, seeing as how it didn't seem to have too many parts, I decided to breadboard it. It's a weird sounding fuzz. The video doesn't quite capture the "synthetic buzz" that rings through with the drive full tilt. As a matter of fact, (to me) it only sounds decent flat out.

The only difference between the drawing and my breadboard; I'm using a mix of BC109 and BC109B, the diode is a 1N4148, and the Sensetivity - P2 trimmer is 50K (not 25K as the drawing). The 25K trimmer just wasn't doing it for me, so I auditioned different values. With a 50K, you can really dial in the third tranny, and get it to bite a bit harder. At 35K on the trimmer, it shines the best. That got me to thinking, maybe that's why R6 is marked "X". Maybe the required resistance here is supposed to be matched to the tranny, and the 25K handles the rest? Something like a 22K resistor in the R6 slot, and a 25K trimmer, would work on my setup. Maybe the Motherland was out of 50K trimmers? Who knows? 

Here's my breadboard test;

I don't know what to make of it. Maybe that's why the wall came down? East German's wanted better fuzz boxes? 

[Earthscum]

I had to dig around a little bit. What a funkee munkee this thing is, eh?

Böhm Verzerrer | DiscoFreq's Effects Database

http://www.vermona.de/70er/verzerrer.htm

"data sheet"

[DiscoFreq]

I should listen to that when I'm at home to see if it sounds similar...

I have several of those Trickverzerrers because they were often cheap when I saw them (I gave away a few, but I think I still have about 5 of them).

[LucifersTrip]

Thanx for posting the video/build report....It's great to see especially since the obscure vintage fuzzes don't get much attention here (I've posted detailed vintage fuzz build reports with little or no replies...hahah)

I'm sure you saw this thing discussed on the other forum last week, but that thread didn't go too far, and no build reports.

There are some small oddities on this one:
That is a .22uF electro at the input? Have a choice between .22 and .47?  As you noted, the mystery R6? Why not increase R7 or mark as 100K+ or increase the trimmer? Is Q3C voltage marked as .1 - 5v? Am I reading it wrong, but if the + 9v battery goes thru the 270, why is it marked 9v to the left of the 270?  negligible difference?

I'm not totally surprised at the synth-like fuzz you're getting. I would guess the BC109's are much higher gains than the ones used in the original and I get similar synthy compressed tones when using higher gains in a Fuzz Face....and Q1/Q2 here are similar to a FF.
The BC109's I have are in the 250-300 Hfe range and I'd guess those SC206/7's would be closer to 100.

In addition, the diode is germanium:
http://english.electronica-pt.com/db/cross-reference.php?ref=GA102

What are your actual voltages? Did you get close to what was indicated on the schematic?  .1v on Q3 collector at any point?

thanx again for the report


edit:

[DiscoFreq]

I have no audio here to listen now, but I remember it as an extreme fuzz (or at least capable of extreme and harsh fuzz), not really synth-like, though I also combined them with octavers and filters to get synth sounds...

[digi2t]

Thanx for posting the video/build report....It's great to see especially since the obscure vintage fuzzes don't get much attention here (I've posted detailed vintage fuzz build reports with little or no replies...hahah)

Thanks. It doesn't necessarily have to be a fuzz, but I love these weird old hen's teeth. They're like little "boxes of chocolates".... Yes, you are correct, I did see it "over there".

There are some small oddities on this one:
That is a .22uF electro at the input? Have a choice between .22 and .47?  As you noted, the mystery R6? Why not increase R7 or mark as 100K+ or increase the trimmer? Is Q3C voltage marked as .1 - 5v? Am I reading it wrong, but if the + 9v battery goes thru the 270, why is it marked 9v to the left of the 270?  negligible difference?

I noticed the electro as well, but I'm using an ordinary .22uF cap here. I did try a .47uF, but found it a bit dark. Maybe the .47uF would be better suited for bass? With a 25K trimmer, it's impossible to achieve the .1 - 5v sweep on Q3C. As I mentioned before, I'm thinking that maybe R6 was a "make-up" value, to compensate for the inconsistancies in transistors of the time. Really a guess on my part here. Maybe just made it easier for production purposes at the plant at the time. 100K resistor, 25K pot centered, jumper R6, if you read "x" voltage on the collector, then plug in "y" resistor as R6. Next....

