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Old 14th April 2013, 05:20 AM   #101
mlloyd1 is offline mlloyd1  United States
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nezbleu:

lookin' good!

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Old 14th April 2013, 07:15 AM   #102
PMA is offline PMA  Europe
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Quote:
Originally Posted by nezbleu View Post
I finished this board recently, now working on the power supply. It will be a while yet before I can listen. I also just acquired a low-output MC cartridge, so will eventually have to make some decisions
One of the builders uses step up transformers for MC. I heard it, sounds pretty good.
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Old 14th April 2013, 04:51 PM   #103
nezbleu is offline nezbleu  Canada
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Quote:
Originally Posted by PMA View Post
One of the builders uses step up transformers for MC. I heard it, sounds pretty good.
No doubt, but I hope you aren't trying to limit me to just one phono pre-amp!
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Old 14th April 2013, 05:29 PM   #104
Marra is offline Marra  United Kingdom
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Sorry if I've missed it but are pcb's still available?
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Old 14th April 2013, 06:37 PM   #105
PMA is offline PMA  Europe
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Quote:
Originally Posted by nezbleu View Post
No doubt, but I hope you aren't trying to limit me to just one phono pre-amp!
Of course not, I thought you wanted to use this one for MC.
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Old 14th April 2013, 06:38 PM   #106
PMA is offline PMA  Europe
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Sorry if I've missed it but are pcb's still available?
Not now, sorry. I hope to get more time for production and distribution in future.
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Old 14th April 2013, 07:09 PM   #107
Marra is offline Marra  United Kingdom
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Thanks PMA I will keep my fingers crossed.
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Old 17th April 2013, 01:31 PM   #108
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Default some thoughts

Having worked with similar circuits - derived from the Cello Palette preamplifier - and used in both low and high-gain applications;

1. Add an OPA633 to the "buffer list".
2. the 627 can oscillate under certain conditions. C3 may be necessary - start with 100pf and work up or down.
3. Since the output offset of the 627 can be trimmed, the servo might be unnecessary. Some folks don't like servos.

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Old 17th April 2013, 02:39 PM   #109
PMA is offline PMA  Europe
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OPA627 does not oscillate in this circuit, for 100%. C3 might be important for another opamps. But, R5, that might have been overlooked, is important for unconditional stability.
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Old 3rd August 2013, 04:00 AM   #110
nezbleu is offline nezbleu  Canada
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This has dragged on quite a while now. The case work took longer than I expected, partly because I ordered a chassis that is too small to fit everything. I had to offset the boards vertically so they could overlap horizontally.

I mounted the raw DC supply in a separate chassis:

DSC_4834.JPG

The Salas shunt regulators powered up nicely:

DSC_4880.jpg DSC_4881.JPG

External view: DSC_4885.JPG

This weekend I will double-check for output offset, and hopefully start to listen!
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