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Best way to deal with unbalanced signal?
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devastat
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#1
9th January 2013
Old 9th January 2013
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Best way to deal with unbalanced signal?

I'm planning to get an Avalon M5 preamp, and I found out that it has an unbalanced XLR output. Let's say I want to go from this unbalanced output into a hardware compressor with balanced input, what is the best way to deal with the situation?

I have also have a RNP, which if I understand correctly is able to balance unbalanced signal. Should I use that to balance the Avalon preamp before going into the compressor - or can I just plug unbalanced signal straight from the Avalon into the compressor without worrying about the fact that the input of the compressor is balanced?
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10th January 2013
Old 10th January 2013
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Just connect it with a standard XLR/XLR cable in which you've jumpered pins 3 and 1 in the output connector (going into the compressor) or a XLR/TRS cable with the ring connection jumpered to the shield (if your compressor has a TRS input). That will work fine as far as the signal transfer goes. Pin 3 may be grounded at the M5 output jack. If it is you don't need the jumper. If you do have any induced noise pick-up, you can always balance the connection by installing the Avalon/Jensen JT-1 transformer in the M5. It's designed with the correct impedance for the M5.

Remember, the M5 can put out a very high +30 dBu signal, which is more than many outboard compressors can tolerate, so be careful not to drive your compressor input stage into clipping.
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10th January 2013
Old 10th January 2013
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I should probably try with a regular XLR first, as it might work if the pin 3 is grounded at the M5 output jack?

Thanks alot for the help, i'll be careful with the output signal!
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10th January 2013
Old 10th January 2013
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This is a helpful text - if you, like me, don't fully get it the first time, read it again and again. And then start to wonder why some equipment manufacturers seem to ignore basics.
Sound System Interconnection
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10th January 2013
Old 10th January 2013
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Quote:
Originally Posted by devastat View Post
I should probably try with a regular XLR first, as it might work if the pin 3 is grounded at the M5 output jack?

Thanks alot for the help, i'll be careful with the output signal!
If you have an ohmmeter handy, you can easily check for continuity between pin-3 and pin-1 of the M5 output connector. If pin-3 is not already connected to the output return, you may get a weak, and probably noisy signal into the comp. If pin-3 is connected to pin-1 (very likely), any normal shielded XLR/XLR cable will be fine.
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10th January 2013
Old 10th January 2013
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I have just ordered a Multi Meter few days ago, and should have it by next week so I might be able to test it with that. I have never used one or don't know how to test it, but will read the manual and try to see if it can be done. Thanks alot for you help!
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10th January 2013
Old 10th January 2013
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Quote:
Originally Posted by devastat View Post
I have just ordered a Multi Meter few days ago, and should have it by next week so I might be able to test it with that. I have never used one or don't know how to test it, but will read the manual and try to see if it can be done. Thanks alot for you help!
Everyone needs a multi-meter! Just set it to the "low ohms" range. The meter will typically read "OL" or "open" (assuming it's a digital meter). Touch the probe tips together and the meter should read a very low value, usually less then one ohm. Then touch the probe ends to the XLR pins 1 and 3. The meter should again read a low value (less than a few ohms). The mic pre should be OFF while you're testing the XLR wiring.
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10th January 2013
Old 10th January 2013
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Thanks for the explanation! I will get to do this next week when I get my multimeter. Will let you guys know how it is.

..soldering an XLR cable to get the pins connected is another thing

P.S if the cable needs to be modified (connecting the pins 1 and 3), is it enought to do this ONLY on the side going into the compressor (male XLR connector)?
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10th January 2013
Old 10th January 2013
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Quote:
Originally Posted by devastat View Post
Thanks for the explanation! I will get to do this next week when I get my multimeter. Will let you guys know how it is.

..soldering an XLR cable to get the pins connected is another thing

P.S if the cable needs to be modified (connecting the pins 1 and 3), is it enought to do this ONLY on the side going into the compressor (male XLR connector)?
Yes, as long as the cable started out as a normal, balanced XLR/XLR. That means it has (2) twisted conductors and a shield , with one conductor connected to pin-2 at both ends, and one conductor connected to pin-3 at both ends and the shield connected to pin-1 at both ends.

