Midi Clock noise issue

sicijk · 2014-11-12T06:40:57.000Z

Hi guys…posting here since OT is the clock and transport master…

I have this simple setup:

MIDI ROUTING

• OT out > FB2 inp (sherman filterbank2)

• FB2 thru > A4
> KP3 (kaoss pad3)

AUDIO ROUTING

• OT Cue out to [FB2 > StompBoxes > KP3] > OT Inp A/B

• A4 out > OT Inp C/D

Using this setup, with stomp boxes (overdrives&co.), I can clearly hear the noise generated from MIDI CLOCK (the ticks!).
Also changing the bpm results in a faster/slower noise…

I can hear also the hum and various amplified noises…but that’s part of the deal…but midi noise!!!

I did different trials…it comes out only when I introduce the stompboxes chain…and I can cut it out in two ways:

disabling MidiClock send from OT
phisically disconnecting the Midi cable from OT out -or- from FB2 inp.

No one of these are an option for me…! Other then putting out the overdrives chain from the signal…but I would be really sad…jeez-----FB2 and EHX Germanium OD then LPB-1 is a real scream and pleasure…

Anyway…Did any of you hear this noise coming out from Midi signal??
I am really hoping for an Eureka from some of you crazy Electricians out there =)

Thanks guys…I am really struggling with this issue

t · 2014-11-12T08:24:50.000Z

Sounds like a grounding issue. When you have a ground loop, all kind of weird (digital) noise can get into your audio signal path.

How are your devices connected to power? Do any of your devices have a 3-prong power plug that includes ground? Is this connected to a power outlet that’s (actually) grounded?

You can try taking devices out of the signal chain to see if that alleviates the issue. From what you describe above, the issue is gone when you unplug the signal that’s going into the OT Input A/B, right?

You might want to read http://www.soundonsound.com/sos/1994_articles/aug94/groundloops.html

sicijk · 2014-11-12T10:38:24.000Z

No, It goes away when I put out the stompboxes chain (that is giving huge amount of gain due to overdrives&co).

It goes away if I unplug MIDI cable from OT out --or-- from FB2 inp.

It exists of course on INP A/B since it is coming from the chain that returns on that audio input.

Everything is powered from a single outlet on the wall.

In the stompboxes chain there is also the powering device that is a crappy HarleyBenton PowerPlant Junior.
But I tried also using only internal 9V battery and the problem is the same.

I noticed that I can lower the intensity of the noise by unplugging MIDI cables from other devices (i.e. A4 and KP3). But it is there anyway.

I tried changing MIDI cables (not sure if the All 5 pins connected can cause a problem…) and also swapping the electrical powering using different wall outlets…nothing changed

t · 2014-11-12T11:12:23.000Z

So, the problem goes away when you remove the MIDI connection between the OT and the FB?

sicijk · 2014-11-12T11:18:07.000Z

Yes.

Also if I stop the OT to send clock.

I did another try putting out the FB2.

The CUE out now feeds only this chain: Stompboxes > KP3.

That noise has disappeared…so it has something to do with the FB2.
In the afternoon I’ll try with friend’s FB2 in order to check if this happens also on his device…the fog is growing…

Thanks for your assistance t

t · 2014-11-12T12:12:40.000Z

No fog here, this is just a classic ground loop issue. You could try breaking the loop by taking a MIDI cable, disconnecting ground on one side, and using that cable to connect to the FB.

sicijk · 2014-11-12T14:37:36.000Z

Opening a cable that is plastic-melted its not an option here…since I do not have possibilities to close it back.

Anyway: Herman (the creator of FB) told me that MIDI clock becomes audible with high input level settings…I do not have that (I usually have it at its indented position, 12 o’clock)…but I have huge gain afterwards the FB2 (stompboxes).

I tried with another unit to double-check…same behaviour.

Do you have a FB2 t ?

t · 2014-11-12T14:54:11.000Z

No, I don’t. This might be an issue specific to this device, but it does indicate poor separation of the control circuitry and the audio signal path.

I still think this is mostly a ground loop issue. You’re not only looping audio out from the OT back in the OT, but also MIDI to the same device. The grounds across all those paths are shared and that can really start to pick up and amplify digital noise.

You can create an unshielded MIDI cable by cutting and old cable in half, re-connecting the inner wires, but not the shielding. You want to try this with an old cable you no longer nee since this might actually make things worse.

sicijk · 2014-11-12T15:17:04.000Z

ok ok …

Afternoon in laboratory =)

Herman confirmed me that it could really be a bad grounding somewhere, as you wrote!

