Balanced output to unbalanced input of amp?? Need Preamp? Help!

Hey all,

I have recently been trying to put together a new monitoring setup for my "satellite" studio away from home. I am having some trouble getting things to work. Here's what I'm trying to do:

Output of M-Audio Profire 610 (Balanced) --> Adcom GFA-555 input (unbalanced) --> Yamaha NS-30T speakers

I have a couple TRS to RCA adapters that I plugged into the back of the Profire, and an RCA cable running to the Adcom. The output level is extremely low. I have to turn up the master volume on the profire to like 85% to get a listenable level. I understand that by going balanced to unbalanced I lose 6 dB, but this is just way too low of a signal to work with. What can I do??

If I send the signal to my Marantz 2230 and use the preamp out from it to feed the Adcom, I can get a nice signal - but I don't want to have to do this because 1. The Marantz is used for my living room sound stuff and 2. I am afraid of coloring the signal by introducing yet another piece of gear into my monitoring chain.

What do I need to do to interface the Profire with my Adcom amp??!?! Helppppp!

Thank you!!

IMHO the best way to couple a balanced output to an unbalanced input (or an unbalanced output to a balanced input), is a good quality 1:1 transformer! 

First ask M-Audio Profire 610  support staff for advice for recommended wiring (or RTFM- read the fine manual).

Second check RANE  http://www.rane.com/pdf/ranenotes/Sound%20System%20Interconnection.pdf

Third build your own DIY active Bal to SE using opamps and precision resistors or THAT chip sets.

4th buy expensive transformers

5th buy cheap transformers

JR

The outputs can take either Balanced TRS or Unbalanced TS jacks.  You are using a TRS to RCA cable.  Typically that would mean that you have a TRS 1/4 inch on one end, and 2 RCA's on the other. 

Depending upon the output architecture of the 610, which is not documented, that might not do what you want.

A TS jack would ground one of the two balanced lines - the cold one ( assuming they are TRS - Hot, Cold, Shield which is typical)

Your cable, if you are leaving one RCA plug dangling, is using one half the balanced signal and letting the other float... with unknown results. 

My suggestion before using any of the other lovely and workable suggestions is:

1) Put a TS to RCA connector in there.
2) If you don't have one - you can make the equivalent using your cable (assuming your cable has TRS on one end, and Red and White RCA on the other).    The Red is right, the white is left.  to duplicate a TS to RCA cable using that cable, you would ground the Tip of the RED connector (because it is right, and thus connected to sleeve) and then plug in the White connector.

TURN THE VOLUME down on the amp first - obviously, and try it with a paper clip!.  THE 610 says it puts out 15dbu max (4V is RMS) and the amp you have generates 200 W into 8 ohms at 1.7 V.... So even if you had half the RMS out, you should be getting a usable signal.

By the way, this is all really JohnRoberts suggestions #1 . Read the manual.  it is online under the support section and it says you can use TS cables on the 610's outputs (though it doesn't specify what levels you will get, you probably get Full or Half the spec'd levels, either of which will get you 200 watts at unity.


If you don't have a meter, here is how to tell which part of a trs cable is Left and right etc.

<http://en.wikipedia.org/wiki/TRS_connector>

And here is how to tell that the red one is right

http://en.wikipedia.org/wiki/Rca_jack

One other note.  For testing my "paper clip" idea is fine, if it works, for permanent it is better to use the TS plug approach, or modify the cable at the TRS end, because otherwise you are grounding the sleeve using a cable that is twice the cable length, and you might get noise.  Unlikely because the transmitted levels are high.

(PS This is actually John Roberts second idea, I reviewed the Rane note.. and it makes the point to ground at the sending end on one schematic)

I have made dozen of balanced to unbalanced cables in my time. Yes usually people will wire a balanced connection into 2 unbalanced connections with each connection on the unbalanced side sharing a ground. It's typical to see that kind of action in headphones. Anyway if you needed balanced to single unbalanced cable, you wire it as follows Wire the balanced side as normal with hot(pin2, tip), Cold(pin 3, Ring), and Ground(pin1, Sleeve, etc) Then on the un balanced side wire hot to Tip and cold to Sleeve and omit the ground. This is the easiest way to have this work and can be found in the rane notes link below.

http://www.rane.com/pdf/ranenotes/Sound%20System%20Interconnection.pdf

However note that you will drop about 6dB per side.

Hey guys - thanks for all the suggestions...

Maybe I should clarify what I'm using here. I've got a couple of these connectors plugged into my Profire outputs: www.monoprice.com/products/product.asp?c_id=104&cp_id=10429&cs_id=1042907&p_id=7172&seq=1&format=2

And the rest is just a pair of RCA-RCA cables to the amp.

I did read the manual, and all it says is: "These 1/4" TRS jacks provide eight channels of discrete balanced or unbalanced analog output."

I read on this thread that the outputs are "autosensing" or something? See here: http://forums.m-audio.com/showthread.php?6713-Profire-610-balanced-unbalanced-output-cabling

Anyway, Bruce -  so that I'm understanding your suggestion clearly - you're saying that I should try just a simple TS to RCA connector instead of my current  TRS - RCA? I will give that a try. Maybe there is something weird about the way my monoprice connector is put together that it's not grounding the ring... I could measure it when I get home...

Thanks John and Bruce!

I looked at the link you provided and the company service rep didn't sound like he knew.

In cases like that you can generally experiment and figure out what works from a short list of options.

JR

Wow. Ok, this issue seems to be solved... I got out my multimeter and checked the connectors I bought from Monoprice. The tip and the ring are shorted together!!! Why would they sell a connector like that?!?! I could understand ring and sleeve, but why would anyone ever want this type of connector?

Anyway, bought some $2 Hosa connectors at best buy and all is right again. Ugh! Thanks for your efforts guys, I appreciate it.

May I suggest that you safely dispose of those connectors that short tip and ring... (in a place where I will never pick it up and try to use it.)

I have never heard of such a thing. and ... it could do some damage in numerous configurations.

Glad you are up and running.

statzern said:

Wow. Ok, this issue seems to be solved... I got out my multimeter and checked the connectors I bought from Monoprice. The tip and the ring are shorted together!!! Why would they sell a connector like that?!?! I could understand ring and sleeve, but why would anyone ever want this type of connector?

Click to expand...

A 1/4" TRS plug with tip and ring connected together can be used to make a direct out from a console with a single TRS insert jack.

-a

You are right, and I never thought of that. 

(I always just push a TS connector in part way (to the first click)).

I still don't want one of those around my shop!  <grin>

b

Andy Peters said:

statzern said:

Wow. Ok, this issue seems to be solved... I got out my multimeter and checked the connectors I bought from Monoprice. The tip and the ring are shorted together!!! Why would they sell a connector like that?!?! I could understand ring and sleeve, but why would anyone ever want this type of connector?

Click to expand...

A 1/4" TRS plug with tip and ring connected together can be used to make a direct out from a console with a single TRS insert jack.

-a

Click to expand...