Fuzz face clone with bias control

[Spencerleehorton]

On my continued journey tone chasing I came across this pedal

https://www.kaisertronics.com/ac125-fuzz

I’ve got some ac125 transistors and have built a few fuzz faces but I quite like the idea of this bias control and wondered within the basic circuit which resistor it is? Is it the 33k or the 8.2k ?

Dallas arbiter fuzz face is the original schematic I think!

https://fuzzcentral.ssguitar.com/faq.php

Regards

Spence.

 

[mhelin]

33k for Q1...

 

[Spencerleehorton]

Yeah that’s what I thought but it also has a trimmer in there which I think maybe the 8.2k?
Also would the bias pot(33k) be 100k?
And if the trimmer is the 8.2k would that be 50k or 100k as well?

 

[Spencerleehorton]

Pretty sure the trimmer says 50k on the side, will change and twiddle.
So far with 100k pot in 33k position getting some different sounds, some good some bad!!

 

[Gus]

Search better, try harder
There is a bunch of stuff on the web however some/most of it is crap
You screw with the output resistance when you change Q2 collector resistor
Myself and others have posted about adjustable bias for FF like circuits about what adjust what
I even shared a Si version of the supa/tonebender at Diystompboxes a person even made a nice youtube of their build
Search at Diystompboxes

 

[Spencerleehorton]

I found this and was very helpful

http://guitarpoppa.com/biasing-a-fuzzbox/

Still haven’t found any of what you have specified but I’ll keep looking.

 

[Gus]

Links are broken at my posts at diystompboxes
here is a nice one knob fragment I like don't believe the web crap that the output needs to be at 1/2 the supply voltage
Add a pull down resistor(1 meg or what ever) and input cap at the input try .01uF on up to 10uF.
Bypass R1 with 100uF or change the 1K to a C taper 1K potentiometer with a cap to ground on the wiper like a FF if you want two controls.
Pick an output cap value and volume control. I like 100K A for the volume. The output is between R5 and R4
For basses I often like a small value cap at the input so the highs get clipped more that than lows and the sound does not get indistinct unless you want that.
LT spice 2N2222 and 2N5088/89 model sim very close to the real build
So you can sim FF like and other effects that use them, often the build measures close to the sim

I just looked at the link in the post there is that 1/2 again. Sim and test by ear, ever resistor affects the biasing and the most simple is to change Q1 collector before Q2 collector but it can be better than that.

I often put a bias adjust in my build and it is not in the collector sides. the feedback resistor adjusts the biasing/1st stage closed loop gain R3 changes thing as well IMO some of the stuff on the web is ?. All the resistors adjust biasing in the gain stage sections.


A nice Si fuzz R12 is a 100k volume I did not need a bias control it R11 was not used. The voltages are what Supa Fuzzes measure around.

 

[Gus]

some more


R12 is a 2k or 5k control. R13 and R14 are a 100k volume control

 

[CJ]

Gus have you ever heard this Korg Hard Dist ?

 

[Gus]

CJ
I have not seen that distortion.
Buffer to transistor gain stage to IC gain into a clipper(RAT influenced?) then a BMP type tone control into a buffer looks like it sounds good.

 

[Spencerleehorton]

Thought I’d continue with this thread as I’m building the other version of the axis fuzz called the west coast fuzz by Dave Weyer.
There seems to be some slight differences in the schematics I’ve found but won’t really no what to make of it until I fire it up.

Here is the schematic I feel is the original



I’m waiting on some low gain germanium pnp transistors which are pretty close to the originals.
Dave allegedly made this for Hendrix from the info I’ve found?
And it’s been reported that Randy Hansen uses it and it’s much closer to the axis bold as love and BOG fuzz tone.

 

[13engrsapper]

I have a TON of real NOS germanium if you need any. Fuzz Face are fun and easy builds.

I will have to find my second one from years ago - after completing my first one, I wanted to know what each component was doing as far as the operation of the amplifier and tone. As I knew absolutely nothing then (and little more now), I built one with rotary switches for nearly every component. It was built into a big like 40mm ammo box. The combinations with all the switching gave it wild variations in tone of course - there were something like 10,000+ potential combinations.