The reason that pin 3 must be connected to pin-1 (either in the cable connector or through the output connector on the mic pre), is that at the input, pin-3 is the "low" or sometimes called the (-) side of the balanced input. When the "high" side or (+) side of a balanced input is being driven from an unbalanced source, the "low" side must be referenced to the common or ground because that's the low or "ground" reference for the source signal. On a balanced output, the low side is not referenced to ground at all.
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15th January 2013
Old 15th January 2013
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My Avalon has arrived (I'm still waiting for the multimeter to arrive) and it does say in the manual that "Always connect pin 3 to ground to ensure correct loading on balanced line inputs following the M5 in the signal chain" so it seems like the pin-3 is not grounded in the output jack of the Avalon M5?

All the rest of my gear is balanced and I'd like to connect the Avalon to the patchbay of the rack. To be able to do so, should I connect the pins 3 and 1 on the XLRf connector that goes into the Avalon - and on the other end have a regular TRS that goes into the patch bay, is that this the right way to do it?
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15th January 2013
Old 15th January 2013
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It has an earth lift switch. So the ground should be connected.. until you use this switch. Hook it up to your patchbay and play a little with it, try different scenarios what you connect with what - you should hear in which cases you'd need the ground lift switch. It's a matter of how different companies handle their grounding schemes. There's circuit ground, PSU ground ... a few things to consider. BUT with good gear and balanced lines you're less likely to run into problems. If you have stuff that's not balanced and try to include, that's where the trouble starts... and that's what you have your ground lift switch for.

Quote:
Originally Posted by devastat View Post
.. an Avalon M5 preamp, and I found out that it has an unbalanced XLR output
From the Avalon website info: "Output Connectors (2):XLR type, pin 2 hot electronic balanced" should be good to go.
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15th January 2013
Old 15th January 2013
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I think that you might be looking at the AD2022 preamp? The M5 has unbalanced output and there is no switch. In the manual it says "Male XLR-3 unbalanced DC coupled, +30db maximum into 600 ohms. Pin-1 ground, Pin-2 hot (+), Pin-3 ground"

But from reading this - it seems that the pin 1 and pin 3 is already connected, so there is no soldering required and this can be connected with a regular XLR cable into balanced gear, right?
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15th January 2013
Old 15th January 2013
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Oups! I see you're right.. I landed on the wrong link (U5)
"Maximum Output Level: +30dB unbalanced 600 ohms, DC coupled, discrete symmetrical Pure Class A.
Output Type: XLR connector, pin 2 hot (optional balanced JT-1 transformer)."

Which adds that you can fit a balancing transformer in there... which would be a good thing for an ace box like that..
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15th January 2013
Old 15th January 2013
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The transformer is most likely only useful if you run very long cables..
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15th January 2013
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Depends on all the gear that's interconnected. A transformer is also a good way to deal with unbalanced things that are connected to balanced things. As I already said, connect all your stuff and see how it behaves. Long cable runs are a matter of the output stage of one piece of gear and how low it's output impedance will go.
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15th January 2013
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The best way is to use a line level shifter. I have two Ebtech LLS-8 to convert between unbalanced/balanced and back. They also acts like hum eliminators removing ground loop hum.

Ebtech - Audio Solutions - Line Level Shifters

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15th January 2013
Old 15th January 2013
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Quote:
Originally Posted by devastat View Post
I think that you might be looking at the AD2022 preamp? The M5 has unbalanced output and there is no switch. In the manual it says "Male XLR-3 unbalanced DC coupled, +30db maximum into 600 ohms. Pin-1 ground, Pin-2 hot (+), Pin-3 ground"

But from reading this - it seems that the pin 1 and pin 3 is already connected, so there is no soldering required and this can be connected with a regular XLR cable into balanced gear, right?
That seems to confirm that pin-3 is already grounded, but it won't hurt to check with the ohmmeter as stated in post #9. Again, adding a transformer to take advantage of the balanced input is not necessary if you are not having any noise of hum pick-up on the output cable. With the relatively low output impedance of the M5, and a short cable (1 or 2 meters) that should not be an issue. Like any unbalanced signal line, it's always a good idea to keep the output cable away from any power cables (don't bundle signal and power cables together).
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16th January 2013
Old 16th January 2013
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Quote:
Originally Posted by Demokid View Post
The best way is to use a line level shifter. I have two Ebtech LLS-8 to convert between unbalanced/balanced and back. They also acts like hum eliminators removing ground loop hum.