He tried as well with huge amount of input gain, without ever hearing the midi clock noise…

I have to disassemble all my rig…shit

avantronica · 2014-11-12T17:06:12.000Z

If all is well with your midi cables then the opto isolation ought to rule that aspect out

Always keep it really simple, then add things in until the issue starts

Swap just the fb2 for another device, see if it’s the same etc etc !

mezz303 · 2014-11-12T17:40:56.000Z

I used to get midi noise and hum from grounding issues.
The solution was to swap all of my audio cables for balanced ones. It cost a fortune but it was definately worth it. Never had a problem since.
I can now have 10 synths switched on and enjoy absolute silence when nothing is playing.
This might be amazing to some but in 20 years of using midi, I have never once come across a faulty midi cable.
I would look at the audio cabling first.

sicijk · 2014-11-12T17:46:10.000Z

Indeed!

I tried with only the OT and FB2 connected (both audio and midi).
Result = no noise.

Then I connected one of the FB2’s THRU and the noise was injected.
Added the second THRU.
Result = more noise (level).

The Huge Herman, finally, came with a possible solution: short circuit on the coil next to the optocoupler.

The iron is warming…

I’ll report back test results.

sicijk · 2014-11-12T17:54:55.000Z

""mezz303"":

I used to get midi noise and hum from grounding issues.
The solution was to swap all of my audio cables for balanced ones. It cost a fortune but it was definately worth it. Never had a problem since.
I can now have 10 synths switched on and enjoy absolute silence when nothing is playing.
This might be amazing to some but in 20 years of using midi, I have never once come across a faulty midi cable.
I would look at the audio cabling first.

It is not recommended to use TRS (balanced) connection on the FB2.
Also the Midi INP on it doesn’t have the ground (PIN2) connected. So a screen-cutting on the midi cable would not make any difference.
Also I have manually wired all the audio cables, using screened pairs (balanced) within an 8-core loom.
Doesn’t make any sense to use balanced cables on unbalanced source.
It would, if connected in pseudo-balanced configuration (connection #14)
On my rig only the OT’s outs (Main and Cue) and A4 (outs) are wired with real balanced connection (even if they are “only” impedance balanced)
.
Other wirings (involving unbalanced source and inputs, i.e. FB2 and KP3) are connected using that Rane’s scheme.

sicijk · 2014-11-12T18:11:50.000Z

I did what Herman told me to do…and that clock noise has disappeared!!

SuperYESSSS!!!

t · 2014-11-12T19:38:03.000Z

""avantronica"":

If all is well with your midi cables then the opto isolation ought to rule that aspect out

I’m not sure that what’s stated in that SoS article is actually correct in all practical cases.

The optical isolation on MIDI IN ports applies to the signal, not to the cable shielding connected to pin 2.

It is true that according to the “MIDI Electrical Specification”, device manufacturers are supposed to only ground MIDI OUT connectors, and to not ground the MIDI IN connector to chassis or common ground. In practice, this is not always the case.

Since the issue only occurs when the MIDI cable is connected to the FB, I suspected that the grounding on the MIDI IN on the FB was incorrectly connected.

sicijk · 2014-11-12T20:26:07.000Z

""t"":

[quote=“avantronica”]If all is well with your midi cables then the opto isolation ought to rule that aspect out

I’m not sure that what’s stated in that SoS article is actually correct in all practical cases.

The optical isolation on MIDI IN ports applies to the signal, not to the cable shielding connected to pin 2.

It is true that according to the “MIDI Electrical Specification”, device manufacturers are supposed to only ground MIDI OUT connectors, and to not ground the MIDI IN connector to chassis or common ground. In practice, this is not always the case.

Since the issue only occurs when the MIDI cable is connected to the FB, I suspected that the grounding on the MIDI IN on the FB was incorrectly connected.[/quote]
As I wrote above, the MIDI INP doesn’t give any noise. It happens only when I start to connect also the THRUs

t · 2014-11-12T20:32:12.000Z

""sicijk"":

As I wrote above, the MIDI INP doesn’t give any noise. It happens only when I start to connect also the THRUs

Ah, I missed that. Glad you got it sorted out.

robotunes · 2014-11-12T21:17:21.000Z

@sicijk

nice setup. link to your tunes?

sicijk · 2014-11-13T10:13:15.000Z

@All
thanks for your support guys!

Actually the noise is not disappeared at all.
But now it is acceptable as the hums and demons coming out from the stompboxes!

@robotunes
the setup is in progress…I mean: it is getting to a comfortable state of fun since I am also trying to implement the TimefrogIII, but the variables increase.

I do not have any released tracks…only some experiments and two remixes for two contests (one was an OT lab)

Anyway…the project is Dinosaturo

mess5 · 2016-10-01T18:20:27.621Z

Hi, i know its an old tread but i have the same problem with a4 and sherman 2. What was the solution?