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Patchbay -- Half Normalling Is Cutting The Volume
Old 24th June 2009
  #1
Lives for gear
Patchbay -- Half Normalling Is Cutting The Volume

I've just installed my first patchbay (experimenting with OTB compression), and I'm finding something odd--for half-normalled outputs, the volume drops drastically when I plug into them (i.e., on the top row). Output drops by about 25 db in both the normalled input and the mult input. In fact, the volume drops even if the plug isn't connected to anything. I've tried on several different points, so clearly it's not because one or two are defective. All the connections are balanced, by the way. What gives?
Old 24th June 2009
  #2
Gear Guru
 
drBill's Avatar
?? But you've got something hooked up incorrectly. Try to trace it down and figure it out. That is not normal. Sorry, bad pun.
Old 24th June 2009
  #3
Lives for gear
I've gone over it several times. Hain't found anything yet. But thanks for the clarification that this isn't "normal," since I have no experience to compare it with.
Old 24th June 2009
  #4
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drBill's Avatar
You say everything is balanced? Is this a TT bay?
Old 24th June 2009
  #5
volume drop in patchbay...

Are you 100% certain that the patchbay, the devices and ALL cables are in fact trs?
It sounds like you may be only getting the high side (+) or something connecting.

I have seen thousands of problems in the studio with plain old mismatched cabling and connectors.

Still catches me if I ain't paying attention.

I Have seen WEIRD things....like signals being replicated at low levels across the whole patchbay etc. Always a mismatch in cabling.

A connection either hitting something it's not supposed to, or connecting with nothing at all....swinging in the breeze.

Is the patchbay the kind that uses a switch to configure, or do you reverse the modules? Maybe faulty switch, or solder joint there? Is the signal distorted?
Also,
Are you certain your insert is balanced itself? Is this a console? Digi PT box? Is it a send and return on a trs, or a separate send and return?

Not enough info to diagnose, but that is where I would start. Some pseudo- balancing schemes will have a -8- -10 db drop if used with a regular ts connector too.

Got a multimeter? Start probing for continuity?

Hope this helps,


jm
Old 24th June 2009
  #6
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drBill's Avatar
One thought....you don't have the patchbay upside down do you? Returns on top and Sends on bottom?? heh Wouldn't be the first time I've seen it. Some people actually WANT it that way. Messes up everyone who's used to the normal way. DAMN! Another bad pun..../
Old 24th June 2009
  #7
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drBill's Avatar
Quote:
Originally Posted by NEWTON IN ORBIT View Post
Got a multimeter? Start probing for continuity?


That's what you need to do.
Old 24th June 2009
  #8
Lives for gear
All is definitely balanced, with TRS connectors. My unbalanced sources are going thru bump boxes, just to make sure. The patch bay is the cheapie Samson S patch plus, with switches that go from through to normal and half normalled--real easy. It's about a month old, and has shown no wierdness until now.

Today I hooked up a second output running to my Coleman M3, so I could compare the sound of my tracks & mixes both ITB and with the OTB processing I'm running. That is, my plan was to have the ITB go straight out to one Coleman input, and mult the ITB via half-normallying, run that thru my OTB boxes, and then send that signal into another Coleman input, so I could toggle between them for instant comparisons. Is there a flaw in that plan? Can I not run a send and a mult of that send to the Coleman without a problem?

THANKS!
Old 24th June 2009
  #9
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drBill's Avatar
You CAN send outputs to multiple places without (theoretically, obviously not in your case for some reason) degredation or signal loss. I regularly send to 3 or sometimes even 4. I'm using a TT bay though. No experience with those switchable bays.

Do like jm suggested and start tracing it down. You'll find the problem.
Old 24th June 2009
  #10
Lives for gear
OK. Will let you know what I find.
Old 24th June 2009
  #11
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White Falcon's Avatar
I have four Samson S-Patch +. The first two are five years old and i've never had a problem (i've dumped a few other brand p-bays that developed problems and bought two more Samsons!), and i really love them! If you search the forum you'll find that these patchbays are one of the favourites among the cheaper ones.

The problem you have happened to me once, in that case all the cables and connections were fine, but the destination for one of the outputs "loaded" the outputs pretty much, so i got a volume drop like you, but not so many dbs.
Old 24th June 2009
  #12
Lives for gear
Hi--

Yeah, the positive reviews on the Samson were definitely a factor in my selection of it!

Can you explain a little more your experience with "loading" an output? Thanks!
Old 24th June 2009
  #13
Lives for gear
 
White Falcon's Avatar
Well i'm not very good with the theory, i think i made my connections and mismatched the impedance or something

I'm sorry, but this is something a friend told me when i told him about it. It did not bother me that much at the time; the sound quality was fine.

I'm sure someone here can explain it.
Old 24th June 2009
  #14
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nosebleedaudio's Avatar
 

Did you double check that tip on the bay is tip at the gear end?

And that you DO NOT have continuity between tip and ring?
You could have all signals are reversed in the bay some how, tip connects to ring...
Old 24th June 2009
  #15
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jproc's Avatar
Sorry for asking the obvious... you say all the connections are balanced... is the patchbay itself a balanced patchbay ?
Old 24th June 2009
  #16
Lives for gear
Quote:
Originally Posted by nosebleedaudio View Post
Did you double check that tip on the bay is tip at the gear end?