Ebtech - Audio Solutions - Line Level Shifters

Kind regards
Demokid
The line level shifters from Ebtech are nothing more than tiny, shitty-sounding transformers mounted on a small circuit board with some additional resistors.

Absolutely no comparison to a real, carefully chosen transformer.
Hint: run some audio thru your Ebtech and take a look at the roll-off under 100 Hz. Not suitable for professional use.

It's also very telling that they publish no specs or technical information about the product.
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16th January 2013
Old 16th January 2013
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TRJanuary:
Thanks for the information.

I haven’t checked the roll-off under 100 Hz on my tracks but as a home recording artist at least they sounds fine. I have many things in my home studio which probably aren’t suitable for professional use.

A lot of musician’s today record with cheap audio interfaces, microphones and do ITB mixes and seems to release songs. This is both a good and bad thing.

Anyway this is the “Newbie audio engineering & production question zone" and not "High end" forum so spending $180.00 for a transformer per channel and installation cost might be a bit over the top for some people. That’s why I added a link to Ebtech, great bang for the buck.

Kind regards
Demokid
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16th January 2013
Old 16th January 2013
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Quote:
Originally Posted by Lotus 7 View Post
That seems to confirm that pin-3 is already grounded, but it won't hurt to check with the ohmmeter as stated in post #9. Again, adding a transformer to take advantage of the balanced input is not necessary if you are not having any noise of hum pick-up on the output cable.
I checked with the ohmmeter and the pin-1 and pin-3 are indeed connected. The Avalon M5 works beautifully with the rest of my outboard gear with a normal XLR cable.

That being said, I have decided to send my Avalon M5 back and order Avalon AD2022 instead. The only reason why I decided to do this is that I realized that I actually do need a preamp for two channels. The AD2022 will have both outputs, balanced and unbalanced, so I will probably use the balanced output with the preamp once it arrives.

Thanks for all the help in this thread, I think I am much more wise now when it comes to unbalanced signal
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16th January 2013
Old 16th January 2013
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Quote:
Originally Posted by devastat View Post
I checked with the ohmmeter and the pin-1 and pin-3 are indeed connected. The Avalon M5 works beautifully with the rest of my outboard gear with a normal XLR cable.

That being said, I have decided to send my Avalon M5 back and order Avalon AD2022 instead. The only reason why I decided to do this is that I realized that I actually do need a preamp for two channels. The AD2022 will have both outputs, balanced and unbalanced, so I will probably use the balanced output with the preamp once it arrives.

Thanks for all the help in this thread, I think I am much more wise now when it comes to unbalanced signal
Two preamps are always better than one, especially if they're the M5/2022. The balanced output is definitely the way to go since you will have the choice. Again, the only caution is to guard against overload of the following input stage (your compressor). In balanced mode the AD2022 can actually put out a peak signal of around 48 volts (+36 dBu). That gives you tremendous headroom in the mic pre, but that does no good to prevent clipping if the next stage can't handle it.

Since you'll soon have (2) Avalon mic channels it's time to think about a pair of Shadow Hills Mastering Compressors for the next stage.
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16th January 2013
Old 16th January 2013
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Shadow Hill Mastering Compressor would be really great, altho it is WAY over my budget at the moment. However, I do have a Manley Vari-mu which I just got, to follow my Avalon preamps
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1st March 2014
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Quote:
Originally Posted by TRJanuary View Post
The line level shifters from Ebtech are nothing more than tiny, shitty-sounding transformers mounted on a small circuit board with some additional resistors.

Absolutely no comparison to a real, carefully chosen transformer.
Hint: run some audio thru your Ebtech and take a look at the roll-off under 100 Hz. Not suitable for professional use.

It's also very telling that they publish no specs or technical information about the product.
I just bought the Ebtech HE-2 XLR and confirmed there is no roll-off under 100 hz. I don't know about the line level shifter model... but the HE-2 worked out well for me and there's no roll off.
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