Caps and charging time

DrNomis · Post by **DrNomis** » 25 Dec 2010, 00:07

Greg_G wrote:I don't think you can define a cutoff point for guitar harmonics, and they can certainly go above 5000Hz...
Generally the lower ones will overpower them, but when you're playing with electronics anything's possible and those high harmonics can be fun.
There's also subharmonics when you start distorting, which extend below the fundamental.

The Ram's Head Muff did use a 10uf Input cap, but you're right that most versions used a .01uF.

JakeAC5253 wrote:Thanks! So caps block DC because it is constant, and cannot block AC so easily because it is constantly changing? It can only slow down the lower frequencies? Maybe because lower frequencies are closer to DC because they are more slowly changing?
I think a good way to visualise it is to consider that DC current involves the flow of electrons in one direction, and they can't flow through a capacitor.
AC is really a pulsing back and forwards of electrons.. so they can collect on one side of the capacitor, and then discharge and collect on the other without the need to flow through it.

Thanks for correcting me about guitar harmonics Greg_G,and you are right.....

I was mostly going by the original Transistor Big Muff Pi circuit,and my reccollections from when i built one a few years ago.....

Also,that visualization of AC and DC is a good one so I'll accept it.....

When I did my Certificate In Basic Electronics back in 94 and 95,we studied the effects of AC resistance of Capacitors a fair bit,I'm thinking of doing a quick demo of the effects on a breadboard,doing some screenshots that I can post,for the benefit of fellow members of course,I can do basic frequency response testing with my test gear at home too....

Would there be much interest in it?....

JakeAC5253 · Post by **JakeAC5253** » 25 Dec 2010, 00:48

Sure, I would be interested in that.

Since this thread I am actually leaning toward the fact that maybe my unit may not be fully functional. The unit, for quite a while, was reduced to scratchy noises and white noise fuzz. Out of the blue and for apparently no reason at all, it became functional again. I have reason to believe that there may be other problems at work here than simply poorly chosen component values. I would love some advice if that were possible

There are a few lifted lands and while the circuit seems to be functional now, it is entirely possible that something is grounding out somewhere in the circuit. It just seems like the circuit has no power really. In its stock form (literally every component has been modded from stock form) the circuit went from high gain to really high gain. Now it seems that it goes from anemic to mild gain. The tone of the circuit seems fine, but it just doesn't seem much like a fuzz level gain to me. The input resistor is 1M (Ram's Head Spec) as opposed to stock 2.2M. I think this could also be related to lack of grind. The emiter resistors on the clipping stages.have been jumpered in hopes to get more gain, but it did not fix the problem.

DrNomis · Post by **DrNomis** » 25 Dec 2010, 01:00

JakeAC5253 wrote:Sure, I would be interested in that.

Since this thread I am actually leaning toward the fact that maybe my unit may not be fully functional. The unit, for quite a while, was reduced to scratchy noises and white noise fuzz. Out of the blue and for apparently no reason at all, it became functional again. I have reason to believe that there may be other problems at work here than simply poorly chosen component values. I would love some advice if that were possible

There are a few lifted lands and while the circuit seems to be functional now, it is entirely possible that something is grounding out somewhere in the circuit. It just seems like the circuit has no power really. In its stock form (literally every component has been modded from stock form) the circuit went from high gain to really high gain. Now it seems that it goes from anemic to mild gain. The tone of the circuit seems fine, but it just doesn't seem much like a fuzz level gain to me. The input resistor is 1M (Ram's Head Spec) as opposed to stock 2.2M. I think this could also be related to lack of grind. The emiter resistors on the clipping stages.have been jumpered in hopes to get more gain, but it did not fix the problem.

I'd be willing to bet that there's something like an intermittent dry solder joint lurking somewhere on the circuit board,one of the lifted lands could be intermittently breaking/making contact,if you have a strong magnifying glass and a bright torch,try giving each solder joint a good examination.....

Also try flexing wires soldered to the board.....

Greg · Post by **Greg** » 25 Dec 2010, 01:32

JakeAC5253 wrote: The input resistor is 1M (Ram's Head Spec) as opposed to stock 2.2M. I think this could also be related to lack of grind.

That resistor is just a pulldown (to reduce switching pops) and won't affect the sound... 2.2M is fine.

Frabbio · Post by **Frabbio** » 22 Mar 2011, 20:39

Probably you just wired the switch grounding the input of the fx, so everytime you switch off the pedal the large input cap (10 uf right) discharge to ground and have to recharge completely when you turn on the Muff again.

Hides-His-Eyes · Post by **Hides-His-Eyes** » 23 Mar 2011, 10:14

Uncharged caps pass AC just fine.

Greg · Post by **Greg** » 23 Mar 2011, 10:18

Hides-His-Eyes wrote:Uncharged caps pass AC just fine.

Yes, that's the point...
it makes no difference to the function of the circuit.

DrNomis · Post by **DrNomis** » 23 Mar 2011, 11:34

Hides-His-Eyes wrote:Uncharged caps pass AC just fine.

True, I tend to liken them to frequency dependant resistors where the resistance drops as frequency goes up, at DC, they should present an infinite resistance, or practically an open-circuit.....

By resistance, I really mean impedance....

Frabbio · Post by **Frabbio** » 23 Mar 2011, 15:29

You're right

but everytime this happens to me (and happens only with fuzz-type circuits) the problem vanishes once i remove the input grounding, so i thought the charging time of the cap was the issue. Being a chemical engineer student i've only studied really basic things of electronic!

However, if i'm right also in the Black Russian Big Muff (true bypass version) the circuit input is not grounded.