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Post by christopher on May 29, 2020 17:58:57 GMT -6
For the past few months I've been testing monitoring straight off my console's master bus into an unbalanced amp for NS10's. I like it. So I want to wire my monitor amp to the bay so I can easily switch to DAC monitoring.
Here's my issue: In order to go from XLR out to RCA I've been using my R6 lunchbox which kind of has a patchbay on the back to turn XLR's into 1/4" trs. I then patch my TS-RCA cable to the amp. Has worked perfectly.
However I've been trying to bypass the R6 and just go straight patchbay > RCA and there's been hum. I've narrowed down that the hum is because the R6's IEC power cable is grounding things. If I use the original setup R6 without IEC connected to power, I get the same hum as I do TT>RCA. As soon as I attach the IEC, hum goes away.
to sum it up..
No hum: TRANSFORMER OUT XLR --> R6 (IEC plugged in) --> TS/RCA CABLE --> RCA AMP (2 prong power)
Hum: TRANSFORMER OUT XLR --> TT BAY --> RCA AMP
Any ideas how I can ground it better?
thanks
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Post by svart on May 29, 2020 18:44:56 GMT -6
Sounds like maybe the XLR shell is or isn't grounded to pin 1. Open it up and take a look which one it is and try it the other way.
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Post by stratboy on May 29, 2020 20:16:22 GMT -6
Rane Note 110 has the best tutorial on grounding and proper interfacing with cables I have ever found. It also has diagrams for almost all the interfacing you will encounter in audio. Check it out. However... your situation is complicated by the patch bay, which offers multiple additional paths to ground when you want only one. It’s too complex and situation-dependent to try and cover all of your the possibilities here, but if you understand how to properly wire an XLR to RCA cable using Rane 110, and you correctly insert your PB into that circuit in a way that preserves the integrity of the ground scheme, you will succeed. Can someone suggest a good tutorial on patch bay grounding? I can’t think of one at the moment, but if I was looking, I might start with the resources on the Mr Patchbay site.
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Post by christopher on May 31, 2020 12:12:54 GMT -6
Sounds like maybe the XLR shell is or isn't grounded to pin 1. Open it up and take a look which one it is and try it the other way. Thanks for suggesting this. I opened it up and sure enough pin1 was isolated from the shell. I tried connecting and it didn’t work, but it did make me think about my setup and what might be the problem.
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Post by christopher on May 31, 2020 12:15:28 GMT -6
Rane Note 110 has the best tutorial on grounding and proper interfacing with cables I have ever found. It also has diagrams for almost all the interfacing you will encounter in audio. Check it out. However... your situation is complicated by the patch bay, which offers multiple additional paths to ground when you want only one. It’s too complex and situation-dependent to try and cover all of your the possibilities here, but if you understand how to properly wire an XLR to RCA cable using Rane 110, and you correctly insert your PB into that circuit in a way that preserves the integrity of the ground scheme, you will succeed. Can someone suggest a good tutorial on patch bay grounding? I can’t think of one at the moment, but if I was looking, I might start with the resources on the Mr Patchbay site. Thanks for this. The Rane note110 I didn’t know about. I wish I watched those Mr Patchbay videos before wiring the patchbay, so that was nice. The Rane doc basically said always use balanced, always pin1 to chassis ground. Choose to do what I’m doing and expect many hours of troubleshooting “may the force be with you” LOL
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Post by christopher on May 31, 2020 12:29:08 GMT -6
Just wanted to update.. I SOLVED it. Many hours of my wife upset that I was ‘ignoring her’ by being on my phone reading about grounding theory, cable wiring diagrams, and crawling around behind the rack my brain a scrambled mess. Turns out I had a few problems that hadn’t been an issue until now. One was since my bay point was half normaled, the unbalanced RCA wires were acting like an antenna when I tried to patch the master output direct to other stuff, like headphone amp. I could move the RCA cables and make it quiet or super loud. Took that off the bay, perfection. So I realized the R6 was an audio ground, and the amp must not have audio ground connected to chassis ground. That would explain why touching wires between chassis had no effect. So I looked for an audio ground screw.. sure enough a little screw by the RCA jacks, ran a wire between console chassis and that screw: hum gone. !!!
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Post by stratboy on May 31, 2020 15:27:13 GMT -6
Rane Note 110 has the best tutorial on grounding and proper interfacing with cables I have ever found. It also has diagrams for almost all the interfacing you will encounter in audio. Check it out. However... your situation is complicated by the patch bay, which offers multiple additional paths to ground when you want only one. It’s too complex and situation-dependent to try and cover all of your the possibilities here, but if you understand how to properly wire an XLR to RCA cable using Rane 110, and you correctly insert your PB into that circuit in a way that preserves the integrity of the ground scheme, you will succeed. Can someone suggest a good tutorial on patch bay grounding? I can’t think of one at the moment, but if I was looking, I might start with the resources on the Mr Patchbay site. Thanks for this. The Rane note110 I didn’t know about. I wish I watched those Mr Patchbay videos before wiring the patchbay, so that was nice. The Rane doc basically said always use balanced, always pin1 to chassis ground. Choose to do what I’m doing and expect many hours of troubleshooting “may the force be with you” LOL Well, there's more to it than that. But you're right, it does present the simplified view of the subject. The main feature of that note is the wiring diagrams illustrated in the table at the end of the note. They show how to maintain that ideal situation consistently with a variety of interconnect scenarios. For a much more in-depth exploration of the subject, read Rane Note 151. In the meantime, congratulations on solving your problem! The great thing about problems is, when we solve them, we learn. Your explanation of the problem and solution is a great illustration of this. Obstacles ARE opportunities.
