Phase inverting problem


Hello,

I have a Conrad Johnson PV-12A pre-amp. It is phase correct for the phono stage, phase inverting for the line stage.

My power amplifier is a conrad johnson MF2100. It is phase correct.

So my first idea was to connect the speakers to the power amplifier the wrong way (black to red, red to black) and then connect the cartridge the wrong way around as well (R: + and - reversed, L: + and - reversed). Then the phase should be correct for everything.

But there lies the problem. When I switch the connections on the cartridge, I get a really loud hum, makes the music barely hearable. Perhaps it has something to do with the fact that R- is connected to the cartridge body, it is some kind of earth? Anyway, switching the connections on the cartridge is not an option. So, what to do?

My only idea so far is, seeing that I only have one line input (cd), is cutting open the RCA cable and switching + and - of the line, and connecting the speakers to the power amp the correct way. So, I'll do just that. But maybe there's a better solution that I'm missing. Any ideas?
swaf

Showing 3 responses by hifitime

Definitely don't switch the interconnect wires. Way to many risks in doing that. The only way I can think of doing this without getting a different preamp, would be to add a switch to each speaker wire. That way, you can flip a pair of switches and reverse the speaker polarity. It can be done with a pair of double pole, double throw switches.
I found a picture on the net for wiring the switches that way. It's a lot easier than trying to explain it. It's the second picture from the bottom, and even shows two. The view is from the rear of the switch, with it flipping/sliding up and down.
[http://www.1728.com/project2.htm]
Swaf said the minus is tied to his cartridge body. So when he reverses them, the plus may be tied to the whole tonearm. That would explain the hum. Then if he grounded the whole arm with the cartridge wires reversed, it might short the signal (plus)to ground also.