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nw2s::io bleed between channels
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Author nw2s::io bleed between channels
ThinLazy
I have an unbalanced nw2s::io that I bought already built and Im getting significant bleed between channels coming out of the modular. Has anyone else had this problem? Does anyone know of a modification to increase the isolation between channels?
Thanks,
Thinlazy
scottwilson
Sorry you're having trouble.

The unbalanced module has a passive output circuit - meaning no electronics at all between the input and the output, so the crosstalk must be coming from somewhere else.

Can you describe your setup? What case and power? What cabling and interface/mixer, etc?

Thanks,

Scott
ThinLazy
Thanks for your quick reply to my problem!

Yes, Ive done some testing and I believe Ive isolated the bleed back to the nw2s::io by removing the mixing board and interface from the signal path.

If I have two different modular oscillators running out through the nw2s::io over a db25 cable (Seismic Audio) to a Neutrik NYS-SPP-L1 patch bay I get bleed between channels. This bleed is independent of the patch points on the patchbay. I have also tried disconnecting the patch cable into the back of the patchbay from oscillator 2 but I still get bleed into oscillator 1.

If I unplug oscillator 2 from the nw2s::io the bleed disappears from oscillator 1. My case is a Doepfer monster base case that I have not had any issues with.

The only other part that isnt the nw2s::io at this point is the db25 cable, which I can try switching out tonight.

Let me know if you have any thoughts about what might be happening.
scottwilson
I have had reports of the unbalanced 'io module not working in balanced patchbays before.

Again, just to get to specifics... I assume the Seismic audio snake is a DB-25 to 1/4" TRS?

From the patchbay, where are you going?

Have you tried non-consecutive channels? Say ch1 and ch7?

From the patch bay, where are you routing the signal? You say you're bypassing the mixing board and audio interface, so how are you monitoring?

Have you tried removing the patchbay from the test?

Thanks,

Scott
ThinLazy
I have had reports of the unbalanced 'io module not working in balanced patchbays before.

I monitored the TRS jack out of the DB25 cable directly using headphones and the bleed is present with the patchbay removed from the signal path

Again, just to get to specifics... I assume the Seismic audio snake is a DB-25 to 1/4" TRS?

Yes, thats correct

From the patchbay, where are you going?
Have you tried non-consecutive channels? Say ch1 and ch7?
From the patch bay, where are you routing the signal?

Have you tried removing the patchbay from the test?

Its not the patchbay or other parts of the signal chain because Im getting bleed directly out of the TRS jack of the DB25 cable not connected to the patchbay. Im getting the bleed in all the output channels of nw2s::io.

You say you're bypassing the mixing board and audio interface, so how are you monitoring?

With headphones (beyerdynamics DT880s) directly attached to the TRS end of the DB25 cable with a (female TRS)-(female TRS) adapter

Switched the DB25 cable

I tried a different DB25 cable and I still get the bleed

Thank you again for your help with trying to figure this out.
scottwilson
Okay, so at this point, you are getting bleed from OSC1 into the output of OSC2 when monitored through the output directly into headphones patched to the 1/4" outputs.

If OSC1 is not patched to the 'io module, but is running, does its signal still bleed into the output of OSC2?

If you monitor OSC2 diectly (without the 'io module in the path), does OSC1 bleed into its signal?

What are the two oscs that are producing this behavior? Are they the only two doing this? meaning if you disconnect those two from the power bus and use two different oscs, are they behaving the same?

Thanks for trying all the combinations. I'm a bit stumped, but I'm guessing it's either a poorly behaved module or a grounding issue as the unbalanced IO really doesn't have many things to go wrong in it unless the LED drivers go bad. The signal portion is passive.

Scott
ThinLazy
If OSC1 is not patched to the 'io module, but is running, does its signal still bleed into the output of OSC2?

No, if Oscillator 1 is not plugged into the nw2s:io there is no bleed into Oscillator 2

If you monitor OSC2 directly (without the 'io module in the path), does OSC1 bleed into its signal?

