Need advice from the Fuzz Lords

[Synchrony Pedalworks]

I am making a perfboard fuzz face, but was going to add a bias knob, a la Analogman SunFace. My Ge transistors are matched (Smallbear) and Q2 collector was measured best (4.5V) with a 8.2K resistor.

I have a B5K pot. Would putting a 5K resistor in series with the pot allow me to mimic the Sunface (Sundial knob), but reach the ideal biasing for this transistor? Would you all recommend a different value or approach?
Thanks
AE

 

[Big Monk]

Yes.

 

[Coda]

Yes.

I concur…

 

[fig]

Slide over, I'll round out this menage a tois

 

[Synchrony Pedalworks]

Slide over, I'll round out this menage a tois

That is hilarious! Thanks to you all.

 

[Deperduci]

quits being a trois when the camera guy joins the scene... but I see a project for 1of the perf boards coming in my next SBP order....

 

[Chuck D. Bones]

I'd use a 10K pot with 3.3K in series for more adjustment range. Really depends on how far you want to skew the bias. Are you looking to get some gating at one end of the BIAS pot?

 

[cdwillis]

I know it's different values, but I was messing around with a DAM Meathead on the breadboard a few weeks ago and added a bias pot. I didn't measure the voltages (d'oh), my notes say I had a 1k resistor between the q1/q2 collector resistors and a 470ohm resistor in series with a linear 10k pot going to the q2 collector for my bias knob.

Charles Douglas Willis on Instagram: "Testing this two transistor fuzz #diypedals #fuzz #fuzzpedal"

Charles Douglas Willis shared a post on Instagram: "Testing this two transistor fuzz #diypedals #fuzz #fuzzpedal". Follow their account to see 2146 posts.

www.instagram.com

 

[Chuck D. Bones]

Catchy tune!

 

[andare]

Menage a trois you say? You mean a Tone Bender?
or maybe this

 

[Feral Feline]

Kajh, the way that track builds and then when the bass finally kicks in...

 

[Synchrony Pedalworks]

I'd use a 10K pot with 3.3K in series for more adjustment range. Really depends on how far you want to skew the bias. Are you looking to get some gating at one end of the BIAS pot?

I did want some gated fuzz. I finished up the board. I used a 3.9K resistor + B5K pot and it did the trick. I liked the variety of fuzz it would produce. Unfortunately, I messed up drilling the enclosure, so I will have to wait to box it. This exercise reminded me- I dislike off board wiring!

 

[hamerfan]

5k was not enough in my case. I'd say, go with a 10k

 

[Feral Feline]

Just like Chuck said.

 

[Big Monk]

I think about it like this…

1.) How high do you want the voltage to go?

Use your limiting resistor in series with the trimpot to set the upper threshold. For Q2 in a Fuzz Face with silicon transistors, if I want the voltage to be able to swing up towards or over 8vDC, I start with 750 ohms.

2.) How low do you want the voltage to go?

Use the trim pot value to set the lower threshold. For instance, a 20k trimmer in series with a 750 ohm resistor will likely swing below 1vDC to above 8vDC.

3.) Tweak to taste based on leakage.

 

[fig]

I'm just psyched nobody asked to see my Fuzz Lord credentials.

 

[Big Monk]

I'm just psyched nobody asked to see my Fuzz Lord credentials.

Feels like the few times we sneaked off after buying beer with a fake ID....

 

[fig]

My second job was at a Pizza joint washing dishes, grinding sausage and mozzarella, and of course taking out the garbage. Not a bad gig for 14 (16 as far as they knew). One of my buddies from school also conveniently worked there on weekends when it was slammed. This proved useful as the wine cooler was in the hall on the way to the back door....the same back door we had to roll the garbage out to the dumpster. Got the picture? After shift, we retrieved a cabernet and a merlot from behind the dumpster. His dad kept an old cabin cruiser in the backyard, it was our man-cave and where we drank both those bottles that night. I don't remember much else. It was the last summer job I had before my world disintegrated a month later when my mom passed. Permanently associated in my memory, yet at opposite ends of the joy-spectrum for sure....much like this post turned out I guess. But hey, that was a lifetime ago...and me? I'm a Fuzz Lord!

 

[andare]

My second job was at a Pizza joint washing dishes, grinding sausage and mozzarella, and of course taking out the garbage. Not a bad gig for 14 (16 as far as they knew). One of my buddies from school also conveniently worked there on weekends when it was slammed. This proved useful as the wine cooler was in the hall on the way to the back door....the same back door we had to roll the garbage out to the dumpster. Got the picture? After shift, we retrieved a cabernet and a merlot from behind the dumpster. His dad kept an old cabin cruiser in the backyard, it was our man-cave and where we drank both those bottles that night. I don't remember much else. It was the last summer job I had before my world disintegrated a month later when my mom passed. Permanently associated in my memory, yet at opposite ends of the joy-spectrum for sure....much like this post turned out I guess. But hey, that was a lifetime ago...and me? I'm a Fuzz Lord!

Right in the feels @fig !

To lighten up the mood, here's some fuzz:

Also early fuzz bass by Frank Zappa:

 

[Chuck D. Bones]

I think about it like this…

1.) How high do you want the voltage to go?

Use your limiting resistor in series with the trimpot to set the upper threshold. For Q2 in a Fuzz Face with silicon transistors, if I want the voltage to be able to swing up towards or over 8vDC, I start with 750 ohms.

2.) How low do you want the voltage to go?

Use the trim pot value to set the lower threshold. For instance, a 20k trimmer in series with a 750 ohm resistor will likely swing below 1vDC to above 8vDC.

3.) Tweak to taste based on leakage.

The limiting resistor + Bias trimmer also limits the collector current in both directions. In the FF, the collector voltage can never get below the emitter voltage. Once the 2nd transistor (Q2) saturates, increasing the Bias trimmer won't affect the collector voltage, but it will reduce the collector current and that will affect the tone. Having Q2 in saturation with no guitar signal coming in is how we get gating. It takes a sufficiently large signal to drive Q2 out of saturation and get set sound to pass thru the circuit. When the guitar signal decays below that threshold, the signal is blocked.