Wolfgang 61 no sound

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FreewayRoss
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Post by FreewayRoss »

Hey guys,

I need some help with biasing the transistors in this Build the Wolfgang 61. I adjusted the drain voltage to around 4,4-4,5V expect for Q11 because I only have a range of 9-6,5V? I’ve got some sound out of it but the volume was so low I had to crank the volume of my 120w stereo combo to like 7-8 to be able to hear it very quietly when I wanted to increase like postgain r for example it started to make weird sounds and would get loud as fuck also there wasn’t any real fx applied to the guitar signal furthermore Channel L has no sound at all.

Build docs: https://pcbguitarmania.com/wp-content/u ... g-Docs.pdf

Thank you guys in advance for any help or information

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micmac
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Post by micmac »

Hi there,

I'm a newbie, so take what I write with a grain of salt. You posted a picture earlier: Wolfgang 61 footswitch wiring

Above BIAS8 there's a hole in your photo. The PCB has a resistor marking there but it doesn't mention which resistor. I guess that's why you left it out.

I had wondered where R4 (1M) is. Couldn't find it. But then I was looking at the unlabelled resistor on the PCB and to me it looked like that's supposed to be R4. I put a 1M into it and the pedal seems to work (it sounds musical).

I don't know if my finding is correct. And I don't know if it could cause what you're describing. But Q11 seems to be shared by both channels on the pedal and R4 is connected to it.

Maybe somebody else can chime in.

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FreewayRoss
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Post by FreewayRoss »

micmac wrote: 29 Mar 2023, 20:51 Hi there,

I'm a newbie, so take what I write with a grain of salt. You posted a picture earlier: Wolfgang 61 footswitch wiring

Above BIAS8 there's a hole in your photo. The PCB has a resistor marking there but it doesn't mention which resistor. I guess that's why you left it out.

I had wondered where R4 (1M) is. Couldn't find it. But then I was looking at the unlabelled resistor on the PCB and to me it looked like that's supposed to be R4. I put a 1M into it and the pedal seems to work (it sounds musical).

I don't know if my finding is correct. And I don't know if it could cause what you're describing. But Q11 seems to be shared by both channels on the pedal and R4 is connected to it.

Maybe somebody else can chime in.
Hey,
thanks for the reply. I tried it but still no real change I biased them all now arround (even Q11) 4,5V but still have werid noises and no real signal output :( Channel L is still dead. What Voltages do you have set? could it be that my j201s are not performing well enough?

Edit: https://www.retroamplis.com/epages/62070367.sf/en_GB/? j201 / MMBFJ201 JFET SMD (62P), Original Fairchild
should i buy those and replace the ones i have?

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micmac
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Post by micmac »

Hello!

I attached some pics if you want to compare. If you look at the transistors on the images the leg on the left is the drain, right? I mean that's where you measured, right?

I tried 4,5V and I also tried around 6V. They both worked. Rhythm channel is basically a clean channel. When you increase pre gain it gets a bit crunchy. Lead channel has more gain. But actually I was expecting more gain/distortion. With a tube screamer in front it's fun, though.

The problem I have is that with both channels when I increase their post gain to about 1/3 the pedal starts to fart badly when I dig in. When I keep post gain below a certain level it's OK. But it's a bit weird. I found that when I increase drain voltage on Q11 the farting goes away (unless I increase post gain some more), but at the same time the volume decreases, so no point in doing this, really.

But anyway, I was hoping for more gain without the need to put a TS in front, so I'm not going to put more time into this :-)

Edit: In case you're wondering, I put C3 and C33 onto the backside of the PCB because there was not enough space for them on the front where they normally go.
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FreewayRoss
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Post by FreewayRoss »

Hey, I guess this must be an issue with the transistors. I bought now the MMBFJ201 and a transistor tester. I red that the smds are more accurate and better perfoming and I also think yours are also not working perfectly fine thats why you have low gain and somtimes farting noises but your transitors must be a better match than mine. Did you bought the kit from Musikding?
Btw you did nice job on the wiring!

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Post by micmac »

Hi, thanks!

Yes, through-hole J201s included in Musikding kit. They were fine, though. My cheap T-7 tester recognized all of them as N-JFETs and I also used a breadboarded tester from ROG to measure Vp and Idss. Vp from -0.5 to -1.0. I also have some SMD J201s from retroamplis. They work fine, too, but average Vp in that batch was a bit lower than the through-holes from Musikding. From my experience with a Dr. Boogie clone higher Vp can prevent oscillation. That's also written by Aion in their Dr. Boogie doc (I used PedalPCB's Boogie Monster). But for the Wolf61 it didn't matter as there was no oscillation. Probably because it has less gain. Or maybe not, I'm a newbie and could well be wrong.

Anyway, I was looking for a distortion. In parallel to the Wolf61 I built the PedalPCB Cetus and I really like it. I've got two more kits ordered, the Thermionic Deluxe and the Pathogen. And then I'll see which one I like the most :-D Can't wait.

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Post by micmac »

Oh, for giggles and because I was bored I removed the "R4" again, to see what difference that'd make for me. I can dial the post-gains up now a bit more, but eventually the pedal stills starts the farting. I also reordered the JFETs. The first time around I had placed them from highest to lowest Vp between Q1 and Q12. Now I put them in in the other order. But that didn't help either.

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