DAM Buzzotron

[rocket88]

Figured people may be interested in this ultra rare, only 5 made, dam version of the buzzaround. it has all the same characteristics as the original, but has a little more low end, and a little gainier.





obviously since the odds of any of us having NKT213's just use any old PNP Ge transistors.

and one with an on board inverter

[tabbycat]

rocket88 wrote

Figured people may be interested in this...

figured right, rocket. thanks for the layout.

i listened to a demo for one of these (buzzotron II) last night and the degree of grit and sustain reminded me of 'forged'-era spacemen3. think they used all vox kit at that time but same kind of feel.

the long to-build list just got longer. this will be one of my first germanium builds when i finally grasp that nettle.

[Beaker]

Zach you're the DUDE!

Ok, with the risk of sounding like a scratched record, I built this as an NPN version (flipped the electros around).

Not had time to thoroughly test it, but it sounds good with MP38s, but sounds freaking amazing with Tesla metal can 104 NU 71 transistors, and playing around with any diodes you have - either germ or silicon can tweak it to your taste.

I don't have an anti-log 100k for the sustain, but linear works just fine.

I have tried 1N34, D9, D311 germs and D220, 2D5036, 1D507A, 1N4148 and KD521A silicons so far.

D311 Germs and KD521A silicons sond best so far, but I need to do some more comparison testing on all settings.

So if you want to post up a NPN version Zach, go ahead - it's verified.

BUILD IT - BUILD IT NOW!!!

[Chris60601]

Sweet! Now that's what I want to see, a vero WITH the schem!!!!
FANTASTIC rocket!

[Kinski]

Oh hell yes!

[Kinski]

Man, I gotta start a collection of GE diodes. Is there someone on eBay that would put together a small collection of various GE diodes? A flight of diodes ?

[Beaker]

I would try our Bulgarian friend.

Email him, mention that you are a member on here, and ask if he would be willing to put together a selection of Ge and Si diodes - especially Russian ones.

I am sure he would be willing to help you out.

Failing that, I've used almost all of the sellers of Russian Ge parts on ebay, that are based in Bulgaria, Romania, Russia and Ukraine, and never had a bad deal. I've managed to get quite a collection without having to spend more than a tenner per order - often for 200 diodes.

[anders]

Yes! Just built it and it's awesome, reminds me alot a of an Elka Dizzy Tone. Built it as NPN as well with MP38's for Q1 and Q2 and a high gain AC187 in Q3. It roars!

[Beaker]

Roughly what HFE reading is the AC187 Anders - and what diodes have you used?

I might end up putting a diode selection on a switch.

It really is a great circuit, with highly interactive controls. It nails that Buzzaround "trumpet" tone.

[anders]

Well, for the diode I used a D311 and for the AC187 I got 160 hfe according to my calculations with a leakage around 180aU...it's sounds much better to my ears with some leakege in Q3, MP38A's tends to sound a bit dark and muffled in some circuits.

[Beaker]

Thanks, I will have to see what I've got in that range.

[rocket88]

HOLY SHIT!!! i figured others would want this, but had no idea everyone would pounce on this like a hungry lion. your emperor is pleased.  

i made this when i couldn't sleep last night, when i finally come on to it's been verified. pretty amazing guys.

I did a lot of research on the transistors and leakage for the buzzaround, and thereby this, should be as follows:

Q1 & Q2 - around 55-75hfe little to no leakage
Q3 - 75-125hfe around 300uA leakage with the balance full -.85V
 
so now i'm curious to know  what hfe and leakage transistors you used beaker. it's funny you mention the tesla 104NU71's, cause i started stocking up on them. i've got 50 now, and another 150 on the way. they seem to be awesome NPN Ge transistors and a little crisper sounding the MP38A's to my ears. another winner.

stupid question, how does the the diode change the sound of the effect? from my understanding the diode is supposed to offset Q3 with the biasing and stabilize the transistor.

if the NPN is verified then the PNP should be verified as well. which is the one i'll be building, probably with the on board charge pump so i don't have to deal with a daughterboard floating around.

As requested NPN Layout

[Beaker]

Hi Zach, well you know that when the Emperor commands, it's a good idea to obey - and smartish. Besides I'm only Darth Silvers' tea boy.

Q1 reads 72, Q2 reads 73, and Q3 reads 126 on my multimeter. This was an absolute fluke, as I just grabbed three from the bag, and shoved them in. I've no idea about leakage, as I'm embarrased to say I still don't have a transistor tester!

No idea about the diodes - as I said, I tested a few in a real hurry, before I had to go out to take my little grandson to the park (summer has broke out over here!). My guess - and it's only a guess, is that any difference in sound, (and it's very subtle to be honest) is due to their different voltage drops?

[rocket88]

lol. don't forget you've got a job on the Ge Deathstar too. you're one of us.

[Beaker]

Had a chance to have a thorough play with this today, so here is what I have ended up using.

For Q1 and Q2 I'm using MP38s with a HFE of 60.

For Q3 I'm using a Tesla 104NU71 with a HFE of 95

Diode is a D311.

This set up sound slightly better across the range than using three Teslas, and way better than three MP38s.

I tried higher and lower gain for Q3, but 95 seemed to hit the sweet spot.

This thing is sooo good, I can't stop grinning.  

[KT]

Hi, I bought these http://www.ebay.com/itm/104NU71-Germanium-Ge-NPN-Transistors-104NU71-by-TESLA-Gold-20V-250mA-LOT-OF-25-/260170306632?ssPageName=ADME:L:OU:BE:3160. Cause I wanted to use them for q3. But 20 out of 25 were below hfe 50. I got only 1 with hfe79 which is still too low for q3. Is it normal that their hfe is so low and you just have to be lucky to get a high gain one? Or did i order a wrong subcategory of them?

[rocket88]

You ordered the right ones, it's just that you have to remember when ordering non sorted Ge transistors it's all in the luck of the draw. I'll check my last order of them and see what my gain ranges where. I may have had similar results to yours, but I ordered 200.

[jalmonsalmon]

Thanks for this!
I will have to try the layout with the power converter.

[jalmonsalmon]

I finished this one up today using the layout with the power converter .
 GT108V for Q1 & Q2 hFE 63 for both and leakage is approx .04
For Q3 I used a NKT219 that has some good leakage with hFE at about in the 70s.
So far this pedal sounds pretty good. Massive sustain and is really buzzy in a good way. Sounds more or less like my madbean bumble bee and I need to get my transistors out and tester so I can fine tune this one. Diode I used is a D9E
I am thinking though that the NKT219 is going to be replaced since it does not bias properly with the attack knob... When I dime the attack it does a woooop oscillation when you tap on a string... I am not sure what is up there but I suspect if I just try some other transistors for Q3, I should find the one that works.
Thanks again for the great layout!