Fuzzface NPN trouble with DC power

[angelodp]

Hi I have a recent build based on various intel used to create the NPN EJ Fuzzface. It has a great smooth sustain and buzz on the bass notes, I love it. It works very well with battery, but when I plug in a One Spot, its a mess, all noisey and unplayable. Here is the layout, I wonder if you might see my error. The NPN Silicon T's are hi-gain, 200/450 aprox

[thetragichero]

maybe a dumb suggestion, but how about like a 100uf electro cap from the power supply to ground. first thing before v+ goes anywhere else. should be able to try it with clip leads without modifying the circuit in case it doesn't work. the rest looks kosher at quick glance between it and other npn schematics, besides the fact that most use pretty low gain transistors

I am *hoping* that it's just a case of inadequate supply filtering made an issue by high gain. if not then we may need to get our hands dirty

[thetragichero]

if 100uf helps a bit, try 150uf or 220uf as well before soldering anything. been messing with some muff variations and they go up to 220uf. obv you'd want to use the lowest value that gets you where you want to go

[angelodp]

I can try it. So 100uf between 1 &3 on the DC jack right.

A

[thetragichero]

looks like 1 and 2. 3 looks like it is v+ from the battery
negative side off the cap to ground, of course

[angelodp]

Ok thanks, tried that and it kind of works. I have a Pedal Power ISO 5 to feed that pedal. I have to button up the pedal with its cover to check. I may have a 6V6 in my Champ that is starting to go as it seems to oscillate at times. Since this pedal is NPN with negative ground, i am surprised that I am having these issues.

A

[JohnH]

If the cap helps, it might work even better with a resistor in the + power lead, between + supply and cap. Ive done it this way on my builds. It seperates the circuit further from the supply, letting the cap do an even better job of smoothing and filtering.

So, the cap goes from + to gnd of the fuzz circuit itself (not the LED circuit), then feed that through the resistor in the + supply. Then connect the LED circuit, outside of this smoothed supply, then to power supply.

The R value should be worked out to drop about .25V at the current used by the circuit. Need to work that out or measure it, but if the circuit draws say 1mA, then the resistor could be around 250 ohms, so say 220 for a real value.

On this OD circuit, the resistor and cap are C8 and R14:

guitarnuts2.proboards.com/thread/4987/bluejuice-overdrive-using-jfets

[blademaster2]

Just a thought:

Except for power supply smoothing via the added cap, does your circuit creates its rails by splitting the DC supply locally and considering the mid-point to be 'ground' (I am not looking at the circuit just now so I apologize if this is obvious on inspection)?

If so, then a ground-referenced adapter might not be happy with this circuit if it plugs into a grounded amplifier, since it will short out the bottom half of the split supply that was created from an already-grounded adapter.

Besides that, and power supply smoothing form the adapter I cannot imagine anything else that would be different.

[angelodp]

Thanks John, I will try that. BTW your JFET OD pedal looks like a good one, might try it. Would you happen to know about these small caps. This little silver guy is .22uf 20v. I want to try it in a pedal circuit as I don't have any other .22uf at the moment. I think it might be tantulum?? Can you shed any light please. 

Best A 

[JohnH]

Im not familiar with that cap style, but on spec it should be fine. is the value of 0.22uF clear? Ive never seen a cap of that low a value with that low a voltage spec.

[thetragichero]

you sure it's .22uf?



these look of similar construction and they're in the range of pf (the large one is 4300pf 630v, the others are 33pf and 47pf. the resistor is there for size comparison)

[angelodp]

Yes it measures out at .22uf, just never seen this type before.

[sumgai]

Dec 14, 2018 15:19:06 GMT -5 angelodp said:

.....
Would you happen to know about these small caps. This little silver guy is .22uf 20v. I want to try it in a pedal circuit as I don't have any other .22uf at the moment. I think it might be tantulum?? Can you shed any light please. 

Those are known as polystyrene capacitors. Over the years, there have been many arguments in the guitar world as to whether they affect the tone in some negative manner. My only beef with them is that they can be all over the map where the marked value is not reliable, i.e. it may say "0.22mmf", but in reality the value might be 5, 10, or even 20 times that marking! This is one time-and-place where a multimeter that has a Capacitance selection would come in handy.

HTH

sumgai

[ashcatlt]

Dec 9, 2018 15:03:28 GMT -5 JohnH said:

If the cap helps, it might work even better with a resistor in the + power lead, between + supply and cap.

And while you're at it stick a diode in series too just in case some genius plugs in the wrong adapter. A shottky diode will not cause much drop in the power supply, but it WILL save your pedal from burning.

[angelodp]

Thanks for chimning guys. It is at .22uf by way of my cap meter. I decided not to use it on this build. BTW I have just completed a Sola MarkIII tonebender PNP germ. I have a bunch of these "fuzz" types now and I have to say that for my ears the Fulltone 69 clone and the EJ Si clone are my favs. The EJ Si has a singing tone that is beyond real fuzz, more into a sustain nearly Muff feel, not quite. So its a nice step back from the full blown Muff Pi. The Fulltone has the most flexability and great tone. After 50+ years of rock my upper freqs are suffering so I like the Si feel.

Always appreciate your kind and generous responces. Happy happy.

best Ange