With 9.10v at the battery, I'm getting 8.87v after the resistor. Maybe if my battery was fresher, I would get closer to 9v, but the voltage drop here is normal. Could it be that at production, they tested with power supplies set to give them 9v after the resistor? Or, did they just round up the numbers for the drawing, to throw off those cursed American spies!

I'm not totally surprised at the synth-like fuzz you're getting. I would guess the BC109's are much higher gains than the ones used in the original and I get similar synthy compressed tones when using higher gains in a Fuzz Face....and Q1/Q2 here are similar to a FF.
The BC109's I have are in the 250-300 Hfe range and I'd guess those SC206/7's would be closer to 100.

Honestly, I did try the BD139 / PN2369A combination a la Axis Face, along with some others (2N2222, 2N4401, et al), but they all sounded, well, like ass to my ears. Then again, I must add here, I use SS amps, so I don't have any tubes to push. Maybe with a tube amp, lower gain transistors transistors would be just fine to push the preamp section along. But with SS, the pedal has to do most of the work, especially with a super-clean amp like my G-212. Another reason for which I swapped out the Germ. diode for Si. I did try a few different Ge. diodes though, with the 1N270 sounding the best for a mellow fuzz clip.

What are your actual voltages? Did you get close to what was indicated on the schematic?  .1v on Q3 collector at any point?

My readings right now;
Voltage across R1 = 4.8v
Q1E = 3.6v
Q2E = 4.5v (Adjusted with 50K trimmer, instead of 47K resistor)
Q3C = set to 0.5v via P2 trimmer (This was set with the guitar plugged in, volume on guitar on 10, hand muting the strings. Changing anything here will affect the voltage reading, but with the BC series trannies, 0.5v gives the best output from Q3. With the 50K trimmer, you can cover the entire 0.1 - 5v range. Set it to where it sounds best.)

I've yet to figure out the "2v" at Q1B though. 0.2v would make sense as voltage across C1. Or maybe my eyes are missing something here, because to ground I get 4v here.

Any and all thoughts are, as always, greatly welcome  .

[Earthscum]

I was wondering if you were pushing tubes or silicon, lol. I like building through SS, honestly. I can hear what's possibly going to come out of an amp, but I also play Peavey SS amps, so if it sounds like crap at home, there's a good chance it's gonna sound like crap through my rig.

The sound you're getting (at least from what I can hear in the clip) seems like it would be better suited for heavy grinding, like Db or 7string guitar, or bass, IMO. I actually kind of like the sound... it's not singing, but more like grandma smokey yelling at the neighborhood kids.

[digi2t]

I was wondering if you were pushing tubes or silicon, lol. I like building through SS, honestly. I can hear what's possibly going to come out of an amp, but I also play Peavey SS amps, so if it sounds like crap at home, there's a good chance it's gonna sound like crap through my rig.

The sound you're getting (at least from what I can hear in the clip) seems like it would be better suited for heavy grinding, like Db or 7string guitar, or bass, IMO. I actually kind of like the sound... it's not singing, but more like grandma smokey yelling at the neighborhood kids.

I never was too keen on tube amps, although I love listening to a dimed Marshall. It's just that tubes end up coloring my tone to some degree, and I don't like that. I prefer to use an uber-clean SS amp, and let the pedals do the work, whether it be digital, or analog. My normal rig is powered by a QSC-1450 power amp, so the pedals have to be spot on for the tone I'm looking for.

Maybe I'll run this puppy by my daughter's boyfriend, he plays bass. If it works, maybe I'll box it for him. We'll see.

[LucifersTrip]

Any and all thoughts are, as always, greatly welcome  .

thanx for responding to all my points above...I have nothing left to do but breadboard this myself...and I'll try to remember to report back here.

