Balanced signal and RNC = trouble

[blackcom]

Trying to use an API3124+ with an FMRAudio RNC.

The API has balanced out and the RNC has unbalanced in. Also the RNC has unbalanced out and my ADC has balanced in.

API -> RNC -> ADC

The RNC us suposed to be pretty transperant, but when using this combination the sound will get very trebly/thin and and loses A LOT of gain/volume.

So, perhaps it has something to do with that ground signal..

Should I try to cut the ground (pin1) on my XLR to balanced jack-plugs, do you think it would solve the problem?

[tele_player]

FMR's website mentions how to hook that up - you need cables which connect XLR pins 2-3 to the Tip and Sleeve of the 1/4" plug.

(I edited this - changing Ring to Sleeve, which is what I'd intended)

[bloodstone]

Originally posted by tele_player
FMR's website mentions how to hook that up - you need cables which connect XLR pins 2-3 to the Tip and Ring of the 1/4" plug.

I tried the above with my setup and all I got was a loud obnoxious buzzing sound like the sound you get when you plug a guitar cable into an amp that's turned up loud then you touch the other end of the cable. In my world (mostly balanced gear with balanced bays) the only thing that works for me is TRS on the balanced gear end (or into a balanced patch bay), and lift the ring (cold) on the RNC end. So basically you've got TRS on one side and TS on the other.

To get the RNC to work with my patch bay in stereo, I have to use Y insert cables into my console, then plug the unbalanced Send & return cables into the in out of the RNC. Trying to patch the RNC in or out of balanced gear in the bay doesn't work no matter what type of cable I've experimented with. One side of the RNC shorts out (doesn't provide any signal).

Also, an unbalanced signal is 6 db lower than balanced, I believe. That might explain why it's so quiet.

Good luck, YMMV.

[tele_player]

Bloodstone - doesn't sound right to me. The output of the API is a transformer on XLR 2-3. If you don't connect both 2 and 3 to the load, no current flows in the secondary of the transformer, and it won't sound good.

[bloodstone]

Originally posted by tele_player
Bloodstone - doesn't sound right to me. The output of the API is a transformer on XLR 2-3. If you don't connect both 2 and 3 to the load, no current flows in the secondary of the transformer, and it won't sound good.

It's definitely right in my world with my gear. I don't have the API item in my arsenal. I promise you, I've experimented with this and nearly drove myself crazy trying to arrive at a solution. I soldered every configuration of cable imaginable before I arrived at what worked for me. Maybe with the API item you do need to do as you say on the RNC side. When I did that, it didn't work for me. He'll have to experiment to find out. I just meant he should go cautiously.

[Paul Gold]

Do you have any of your AC power cables ground lifted? If so this could be part of the problem. You have to get ground from somewhere.

[tele_player]

The output from the API is transformer balanced, not ground-referenced.

[max cooper]

I've got 512c's, an RNC and I just connected them to a Rosetta 800 (512's/RNC/Rosetta). The cables are all ones I've made, and they're all pin 3 hot, pin 2 (-) and when they're terminated on one end with an unbalanced, pin 1 goes nowhere.

It sounds fine to me. When I plug the 512's directly to the Rosetta with a balanced cable, it sounds the same but without an RNC in the line.

In case that helps.

[max cooper]

Mebbe the diff is that I use "mono" 1/4" on my unbalanced stuff, and if you use "stereo" to terminate unbalanced, it doesn't connect to the right part of the jack. Anyhow, that would mean that you could jumper the sleeve to the ring and it should work, right? That makes a "stereo" 1/4" into a "mono"

[bloodstone]

Originally posted by max cooper
I've got 512c's, an RNC and I just connected them to a Rosetta 800 (512's/RNC/Rosetta). The cables are all ones I've made, and they're all pin 3 hot, pin 2 (-) and when they're terminated on one end with an unbalanced, pin 1 goes nowhere.

It sounds fine to me. When I plug the 512's directly to the Rosetta with a balanced cable, it sounds the same but without an RNC in the line.

