Build Your Own Clone Message Board

Hi all,

I just finished my first Bazz Fuss clone, I modified by adding a switch that allows clipping choices between red LED or the standard diode as well as a volume knob of course. I enjoy the pedal currently and want to keep developing the circuit, but not sure where to go with alternative components, I hear cap changes can make a big difference.

Components used are below:

Transistor: MPSA13
Resistor: 10K (5%)
Capacitor In: Electrolytic 2.2uf
Capacitor Out: Film Cap 100nf
Diode: 1n4148 & red LED running through a switch.

yep, those "in" and "out" caps do a lot to set the threshold for the low end of your EQ. Larger (i.e. higher capacitance) values will allow more lows to pass thru, smaller (lower capacitance) caps will block lows. These caps are nice and large, since it's designed to be a bass fuzz. You could make them bigger, but your amp may not be able to reproduce those lows, and you might end up just muddying the sound. Smaller caps will make the overall tone brighter but less beefy. Best to socket and experiment until you find what you like or what works best with the rest of your rig.

Note that just because you've used big caps to allow bass frequencies through doesn't mean they'll come thru your other pedals when stacking. Hell, even if you've only got a buffer after it in the chain, you might lose some lows due to smaller coupling caps in those circuits.

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Thanks for the reply, good to know about the capacitors. I was planning on starting a fresh breadboard and swapping out caps and different LED's before I build another version. I'm going to try and do some research on caps, but when you say lower resistance, you mean like going from 100nf to 50nf for example, correct.

Would it be worth it to start experimenting with different transistors?

Correct, lower capacitance will allow fewer low frequencies thru. Generally, 100nF (like the "stock" output cap) is enough to allow all a guitar's frequencies to pass thru. It might be cutting a little low end if you're using the circuit with a bass.

In a circuit as simple as this one, a change of transistor could make a HUGE difference in the way it sounds. Generally, a transistor with a higher hFE rating will produce more gain (i.e. will clip harder or more easily). In this case, the "stock" MPSA13 will produce tons of dirt. It's a Darlington transistor (basically two high-gain transistors in one package) with a hFE rating of 10,000 - which is insane LOL. Dropping down to a different NPN transistor with lower gain, like a 2n5088, will let you explore cleaner sounds. Just check datasheets for the pinout.

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Hello, I have another question I wanted to run by everyone regarding this circuit. I've been playing with caps and have some new ones coming in the mail this week to try, I've also installed a B10K pot that intercepts the voltage going to the collector leg of the MPSA13 transistor. I basically have the 9V battery running into the stock 10K resistor the schematic calls for, but then the 10K resistor goes into the potentiometer. This is allowing me to control the voltage from the stock 1.20v down to 0v on the collector side of the transistor. I'm finding this allows me to get a bit more control of the gain and fuzz in the transistor and also even can create some octave sounds I like if you also turn up the volume. I'm curious what you would classify this adjustment as? Is it biasing, just choking the transistor of voltage - I'll be putting the pot on the enclosure and want to figure out how to describe it.

Thanks!

often referred to as the "voltage sag" or "dying battery" mod. Just lowering the supply voltage can have a dramatic effect on the sound. It moves the bias of transistors, and encourages clipping. In a circuit this simple, it would certainly be fair to call it a bias control.

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Thanks. Definitely found some input caps that bring out a far more mid-range punch i was looking for. With the vol, bias adjustment and a diode clipping choice, you can get quite a bit of adjustability out of such a simple circuit.

Yo yo yo, got a few more questions.

I just added a little passive tone control to the front of the circuit. I'm using a 100nf capacitor on one side and then a .022nf capacitor on the other, so far I'm enjoying the sweep it's giving me. I've kept the stock 100nf cap on the output end of the circuit. Right now I'm using a crappy 100KB2 pot I pulled out of a dead DS-1 and it seems to be working well, but I'm curious what pots you would recommend for this tone purpose?

Also, is it true that whatever caps I put on the input of the circuit in this tone control are limited by the output cap. For example, if I have a 2.2uf cap on the input which lets a ton of bass through, but then a 100nf on the output, all that extra bass I let through will be limited on the output end?

Dead DS-1 you say? Think you'd be interested in a trade for the carcass? DM me if so.


K, so generally speaking I 'caveman' this sort of shit—socket/breadboard, swap, settle on something I like, solder.

That being said, you should research high and low pass filters. There's more to this than the value of the cap alone. I think if you look into the relationship between the output cap and the resistance to ground (through the volume pot), you'll see if the cutoff frequency interplays with the sweep of the tone control or not.

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Bikers have more fun that people do.

Free "open source" EagleCAD files: 99ZuluFX

So regarding using this method (a pot and 2 caps) to control tone, am I missing components and other parts to this adjustment or is this an appropriate tone method?

I could also go the route of just routing the signal through an on/on 2 way switch as well.

Otherwise, just curious as to where to begin with potentiometer rating, I'm assuming I'd need a linear pot.

There are a lot of different passive tone stacks out there. If what you're doing works, it works.

Something to keep in mind though is that passive tone stacks work by cutting signal and some cut more signal than others (perhaps necessitating gain recovery stages, etc).



"Need?" Probably not so much. If you have an A100K, B100K, C100K, etc and try them all in your tone stack, they're all going to effect the circuit the same way. What will be different is how the sweep feels to the human user. B-taper pots are certainly common in tone stacks but that doesn't mean a different taper might feel better to the person using it. It's worth trying out.

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Bikers have more fun that people do.

Free "open source" EagleCAD files: 99ZuluFX

Thanks, so you think 100K is a good range to start at?

Also, just saw your original message about the DS-1, unfortunately I already stripped the whole thing for parts and tossed the enclosure!

Maybe?

If you have a Windows PC there's a program called "Tone Stack Calculator" that can probably help you out quite a bit.


Bummer!

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Bikers have more fun that people do.

Free "open source" EagleCAD files: 99ZuluFX

...from Duncan's Amp Pages. Available for download here: https://www.duncanamps.com/tsc/

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“My favorite programming language is SOLDER” - Bob Pease (RIP)

My Website * My Musical Gear * My DIY Pedals: Pg.1 - Pg.2

Thanks guys, have a bit of an off topic from this thread question, but in the interest of not starting a new thread, I figured I'd work it in here.

I wired up my first pedal so that the foot switch basically turned the power to the entire circuit on or off via one of the poles, essentially the 9V power went straight to the foot-switch. What I'm noticing as I do more research, is that it seems people wire up their foot-switches so that power is always flowing to the actual circuit and the foot-switch is just receiving ground to complete or break the circuit to the signal LED and of course route the input/output jacks true-bypass.

Is this an accurate read and if so, what is the reasoning for not using the foot-switch to cut total power to the circuit?

(I had trouble finding info with the search function,so if anyone has a link, please feel free to send my way)