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JAM Pedals Fuzz Phrase

Posted: 11 Mar 2016, 23:18
by Fender074
Hey Guys,

Newbie here to building I've just started building a few pedals from PCB's and kits online such as a fuzz face, TS and Bluesbreaker and a Dumbloid that all went fine and was quite pleased with my self but Im not too great at working things out from scratch..
I'm amazed at some of the things I see on here you guys are brilliant!

I had a JAM Fuzz Phrase a few years ago and sold it for bills, Havent been able to afford dropping £200 on one again and its got about £15 worth of parts inside its abit too steep..I will say it was by far the best fuzz I have ever used and would love to build one. Obviously its a Fuzz face derivitave, it uses CV7003 transistors but could someone mock up a vero layout with the parts values ?

I have searched through all the requests pages and disected stompboxes section and couldnt see this one mentioned..Apologies if I missed it.

Best regards
Tim

Re: JAM Pedals Fuzz Phrase

Posted: 12 Mar 2016, 00:13
by Fender074
Found a gut shot here its not great but its the best one I can find, if anyone has a better one or even has this pedal and wouldnt mind opening it up?

http://www.guitar.co.uk/media/extendwar ... se-055.jpg

Re: JAM Pedals Fuzz Phrase

Posted: 13 Mar 2016, 02:35
by mictester
First get your two CV7003 transistors....

It's a bit like the old Rabbit Stew recipe: "First, catch your rabbit....."

To make this type of circuit, you need two germanium transistors of roughly the right gains. There's some debate about the best sounding values, but I found a batch of OC71 transistors, all with low leakage and Hfe values around 80. These were absolutely perfect for the "Fuzz Face" circuit. I used the "inverted" version of the circuit that allows the use of a battery-negative grounded case to maintain compatibility with other pedals around it. I also include a series input pot as an optional "smooth" control (it's shorted out when turned all the way down)and have switchable input capacitors to vary the sound from "big, fat rounded fuzz" to "bee in a tin can" sound. I really couldn't be bothered trying to get some bizarre-law pot for the "Fuzz" control, so used a 10k linear and a couple of fixed resistors to "bend" the law. I also don't like the high impedance output, so added a silicon emitter-follower stage to make the output impedance more sane. It doesn't affect the sound of the effect at all, it just ensures that it plays nicely with modern circuits following it and can drive down long cables if necessary.

It's important that the Fuzz Face is the first effect after the guitar. There is a wonderful interaction between touch on the instrument and the voicing of the effect. This is lost if there's anything else in the way - it only really works with passive pick-up guitars, and single-coils are better than humbuckers in this respect. It really is a "player's effect".

It never ceases to amaze me how much can be achieved with just a small handful of components!

Incidentally, it looks like your "best ever Fuzz" was built on a Tonepad PCB

Re: JAM Pedals Fuzz Phrase

Posted: 16 Mar 2016, 03:06
by Fender074
Thanks for the reply mictester! I Have sourced my transistors already, brought a whole bunch of em so will test gain and leakage when It comes to building! Image

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Found this after scouring the internet for a few days..its the best gut shot pic I can find and some quite obvious resistor values here, Seems to use only 3 resistors instead of 4 like most fuzz face layouts on the web. Anyone got anything they can add further?

Re: JAM Pedals Fuzz Phrase

Posted: 17 Mar 2016, 22:31
by Fender074
Now this has been moved to the Disected section, are there any experts here that want to really nail this puppy and try to vero it? It really is the best sounding fuzz face I have played and I've played most of them Oxfuzz, MJM London, Sunface BC108, BC109 & NKT red dot...this one stands out from them all :applause: 8)

Re: JAM Pedals Fuzz Phrase

Posted: 18 Mar 2016, 07:18
by mictester
It's just a standard germanium transistor Fuzz Face. The blue preset on the board sets the bias point (to get the collector of the second transistor to the right point) - collector of the second transistor is the only critical voltage in the thing.

The only thing "wrong" with the Fuzz Face is the high output impedance - I like to add a (silicon) emitter-follower stage after the FF circuit to allow it to drive long cables