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Proper hookup of GT Brick to RNC to use balanced IO via RNP
Old 29th January 2009
  #1
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skiltrip's Avatar
 
🎧 10 years
Proper hookup of GT Brick to RNC to use balanced IO via RNP

So I have a GT Brick preamp. I want to use it with my RNC on the way in to my DAW.

I have my RNC hooked up to my RNP, so I can get in and out of the RNC balanced this way. I wanted to double check the hookup method to be sure I have it right..

Microphone - > BrickIN --- BrickOUT -> RNP XLR IN (gain set to 0) ---- thru RNC via insert ---- RNP OUT TRS -> interface

Is this correct?

Also, could I use the RNP to give the Brick a little gain boost if I wanted to, say +6 or +12 tops? Or is this asking for trouble?
Old 29th January 2009
  #2
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Fast_Fingers's Avatar
 
🎧 10 years
Are you doing long cable runs and are worried about going directly into the RNC b/c of the unbalanced out? I'm not 100% sure the XLR ins are ready for line-level signals...there's always this if something were to go wrong.

As for the gain question, it depends on the level of the signal reaching the A/D converter and its settings. As long as the signal isn't too hot it shouldn't distort. This assumes that the Brick + FMR combo works.
Old 29th January 2009 | Show parent
  #3
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skiltrip's Avatar
 
🎧 10 years
Quote:
Originally Posted by Fast_Fingers ➡️
Are you doing long cable runs and are worried about going directly into the RNC b/c of the unbalanced out? I'm not 100% sure the XLR ins are ready for line-level signals...there's always this if something were to go wrong.

As for the gain question, it depends on the level of the signal reaching the A/D converter and its settings. As long as the signal isn't too hot it shouldn't distort. This assumes that the Brick + FMR combo works.
I'd like to add the reason I want to do this instead of just going BRICK -> RNC -> DAW is because I want to keep my balanced cabling all the way thru. When I used to use my Grace 101 directly in line with the RNC I'd lose some gain because of the drop to the unbalanced connection

Cable runs are all relatively short. Mic to Brick is probably 10' tops. Brick to RNP would be about 5 feet or less. RNP to interface is about 3 feet.

On the description of the the RNP it says one use of it is to balance an RNC or RNLA. I also am pretty sure that the XLR ins on the RNP are truly 0 gain when set at 0.

I also emailed Mark at FMR. But this is the second time I'm asking him, and I have't heard back, so I figured I'd ask around on here as well. Thanks.
Old 30th January 2009 | Show parent
  #4
Gear Nut
 
🎧 15 years
Quote:
Originally Posted by FMR Website
Given these trade-offs, we've made the RNP with a twelve step switch. The lowest gain setting is 0 dB with a clip point of almost +28dBu.
i believe your chain is correct. just start out with the brick at a low gain and work your way up if you want to be careful about it.
Old 30th January 2009 | Show parent
  #5
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🎧 15 years
Quote:
Originally Posted by skiltrip ➡️
I'd like to add the reason I want to do this instead of just going BRICK -> RNC -> DAW is because I want to keep my balanced cabling all the way thru.
actually what you are doing is adding more opamps into your chain to drive each bal/unbal stage, all the pieces will be unbalanced internally anyway. just run unbalanced into Brick -> RNC keeping the cable as short as possible and wire the RNC to your converters quasi-balanced so you dont get extra noise.
Old 30th January 2009 | Show parent
  #6
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Eloheim's Avatar
 
🎧 10 years
Quote:
Originally Posted by aussie_techie ➡️
actually what you are doing is adding more opamps into your chain to drive each bal/unbal stage, all the pieces will be unbalanced internally anyway. just run unbalanced into Brick -> RNC keeping the cable as short as possible and wire the RNC to your converters quasi-balanced so you dont get extra noise.
Wow man I never thought about this. So you're saying the "balancing another piece of gear (the RNC) thing the OP mentioned is really just so you can keep the unbalanced cables short (between the Pre and the Comp) and then go back to using balanced ones for longer distances (and would therefore only be necessary if you needed that setup)?