And that you DO NOT have continuity between tip and ring?
You could have all signals are reversed in the bay some how, tip connects to ring...
I can't really answer this, except to say that before I tried the half-normalling mult thing the 'bay gave me no trouble at all.

The cabling I used is brand new--just received it. Is it possible it was wired incorrectly? Could that be the culprit? How can I determine that?

BTW, the bay itself is all TRS, all balanced connections.
Old 24th June 2009
  #17
Lives for gear
Upon further experimentation, the volume drop only seems to happen when both the original output and the mult output are routed to the Coleman m3. If they go to two different boxes, the volume is unaffected.

Doesn't this suggest something's wrong with the Coleman (or, maybe, with the way the Coleman's wired up)?
Old 24th June 2009
  #18
Gear Guru
 
drBill's Avatar
When they are going to the exact same input - or different inputs. You can mult OUTPUTS, but not INPUTS. You need a summing/mixer circuit for that
Old 25th June 2009
  #19
Lives for gear
I realize that, and what's puzzling me is that this volume loss is happening even though the two outputs are going into different inputs in the Coleman. They ought to be independent circuits, shouldn't they? So there shouldn't be any effect on volume, right???
Old 25th June 2009
  #20
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drBill's Avatar
Phase cancellation?
Old 26th June 2009
  #21
Patchbay troubles.

The poster whom mentioned possible shorting between positive (tip) and sleeve, has got the right idea (smart dude). The only thing is, you are saying there is no distortion present, and usually this would be NASTY sounding, and have more than just a level drop.

You mentioned "bump boxes", what are these? A direct box? Are you going unbalanced t/s, into these, and then taking a three conductor trs out into your summing box?

I am going to go back and reread all the posts on this, and see if I missed anything. I'm afraid that if everything you have told us is accurate, I am at the end of my suggestions though.

You can try a guy named Steve Hogan, he will do a telephone consult (not free, but he's very reasonable) and help you get to the bottom of this. I have had many things modded by him, and he is amazing. He is the former VP of engineering at Jensen Transformers.

I think if he can't help, there are very few who could. Tell him John sent you, if he asks.

Also, maybe check with the manufacturers for schems of all the gear involved I guess. Maybe the people at Coleman have seen this problem before?

Steve's site:
The Sound Steward

I wish you luck, and hope you get this sorted. Sorry I couldn't help any further, but it is hard over the internet.

Peace,
jm
Old 26th June 2009
  #22
Lives for gear
Thanks for that thoughtful post, jm. I'm going to contact Coleman today.
Old 26th June 2009
  #23
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Mike Brown's Avatar
 

Quote:
Originally Posted by drBill View Post
One thought....you don't have the patchbay upside down do you? Returns on top and Sends on bottom?? heh Wouldn't be the first time I've seen it. Some people actually WANT it that way. Messes up everyone who's used to the normal way. DAMN! Another bad pun..../
Quote:
Originally Posted by drBill View Post


That's what you need to do.
As usual Good advice/puns in this thread Bill!

I see you are coping with the emoticon limit nicely!
Old 26th June 2009
  #24
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drBill's Avatar
Quote:
Originally Posted by Mayor999 View Post
I see you are coping with the emoticon limit nicely!
Yeah, but don't go trying to steal any of my emoticons!!!
Old 27th June 2009
  #25
Lives for gear
PROBLEM SOLVED!!! (or answered, at least)

I called Coleman Audio, and Mr. Coleman himself picked up the phone. He knew what was going on before I was done explaining the situation! Here it is: in the original version of the M3 controller (the black face version, not the current green face), sources go to ground when they're switched out, so with two copies of essentially the same signal going in, the signal basically gets shorted out.

As a test to see if this was indeed the cause of my volume drops, he suggested dead-patching the original signal, i.e., plugging cables into the bottom row of the patchbay, unattached to anything else. If that stopped the volume loss, then the grounding in the M3 is the problem, he said. Well, I did, and it did! No more volume drop.



SO--the solution is to cut the traces leading to ground, Mr. Coleman advised. Frankly, I don't feel good about doing that myself, but he offered to do it himself, free, or talk me through it over the phone. I'm going to try to set up the latter alternative.

Interesting, eh?

Thank you, everyone, for your time and suggestions!!
Old 27th June 2009
  #26
Gear Guru
 
drBill's Avatar
Thanks for letting us know.
Old 30th June 2009
  #27
Lives for gear
Problem Fixed!!!

Today, with phone in hand, talking with the head of Coleman Audio, I repaired the problem by cutting the traces on the M3 that led to ground.

Now the mult feed works just fine, and it is indeed most useful to be able to toggle back and forth between ITB and OTB. Just like having a bypass on your compressor . . .



Thanks to everypne who took an interest!!!

Old 2nd July 2009
  #28
patchbay

Glad you got it sorted, always great to get outta the box when you can.
Oh no! I shouldn't have said that here....


Could inadvertently start a itb/otb saga thread....lol
peace,
jpm
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