Just been reading about balanced and unbaalnced inputs & ouputs and now I'm confused!

[altruistica]

Just been reading about balanced and unbaalnced inputs & ouputs and now I'm confused!

Hi Guys,

So here's the deal.

I picked up a rackful of old GPO (BBC) patchbays (1/4" stereo jack type) that are balanced along with loads of connectors (I paid less for the whole rack than to buy even a quarter of the connectors new).
Now I want to incorporate all my machines and mixer into this scheme.

My mixer is a Soundtracs PC Series with balanced inputs, unbalanced inserts, tape returns and group sends (it's an inline console with group outs on every channel) are balanced. These are all on stereo 1/4" jacks.
I want to connect two Tascam MSR16 (unbalanced phonos), and two MS16 (unbalanced phonos or balanced XLRs). I've mocked up a couple of inputs and outputs to see if it works and I can't get past the difference in level between balanced 'group outputs' (+4) going to unbalanced MSR inputs (-10). I have wired the 'hot' tip output on the group output (at the patchbay) to the signal (tip) of the unbalanced lead (at the patchbay) which leads to the phono connector to the MSR input. The signal reads -10 on the mixer group output, but '0' at the MSR. The MS16 is wired to the same point on the patchbay and shows -10 when wired to the XLR.

I wanted to be able to know that when the mixer read '0', that the MSR and MS16 both read '0' but I think I'm probably misunderstanding how balanced and unbalanced equipment playa together (or not).

I am also wanting to incorporate either a Tascam MX2424 or Behringer X32 RACK (both on balanced XLR ins and outs) also into the equation at some point. I'm ultimately wanting to track on tape, then dump to PC /MX2424 whilst perfecting the mix to save wear on the tape machines, then play the final mix back off tape.

Any help much appreciated.

Al

 

[Steenamaroo]

Hi,
The difference in signal level isn't really to do with whether signals are balanced or not. It's to do with the level at which the machines operate.

If you feed a +4 line output signal from a mixer into a recorder that's looking for a -10 line level signal, you'll probably distort it unless you pull back a fader or something.
If the reverse, your signal will come in as being weak.

I think you just have to be aware of the specs of your various pieces of equipment, and handle your gain staging accordingly.

 

[altruistica]

Thanks for that Steenamaroo.......I thought as much but here's the thing.

If I pull the (mono) jack partially out of the desk that on the group outputs, the signal level going to the MSR now looks like the desk (ie....'0' on desk matches '0' on MSR) and likewise when returning the signal from the MSR via the tape returns. Is this because the signal is now being 'amplified' via the hot and cold signals summing?

The desk is a 24 in-line console with a certain twist. It only has 16 group outputs that are configured like this. The first 8 channels can send out to 1-8 (ie. to any of the first 8 channels). Channels 9-24 can send out on 9-16, with 17-24 being a duplicated 9-16 group outputs. Note, anything plugged into 1-8 (XLR or line or tape return....the inputs and tape returns can be flipped) can only send out on 1-8 and the same with 9-16 (24).

I'll post later.

Al

 

[Farview]

It has nothing to do with balanced and unbalanced connections.

Your machines operate at different line levels. So zero db on the mixer will be about 11db hitter than zero db on the tape deck. You would think it would be a 14db difference, but the two db scales have two different reference voltages.

You arent doing anything wrong, you are just trying o feed a -10 device with a +4 signal when going from the mixer to the tape deck. You will run into the opposite problem going from the deck to the mixer.

It isnt that big of a deal, you just have to use the meters on the tape deck to set the recording levels and ignore the ones on the mixer when recording.
During playback, you use the mixer meters.

Ebtech makes level shifters, if it is that important that all the meters read the same. but you would need one for every channel into and out of the tape deck, so it could get expensive.

 

[miroslav]

It isnt that big of a deal, you just have to use the meters on the tape deck to set the recording levels and ignore the ones on the mixer when recording.
During playback, you use the mixer meters.

Ebtech makes level shifters, if it is that important that all the meters read the same. but you would need one for every channel into and out of the tape deck, so it could get expensive.

That's what I do....set my recording levels by the meters on the tape deck, which has been calibrated.
After that....I honestly pay little attention to meters on the mixer while recording...and I don't pay any attention to the meters on my converters when I dump the tracks into the DAW.

Only when I get to the mixdown, and I'm running the DAW tracks back out to the mixer....will I pay attention to the meters on the mixer.

And yeah....I have a bunch of -10/+4, unbal/bal converters.....and I use them less and less. IOW, I've become so use to mixing -10/+4 & unbal/bal gear....that it's not really a big deal.

 

[sweetbeats]

Thanks for that Steenamaroo.......I thought as much but here's the thing.

If I pull the (mono) jack partially out of the desk that on the group outputs, the signal level going to the MSR now looks like the desk (ie....'0' on desk matches '0' on MSR) and likewise when returning the signal from the MSR via the tape returns. Is this because the signal is now being 'amplified' via the hot and cold signals summing?

The desk is a 24 in-line console with a certain twist. It only has 16 group outputs that are configured like this. The first 8 channels can send out to 1-8 (ie. to any of the first 8 channels). Channels 9-24 can send out on 9-16, with 17-24 being a duplicated 9-16 group outputs. Note, anything plugged into 1-8 (XLR or line or tape return....the inputs and tape returns can be flipped) can only send out on 1-8 and the same with 9-16 (24).

I'll post later.

Al

Check your manual...My Soundtracs MX-32 had a neat feature where the outputs were on *unbalanced* TRS jacks...tip at +4 and ring at -10, so if you plugged in an unbalanced TS plug and pulled it out to the first click you were at -10, and inserted all the way +4. Again, the outputs were *unbalanced* but on TRS jacks.

 

[RRuskin]

Just use the -10 connections on all machines and you will have no worries. Tascam specs are slightly better without the extra circuitry in the signal path that bumps things to +4 anyway.

 

[sweetbeats]

Yup...+1 to that ^^^

 

[altruistica]

Hey guys,

Thanks for all the input.

I think Sweetbeats has the answer.....I seem to remember having a Soundtracs MRX in the nineties that did the same.....just checked the manual....yep.....so maybe run the MS-16 at -10dB.

Al

 

[sweetbeats]

That would be my advice and I believe the advice of others as well. The Soundtracs mixer's native interval operating level is -10dBv as is the MS-16. So just keeping everything native avoids a lot of circuitry that is unnecessary.

 

[Steenamaroo]

Thanks for that Steenamaroo.......I thought as much but here's the thing.

If I pull the (mono) jack partially out of the desk that on the group outputs, the signal level going to the MSR now looks like the desk (ie....'0' on desk matches '0' on MSR) and likewise when returning the signal from the MSR via the tape returns.

Check your manual...My Soundtracs MX-32 had a neat feature where the outputs were on *unbalanced* TRS jacks...tip at +4 and ring at -10, so if you plugged in an unbalanced TS plug and pulled it out to the first click you were at -10, and inserted all the way +4. Again, the outputs were *unbalanced* but on TRS jacks.

Sounds like gold.

Is this because the signal is now being 'amplified' via the hot and cold signals summing?

That's an interesting question. I don't know the answer, though.