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Patchbay noise?

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Re: Patchbay noise?

Postby Hugh Robjohns » Fri Jan 11, 2013 5:03 pm

vetsdiggy wrote:Yes the niose came as soon as I put just one output to the desk via the PB..

Oh err... That stirs up the waters a bit... Something weird going on with your patchbay then...

Can I presume that the patchbay metal work isn't touching (or in any other way connected to ) the Apogee or mixer metalwork ?

However this did lead me to think it could be a ballance issue?

Are you sure that the patch bay is balanced, and that all your cables are balanced and wired correctly?

This is reinforced by the fact that now when I try a mono signal sent unpanned out from Logic down a stereo output (so equal signal each chan), but run one direct to the desk and one through the PB (no DI in any chain), I notice that not only do I have hiss on just the chan run via the OB, but I also have a significant drop in signal level?

If the level drop is 6dB that would suggest that only one side of the balanced signal is getting through.

Are you using TRS cables to connect the equipment to the and from the patch bay... and using TRS cables to make the patches? Sounds like you might have some unbalanced TS cables in there somewhere (or the patchbay is an unbalanced patchbay!)

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Re: Patchbay noise?

Postby vetsdiggy » Fri Jan 11, 2013 5:26 pm

hey Hugh...
Yeah the cables are all balanced, and I even just tried a different cable from the PB to the desk, same story.
The 25 Dsubs are tascam format and brand new, and taking the conector apart all wiring seems fine.

The patch bays are PX2000 Ultrapatch which I believe are fully balanced, so...... Gosh I have no idea.

any patch bay I have at my disposal here (multiple beringer PX2000s and a couple of Tascam PB32P) and its the same story as soon as I introduce a patch bay between them.
How can any balanced PB I try, be unbalancing the chain?
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Re: Patchbay noise?

Postby Hugh Robjohns » Fri Jan 11, 2013 5:47 pm

vetsdiggy wrote:Yeah the cables are all balanced, and I even just tried a different cable from the PB to the desk, same story.


Okay -- always worth asking the daft questions! ;)

The 25 Dsubs are tascam format and brand new, and taking the conector apart all wiring seems fine.


You said previosuly that plugging these Tascam cables directly to the desk produced no noise problems.

Can you just quickly test whether there is also a level drop between plugging these cables direct to the desk, and via the patchbay (and how much that level drop is)?

The patch bays are PX2000 Ultrapatch which I believe are fully balanced


They are. What are the normalling switches set to? And what is plugged into the rear sockets for each patchbay channel.

I presume, from your initial description that you have the Apogee outputs connected to the top row rear connectors, and the desk inputs connected to the corresponding bottom row rear connectors, with the normalling switches set to Half-Normalled or Normalled? yes

How can any balanced PB I try, be unbalancing the chain?


It's certainly an odd one. The most obvious possibility is that your input and/or output plugs aren't being fully inserted for some reason, or there is an incompatibility between the patchbay sockets and your patch leads or connectors that prevents (probably) the ring terminal from making proper contact.

If you have a multimeter or a cable tester handy, it would be worthwhile running some simple DC continuity checks to see whether or not the tip and ring contacts from the input connections are making it all the way through to their corresponding output terminal connections.

Plug TRS leads into the rear patchbay input and output terminals, and check that the tips, rings and sleeves of the input and output cables connect together properly via the normalling. Then repeat with a patch lead in place.

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Re: Patchbay noise?

Postby vetsdiggy » Fri Jan 11, 2013 5:55 pm

Can you just quickly test whether there is also a level drop between plugging these cables direct to the desk, and via the patchbay (and how much that level drop is)?

Yeah thats it! I thik it is roughly 6db yes, which is bang on as tell tale!

presume, from your initial description that you have the Apogee outputs connected to the top row rear connectors, and the desk inputs connected to the corresponding bottom row rear connectors, with the normalling switches set to Half-Normalled or Normalled? yes


Exactly, normalled.

I'll try the test, but don't have the cable tester here so will have to try it over the weekend and will get back to you.

Thanks again for all the help.
I just wanna get back to making music now, this is killing me!
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Re: Patchbay noise?

Postby Hugh Robjohns » Fri Jan 11, 2013 11:39 pm

Okay, so it looks like your patch bays are unbalancing the signal for some reason, and that is upsetting te inputs of the desk resulting in additional noise.

As this is happening via the normalling then it's probably incompatible jack plugs that don't mate properly with the sockets in the patch bay (I've heard of this before with behringer patches) or the plugs not inserted fully.... Or it could possibly be miswired cables in the chain somewhere with a screen/signal crossover perhaps. Unlikely, but you never know.

I think making the dc continuity checks will reveal the problem.

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Re: Patchbay noise?

Postby Scramble » Sat Jan 12, 2013 5:28 pm

Deleted - wrong post!
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Re: Patchbay noise?

Postby vetsdiggy » Mon Jan 14, 2013 2:44 pm

Hey Hugh, right just go back in the studio today.

I just tried somthing which seems a little odd....

If I don't use a patch bay, but simply touch the ends of the cables together (TRS output from apogee, and one TRS jack lead plugged directly into a line in on the desk at the other end).... this is what happens....