I get that balanced is twice as loud as unbal because there's two copies of the signal (right??), but is "balancing" something different than just upping the gain on it? (I.e.:--just tryin to come up with somethin here--if the RNP was gaining a signal a lot, as in towards the top of it range, and it then sent this signal to the RNC and back again, would it have to re-up it again to have it balanced going out?? If that's the case, then wouldn't it impart more "noise" too, as its applying for gain?? If this makes no sense ignore it , ive read up on this stuff on google/wiki before but i dont remember learning this)

Peace.
Old 30th January 2009 | Show parent
  #7
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🎧 15 years
Quote:
Originally Posted by Eloheim ➡️
Wow man I never thought about this. So you're saying the "balancing another piece of gear (the RNC) thing the OP mentioned is really just so you can keep the unbalanced cables short (between the Pre and the Comp) and then go back to using balanced ones for longer distances (and would therefore only be necessary if you needed that setup)?
pretty much

Quote:
Originally Posted by Eloheim ➡️
I get that balanced is twice as loud as unbal because there's two copies of the signal (right??), but is "balancing" something different than just upping the gain on it?
not quite, gain or signal strength can be measured the same despite if its balanced or unbalanced. although if the sending device is fully balanced and you loose one leg then the gain would drop by 6db (an easy way to spot a bad cable). most cheaper pieces (and some very expensive ones) only use impedance balanced circuits which means the second leg is only used for noise pickup, if that leg is disconnected then the signal would not drop (although there may be noise)

the process of electronically balancing an output circut will add 6db and so it must be reduced by 6db to achieve unity gain. so from that alone your S/N would be 6db worse, by the process although if your dealing with line level signals it probably does matter anyway.

every gain stage (unity gain is still a gain stage) will add some noise and distortion. this is why many top notch manufactures will use an impedance balanced output on an XLR so that the equipment can be as clean as possible.
Old 30th January 2009 | Show parent
  #8
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🎧 10 years
The way you describe should work and might sound fine. You would have to listen.

If you want to connect the brick inline to the RNC you could make a special cable:
XLRF on Brick end hooked up the usual way, 1/4 TS on RNC end. On 1/4 male connect the hot to tip and cold to sleeve. Leave the shield on the wire disconnected on the 1/4 TS end.
This would only work on a transformer balanced output like the Brick.
Old 30th January 2009 | Show parent
  #9
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skiltrip's Avatar
 
🎧 10 years
Quote:
Originally Posted by mixedupsteve ➡️
The way you describe should work and might sound fine. You would have to listen.

If you want to connect the brick inline to the RNC you could make a special cable:
XLRF on Brick end hooked up the usual way, 1/4 TS on RNC end. On 1/4 male connect the hot to tip and cold to sleeve. Leave the shield on the wire disconnected on the 1/4 TS end.
This would only work on a transformer balanced output like the Brick.
When just going BRICK -> RNC - > RME ADI-2 balanced in...

what cable should I be using to go from the unbalanced RNC to the balanced RME input? I have the RME hooked up via TRS to a TRS patchbay, can I just come out of the RNC via unbalanced into my patch bay, and then patch those two connections with an unbalanced patch cable?
Old 30th January 2009 | Show parent
  #10
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skiltrip's Avatar
 
🎧 10 years
i just wanted to add that I checked with Mark from FMR, and he said my original cabling scheme was just fine for using the RNP sort of as a bridge in and out of the RNC (provided the RNP gain is at 0). Any increase in the gain on the RNP can be done, but screws up the signal/noise ratio as some of you have mentioned.
Old 30th January 2009 | Show parent
  #11
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🎧 10 years
Quote:
Originally Posted by skiltrip ➡️
When just going BRICK -> RNC - > RME ADI-2 balanced in...

what cable should I be using to go from the unbalanced RNC to the balanced RME input? I have the RME hooked up via TRS to a TRS patchbay, can I just come out of the RNC via unbalanced into my patch bay, and then patch those two connections with an unbalanced patch cable?
RNC manual says connect with 1/4 TS if going from unbalanced to balanced.
Best to verify with FMR.
Old 30th January 2009 | Show parent
  #12
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Eloheim's Avatar
 
🎧 10 years
Quote:
Originally Posted by aussie_techie ➡️
pretty much
not quite,
First off, thank you for the reply. There's no substitute for someone taking the time to explain something. Second off...ya..reading your post made me realize i actually know nothing!heh (Very sad, I know.) I'll have to go back through your post again when I have a few mins to get it fully, but I think i get your jist.
Old 31st January 2009 | Show parent
  #13
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🎧 15 years
Quote:
Originally Posted by skiltrip ➡️
i just wanted to add that I checked with Mark from FMR, and he said my original cabling scheme was just fine for using the RNP sort of as a bridge in and out of the RNC (provided the RNP gain is at 0).
of course it will work, but unless you need to use balanced cabling then its pointless to add it into your chain. you also loose to option of using it as a pre.

Quote:
Originally Posted by skiltrip ➡️
When just going BRICK -> RNC - > RME ADI-2 balanced in...

what cable should I be using to go from the unbalanced RNC to the balanced RME input? I have the RME hooked up via TRS to a TRS patchbay, can I just come out of the RNC via unbalanced into my patch bay, and then patch those two connections with an unbalanced patch cable?
unbalanced TS will be fine, if you wannt the noise rejection of a CMR circuit then wire it quasi-balanced TS -> TRS.
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