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Old 27th March 2008, 01:54 AM   #1
ALBQ is offline ALBQ  United States
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Does anyone know where to find a schematic for a Cambridge Audio 640P phono preamplifier?

Thinking about modifying mine but, would like to understand the circuit in order to know what changes would make the most sense. There is a pretty long thread on Vinylengine but, no schematic. Any help is appreciated

Thank you - ALBQ
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Old 30th March 2008, 01:05 PM   #2
ALBQ is offline ALBQ  United States
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Cambridge Audio 640P - Update

Well, schematic or no, I took the plunge and installed gold plated sockets and OPA2134 OpAmps in the MM section yesterday.

Because of the type of solder used, getting the NE5532's out was a total pain but, the improvement in sound was more than worth it. Less congestion, greater space and better imaging yet, retains smoothness the 640P is known for.

Next step is to enjoy it for while as I research an input and output cap change - get rid of the electrolytics in the signal path

-ALBQ
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Old 30th March 2008, 03:36 PM   #3
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http://media.bestkiteboarding.com/mm/640p.jpg

op637's on the gain stage and lm4562 on the Riaa
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Old 30th March 2008, 10:48 PM   #4
ALBQ is offline ALBQ  United States
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sq225917
I read your post on vinylengine – nice work. Any future plans or is it done?

Thank you for the advice -ALBQ
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Old 14th April 2008, 03:34 PM   #5
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I think it's pretty much done to be honest. I am considering splitting the power supply off the PCB and putting it in all a full width case.

Maybe replace the regs with discreet units, not sure i need to probe their output noise first.
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Old 22nd December 2009, 08:56 AM   #6
jpak is offline jpak  United States
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Quote:
Originally Posted by sq225917 View Post
I think it's pretty much done to be honest. I am considering splitting the power supply off the PCB and putting it in all a full width case.

Maybe replace the regs with discreet units, not sure i need to probe their output noise first.
Has anyone looked underneath the metal enclosure labeled "discrete low noise MC stage"?
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File Type: jpg 640pInside.jpg (574.3 KB, 573 views)
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Old 21st January 2010, 05:40 PM   #7
marco70 is offline marco70  Italy
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Hi
link http://media.bestkiteboarding.com/mm/640p.jpg
doesn't work anymore or I'm doing something wrong ?
does someone have a working link / schematic ?
cheers
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Old 21st January 2010, 07:12 PM   #8
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Ca 640p
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Old 22nd January 2010, 02:06 PM   #9
marco70 is offline marco70  Italy
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Many thx, next time I'm searching deeper in other threads :-)
cheers
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Old 31st January 2010, 04:27 PM   #10
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Sorry guys I have to clean the worked served stuff out sometime. The vinylengine thread is the best reference, pages 28-29.

i do still have the 640p in a box somewhere, if someone wanted pics. I've done nothing to ti since, and to be honest KCS's version was taken much further than mine was.
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