In case that helps.

The above is what I was trying to explain works for me in my mostly balanced gear world.

[max cooper]

Yes, I just realized that. I'm slow sometimes.


So to summarize before the exam tomorrow:

The "ring" on the RNC input is the (+) for the OUTPUT. If you're connecting the signal ground on the input cable, balanced or not, to the ring on the RNC input, it's an "undefined" connection.

The tip on the RNC input is the (+) for the INPUT, the sleeve is the "common" signal ground for INPUT and OUTPUT. Proper connection of a balanced source to an RNC input would be:

source:

Pin 2: (+) TO tip
Pin 3: (-) TO sleeve
Pin 1: fuggedaboudit : ring


The output jack on an RNC is probably a "mono" 1/4", so if you're terminating to a "stereo" connector, you could probably go to the ring or the sleeve, since they don't specify. I keep a supply of "mono" 1/4" connectors, along with "stereo" especially for these occasions.

There is sometimes confusion created by the fact that 1/4" TRS connections may be "balanced" or "TRS insert".


Please disregard this if I'm saying stuff everyone has known since day two.


The exam will be one (1) closed book essay question.

[Paul Gold]

Originally posted by tele_player
The output from the API is transformer balanced, not ground-referenced.

Right, but the RNC is (I think) , so the circuit is ground referenced. This situation is common and can only be properly sorted out by knowing the type of circuit at each in/out. A transformer is happy when floating (not ground referenced). If something is "active balanced" it could be one of a number of things. Sometimes it will like to have the ground floated, sometimes it will like to have a signal phase floated. With all kinds of level and distortion possibilities.

[DannyDay]

I work out quite a few different studios with a total of about 12 RNCs. A couple of high end studios and a couple of ghettofied rooms. The gear, as you can imagine, varies from balanced, unbalanced, x-former, non x-former, and every combo of... no problems.

Awesome box.

Perhaps a faulty unit? An email to FMR should do the trick: http://www.fmraudio.com.

DD.

[bloodstone]

Originally posted by DannyDay
I work out quite a few different studios with a total of about 12 RNCs. A couple of high end studios and a couple of ghettofied rooms. The gear, as you can imagine, varies from balanced, unbalanced, x-former, non x-former, and every combo of... no problems.

Awesome box.

Perhaps a faulty unit? An email to FMR should do the trick: http://www.fmraudio.com.

DD.

Do the places you work in have patch bays? Do you know what cables are used to route to and from them? Thanks.

[tele_player]

Originally posted by Paul Gold
Right, but the RNC is (I think) , so the circuit is ground referenced. This situation is common and can only be properly sorted out by knowing the type of circuit at each in/out. A transformer is happy when floating (not ground referenced). If something is "active balanced" it could be one of a number of things. Sometimes it will like to have the ground floated, sometimes it will like to have a signal phase floated. With all kinds of level and distortion possibilities.

We're talking about a transformer output to an unbalanced input.
If you cable it as described on the FMR site, it will work correctly. Whether or not you connect the grounds on the two devices will depend on if you get ground-loop induced noise. The important thing form a signal delivery standpoint is that the two output terminals from the API transformer need to be connected to the two input terminals on the RNC, regardless of the specifics of the RNC's input device.

[crypticglobe]

I actually messed around with this for some time. I ended up buying inline XLR transformers, and just restored the connections on my patch bay to standard (XLR for send and return).

This works great... but there is definitely a drop in level (I would guess about 6db). Frankly.... I am about to give up on the RNC. It's good and all... but not worth the hassle for me any more.

Anyone know if there is a mod to convert it to a balanced device? It might become more valuable to me if it were balanced... thus the cost to mod it might be worth it...

[tele_player]

You can use the RNP to balance the RNC, but that's an expensive solution.

[crypticglobe]

Originally posted by tele_player
You can use the RNP to balance the RNC, but that's an expensive solution.

I have one of those... Very nice... but not my first choice for pre-amps these days.... .. and certainly I don't want to only be able to use ONE pre-amp with my RNC...