Balanced Output Gain

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4pyros

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I need to up the gain of the output from a Gemini CDMP-1400 Player. It came with XLR outputs that should supply +4dbV, but uses the same level as a Unbalanced output -10dbV. I think all I need to change is one resistor but what would the right value be?
 

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hi,
The gain of the 1st stage non inverting is *2 and the 2nd buffer inverting stage is *-1.
If you increased the marked 10K to say 20k, this would give a gain of *3.

The gain for a non inverting stage is G= 1 + [Rf/Rin]
 
If you increased the marked 10K to say 20k, this would give a gain of *3.
Click to expand...
Thats what I thought and I should not have to do anything with the 2nd stage, right?
 
4pyros said:
Thats what I thought and I should not have to do anything with the 2nd stage, right?
Click to expand...

No, just ignore it - however, the single ended output shouldn't be much lower than the balanced output, and certainly not only -10dB.

It should work perfectly fine without needed any modification.
 
however, the single ended output shouldn't be much lower than the balanced output, and certainly not only -10dB.
Click to expand...
Sorry Nigel; you lost me on this one. Did you mean the input to the output stage?
 
4pyros said:
Sorry Nigel; you lost me on this one. Did you mean the input to the output stage?
Click to expand...

You said in the first post that the balanced output was +4dB, and using it as unbalanced was -10dB, this shouldn't be so, the unbalanced output should be close enough not to require any modification - it only loses 6dB (giving -2dB).
 
You said in the first post that the balanced output was +4dB
Click to expand...
No I said it should be +4dbV.
and using it as unbalanced was -10dB
Click to expand...
No the balanced output is only -10dBV. This output will not fully drive the input to a Behringer dcx2496. It needs to be +4dbV.
the single ended output shouldn't be much lower than the balanced output, and certainly not only -10dB
Click to expand...
The two outputs are at the same level -10dBV. It is not shown in the diagram but the unbalanced output is taken off the output from the 1st op amp.
Hope that explains it. Andy
 
Last edited:

The spec on the Behringer doesn't give the sensitivity, only a maximum of +22dB - however, it does say that all inputs and outputs are balanced, as you would expect.

So why the problem?.

But if you want to increase the output, increase the marked resistor - try something like a 56K for a start.
 
So why the problem?.
Click to expand...
An input of only -10dBV to the DCX will only drive the input to about 1/3 of max at the most.
You should have at least 3/4 of max input on the DCX so as not to loose bits in the A to D convershoin.
Andy
 
I will try and change the resistor today. I will srart with a pot and then put in a fixed resistor.
 
4pyros said:
I will try and change the resistor today. I will srart with a pot and then put in a fixed resistor.
Click to expand...

If you must use a pot, keep the fixed 10k in circuit at one end and connect the pot in series with the 10K
 
But if you want to increase the output, increase the marked resistor - try something like a 56K for a start.
Click to expand...
56K worked perfectly. Thanks All Andy
 
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