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Well, I have my answer (and a schematic)!!

Posted by FidPup (A) on July 7, 2007 at 08:24:16

In Reply to: Easy Polarity Switching for Marantz SA-11... Would this work? posted by FidPup on July 4, 2007 at 12:35:13:

Hi, Again,

I got hold of a schematic for the SA-11!

As I deduced from the photos I've seen of the inside of the SA-11, there ARE six HDAM modules in the analog output stage. One of the modules drives the non-inverting side of the balanced output, and another drives the inverting side.

However, the other four HDAMs are used, two per channel, to implement the analog filter stages for the output stage, in the same way that op-amps are used in many other players. (I had previously assumed two HDAMs for the RCA outputs and four HDAMs for each of the R and L "hot" and "cold" balanced outputs.)

In the SA-11 the "hot" center contact of the RCA jack is directly hard-wired to pin 3 of the balanced XLR socket. The outer ground of the RCA jack, pin 1 of the XLR jack, and the socket/shield of the XLR jack are all connected directly to chassis ground.

This means that the inverting side (pin 2) of the output circuit, which is otherwise identical to the non-inverting side, is simply left floating when the unbalanced RCA outputs are used.

So, If I make up an interconnect with an XLR plug on one end (connected "hot" to pin 2 and ground to pin 1) and a normally-wired RCA plug on the other end I will have a nice inverted signal! There should be no problems at all leaving the positive side of the circuit floating!

I should be good to go, and will be able to change polarity by simply switching between the inputs!

Ken

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