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Using unbalanced outputs with balanced inputs?

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Using unbalanced outputs with balanced inputs?

Postby Arpangel » Tue Apr 30, 2019 8:36 am

I've accumulated a number of effects pedals, I should know the answer to this post but I'm still a bit unsure. I'm running some pedals on balanced aux sends, the outputs of the pedals go back into the mixer balanced line inputs, now if I'm correct, pin 3 (cold) on the balanced input will be left floating at the unbalanced output of the pedal, pin 2 will be connected to the tip, and the screen will be connected as normal at the unbalanced end.
I haven't noticed any ill effects or noise etc, everything works fine, I'm just unsure about damaging the outputs of my pedals?
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Re: Using unbalanced outputs with balanced inputs?

Postby Hugh Robjohns » Tue Apr 30, 2019 1:43 pm

If it's working as you want I'd leave it alone...

But the correct wiring requirements will depend on the specific design of the balanced output of you console.

Most semipro desks use impedance-balanced outputs for aux sends, and they can feed unbalanced destinations directly. Pin 2/tip is signal, pin3/ring can be left floating or grounded. Signal level is full -- so nominal +4dBu. Pin1/sleeve is ground reference.

Most active balanced outputs send symmetrical inverted signals, though, and they can be more fussy about wiring. Generally, leave pin3/ring floating. Pin2/tip carries the signal but the level will be 6dB lower than nominal -- which is often helpful when working with fx pedals anyway. Pin1/sleeve is ground reference.

For the fx pedal output feeding a balanced input, best to use differential mode. So unbalanced fx signal to tip/pin2 and unbalanced fx ground reference to ring/pin3. No connection to balanced input screen /sleeve/pin1.
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Re: Using unbalanced outputs with balanced inputs?

Postby James Perrett » Tue Apr 30, 2019 2:04 pm

It would really help if you could give us makes and model numbers of the bits of gear you are using - especially the mixer. Hugh has covered all the common permutations but there are other possibilities too...
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Re: Using unbalanced outputs with balanced inputs?

Postby Arpangel » Wed May 01, 2019 8:36 am

Thanks Hugh, I wasn't aware of not connecting the screen on the pedal outputs at the balanced input, and just using pin 3, I've always been a bit quezy about doing that for some reason! I don't think I have differential inputs though???
I'm using a Behringer QX2442 mixer, a Strymon Big Sky, EHX Delay, Chase Bliss Thermae, and Behringer Tremolo. As I said, I'm not getting any issues, the Big Sky is capable of taking levels up to +8 db, and EHX stuff to me has always been very tolerant of line levels.
I find I'm using pedals more, as there are a lot of interesting ones around now, but they are a pain in some respects.
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Re: Using unbalanced outputs with balanced inputs?

Postby Hugh Robjohns » Wed May 01, 2019 12:28 pm

All balanced inputs are differential inputs.
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Re: Using unbalanced outputs with balanced inputs?

Postby Wonks » Wed May 01, 2019 5:25 pm

Hugh Robjohns wrote:All balanced inputs are differential inputs.
Oh no they're not! And you know it! Balanced does not automatically equal differential.

But it is pretty much the norm.
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Re: Using unbalanced outputs with balanced inputs?

Postby Hugh Robjohns » Wed May 01, 2019 5:37 pm

:?: I'm struggling to think of a balanced input that doesn't process the signal differentially, Wonks. ;-)
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Re: Using unbalanced outputs with balanced inputs?

Postby Wonks » Wed May 01, 2019 6:42 pm

It's more the fact that 'balanced' doesn't mean 'differential'. You'd pick me up If I said the same thing.
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Re: Using unbalanced outputs with balanced inputs?

Postby Hugh Robjohns » Wed May 01, 2019 8:16 pm

Ah. I see what you mean -- you're thinking symmetrical inverted signals and how they aren't necessary for a balanced interface, whereas I was referring to differential receivers which are. ;-)
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Re: Using unbalanced outputs with balanced inputs?

Postby Arpangel » Thu May 02, 2019 7:16 am

I'm out of my depth here, but....if a balanced signal isn't symmetrically balanced, how can the phase cancellation effect occur that cancels out interference in a balanced system?
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Re: Using unbalanced outputs with balanced inputs?

Postby Kwackman » Thu May 02, 2019 8:57 am

There's a reply from Hugh in this thread which might help?

https://www.soundonsound.com/forum/view ... al#p332077
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Re: Using unbalanced outputs with balanced inputs?

