Sunflower fuzz

[piapium]

Did you ever get your build bias correctly ? I just got done building 2 of them and like you I couldn't get the right voltages. I would suggest to try out what I did, socket r2 and r3, use a jumper on r3 and place your bias pot knob on the pedal to noon and try to get 4.5v on the collector via the bias trimpot. I also had to change r2 to 15k to get the 0.7v needed for the collector of q1 and base of q2. Now it sounds much better !

I basically used the fuzz face voltages from electrosmash, I also used a standard boss 9v power supply and my guess this and the charge pump maybe screwing up the voltages on my builds

I also tried soooooo many different ge transistor before that .... Low gain, high gain, no leakage, mid to high leakages and it didn't matter I couldn't get it bias :/

I guess it's impossible to get 4,5V while the bias pot is placed to noon. I get 5V when I turn it cw all the way. And I don't care anymore, it sounds good to my ears. Try AC128s then you will love what you have. They sound shit.

 

[TheSin]

I'd focus less on the model number and more on the hFE and leakage, which are the biggest factors for how your fuzz face will actually sound. Many, if not most of the NKT 275s you'll find on eBay et al. are fakes. Even if you do find a real pair, it's highly likely that they are out of spec. Due to their popularity in fuzz face builds over the past few decades, what little stock remains has already been picked over by builders, and you're just seeing the rejects. I had great luck with Japanese transistors like these in my fuzz face builds—cheap, low noise, and in spec for gain and leakage. They clean up nicely and otherwise sound and behave exactly as a fuzz face should.

What are the acceptable transistor gain and leakage readings for this pedal? Currently looking to build one. Thanks.

 

[caiofilipini]

I guess it's impossible to get 4,5V while the bias pot is placed to noon. I get 5V when I turn it cw all the way. And I don't care anymore, it sounds good to my ears. Try AC128s then you will love what you have. They sound shit.

If you can't get the Q2 collector biased to 4.5V, it's likely that Q1 is underbiased. Because Q1 and Q2 are DC coupled (Q1's collector is connected directly to Q2's base), Q1's bias will directly affect Q2's. If that's the case, you could try lowering R2 to raise the voltage on Q1.

 

[caiofilipini]

What are the acceptable transistor gain and leakage readings for this pedal? Currently looking to build one. Thanks.

Same specs as a regular Fuzz Face. I highly recommend the ElectroSmash analysis of the Fuzz Face: https://www.electrosmash.com/fuzz-face

 

[gingerale]

Did you ever get your build bias correctly ? I just got done building 2 of them and like you I couldn't get the right voltages. I would suggest to try out what I did, socket r2 and r3, use a jumper on r3 and place your bias pot knob on the pedal to noon and try to get 4.5v on the collector via the bias trimpot. I also had to change r2 to 15k to get the 0.7v needed for the collector of q1 and base of q2. Now it sounds much better !

I basically used the fuzz face voltages from electrosmash, I also used a standard boss 9v power supply and my guess this and the charge pump maybe screwing up the voltages on my builds

I also tried soooooo many different ge transistor before that .... Low gain, high gain, no leakage, mid to high leakages and it didn't matter I couldn't get it bias :/

Hey, I had some biasing issues with my Sunflower build too so I searched the forum and found your post. Very helpful, I wish Pedalpcb could have more detailed build docs, if they had stated that you can try different resistors on R2 and R3 in order to help with biasing I would have put sockets there from the start. After reading your post and reading on Electrosmash it makes sense.

Now I did what you described and could get my Q2 to bias correctly to -4,5. It took a lot of trial and error though... The transistors I used were old Russian ones and tricky to get to bias properly.