DBA Soundwave Breakdown

[Plexi]

Hi forum!
I was trying this very rare fuzz.



No succes at all...only rare/bad sounding fuzz.

Both transistors BCE (collectors to ground).
I used KSP13 (MPSA13), and MPSA29 (Hfe around 10.000).

When Bias is fully closed (no k's at all), the Collector of Q2 eat a LOT!

[nordine]

to be true, everytime ive built successfully a DBA pedal it has sounded like crap. i think they do awesome demos for what those pedals sound like. i like noise and i like abrasive stuff a lot. but a super misbiased transistor (like all their fuzz designs) will sound crummy and shitty no matter what.

[Digital Larry]

My first guess is to either use PNP transistors or swap the polarity of the battery and electrolytic caps.

[Plexi]

Yes... I have the same experiencie...

I'm building this for a friend, when he told me and I saw the demo, after see the schematic I asked him, literally; "..dude...are you f*cking kidding me???"

My first guess is to either use PNP transistors or swap the polarity of the battery and electrolytic caps.

I'll try PNP transistors... I hope the copper traces can handle any more swapping.
I tryied every NPN Darlington I had on hand... reduce the 4M3 resistors, and nothing.

Inverted transistors and polarity is the reason why Q2 heat a lot?

[nordine]

transistors heat when you short them, so yeah, probably a polarity issue.

if your friend wants a noise device, maybe you should try building him some devi ever circuit.. still unconventional stuff, but they can sound quite decently, be sure to put some sort of  tone control at the end, so you get some tonal flexibility.

[Plexi]

transistors heat when you short them, so yeah, probably a polarity issue.

if your friend wants a noise device, maybe you should try building him some devi ever circuit.. still unconventional stuff, but they can sound quite decently, be sure to put some sort of  tone control at the end, so you get some tonal flexibility.

Thanks
I'll take a look to some Devi Ever fuzz, and maybe suggest some Karl Fuzz, Octavia, Foxx, something more "musical".

[PRR]

As drawn, it can't work for crap.

_I_ speculate the emitters/collectors are swopped. Then it becomes a rudely-biased distortion beast.

> why Q2 heat a lot?

If VR2 is ever turned to zero Ohms, Q2 will conduct like mad and burn-up. I suggest some little resistance so current can't reach "infinity". 1K will keep it down to 8mA or 0.016 Watts.

[Cozybuilder]

Assuming Paul's right, look at the polarity of C1 also. The base of Q1 should be around +0.6V, is your input tied to ground from the previous pedal by a volume pot?

[Plexi]

I'll flip the transistors collectors/emitters..and see how it goes.. 

[nocentelli]

As drawn, it can't work for crap.

_I_ speculate the emitters/collectors are swopped. Then it becomes a rudely-biased distortion beast.

I can't claim that the schematic posted above is correct (there's another here that is totally different, maybe different version?) but the npn-with-collector-to-ground-and-emitter-to+9v thing is quite common in DBA pedals, and probably the reason so many DIY-ers have trouble getting the circuits to work.

[allesz]

The first schematic may be right: death by audio is famous for using reveresed transistors.
Only tried it with single bjt, as a booster, with so an so results, never tried multiple stages.

They can be fun, but mostly at home or in a recording studio.

[Plexi]

Update: transistors fliped... nothing happened.

I give up at the moment...

nocentelli: yup, that's another version, the new one.
The one I posted isn't verified, I'll keep trying into my protoboard to modify and make it work.

I'm 99% sure that the problem is the kind of transistors they used...
I used MPSA29, Darlington NPN with about 10.000 hfe, but maybe some voltage or hfe secret with 2N5306.
They have about 70.000 hfe... that's crazy.

[Kipper4]

70K hfe
Can you make a Darlington out of Darlingtons?
Hfe 100K

[Plexi]

70K hfe
Can you make a Darlington out of Darlingtons?
Hfe 100K

Yeah..!