There is no bleed if I monitor the oscillators directly out of the modules nor if I monitor from the VCA module I usually run them through (Intellijel HexVCA), basically there is no bleed in the signal path prior to the nw2s::io

What are the two oscs that are producing this behavior?
Are they the only two doing this? meaning if you disconnect those two from the power bus and use two different oscs, are they behaving the same?


The 2 oscillators are Buubblesound VCOb's, I get the same problem using a Harvestman Hertz Donut and Piston Honda that are in a separate case (another doepfer case)

I'm guessing it's either a poorly behaved module or a grounding issue as the unbalanced IO really doesn't have many things to go wrong in it unless the LED drivers go bad. The signal portion is passive.


Maybe there is something strange happening when plugging a balanced DB25 cable into the unbalanced outputs of the nw2s::io. Or, something is wrong with the module that even passively the channels are bleeding (considering this doesnt seem to be a known issue with the module)

I like this module and its covers some essential tasks for me so I really would like to get it working.[/b]
scottwilson
Crazy... my last chance - if you look at the board-to-board connectors and the board to ribbon connectors, are they all lined up? no pins exposed or anything making it look like the connections are misaligned?

Assuming not, I'll reach out to you. You emailed me, so I'll reach out directly and we can swap for another one.

Scott
ThinLazy
Yes, the headers all seem to be lined up correctly, no exposed pins. Yes, please contact me directly about taking a look at my module.
Thanks!
ThinLazy
Sent you a PM
Midiot
I'll take a stab.....

So you are sending unbalanced signals out of your modular rack (two wire; signal (high) + ground) ?

Is your snake cable wired for balanced connections ? (three wire; High, Low, ground) ?
Balanced:
Pin 1 = negative (low)
Pin 2 = positive (high)
Pin 3 = ground/shield/case

If so, I wonder if Pin 1 is not tied to Pin 3 somewhere, and is acting like an antenna. I dunno.
Rumor has it, it's best to tie Pin 1 to Pin 3 ....at the source (the output).



Quote:
Here’s an alternative and better method of wiring between an unbalanced output and balanced input. By using two-conductor shielded cable, you are at least taking partial advantage of the noise-canceling characteristics of the differential amplifier at the balanced input. Such a connection can provide 20 to 30 dB of common mode rejection—not as good as the 60 dB or more that you’ll get with a balanced source but it’s better than nothing. The disadvantage is that cables wired this way are difficult if not impossible to find off the shelf. Nearly all premade XLR-TS or XLR-RCA cables, and even XLR adapters, are wired with single-conductor cable. For connections like this, you’ll nearly always have to make your own or modify a premade cable but that’s a good skill to develop.

https://www.presonus.com/learn/technical-articles/Balanced-Unbalanced

Though, I'm just guessing your situation.
Have you eliminated the cable to test ?
Here's a similar story from another site:
Quote:
I was writing to ask if its normal to expect signal 'bleed' in audio snakes. I have a number of items connected to my interfaces, and I am encountering where I am getting a weaker 'clone' of my intended output on different channels depending on which plugs I use. This is a Livewire 8 channel TRS to TRS 10ft snake. Is this just a matter of inferior (or defective) equipment or is this 'standard operating practice' for all audio snakes and should I just invest in seperate TRS cables for each and every input to prevent any 'bleed'?

ANSWER:
I figured I would come back and let everyone know that I've identified the problem and....I feel a little dumb. I will post it for all the other newbies out there so they don't have to learn it for themselves...

I was treating the channels of the snake as I would 8 separate cables - any of them could go to any others as long as the colors on the inputs matched the colors of the outputs (if that makes any sense)... little did I know that this snake is apparently designed to be used in pairs... hence the little stenciled numbers on the inner jackets of the connections. Numbered 1 through 8.

The cross-talk was eliminated by keeping 1 with 2, 3 with 4, 5 with 6, and 7 with 8. So it appears this cable is only shielded in pairs to keep the pairs from cross-talking to each other... but not each other. Huh. I'd imagine this would still be a nightmare for anyone trying to use the individual cable ends... but it kind of makes sense for mass connections between instruments.

Not sure if all snakes are wired this way, but figured I would let everyone know that I appreciate all the help and quick replies to my first question on this board.
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