A well-known local guitarist who used my first version and loved it came over to try this test model I had created, he was very excited. He got all set up, and started playing and it sounded wonderful. Then he asked, "what are all the knobs for?" I replied, "they change the value of nearly every component one at a time so you can hear and measure the results. There are something like 10,000 possible combinations." He just shrugged his shoulders, smiled and said, "I guess I better get started."

I left him alone up in the studio for hours, he came back the next day and tried it again for hours, then asked if he could take it home. A week later he came back and said, "don't touch the knobs, and please build a normal one for me with the components I have selected on the switches."

Fun stuff.

 

[Youngwhisk]

I left him alone up in the studio for hours, he came back the next day and tried it again for hours, then asked if he could take it home. A week later he came back and said, "don't touch the knobs, and please build a normal one for me with the components I have selected on the switches."

Fun stuff.

When it was built, did it actually sound like the one with knobs, or did you have to tweak it some more?

 

[Spencerleehorton]

Looking at the sabbatius fuzz pedals they do a rainbow fuzz which I have seen on Randy handsen pedal board and he has wah wah first in line then the fuzz.
It says in the write up about the fuzz that it has a pot so it interfaces correctly with a wah either before or after.
I bet it’s a 50k pot on the input?

 

[Spencerleehorton]

Bc109B is a good choice for a silicon version so I’ll try this as well and compare.

 

[Spencerleehorton]

Here are the 3 versions I’ll be testing against each other.
From
Left to right silicon JH-2 fuzz with BC109B, AC128 with carbon resistors, west coast fuzz with 2N525 and 2N527 (Randy Hansen uses this fuzz)

 

[Spencerleehorton]

mods i'll try on the JH-2 fuzz are the standard, change 1k pot for 2k, 330ohm for 1K, 8.2k on collector of Q2 for 10k trimmer and use low gain BC109B for Q1/Q2.

 

[Spencerleehorton]

Jimi Hendrix's wah-wah pedal, amp and fuzz prototype pedal go up for auction on New Year's Day at J. Levine Auction & Appraisal in Scottsdale, Arizona. Dave Weyer, "Amp Doctor" to many rock stars, has consigned the prototype he built that was used to create the three-transistor "always on" fuzz pedal (left). Weyer also repaired and modified the amp that Hendrix used in his early Experience days. The wah-wah pedal was custom-built by Weyer for Hendrix prior to Woodstock (right). The auction starts at 11 a.m. MT on January 1, 2017. www.jlevines.com. Photo credit: Antoine Gedroyc, J. Levine Auction & Consignment.​

other pictures here

https://hibid.com/lot/62355-92122-147272/fuzz-prototype-by-dave-weyer-for-jimi-hendrix

 

[Gus]

I found this and was very helpful

http://guitarpoppa.com/biasing-a-fuzzbox/

Still haven’t found any of what you have specified but I’ll keep looking.

I disagree adjusting the 2nd collector value works somewhat but it also changes the output resistance. 4.5 VDC more web nonsense you often want to misbias a fuzz for gating to compressing. I often add a control to do this to fuzzes I build.
Some fuzzes have the 2nd collector output at 7 to 8 something VDC

Almost all the resistors in a FF type fuzz affect the bias
You can adjust the first collector value or the 2nd emitter value or the AC feedback/part of the DC bias resistor value or

Look for the wooly mammoth schematic for more hints

I gave you good hints in the screen shots the one fragment is a good one knob fuzz using common 2n2222/pn2222 Add the cap across the 1K and other parts.

Get LT spice and sim the circuits the 2n2222 and 2n5089 model sim very close to the build that should help understand the circuit better
2n2222s can sound very good in a FF like fuzz
Si Power transistors are fun to use as well. I also use tip29s in treble boosters

There is also the roger mayer axis fuzz schematic you can look at.

 

[Spencerleehorton]

Transistors I’m using are 2N525 and 2N527, pretty close originals

2M pot is actually a 1M trimmer with a 1M on a 3 position switch so it can have an off position in the middle to bypass the feedback loop

40k for 50k yep

Not sure about the pot but I’ll try B1k and B5k

I think they are electrolytic, or at least that is what I’ll use first of all but I will look at that prototype picture and see if I can tell what they are