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Old 26th July 2016, 09:09 PM   #1
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Default Adding 3db gain at differential opamp output?

Hi,
I have an diy Sabre32 ES9018 with a standard data sheet op amp I/V converter and differential amp output
ess 9018 output circuit.pdf.

I need just 3db more gain to drive amp with 10x gain (F5) and my speakers.
Can I just reduce (parallel so no un-soldering needed on pcb)slightly the 470 ohm to 370 to gain the x1.4 voltage ratio I need for 3db?

What is the noise penalty for such an marginal increase in gain in a differential amplifier?

I have 17v rails for op amps so doubt that headroom would be an issue? I would prefer not to add another gain stage.
All comments welcome.
Thanks
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Old 26th July 2016, 09:15 PM   #2
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Would this small adjustment require an adjustment of the output filter capacitor values or is the effect negligible? Thanks in advance for nay comments.
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Old 27th July 2016, 01:03 AM   #3
sreten is offline sreten  United Kingdom
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Hi,

I'd say an I/V converter always needs more resistance for more voltage.

rgds, sreten.
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Old 27th July 2016, 09:54 AM   #4
DF96 is offline DF96  England
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Reducing the value of the 470 (R6+R11) will raise the gain to the unbalanced output, and possibly change the frequency response too. It will not affect the gain to the XLR output - for that you need to increase R1+R17. Unclear what you want to do.
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Old 27th July 2016, 11:30 AM   #5
AndrewT is offline AndrewT  Scotland
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What does the "AGND" mean?
Is it audio ground, or analogue ground, or chassis/enclosure, or screen/shield of the XLR cable?
Can any of those "ground" options be interconnected?
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Old 27th July 2016, 11:32 AM   #6
AndrewT is offline AndrewT  Scotland
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are the first two opamps the DAC?
i.e. they convert the digital to analogue,
or is the DAC conversion done before we connect the "external current mode" circuit?
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