Midi Clock noise issue

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?

alfred · 2016-10-01T18:39:18.558Z

Essentially it is a grounding problem. Neither the Sherman nor the A4 have safety grounds on the mains plug because both use power adapters and. Do you have any other gear (like mixers) connected that have a safety ground and that use shielded cables for connection? It might help to try around with that. Or try to use line isolators or di boxes with ground lifts in between.
These problems can be annoying and sometimes hard to fix because it can also be caused by the local power in your house.

mess5 · 2016-10-01T18:54:49.149Z

Thanks for quick replay!

Yeah, I have a grounded mixer, a4 midi going in to lxr, who transmits midi clock to sherman midi in, and from there, midi clock gets distributed to some other synths and computer.

Basicli I am using sherman filterbank as a midi spliter. But for now i get this noiz , like i am hearing midi clock in the sherman audio channel. Breaking the ground loop (( unplugging the cable )) at any point in midi or audio chain stops that noiz, but that is not a solution i am looking for.

alfred · 2016-10-01T19:01:18.986Z

There’s other ways to break the ground loop than to unplug the cable. As I said you can use a DI box or a line isolator.