Moodring white noise

[Boba7]

EDIT: problem solved. C11 is back to the original value, and I had to tweak R9 and R27 to get the proper voltages, and that's it


Sorry for starting yet another topic on a white noise issue in a Moodring build. But if anyone could help me and provide some voltages from a working Moodring, it'd be just awesome!!


Description:
My build works perfectly well, it even sounds amazing, but there's some obvious white noise pretty much all the time on the wet signal (unless of course the level pot is turned all the way down). My build is true bypass, so of course no noise when the effect is disengaged.
If I turn up the tone control or the ring (level) control, I hear more white noise.

I double checked all the components values, the diodes and electros (which by the way are good ones) orientations, the pot values. I took out the limiter led just in case, then put it back.
The only thing I did was put some 1/8w resistors here and there. Pretty much all the 10ks are 1/8w. EDIT: I changed for regular 1/4w but it didn't change anything (of course)

I tried 3 working (tested in another build) PT2399s, and 8 different opamps, all fully functional. It didn't change anything.

Voltages:
Of all the ICs voltages, 2 look quite suspicious to me: pin 3 and 5 from IC4. I tried to change R9 and R27 to get higher voltages on pin3 and 5 (resp. 3,97 and 4,04v after that) but it didn't change anything.

Here are the recommended voltages for IC4 (from the madbean doc, please note it included a 10r power supply resistor) :
1- 4,16
2- 4,5
3- 3,95
4- 0
5- 3,7
6- 4,15
7- 4,14
8- 8,3

And here are my voltages
1- 4,54
2- 4,54
3- 2,26
4- 0
5- 2,26
6- 4,54
7- 4,54
8- 9,05

Pin 3 and 5 look odd to me.
All other voltage from the brick, the pt2399 or IC1 look perfect (exactly like on the build document. I can measure them again if need be)

Audio probe:
Using an audio probe, it seems that essentially the white noise starts at pin1 of IC4a (pin 3 is quiet) and pin7 of IC4b (pin5 is quieter, though not quiet of course, since the noise from pin1 went through the PT2399 and the Belton brick)
Pin5 or 6 on the brick are a bit noisier than pin3, but not much.

What I've tried so far:
- Opamps: tried 8 different ones, all functional. Now it's loaded with 2xNE5532
- PT2399: tried 3 tested ones, no difference.
- Voltages: tried to change R9 and R27 to get higher voltages on pin 3 and 5 of IC4 (resp. 3,97 and 4,04v after that), but it didn't change anything.
- Adding a 10r at the power input didn't change anything
- Raising C24 to 100nf (instead of 100pf) reduced the noise but affected the wet signal too much to be a solution.
- Same with C7 at 1nf (instead of 330pf), a bit less noise, but the wet signal was too affected.
- Adding another 100uf to C36 or C34 didn't change anything.

I just dont understand why the opamp adds so much noise.

Any help is greatly appreciated!

Thanks a lot guys.

[neandrewthal]

If you've checked it as well as you say then your noise is probably just coming from the brick.

Or maybe I'm just saying that because mine has the same problem, the first appearance of the noise is on the output of the brick and I'm too lazy to check everything else as well as you did.

[Boba7]

I'm gonna audio probe it more thoroughly tonight if I can, cause I'm not entirely sure the noise comes the brick (I checked really quickly the other day)

I'm wondering if the difference in voltages between my build and madbean's build could explain the noise also. No idea.

And I've changed my 1/8w 10k's for 1/4w, and of course it didn't make any difference...

[Boba7]

Nope, I definitely have white noise coming out at pin 1 of IC4. Pin 3 is quiet (just a little noise, same as pin 1 of IC1), and pin 1 is (very) noisy.

But also at IC1, pin 1 is a little noisier than pin 2.

It's like both opamps, but mostly IC4, provide and amplify noise.

Could there be anything wrong in the way IC4 get powered? I've triple checked everything I think. Still pin 3 and 5 of IC4 seem to not get enough power. Is it a possible cause for noise?

[Boba7]

Edit, see 1st post.

[Boba7]

Edit, see 1st post.

[Boba7]

Just thinking out loud, again! Sorry for those very lonely posts, I hope someone chimes in sometime

I tried to put back the 10r (as on the previous version), and it didn't change anything.

Could it be that I hear noise from the power rail? Should I try and isolate (100uf and 100r resistor) the power cable going to the opamps etc and the one going to the 5v regulator?

[Boba7]

Edit, see 1st post.

[Boba7]

Edit, see 1st post.

[Boba7]

Edit, see 1st post.

[Boba7]

I edited the first post of this topic to be clearer.

If anyone has any idea, they're welcome.

It's very frustrating that this amazing reverb is so noisy.

Thanks!!

[Boba7]

Forgot to mention I have a TH custom relay true bypass board in this build, but it seems impossible that it could affect the sound right?

(Up )

[Boba7]

So... No one has any idea why ic4 produces so much white noise on pin1 and 7? Anything I could try?

Apart from that, I've been playing the pedal a lot and it's a really awesome reverb.
I just modded today the tone section a bit to have a flatter response in the middle of the pot's course. It didn't affect the noise of course.

[Boba7]

In case anyone thinks this topic has got many answers already... I'm pretty much the only one replying!

So does anyone have any idea where to start?

[madbean]

Sorry for the late check-in on this thread. I appreciate you sticking with it.

The lower voltage reading at pin3 of IC4 could be explained by the added series resistance of R10-12. Since you have done this true-bypass I assume you omitted either R8 or R9 and jumpered the BYP switch, correct?

The voltages could explain the noise, certainly, so let's see if we can raise it a bit. Possibly we need to lower the overall resistance in your case to see if it increases the VB voltage supply to IC4. This would mean putting in another 1M resistor in the R8 or R9 you omitted to come out with 470k instead of 1M. Or, even going down to 220k overall.