Mudbunny: Filter cap

[henryadams]

Ok, one more MB question (and thanks, all, for the help on my last one). I want to bump up the value of the caps that filter the 9V source to help decrease the noise of the pedal. I'm a bit of a newb at reading schems, but from what I can tell the filter cap is either C15 or C14 (or both?). Can anyone clear this up for me?

[jkokura]

I understand wanting to decrease noise, but since the power filter cap (C14) is already 100uF, there isn't going to be much improvement. You could increase it to 220uF if you'd like, and see what happens. I don't think there will be any difference in noise, but there won't be any difference in tone as far as I can see. Try and it and tell us what happens!

The reason I don't think the noise will decrease is because the noise isn't generated from the power to the circuit. It's generated, as fas as I can understand, it's generated in the gain stages of the transistors. It's an inherent problem that all Muffs have, regardless of transistor type, it's just because the transistors together create noise.

While I'm thinking about it, if you wanted to try increasing the output cap (C13) that might reduce some noise. Noise is sometimes introduced into a circuit, and your output cap's job is reduce the DC so that your signal is clean AC. 100nF *should* be enough, but you could try bumping this to 220, 330, 470, 680, 820, or even 1uF Film. If need be, you could even go up to 1-10uF Electrolytic. I'm not sure what this would do to the sound of the pedal, but you could try it and see, because if you want to reduce noise, this would be the best method I can think of.

Jacob

[madbean]

I've never met a non-noisy Muff. If you want the gain, you have to take a little noise with it. Best case scenario is to use all metal film resistors. You could add an extra stage of power filtering which may help. What you would do is take the 9v wire into a 100R resistor and a 100uF to ground. This doubles up the filtering. If you are running battery it won't make a difference though.

9v----  -[100R in series]-  ----  100uF to ground ----- to 9v input on the PCB.

[henryadams]

Hmmmmm, ok all of this helps and, since I already have a muff and don't mind the noise too much (except with my semi-hollow danelectro), I may just forget it. But here's the info I got:

make the filter cap that comes off your 9VDC source as big as you can. I now make it 470uF always, and I've seen at least one builder (Dice Works) use 1000uF. BJT transistors in these old crude circuits can be fantastic hum amplifiers with the sustain control all the way up - the big filter cap REALLY helps.

[stecykmi]

Ok, one more MB question (and thanks, all, for the help on my last one). I want to bump up the value of the caps that filter the 9V source to help decrease the noise of the pedal. I'm a bit of a newb at reading schems, but from what I can tell the filter cap is either C15 or C14 (or both?). Can anyone clear this up for me?

Both C15 and C14 are power filtering. The reason C15 is poly-film and C14 is electrolytic is because electrolytic have a hard time filtering really high frequency signals. Even though poly-film caps have much less capacitance, they will pass high frequency much easier. Since they're in series, you get the best of both: good high frequency and low frequency filtering.

So you can increase these caps as much as you want, just as long as you keep one electrolytic and one poly.

I understand wanting to decrease noise, but since the power filter cap (C14) is already 100uF, there isn't going to be much improvement. You could increase it to 220uF if you'd like, and see what happens. I don't think there will be any difference in noise, but there won't be any difference in tone as far as I can see. Try and it and tell us what happens!

The reason I don't think the noise will decrease is because the noise isn't generated from the power to the circuit. It's generated, as fas as I can understand, it's generated in the gain stages of the transistors. It's an inherent problem that all Muffs have, regardless of transistor type, it's just because the transistors together create noise.

While I'm thinking about it, if you wanted to try increasing the output cap (C13) that might reduce some noise. Noise is sometimes introduced into a circuit, and your output cap's job is reduce the DC so that your signal is clean AC. 100nF *should* be enough, but you could try bumping this to 220, 330, 470, 680, 820, or even 1uF Film. If need be, you could even go up to 1-10uF Electrolytic. I'm not sure what this would do to the sound of the pedal, but you could try it and see, because if you want to reduce noise, this would be the best method I can think of.

Jacob

I don't think C13 will do anything for noise. It's a decoupling cap so it blocks ALL DC, but it's also series cap so it's acting as high pass filter. If you increase this cap, the sound will be darker, but it's fairly large so it may not do anything at all.

[bigmufffuzzwizz]

Can you hear the noise when you rocking out w/ volume maxxed?  

[garfo]

Ok, one more MB question (and thanks, all, for the help on my last one). I want to bump up the value of the caps that filter the 9V source to help decrease the noise of the pedal. I'm a bit of a newb at reading schems, but from what I can tell the filter cap is either C15 or C14 (or both?). Can anyone clear this up for me?

The best way to decrease noise is to make a clean wiring.Wire and solder the grounds all to the same spot, and make it as clean as possible in terms of wiring, that will reduce the noise.

[bigmufffuzzwizz]

Has anyone tried the gate mod for muffs? I've still yet but its supposed to suppress all the floor noise!

[jtn191]

Skreddy/aka Marc likes BC550C as the least noisy transistors 

[garfo]

I've had abad experience with muffs in terms of noise and I dizcovered that doing a good job with wiring(clean and short), as well as soldering all of the grounds on the same point have solved 90% of the noise floor.

[pickdropper]

Skreddy/aka Marc likes BC550C as the least noisy transistors 

Lots of folks love the 550c, but they sound quite different to me.  To me, whether or not that is the sound that I am going for is more important than the noise improvement.

They do sound good, just a bit tighter and less muffy to me.

[RobA]

I agree about the BC550C/BC549C. I like them. They are great transistors in the right place. But, I really dislike them when they are overdriven. They seem harsh to me compared to say the 2N5088.

I did one build of the Big Muff where I put a BC550C in Q1 and Q4 and 2N5088's in the middle two clipping sections. It's a good compromise as long as I don't drive it too hard on the input.

On another build, I used AC187's for Q1 and Q4 and 2N5088's in Q2 and Q3. On this one, the harder you drive the input, the better it sounds. It's really nice with active pickups. Also, when I use it with the Duncan Blackouts, it's dead quiet.