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Author Topic: Balanced send output to unbalanced amp input  (Read 10774 times)

Jordan Wolf

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Re: Balanced send output to unbalanced amp input
« Reply #10 on: May 01, 2012, 08:28:33 pm »

Quote
If you take a strong balanced signal or balanced line (they're two different things) to span the distance, then at the Keyboard amp, pad it down with a "H" pad  or similar, to feed into the "balanced" mic input... it should work fine.
That method is what I was thinking would be "second best".

Quote
Note: the OM calls that a mic/line input, so you might plug right in.
Really?  Huh…I must have missed that - if that's the case, then the OP should definitely just plug right in.

For the adapter in question, it's simply a TRS barrel with a TS connector wired only to the Tip and Sleeve of the TRS. 

I do have one question: does a balanced output invert the signal also, or does only a balanced input do that?  If it's device dependent, then I guess I'll have to look for it in block diagrams.
« Last Edit: May 01, 2012, 08:36:42 pm by Jordan Wolf »
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Gordon Waugh

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Re: Balanced send output to unbalanced amp input
« Reply #11 on: May 01, 2012, 08:45:37 pm »


I'd plug it balanced into the mic/line input and see how it goes.

If you must plug into the T-S input, consider using an isolation transformer.

JR

There are two inputs for channel 1. The mic input is a balanced input that uses a mic preamp. The line input is an unbalanced TS jack that does not use a mic preamp (i.e. it is line level). I can use one or the other.
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Gordon Waugh

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Re: Balanced send output to unbalanced amp input
« Reply #12 on: May 01, 2012, 08:59:44 pm »

There are two inputs for channel 1. The mic input is a balanced input that uses a mic preamp. The line input is an unbalanced TS jack that does not use a mic preamp (i.e. it is line level). I can use one or the other.

Well, since the little amp in question has a "built in 4 channel mixer", you can use the balanced input for what you like and plug the keyboard into one of the other (line) inputs.  Just watch your send level to the mic input.......
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Mac Kerr

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Re: Balanced send output to unbalanced amp input
« Reply #13 on: May 01, 2012, 09:01:48 pm »

I do have one question: does a balanced output invert the signal also, or does only a balanced input do that?  If it's device dependent, then I guess I'll have to look for it in block diagrams.

A balanced output that either has a transformer, or a differential output, puts out a signal that goes positive on pin 2 as it goes negative on pin 3. A balanced input "inverts" the signal on pin 3 and adds it to the signal on pin 2. Any common noise on both pins is cancelled out, and the voltage sum is 6dB hotter than just a single leg would be. The noise is still canceled if the output is only "impedance balanced, where both pins have the same impedance to ground, but there is only audio signal on pin 2. A balanced input will still cancel the common noise.

Mac
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Bob L. Wilson

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Re: Balanced send output to unbalanced amp input
« Reply #14 on: May 01, 2012, 09:27:18 pm »

I like the 16 ohm passive monitors like the HotSpot.  They can only be turned down........

Players get wise to that pretty soon they start sandbagging during rehearsal and turning down the pots just so they can turn them up later. If a player wants control of the level or the mix it needs to be in their ear so only they have to listen to it.
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John Roberts {JR}

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Re: Balanced send output to unbalanced amp input
« Reply #15 on: May 01, 2012, 09:29:01 pm »

That method is what I was thinking would be "second best".
Really?  Huh…I must have missed that - if that's the case, then the OP should definitely just plug right in.

For the adapter in question, it's simply a TRS barrel with a TS connector wired only to the Tip and Sleeve of the TRS. 
Might work, might not... not my first choice.
Quote
I do have one question: does a balanced output invert the signal also, or does only a balanced input do that?  If it's device dependent, then I guess I'll have to look for it in block diagrams.

Neither one, but this topic is confusing enough.

To KISS, think of all audio interfaces as either 2 wire or 3 wire.

2 wire inputs or outputs have one hot and one common or ground.

3 wire inputs and outputs have one hot + polarity, one hot - (or opposite) polarity, and one common or ground. The 3 wire input subtracts the - hot from the + hot to extract clean signal independent of the grounds.

Obviously 2 wire is cheaper and Ok for short distance, but the ground lead is shared with one of the audio leads so signals can get contaminated easily. 3 wire cost more but works better for more difficult environments and small signals (like mic outputs).

There are multiple variants of 3 wire inputs and outputs, but the differences generally don't matter when connecting 3 wire to other 3 wire interfaces.

Mixing and matching between 3 wire and 2 wire can be a source of problems, depending on which of the sundry variants you are dealing with.

I'll stop now, to keep it concise but there is much much more...  when dealing with the dreaded 3 to 2 interface.

JR

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Gordon Waugh

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Re: Balanced send output to unbalanced amp input
« Reply #16 on: May 01, 2012, 10:02:46 pm »

Well, since the little amp in question has a "built in 4 channel mixer", you can use the balanced input for what you like and plug the keyboard into one of the other (line) inputs.  Just watch your send level to the mic input.......

I will try that. I Will keep the aux send level really really low.
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Gordon Waugh

Jonathan Johnson

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Re: Balanced send output to unbalanced amp input
« Reply #17 on: May 03, 2012, 01:28:57 pm »

In a situation like this, I have run a balanced signal line all the way to the keyboard amp, then connected a passive DI box backwards with the balanced line on the "output" and the unbalanced on the "input" connected to the line in on the amp.

I don't know if it's the right way to do it or not.
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John Roberts {JR}

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Re: Balanced send output to unbalanced amp input
« Reply #18 on: May 03, 2012, 02:47:56 pm »

In a situation like this, I have run a balanced signal line all the way to the keyboard amp, then connected a passive DI box backwards with the balanced line on the "output" and the unbalanced on the "input" connected to the line in on the amp.

I don't know if it's the right way to do it or not.

Audio transformers are symmetrical so can be hooked up backwards and should pass signal. A DI is typically stepping down the voltage to mic level and expecting a high Z input side impedance.

If you keep levels sent into the output side relatively low voltage and not bass heavy, your send source impedance is low, and the keyboard line input impedance is high z, it could work.

A 1:1 line level isolation transformer would be the correct tool for that job.

JR
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