help w/ noisy TS-9 clone

[Unclerny]

Hi All, I hope someone can help me with this.  I've built a TS-9 clone that is giving me trouble.  The unit is working and don't sound too bad and actually sounds really nice with a Strat.  It is actually the Overdone Fulldrive 1 listed on General Guitar Gadgets if the schematic helps.

Here's my problem, as I roll the volume off the guitar a crackle or static-like noise begins as soon as the volume is below full and gets worse as the volume goes down.  When the guitar is off the noise is actually less but it's obviously there and is unacceptable.  It has reasonable hiss with the guitar full up.  This doesn't sound like a ground more like a grind or growl.

I used the RC4558 and 2n3904 xters.  I had the problem when it was on the bread board but I figured it was noise being picked up from the extra leads and exposed circuit.  I guess I was wrong there.  I wonder if one of the xters is bad?

I'd also have to say the drive doesn't have a lot of variation.  After about half it has little change.  This may also be part of the problem.  It has lots of distortion and cleans up fairly well.  There diodes may be going into full clip too early and that's why the distortion range is limited.  I used silicon and assemetric configuration.
Any help would be greatly appreciated.

[Unclerny]

No one replied but I figured it out.

It was the 2N3904 xters.  Sorting them showed that they had very wide gain tolerances and about 8 in 10 were unsuitable for use.

I've bought a large batch of 2N5088 and found them to be very close gain wise and extremely clean by comparison.

This may help some one eventually.

[oldrocker]

I just built a TS-808 and used the 3904's and it works great.  It might be the resistor change at the end of the circuit I don't know.  I have question though.  Where the diodes are off of pin 2 there is a .047uF cap and a 4.7 resister.  On Tonepad they trail off to ground and on General Guitar Gadgets they go to Vb or Vr.  Where did yours trail off to ground or Vr?  Just curious.

[Unclerny]

I use the tonepad board but I know mine goes to Vb.  You should check that you have the version 2 drawing.  I had problems with the first version.

[oldrocker]

Oh yeah I see the newer version is different.  I guess I'm going to rewire mine but it's working good now.  Sometime I go throught all this trouble to change some small thing and either end up changing back or I don't see much difference either way.  I guess that's how you learn.  Thanks for the heads up on that.

[Unclerny]

No problem, I've gotten pretty good at the TS since my OverDriver is a clone with a couple tweaks.

I find that setting up a gain structure to a 4558 type opamp is easier and cleaner using Vb for referance.  Going to the ground usually ends up needing a polarized cap and possibly a voltage divider on the input.

Hope that helps.
UE

[Unclerny]

One other thing, sort your 2n3904 xters and see if you have a wide variation in gain.  I'm just curious.

UE