I have to say that I think the biggest "problem" I've seen builders make time & time again when trying to duplicate the sound of vintage distortions is using much higher hfe's than the original....and it's easy to do since most modern silicon  has hfe >150 or 200.  I will definitely experiment with a full range for this one....

[digi2t]

I just got some BC639's, so I'm going to try those. They're lower hfe (40 - 160), so it'will be interesting to see what they produce.

Stay tuned...

[digi2t]

OK, I've made the recording below. Q1 is a BC109, and Q2 - 3 are BC639's. The diode is a 1N270. I was VERY surprised by the result. As a matter of fact, I had ordered the BC639's for something, but I can't recall what exactly right now  . They sure sound good in here though.

I have 3.5v on Q1E, 4.5v on Q2E (adjusted via 50K trimmer, replacing 47K resistor), and Q3C is set to 0.1v (via P2) with guitar plugged in, guitar volume on 10, hand muting strings, (and all flourescent lighting within sight OFF!  ).

I'm recording directly into a BOSS BR-600, no added effects. Guitar is a Dillion Korina Explorer, GFS Dream 180 bridge pup. I'm going from minimum drive, and bass, mid, and treble tone. Then 1/2 drive, bass, mid, treble. Finally, full drive, bass, mid, treble.

http://www.soundclick.com/player/single_player.cfm?songid=11557776&q=hi

Sounds like a fuzz monster to me!

[Earthscum]

Sounds like a fuzz monster to me!

+1 to that!!! Damn... I gotta dig through and find these low gain Si's I have, try this out. Even this one I would say to run by that bassist.

[digi2t]

Here are the hfe readings for the trannies, as per my Wavetek Meterman DMM;

Q1 = BC109 - hfe 201
Q2 = BC639 - hfe 131
Q3 = BC639 - hfe 129

These are what I have on the breadboard right now, in the recording as well. Got the bassist coming over tomorrow, that's going to be interesting. I'm going to try the 0.47uF input cap on bass as well. I tried it on guitar, but it's a bit dark for my liking. I'll record a bass sample as well.

[pinkjimiphoton]

does sound synthy...like an uglyface almost!

i like it!

it's in the build list now.

[digi2t]

Well, I promised a bass track with the fuzz, so here it is. Same circuit as the guitar track, .22uF input cap.

Same play as the guitar track, low, medium, high gain, turning up the tone through each gain stage.

Bass is a Schecter 5 string, EMG Hi-Z pups (both on, onboard EQ set flat), fuzz, BOSS BR-600 (no added effects).

My profuse apologies for my crappy bass playing. Not my instrument by any stretch of the imagination  

http://www.soundclick.com/player/single_player.cfm?songid=11560147&q=hi

Goes from ultra low velcro, to real buzz-saw. Me like  .

Enjoy.

[digi2t]

Alrighty, here's a vero;



There is a vero already around (E. Coffey), but right off the bat I noticed an error on that one. So, I drew up another one. Slighty bigger, but I made room for a larger power rail cap (up to 1000uF if necessary), and protection diode. Also, there's some extra room if one wishes to mess around in the clipping diode area. Made the 47K resistor a trimmer as well, for fine tuning the voltage at Q2.

The tone pot can also be sub'd for a 50K in a pinch. I've tried both, and the audible difference is minimal.

Just beware is you're going to use different trannies in the Q2 / Q3 slots. BC639's are ECB pinout. You've been warned.

As always, unverified until built, and please let me know if anyone notices an error.

[digi2t]

Updated, and verified, vero...



Nothing major. Changes;
- Had the wrong value on one of the trimmers,
- added an optional 150pF cap to help tame some high end fizz,
- moved some stuff around to make more room for playing with the clipping diodes (if one is so inclined),
- and to facilitate grounding of shielded cables to the board,
- changed tuning instructions for adjusting Q3C voltage.

It's not bad with guitar, real synthy sounding buzz/fuzz all over, but sounds much better with bass IMHO. Going into the lower registers, I thought the kid's amp was going to puke up it's one and only speaker! 

Video to come, once it's boxed up.

Cheers,
Dino