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I don't know if this is of interest to anyone, but I was asked by a friend to clone his original 1968 Fuzzrite - he would like to use it on-stage but is afraid his original might get stolen.
There's plenty of information about this fuzz on the web, including schematics for different versions (there's a nice write-up of all the different versions here, no schematics though: https://fuzzboxes.org/features/fuzzrite).
I traced the circuit myself and took all the measurements I felt were necessary. Component value measurements were done out of circuit. See the annotated schematic attached to this post.
I did include the bypass switching as it's rather unique/weird and none of schematics I looked at included it.
On that note: if anyone can tell me what purpose C5 serves I'd be happy to be educated. When the effect is "on" (e.g. not in bypass) C5 is shorted/bypassed by SW2A, when the circuit is bypassed, C5 negative terminal is connected to battery minus and the positive terminal is connected to the input (and output) signal.
Some sort of anti-pop? How does it work?
The measurered R/C values aren't of real interest for a general clone of the Fuzzrite but it's interesting to see how far off of their nominal value some of the parts are.
The clone was built with metal film resistors and film capacitors, except for C5 where I used a low ESR electrolytic. I matched the values with the measured values from his original, sometimes using things in series or parallel to get the right value.
Finding the right transistors took some time. I believe these are Sprague and the type nr. is an in-house number.
I tried anything I had within the measured hFE range and the only ones that worked, i.e. where the end result sounded like the original, were 2N3904. Where these differ from all the other transistors I tried, is that they had similarly low Vcesat values as the TZ-82 (when measured with a DCA75 Pro), between 20mV and 25mV, whereas all the rest measured upwards of 100mV.
Whether there's causality here I don't know, it was just something I noticed.
Other transistor types I tried were 2N2222A, BC174, BCY59A, BC549A, 2SC752.
One last observation: it did appear as though the pedal sounded different when powered from a power supply compared to a battery. With the power supply the sound was noticably brighter to my ears - even with the supply voltage set to 8.37V. I didn't spend much time thinking about this, but I do know that the original and the clone sound the same when powered from the same source - battery or power supply.
I have no build pictures as the clone is still on the breadboard. The reason for this is that while my friend agrees that it does sound just like the original, what he was actually expecting was the same sound but louder. And I have to agree with him, when played with humbuckers the perceived loudness is barely unity. So I'll have to see about that, maybe a simple makeup gain stage.
I do have pictures of the original - if anyone's interested I'd be happy to post them here.
This was the first time I ever had to build something which sounded identical to something existing. It was also the first time I was able to open up and look at a vintage pedal. All in all a rather educating, enjoyable and satisfying experience.
Lastly, while I'm not much of a Fuzz(-pedal) fan, I do think the circuit is rather neat in its simplicity and the range of sounds you're able to get from varying the "Depth" control, and I quite like the sounds.
Happy Easter
There's plenty of information about this fuzz on the web, including schematics for different versions (there's a nice write-up of all the different versions here, no schematics though: https://fuzzboxes.org/features/fuzzrite).
I traced the circuit myself and took all the measurements I felt were necessary. Component value measurements were done out of circuit. See the annotated schematic attached to this post.
I did include the bypass switching as it's rather unique/weird and none of schematics I looked at included it.
On that note: if anyone can tell me what purpose C5 serves I'd be happy to be educated. When the effect is "on" (e.g. not in bypass) C5 is shorted/bypassed by SW2A, when the circuit is bypassed, C5 negative terminal is connected to battery minus and the positive terminal is connected to the input (and output) signal.
Some sort of anti-pop? How does it work?
The measurered R/C values aren't of real interest for a general clone of the Fuzzrite but it's interesting to see how far off of their nominal value some of the parts are.
The clone was built with metal film resistors and film capacitors, except for C5 where I used a low ESR electrolytic. I matched the values with the measured values from his original, sometimes using things in series or parallel to get the right value.
Finding the right transistors took some time. I believe these are Sprague and the type nr. is an in-house number.
I tried anything I had within the measured hFE range and the only ones that worked, i.e. where the end result sounded like the original, were 2N3904. Where these differ from all the other transistors I tried, is that they had similarly low Vcesat values as the TZ-82 (when measured with a DCA75 Pro), between 20mV and 25mV, whereas all the rest measured upwards of 100mV.
Whether there's causality here I don't know, it was just something I noticed.
Other transistor types I tried were 2N2222A, BC174, BCY59A, BC549A, 2SC752.
One last observation: it did appear as though the pedal sounded different when powered from a power supply compared to a battery. With the power supply the sound was noticably brighter to my ears - even with the supply voltage set to 8.37V. I didn't spend much time thinking about this, but I do know that the original and the clone sound the same when powered from the same source - battery or power supply.
I have no build pictures as the clone is still on the breadboard. The reason for this is that while my friend agrees that it does sound just like the original, what he was actually expecting was the same sound but louder. And I have to agree with him, when played with humbuckers the perceived loudness is barely unity. So I'll have to see about that, maybe a simple makeup gain stage.
I do have pictures of the original - if anyone's interested I'd be happy to post them here.
This was the first time I ever had to build something which sounded identical to something existing. It was also the first time I was able to open up and look at a vintage pedal. All in all a rather educating, enjoyable and satisfying experience.
Lastly, while I'm not much of a Fuzz(-pedal) fan, I do think the circuit is rather neat in its simplicity and the range of sounds you're able to get from varying the "Depth" control, and I quite like the sounds.
Happy Easter
Thank you for sharing this with us.
at first a 2N3904 and a Fairchild PN2222A
