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Old 2nd November 2017, 12:41 AM
John Caswell John Caswell is offline
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Join Date: Dec 2005
Location: Wokingham, Berkshire
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Default Re: Balanced circuits for Pre/phono/psu 2and3

Hmmm interesting thread.
I have just done something similar to a Phono3.
Converting the input to balanced is fairly easy IF you have a MC cartridge and balanced wiring a la SME 5 pin DIN to phono cable, plus of course a step up transformer. That is how I run my Phono 3 input. Trying this with a MM cartridge could be very difficult to impossible if the cartridge has the R/H signal return (green) connected to the body of the cartridge. In this case I would be inclined to use a proprietary balanced to unbalanced line receiver IC, of which there are many giving excellent results, but you would need a balanced 18V DC supply.
The phono3 output can also be converted to balanced by using a 1:1 isolating transformer designed as a 10k:10K input isolating transformer. Surprisingly this works very well as it just just wired across the output of Phono3 after the output cathode DC isolating capacitor (2.2F)
Converting Pre3 to balanced input is a different kettle of fish unless you only want one input eg Phono in which case a simple 1:1 10K:10K input matching/isolating transformer will suffice very well mounted in a small box with balanced input connectors (XLR or DIN) and unbalanced output connectors (RCA/phono). Once again instead of the transformer you could use the aforementioned IC converter. The main problem with transformers is cost and availability.
Food for thought so....any questions stick them up here and I and others will try to come up with solutions.

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