Noise issues - should I try screened cable?

[Just1More]

Yesterday was the fist time I got to try out my Rat build at anything like performance volume and I discovered some noise issues that weren't evident at quite bedroom levels.  It's basically white noise, but there is a touch of hum with the drive pot set between about 10 and 3 o'clock.  Other than that it sounds fantastic, so I really want to get the noise cleaned up if I can.

I did an isolated test with a battery and the noise is still there at similar levels, so the problem is inherent in my build (ie. not the power supply).   Guitar is a strat with single coils, but it's far noisier than the standard level of noise with this guitar (BSIAB2 is much quieter at equivalent volume levels).

I modified the circuit to have switchable clipping diode options to give more flexibility.  I suspect the placement of these may be the source of the problem.  One is right above the input jack and one is right above the output jack which in retrospect may not have been the most sensible position for these.  I've tried to keep the hook-up wires as short as possible, but it's a fairly high gain circuit so they may still be longer than is desirable.  Here's a shot of the internals if it helps  (green wires link the PCB to the switches):


Questions:
1. Is this the likely source of noise or am I barking up the wrong tree?
2. What should be replaced with screened cable?  Just input and output leads?  Should I also replace the leads from the board to switch?
3. Is there anything else I should be looking at?

Thanks in advance.

[GibsonGM]

Nice clean build, Just1.  That noise seems to suggest either your idea, or a ground problem.  I'd free the board, plug it in, and audio probe the thing around the IC and diodes, see where the noise first occurs. Spend time there rather than rewiring first.  Using shielded cable at the input or whatever could help with hiss, but the Hummm you describe sounds like a ground issue to me - like, something is grounded that shouldn't be.  Your switch wiring COULD be off, it's hard to tell from the little pic {labeled diagram would help us see that}.  Check ALL your solder connections, parts orientation.  Read the "What to do if it doesn't work" post, and post voltages for us.

Try "chopsticking' those wires around as you listen to it, see if it changes, which would be a giveaway.  Try measuring for DC on the pots, and measure across your output jack to see if there is any DC there.  I've had a few projects Hummmm and it's always been something like a short to ground somewhere or a ground loop (is your output jack grounded? I usually just have mine connected to the enclosure, no wire to it) - an unconnected part, component orientation (IC in there the right way?)  or something.  The final causes for me have been opamp oscillation and wire placement, so don't rip it all up just yet!  lol It's usually just something simple and overlooked...

~Mike 

[petemoore]

 Doubt falls on circuit as suspect...
  Because it looks like really neat/clean and tidy Rat guts.
  Not sure which are the signal wires etc. Try to keep the sensative input from running adjacent a V+ or output signal wire, basically try to have X shape where wires cross instead of parallel wires, and that said 'it's probably not the source of your noise.
  Test...what is introduced as noise at the input when your guitar is/isn't plugged in, does noise stay when guitar volume is effectively at 0 ? Is it a HB guitar...ie some/most of that noise could be a from a source besides in that pedal? Try a different guitar, waving the 'antennae' [strings] around helps tune in/out noise.
  Hum...eliminate PS from operation to test for that as hum source.
  Hiss...that one..I don't like to say opamp but opamp, Rats hissing is not necessarily a centuries old wives tale, mine does that, and I don't remember for sure but I think it is neccesarily inherent that some hissing occurs with this species, regardless of what it's fed.

[Just1More]

Mike and Pete, thanks for your replies.

Followup from Mike's post:
Switch wiring was done using the Tonpad Offboard wiring #5 project (http://www.tonepad.com/getFileInfo.asp?id=76).  There is a ground wire from the output jack back to the input jack.  I won't have much time to poke around with it over the next few days, but I can see some opportunities for repositioning of wiring to get the signal leads further away from the power leads.

Followup from Pete's post:
Now I'm really glad I used different coloured wires:
Black = ground
Red = power (+)
White = input
Blue and Orange = output
Green = circuit to switches

Noise is present with a single-coiled equipped strat, a humbucker equipped Ibanez and with no guitar plugged in at all.  There is some change to the sound but it's all at a pretty similar level - similar enough for me to say it didn't make a difference therefore my conclusion is that the problem is with the circuit itself.  I didn't test with the guitar volume at zero last night, but I'm pretty sure I did this previously with no effect on the hiss level.

The noise is also present with the clipping diodes switched out of the circuit.  I'll consider getting another opamp and trying that as a last resort if I don't get anywhere trying other things.

Thanks again for your suggestions.

[petemoore]

I didn't test with the guitar volume at zero last night
  oh that's my favorite though, i can't think of an easier way to ground the input.

[Just1More]

I didn't test with the guitar volume at zero last night
  oh that's my favorite though, i can't think of an easier way to ground the input.

I'll give it a go tonight and report back.

[Just1More]

The plot thickens...

Tested with both single coil and humbucker guitars with the volume pot at zero.  Hum was gone (so I guess we can put that down to the guitars).  It was understandably more noticeable with the strat plugged in.  The hiss is still there - it's noisier than I'd like but probably tolerable.  I've also had a poke around inside to keep leads as far out of each other's way as possible and to avoid running parallel leads where possible - no noticeable difference in the hiss.

When I put the pedal back on my board I noticed a new issue - a high pitched whistle/whine kind of noise - much like you can get if you have a radio that isn't quite tuned to the station properly, especially on the AM band.  This seems to be related to the Boss RV5 pedal adjacent to the Rat.  When the RV5 is on the whine is present, when it's off it goes away.  This happens irrespective of whether the Rat is powered by a battery or the power supply (Diago Powerstation).  Unfortunately the RV5 is on pretty well all the time to add just a touch of reverb.

I'm out of time tonight, but I guess the next step is to try switching the order of the Rat and the BSIAB2 in the signal chain to get the Rat further away from the RV5 and see if that helps.

[Jered]

  You could try adding a small cap, 100 pF or so, to the input FET gate to ground. Just clip it in with alligator clips. If it kills the noise then solder it in.
  Jered

[Just1More]

I switched the position of the Rat and the BSIAB and the whine is gone from the Rat  but is now present in the BSIAB  .  Again it goes away if I turn the RV5 off so I've found the culprit.  I usually have the RV5 on the whole time for a bit of subtle reverb. Bummer.

Options
1. Reorganise the board - could be difficult, space is tight and RV5 really needs to be last in the chain.
2. Ditch the RV5.

Any one got any other bright ideas?