Rat Clone Noise problems

[trad3mark]

So I just breadboarded a Rat clone. It's based on the schematic from the gaussmarkov.net site. sounds good(ish) so far, but i've had to make a few changes, and I've done some experimenting too. As a result, i've a few difficulties... The main issue is that it is REALLY noisy. It's not prohibitively noisy, but it's not that far off. I'm not sure if it's a naturally noisy pedal, but this is a bit much tbh.
Firstly, I didn't have an LM308. The only opamp i had about was a TL071. I'm ordering a bunch of random opamps for other projects, but it seems to be pretty noisy right at the output of the opamp. One such site suggested that if you're using a different opamp, a jumper may be needed instead of the 30pf between the offsets of the opamp. I've tried both higher and lower values and a jumper. It seems to have little or no difference, so right now, it's a 47pf.
Secondly, I tried a number of diodes for the clipping. It didnt have any effect on the noise, but oddly enough, I favoured LEDs over things like Germs, Silicons, and countless different silicon combinations, so, LEDs it is I think.
Other than that, i've checked the circuit a number of times, and it all seems to be spot on. If anyone's had a similar problem, or built a less noisy rat from a different schematic, please help.
Cheers,
tm

[MikeH]

It's difficult to answer without hearing it, but Rat's are noisy, 741s can be REALLY noisy, and anything will be much noisier on a breadboard than it will be when it's boxed up.

[trad3mark]

Might be worth building, and socketing the opamp or something?

[thedefog]

What kind of noisy, like high end hiss, or buzzy noisy?

It's normal to have a lot of hiss with the rat, since the gain is pretty high on it. But you shouldn't have any buzzy type noise when you're not playing. And I'd definitely put a socket in the real build so you can swap out the ICs and try different flavors. I preferred the sound of the LM308 in my turbo rat build over the TL071 and 741s.

+1 on the LED clipping. Turbo Rat sounds better than the 1n4148 clipping.

[trad3mark]

out of interest, what kind of clipping is the the You Dirty Rat?

Also, it's buzz noise.

[Jhouse]

out of interest, what kind of clipping is the the You Dirty Rat?

I think it's just a pair of 1n34's in there in place of the 1n914's so symmetrical hard clipping.

[MikeH]

out of interest, what kind of clipping is the the You Dirty Rat?

Also, it's buzz noise.

It's likely that you don't have something grounded properly.  Grounds that I would never overlook when boxing up an effect I sometimes overlook when I put one on the breadboard.

[ashcat_lt]

Are you using a battery or a wall-wart?  Does it get any better if you switch? 

Either way, I think it'll be quieter when you put it inside a properly grounded metal box.

Correct me if I'm mistaken, but I thought the TL07x opamps were internal compensated.  That cap is not necessary and has no real effect.  I have no reason to believe this would cause your noise issue, though.

[darron]

the tl071 should work without any compensation cap at all, instead of a jumper. leave the pins floating. not that this will probably fix your problem, but it answers one of your comments...

[trad3mark]

Right, so a little update.

It's running off a Boss power supply (reading 9.4V). I tried it with a semi-old battery (8.8V) and it was much the same. For what it's worth, it's based off the "original" schematic. I notice that a lot of the "newer" ones have an extra fet before the opamp. I've no real intention on breadboarding that into it. It sounds good as is. I think i'll probably go ahead and box it all up. It's only noisy when I'm not playing. Any sort of sound going through it and it's not bad at all. I'll check all the groundings again, but im almost positive it's correct.

Out of interest, I'm always looking for ways to improve my build quality, so whenever I get my hands on a pedal, I crack it open to see whats what. I've just noticed that some of my pedals seem to also have the common ground touching off the metal case somewhere, and others dont. Does this make much/any difference? In a pedal as noisy as this, is it worth doing?

[zombiwoof]

Right, so a little update.

It's running off a Boss power supply (reading 9.4V). I tried it with a semi-old battery (8.8V) and it was much the same. For what it's worth, it's based off the "original" schematic. I notice that a lot of the "newer" ones have an extra fet before the opamp. I've no real intention on breadboarding that into it. It sounds good as is. I think i'll probably go ahead and box it all up. It's only noisy when I'm not playing. Any sort of sound going through it and it's not bad at all. I'll check all the groundings again, but im almost positive it's correct.

Out of interest, I'm always looking for ways to improve my build quality, so whenever I get my hands on a pedal, I crack it open to see whats what. I've just noticed that some of my pedals seem to also have the common ground touching off the metal case somewhere, and others dont. Does this make much/any difference? In a pedal as noisy as this, is it worth doing?

I think that "extra" FET in the newer ones is probably necessary with the OP07 opamp they're using now, but I'm not sure.  I did read that the OP opamp needs and extra component, so that's probably it.

You may find the pedal isn't as noisy when you box it up.  Let us know after you've done that.

Al

[thedefog]

Out of interest, I'm always looking for ways to improve my build quality, so whenever I get my hands on a pedal, I crack it open to see whats what. I've just noticed that some of my pedals seem to also have the common ground touching off the metal case somewhere, and others dont. Does this make much/any difference? In a pedal as noisy as this, is it worth doing?

If you've got metal 1/4" jacks on a metal enclosure, then the ground is running to the case anyway. The only time they might want to run a ground wire to the case is if they're using those isolated plastic 1/4" jacks. As long as you are avoiding ground loops, you should be fine.