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In the Forum: Audio Discussions
In the Thread: It’s mad, mad, mad... electricity.
Post Subject: The differences between…Posted by Romy the Cat on: 12/8/2010
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 TonyB wrote:
The differences between the battery operation and AC operation are to be expected.
One case is isolated (hopefully) from AC, the other case is not. If anybody thinks otherwise,
they are fooling themselves.

Tony, the fact is that the differences between the battery operation and AC operation is expected but it did not exist in practical audible term with former unit. I am very much not fooling myself. That was one of the beauties of PP1500 that I was so hooked 3 year back – there was no differences between battery and AC operation and all subjects of “isolation” just did not raise.

 TonyB wrote:
The first question to ask is to MAKE SURE that the battery is connected even when the
unit is running from AC.

You are right, that is THAT very fist question I asked, many times and PurePower assured me that the buttery are engaged all time. If it was not the case and by a bug of hardware or software the buttery gets disengaged what unit ruins from AC then the fix would be VERY easy to find. I did not open the unit and did not test it myself as PurePower assures me that buttery is on line.

 TonyB wrote:
If we are 101% sure (ideally by measurement of an open unit when it is operating) that
it is connected and that no switches between the battery and the regenerator were
changed between the battery and the AC modes operation, then the cause is the charging
circuit: it is connected in parallel with the battery in AC mode of operation.

There is a number of possible causes and a comparison of the schematics of the current
and previous versions would reveal the cause of the latest change in sound. 

The reasons for the difference between the battery and AC operation could be:

- An extra capacitor after rectifiers is connected in parallel with the battery (it is not there in battery only operation)
- The rectifiers generate noise and pass it in both directions
- Rectification adds spikes/RFI/EMI to DC which are not there in DC operation
- The transformer passes noise form AC to rectified DC
- Caps on AC input
- Chokes on AC input
- Rectification may dump noise, ... into GND line
- and many others...

Yes, good summation. I would like to point out that all of those issuers might be measurable if to measure them properly. There are a few things that have pitched to PurePower that are a bit more “esoteric”, like redaction of in-phase “fuzziness” that in fact might played a positive role by acting as dither… I would however agree that what you have enumerated are the things that need to be tested first and I guess it is what they are doing now. The cool part is they have the old motherboard that sound fine and they can compare the measurable data between them… 

The Cat
 

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