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Thread: Tone Bender- diy?

  1. #36
    Supporting Member John_H's Avatar
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    Quote Originally Posted by mozz View Post
    Watch the rabbit hole. Last time i was building something i sunk $600 into a tele, but at least it's made of good parts.

    Just picked up 3 "solid state" intercoms today at the flea market, sft323, sft325, 2n404, 2sb33 and some other germanium transistors, all useable. One even had tropical fish caps(used in classic wahs and other stuff). Sometimes you find the old small output transformers, they are often good for building a octavia pedal. Finding certain old transistors can sometimes be harder than finding some certain tubes.
    I know how easy it is to spend money once you get started. I bet that's a sweet tele. I always try to keep the projects inexpensive, but it doesn't always work out that way.
    I'll keep my eye out for any electronics from the period tomorrow. You never know what you'll come across. Thanks for the subtle advice.


    Quote Originally Posted by nickb View Post
    Sounds like you are having fun with this. Seems like after the Wah you might be getting into pedals?

    Just, by the by, I happen to have a Vox Tonebender MkIII here right how. One of these (pic grabbed off Reverb com). They are asking amazing prices. The owner had no idea of the potential value...
    This is fun. I've been buying kits, and PCBs for a couple of years now. The wah was a fun project. I like the whole idea of starting from scratch. So yes, after the wah I decided to change my aproach a little.
    The history behind some of these pedals is really interesting. The prices are driven up by crazy collectors. Replica pedals demand high prices also. I know that this is an old road that many have been down, and I don't expect to get amazing, and immediate results, but I'm enjoying the process.

    Thanks for the pictures, and schematic. I've been saving stuff like that.

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  2. #37
    Supporting Member John_H's Avatar
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    There's some progress here. I made the little eyelet board, and mounted the passive components. I put the sockets for the transistors on pigtails.

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  3. #38
    Supporting Member mozz's Avatar
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    Those header pins work for a transistor socket, but they are not really a socket. Try and find some cheaply priced transistors sockets, they don't exist. I have used those before but once i find the trannys i want in q1,q2,q3, and my voltages are correct, i solder the transistor to the header. Watch out, they melt fairly easy.

    Did you use 2 pins for a bias pot on Q2?

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  4. #39
    Supporting Member John_H's Avatar
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    Quote Originally Posted by mozz View Post
    Those header pins work for a transistor socket, but they are not really a socket. Try and find some cheaply priced transistors sockets, they don't exist. I have used those before but once i find the trannys i want in q1,q2,q3, and my voltages are correct, i solder the transistor to the header. Watch out, they melt fairly easy.

    Did you use 2 pins for a bias pot on Q2?
    You're right about the transistor sockets. I wish there were better options available. I've got some header pins that snap together well, so I was planning to mount connectors to the transistors also.

    They do melt easy. I use 63/37, so that helps a little.

    There's no bias pot on this one, and I'll use the 8K2 for now. I can always change it to a trim pot later if I feel the need. It'll be pretty easy to swap any component. Here's the schematic that I'm using.


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  5. #40
    Supporting Member mozz's Avatar
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    As i said, beware of any schematic or info from fuzzcentral, there are many mistakes, some have tried to contact them to have them corrected but to no avail.

    It has been said to use a 100k pot on q2 for bias adjust and leave the 8.2k stock. These don't seem to clean up with your guitar volume control as well as a fuzzface does, but that's how it is.

    Been working on a FZ1 Maestro fuzz clone and trying to get that sorted out, my 5 tonebenders are mostly populated and waiting a few resistors from Mouser. I'm having better luck using older American germanium transistors than any japanese or russian trannys at the moment. You need a certain amount of leakage for certain Q positions. I measured trannys with the same gain and same leakage and they would sound different, so it's really a matter of swapping them around the sockets until you find what you like.

    You may have to up the 470 ohm to maybe 1k if you need more than unity volume. Also just found out the 0.1uf caps i used (ceramic)are microphonic and were really loud when tapped with a pencil, i swapped them out for film caps and got much better.