Postby Wonks » Thu May 02, 2019 9:19 am

'Balanced' doesn't refer to the signal having one leg of the signal at the opposite polarity to the other (i.e. a 'differential signal'). It simply means that both of the input and output connections have the same impedance with respect to ground.

In an unbalanced system, one of the signals is normally connected straight to 0v or ground. The input pre-amp will probably still use a differential amplifier, as packaged op-amps are so cheap and plentiful. However, because the signal on the 'cold' connection is now taken to ground or fixed at 0v, then even if the signal sent (say from a microphone) starts out as being a differential signal, then at the input, that 'cold' half of the signal is lost, so the pre-amp isn't able to reject any noise picked up over the connecting cable.

But the vast majority of balanced audio signal inputs do use a differential pre-amp.
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Re: Using unbalanced outputs with balanced inputs?

Postby ef37a » Thu May 02, 2019 9:30 am

Start here: http://electricalacademia.com/instrumen ... principle/

BTW Hugh, I suppose a transformer input might not "look differential"? It is of course.

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Re: Using unbalanced outputs with balanced inputs?

Postby Hugh Robjohns » Thu May 02, 2019 12:40 pm

Arpangel wrote:I'm out of my depth here, but....if a balanced signal isn't symmetrically balanced, how can the phase cancellation effect occur that cancels out interference in a balanced system?

The interference cancellation takes place in the differential receiver and relies on the fact that the interference is presented as a common mode signal -- meaning identical voltage on both sides of the balanced connection. And that can only be the case if each side of the balanced libe has identical -- ie. balanced -- impedance to ground.

Since a common mode signal presents identical voltages on each input of the differential receiver there is no net difference and thus no output, so the unwanted interference is removed.

The wanted signal must present a difference in voltage between the two sides of the differential receiver. That can either be by using the 'traditional' idea of equal and opposite symmetrical signals each of half the total wanted amplitude , or it could be by having all of the signal on one leg and move on the other -- which is the form employed by impedance-balanced connections. Both are perfectly valid and effective balanced signals.
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Re: Using unbalanced outputs with balanced inputs?

Postby Hugh Robjohns » Thu May 02, 2019 12:49 pm

Wonks wrote:'Balanced' doesn't refer to the signal having one leg of the signal at the opposite polarity to the other (i.e. a 'differential signal'). It simply means that both of the input and output connections have the same impedance with respect to ground.

Absolutely! Spot on! :-D

In an unbalanced system, one of the signals is normally connected straight to 0v or ground.

Semantics I know, but not really 'one of the signals'... because there is only one signal. But one side of the signal voltage generator is tied to ground -- making it unbalanced and the signal voltage is thus referenced to ground -- as opposed to the balanced system where both sides of the signal generator are floating and have no intrinsic ground reference.

...that 'cold' half of the signal is lost, so the pre-amp isn't able to reject any noise picked up over the connecting cable.

For the avoidance of confusion, I should make it clear that no signal is actually lost. The entire signal voltage remains whole and intact, but becomes referenced to ground instead of floating. And any interference now getting into the connection also becomes ground-referenced too, the same as the wanted signal, and cant therefore be separated from it.

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Re: Using unbalanced outputs with balanced inputs?

Postby Arpangel » Fri May 03, 2019 11:04 am

Thanks folks, I stand educated, but all this talk about balancing has made me feel a bit unbalanced!

:)
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Re: Using unbalanced outputs with balanced inputs?

Postby Sam Spoons » Fri May 03, 2019 12:35 pm

Arpangel wrote:Thanks folks, I stand educated, but all this talk about balancing has made me feel a bit unbalanced!

:)

That's almost a requirement to be part of this forum :bouncy: You'll be fine as long as you don't pick up any interference........
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Re: Using unbalanced outputs with balanced inputs?

Postby Arpangel » Sat May 04, 2019 7:15 am

I actually know a sound engineer who's last name is Balance.

:)
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Re: Using unbalanced outputs with balanced inputs?

Postby Sam Spoons » Sat May 04, 2019 9:37 am

:clap: Definitely worth a thread over in the Lounge :D
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Re: Using unbalanced outputs with balanced inputs?

Postby John Willett » Sat May 04, 2019 12:28 pm

Arpangel wrote:I actually know a sound engineer who's last name is Balance.

:)

And I know one who's first name is Michael = Mike Balance :tongue:
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