If I touch tip to tip, or tip to ring, or visa versa, I still suffer the problem (noise and drop in signal).
However I get the full signal and the noise stops if I touch tip to ring and ring to tip at the same time, if that makes sense...?

Does mean I have some miss matched wiring somwhere? (most likely the 25Dsub end of the apogee looms?

Cheers
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Re: Patchbay noise?

Postby vetsdiggy » Mon Jan 14, 2013 3:09 pm

Right... I just used a cable tester and it seems that the PB (whichever one I try) is not making the connection on the ring...
Seems odd, it IS a balanced PB so I don't get it?
I just tried an old MTR one which I found and I think its working....
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Re: Patchbay noise?

Postby Hugh Robjohns » Mon Jan 14, 2013 3:56 pm

vetsdiggy wrote:If I touch tip to tip, or tip to ring, or visa versa, I still suffer the problem (noise and drop in signal).

Yes, because you're only making half of the balanced signal path, adnrelying on the system safety earth to provide a return via the ground.

However I get the full signal and the noise stops if I touch tip to ring and ring to tip at the same time, if that makes sense...?

Yes. You're inverting the polarity, but you are connecting both sides of the balanced signal and hence it works as it should. All of which points to my earlier sugegstion that the patch bay isn't making the full connection (and I suspect it is the cold ring circuits that aren't making properly).

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Re: Patchbay noise?

Postby Hugh Robjohns » Mon Jan 14, 2013 3:58 pm

vetsdiggy wrote:Right... I just used a cable tester and it seems that the PB (whichever one I try) is not making the connection on the ring...

Ba Doom Tish! There ya go! told you... :D

Seems odd, it IS a balanced PB so I don't get it?

As I said, some cheap patchbays -- and especially some cheap TRS plugs -- don't comply with the proper plug dimensions, particularly when it comes to the ring terminals, and hence poor or missing contact, only half a balanced circuit, and a duff signal path.

You will need either to change the patch bays (the Neutrik ones are good valuefor money) or the patch leads, or both.

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Re: Patchbay noise?

Postby nathanscribe » Tue Jan 15, 2013 12:47 am

vetsdiggy wrote:The patch bays are PX2000 Ultrapatch which I believe are fully balanced

The PX2000 is an unbalanced patchbay. Despite what the Behringer site says, look in the user guide - it states unbalanced in there. I've had a couple of these and can confirm that the 2000 is the unbalanced model.

The 3000 is Behringer's balanced patchbay. For what it's worth, the 3000 has a better fit on all the sockets. I find the 2000 a bit tight sometimes.
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Re: Patchbay noise?

Postby vetsdiggy » Tue Jan 15, 2013 9:46 am

Totally.....
Every lead I've tested it with, some cheapies and some more expensive ones, have all shown the same thing..
I can't believe it, I want complain.
What a scam.

Hugh... Thanks for all your help. I'm seeing my friend Mr Jon Burton today, he's got some spare PB options in the lock up so I'll get out my soldering iron and hopefully have a much better set up by the end of the day!

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Re: Patchbay noise?

Postby Hugh Robjohns » Tue Jan 15, 2013 4:37 pm

nathanscribe wrote:The PX2000 is an unbalanced patchbay. Despite what the Behringer site says, look in the user guide - it states unbalanced in there.

Arrggghhh! I was going on the website description. As you say, the handbook says it uses 1/4-inch unbalanced sockets... :protest: :madas: :roll: :crazy:

But it would certainly make sense, given the symptoms and tests, that it is unbalanced.

Ho hum... ;)

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Re: Patchbay noise?

Postby vetsdiggy » Wed Jan 16, 2013 1:25 am

Its an outrage really that they get away with that....
I bought the bays on the pretense that they were balanced, as it said in all descriptions.... Who checks the manual for a 1/4" bay you already bought...... Sheesh!

Anyways..... I got a 96 TT bay I'm wiring up tomorrow so should all be well.
For my needs I want most of the field 'open' which its already wired for on the looms, although I do want to normal (full/single) the apogee ins and outs to the desk line ins/ buss outs...

I'm strugleing to find a straight answer on line as to which of the bits on the back of the sockets I need to bridge to do this....

There are some good recourses on the subject but nothing which spells it out clearly that I can find..

Any more help would be ace!

Cheers

Steve
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Re: Patchbay noise?

Postby Hugh Robjohns » Wed Jan 16, 2013 1:15 pm

I'm not a fan of TT patch bays, myself. They tend to be unreliable in my experience, inconvenient for patching external equipment, and TT patch cords are phenomenally expensive (and need constant cleaning)!

Personally, I'd go for Neutrik NYS-SPP-L1 patch bays every time for your kind of application.

http://www.thomann.de/gb/neutrik_nyssppl1.htm

http://www.neutrik.com/en/products/audio/patch-panels/1/4-patch-panel/nys-spp-l1

They are good quality, surprisingly cost-effective, very quick and easy to configure for normalling, and have very sensible grounding arrangments.

However, if you are locked into the TT patch bay, different sockets are constructed differently. So you'll either have to identify the manufacturer and try their website for wiring details, or -- probably easier and quicker, in practice -- examine the socket visually or with the aid of a multimeter (or both) to identify the contact terminals and the normalling switch terminals, and then wire accordingly.

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