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  6. #41
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    You need a certain amount of leakage for certain Q positions.
    Just an idea:
    If some leakage is necessary for optimal sound, I understand that for given DC gain the leakage changes the operating conditions (circuit voltages) to better clipping characteristics.
    The same effect can be achieved by wiring a suitable resistor (or trimmer pot) of say 100k to 220k between collector and emitter of a low leakage transistor. This way the best operating condition/sound can be dialed in for a given transistor. Also sound will depend less on ambient temperature compared to a higher leakage transistor.
    And you can use lower leakage transistors as well.

    Of course the trimmer could also be added and adjusted when testing transistors for beta and leakage.

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    Last edited by Helmholtz; 02-15-2019 at 02:47 PM.
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  7. #42
    Supporting Member mozz's Avatar
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    Was under the impression that collector to base leakage was needed. Some fuzz designs will not hardly pass signal with low or no leakage transistors. I have a 3meg pot to use for this test later today. The FZ1 (anyway) needs 150ua_200ua before it starts to work. The FZ1 actually has the 470k shown in the fz1a schematic. Many people build it without and have a hard time getting it to work.
    Attached Thumbnails Attached Thumbnails Click image for larger version. 

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    Last edited by mozz; 02-15-2019 at 03:39 PM.

  8. #43
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    Quote Originally Posted by mozz View Post
    Was under the impression that collector to base leakage was needed. Some fuzz designs will not hardly pass signal with low or no leakage transistors. I have a 3meg pot to use for this test later today. The FZ1 (anyway) needs 150ua_200ua before it starts to work. The FZ1 actually has the 470k shown in the fz1a schematic. Many people build it without and have a hard time getting it to work.
    You're right, looking at the FZ schematic the transistors would run at zero idle current without some base (leakage) current. Base current influences gain and clipping symmetry. I wasn't aware of the missing base bias. So it seems a better idea to emulate collector-base leakage by a trimmer in the M-Ohm range wired between collector and base and adjust for appropriate collector leakage current in the tester or circuit.

    The principle is the same: Emulating leakage by external bypass resistance and thus reducing temperature dependancy.

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    Last edited by Helmholtz; 02-15-2019 at 04:40 PM.
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  9. #44
    Supporting Member John_H's Avatar
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    Thank you both for the help on this. It wouldn't be hard to add a trim pot. I primarily want to get a decent baseline design to start out with. I knew that there could be problems, but figured that I could design a layout with what I had.
    Mozz, do you have a schematic that you prefer?

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  10. #45
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    Basically just using the one you posted above, except instead of (2ea)5uf, i am using (2ea) 10uf (like the marshall supa version). I had no 4.7uf or 5uf on hand. Also changed the 470 ohm to 1k ohm to get more volume. Removed the input 0.01uf as some models didn't have that. Q2 collector i have a pot 100k but will sub in the resistor once i figure what works best. Anything i changed i have not A-B tested yet so it's still all up in the air.

    Finally put the FZ1 clone back on the shelf to try and finish up the tonebenders first. I bought the pcb's for these and they have the charge pump so still even tweaking the caps near that to lower noise.

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  11. #46
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    Basically just using the one you posted above, except instead of (2ea)5uf, i am using (2ea) 10uf (like the marshall supa version). I had no 4.7uf or 5uf on hand. Also changed the 470 ohm to 1k ohm to get more volume...
    Thanks for the reply. I'm not committed to anything yet. I'll probably make a different eyelet board before I'm done that conforms better to the size of the components. I have seen a few schematics, and I'm learning a lot as I go along. I will likely change a few things.
    Removed the input 0.01uf as some models didn't have that. Q2 collector i have a pot 100k but will sub in the resistor once i figure what works best. Anything i changed i have not A-B tested yet so it's still all up in the air.
    Cool. I can always lift one end of the 0.01uF at the input to check it out. The 100k pot would be easy. Thanks
    ... Finally put the FZ1 clone back on the shelf to try and finish up the tonebenders first. I bought the pcb's for these and they have the charge pump so still even tweaking the caps near that to lower noise.
    I have a PCB for a three knob Tonebender that uses a TC1044 as a power pump. Coincidentally, It suggests 10uF instead of the 5's, and the 1k ohm resistor to boost power.

    The first of the two cheap transistor testers that I ordered arrived. I haven't had much time to evaluate it yet, but so far, so good. I assumed that the leakage was the variable that played maybe the most importance. Everything else is pretty controllable. I have a few usable transistors now, and I'll be able to move them around. It will be interesting to see how the meters compare. The one I have is the nicer of the two.

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