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Old 10th February 2008, 02:04 PM   #1
jkeny is offline jkeny  Ireland
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Default Variable Voltage Volume control

I'm looking to replace the output stage PS with Battery supply on a Panasonic SA_XR57 amplifier as I believe the quality of the PS is the most important sonic determiner in these non-feedback equibit digital amplifiers.

The volume control in these amps is firstly through DSP & then through PS voltage reduction, I believe.

My hope would be to try and tie the battery PS to this scheme! Has anybody any idea on this?

Or what is needed to provide a separate variable voltage PS supply controlled from a potentiometer?

I have included the schematic of the existing Vol controlled (Circled) PS
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File Type: pdf xr57 schematic part1.pdf (75.6 KB, 63 views)
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Old 10th February 2008, 02:06 PM   #2
jkeny is offline jkeny  Ireland
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Second Part of PS
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File Type: pdf xr57 schematic part2.pdf (77.7 KB, 27 views)
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Old 10th February 2008, 05:11 PM   #3
jkeny is offline jkeny  Ireland
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Thinking about this further, I suppose my request boils down to asking how do I implement a circuit to allow variable regulation of 48V DC from a battery source - rather than the thread title?
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Old 10th February 2008, 07:48 PM   #4
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It's possible - anything is possible. You can design a variable output voltage supply, actually two of them, one pos, one neg, controlled by a dual pot. Most of the advantage of the batt supply would disappear with the reg between battery and circuit, of course. You would need a lot of heatsinking for those situations where you would turn the supply down - the reg should dissipate all unused voltage times the drawn current.
In your switched amp that was easy because the supply was also switched. Anyway, as I said, it can be done.

Or you can just use the volume control. It's a matter of priorities

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Old 10th February 2008, 09:13 PM   #5
jkeny is offline jkeny  Ireland
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Ok Jan,
So the battery is meaningless in this scenario! So best to try improve this SMPS! Added capacitance on the output will probably help! Do you have any suggestions for further improvement.

Don't know what you mean by
Quote:
Or you can just use the volume control
the existing volume is digital from -72 to -40db , then voltage-based volume from -40 to -10db ( 5V to 40V ) , and then digital again from -10 to 0db
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