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jev 20th February 2012 08:58 PM

Help wanted mono not stereo
Help wanted!!

I think I have a weird problem but hope it is perfectly explainable and I am overlooking something obvious.

I have just finished my Hagerman octal phono amp with MC trafos and it is finaly humfree which is a very nice thing. But when I connect my player I have a mono signal. When unplug one of the two rca connectors (left or right the other stays connected) I have no signal.

I am pretty sure it has to do with my arm (VPI 12.7) while bugfixing the hum I dismantled a small plug. I think have put it back on the right way but I am not 100% sure. When I connect my old phono amp (non tube) that always played stereo very fine and that I have not touched recently I have the same problem. hence I think it is the arm. I have also switched the MC cart and the same problem. Also switched cables and the problem persists.

I have measured all leads in the arm and all connect and non shorts between themor with earth.

Where to look? Help!

DF96 20th February 2012 09:47 PM

Yes, it sounds like the arm wiring is wrong. Check that left and right have not been swapped somewhere, or signal and ground. Note that the cartridge may appear to have two quite separate pairs of pins for left and right, but sometimes the two ground pins may be connected together inside.

jev 21st February 2012 07:53 PM

Thanks for your help.
I have solved the problem just now. I had a wiring problem at the mc trafo. I knew this because I routed the mc cart into the mm stage and the problem disappeared. I resoldered everything and I have stereo at last :-) Indeed probably swapped somewhere..

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