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Post by christopher on May 31, 2020 22:36:37 GMT -6
Yes that article was pretty great. Thanks for the other article, I’ll add it to the list. I’m also in the process of reading the full text of the Bill Whitlock article. www.jensen-transformers.com/wp-content/uploads/2014/08/generic-seminar.pdfI’ve skimmed it a few times. Maybe this year I’ll take some time to really understand all this stuff. There could be a college program just in signal grounding I’m sure.
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ericn
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Balance Engineer
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Post by ericn on Jun 1, 2020 8:25:33 GMT -6
Yes that article was pretty great. Thanks for the other article, I’ll add it to the list. I’m also in the process of reading the full text of the Bill Whitlock article. www.jensen-transformers.com/wp-content/uploads/2014/08/generic-seminar.pdfI’ve skimmed it a few times. Maybe this year I’ll take some time to really understand all this stuff. There could be a college program just in signal grounding I’m sure. If you think grounding in the studio is fun you should have been in the world of live sound in the 80’s! Ask my cranky west coast friend John Epstein!
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Post by drbill on Jun 1, 2020 10:10:52 GMT -6
In a traditional console, tape machine, outboard situation - I always say that 85% of grounding is following the rules - perfectly. 13% is breaking the rules - however you have to. And the last 2% requires voodoo, animal sacrifices, and standing on your head. And that has shown itself to be pretty accurate over the years....
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ericn
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Post by ericn on Jun 1, 2020 11:39:06 GMT -6
In a traditional console, tape machine, outboard situation - I always say that 85% of grounding is following the rules - perfectly. 13% is breaking the rules - however you have to. And the last 2% requires voodoo, animal sacrifices, and standing on your head. And that has shown itself to be pretty accurate over the years.... It’s finding the right animal to sacrifice that’s always the hard part, you have to sync your choice to the phase of the moon.
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Post by Ward on Jun 1, 2020 13:58:02 GMT -6
In a traditional console, tape machine, outboard situation - I always say that 85% of grounding is following the rules - perfectly. 13% is breaking the rules - however you have to. And the last 2% requires voodoo, animal sacrifices, and standing on your head. And that has shown itself to be pretty accurate over the years.... You also forgot 'blood-letting' and leeches.
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Post by svart on Jun 1, 2020 14:23:13 GMT -6
In a traditional console, tape machine, outboard situation - I always say that 85% of grounding is following the rules - perfectly. 13% is breaking the rules - however you have to. And the last 2% requires voodoo, animal sacrifices, and standing on your head. And that has shown itself to be pretty accurate over the years.... You also forgot 'blood-letting' and leeches. Gotta get those bad vapors out somehow.
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Post by drbill on Jun 1, 2020 14:25:23 GMT -6
In a traditional console, tape machine, outboard situation - I always say that 85% of grounding is following the rules - perfectly. 13% is breaking the rules - however you have to. And the last 2% requires voodoo, animal sacrifices, and standing on your head. And that has shown itself to be pretty accurate over the years.... It’s finding the right animal to sacrifice that’s always the hard part, you have to sync your choice to the phase of the moon. Indeed. As much as we would like to quantify it to science, there is that pagan ritualistic "thing" that it always boils down too.
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Post by drbill on Jun 1, 2020 14:26:09 GMT -6
In a traditional console, tape machine, outboard situation - I always say that 85% of grounding is following the rules - perfectly. 13% is breaking the rules - however you have to. And the last 2% requires voodoo, animal sacrifices, and standing on your head. And that has shown itself to be pretty accurate over the years.... You also forgot 'blood-letting' and leeches. For me that kind of falls under the general "voodoo" category.
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ericn
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Post by ericn on Jun 1, 2020 14:29:17 GMT -6
In a traditional console, tape machine, outboard situation - I always say that 85% of grounding is following the rules - perfectly. 13% is breaking the rules - however you have to. And the last 2% requires voodoo, animal sacrifices, and standing on your head. And that has shown itself to be pretty accurate over the years.... You also forgot 'blood-letting' and leeches. Leeches ? Isn’t that Avids subscription plan?
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Post by EmRR on Jun 1, 2020 18:21:40 GMT -6
If you think grounding in the studio is fun you should have been in the world of live sound in the 80’s! Oh boy, it still is. The number of places I see that'll bring you a dedicated power drop coming from a twist lock connector on the wall.....and the connector is loose in the wall because no one's tightened anything since it was installed in 1975........come back a year later and it's still not fixed.....tell them again.... guess what happens the year after that?
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ericn
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Post by ericn on Jun 1, 2020 18:23:47 GMT -6
If you think grounding in the studio is fun you should have been in the world of live sound in the 80’s! Oh boy, it still is. The number of places I see that'll bring you a dedicated power drop coming from a twist lock connector on the wall.....and the connector is loose in the wall because no one's tightened anything since it was installed in 1975........come back a year later and it's still not fixed.....tell them again.... guess what happens the year after that? Plug what’s that? Forgive me all those times doing live taps probably screwed up my memory😁
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