2. amps-preamps
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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
atmasphere's avatar
atmasphere
11,841 posts
 
The only way you are going to be able to hear absolute phase is if the recording is done with 2 microphones only.

The vast majority use more than this. As soon as other phase relationships are introduced by any additional mics, the delicate information that allows you to hear absolute phase is destroyed.

On top of that, as pointed out earlier, 1/2 of your recordings are out-of-phase anyway! Unless they are done with 2 microphones, you will not be able to sort out which ones are which.
tbg
5,263 posts
 
While I would quibble about Atmasphere and Geofkait's 50% figure as just a guess that recording engineers are largely indifferent to absolute phase, I would say that with the capability to change absolute phase, I hear very few instances where there is a clear choice. Nevertheless, I understand the nagging concern about having both vinyl and digital in the same phase. It is common for each stage of amplification up to the amplifier itself to invert.

I even went so far once to install double pole/double throw switches on my speaker wires to allow switching of absolute polarity there.
atmasphere's avatar
atmasphere
11,841 posts
 
Tbg, we have had that feature in our preamps for the last 22 years. Its the least used switch on the preamp- by far!
geoffkait's avatar
geoffkait
23,365 posts
 
True or False?

The absolute polarity of about 50% of all home audio systems is the reverse of the other 50%.
tbg
5,263 posts
 
False, but I still say we are guessing that recording engineers randomly chose polarity.
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