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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
magfan
1,583 posts
 
crossovers have phase shift which sometimes makes it necessary to 'flip' polarity on a driver.

And that's a GOOD question. Why wouldn't hearing be the 'test'?
misternice's avatar
misternice
339 posts
 
Hi there,this might not be in this case,but some times a tube drops out,and it appears to be a earth problem,sometimes a channel can go too.
geoffkait's avatar
geoffkait
23,365 posts
 
Tbg - dunno how many or which players invert polarity. I dunno why either, but I don't think they do it on purpose. Maybe they are like recording engineers and just donl;t think about it.

Some speakers must be made on Monday since occassionally you find a speaker with one or more driver miswired. I strobly suggest checking for correct polarity of drivers, sep. if you exhibit any equipment at a show.

"All the testimony regarding recording engineers?" You mean the same meticulous recording engineers that compress the sound?
magfan
1,583 posts
 
Just a question......I guess I'm in that mood.
BUT, do recording engineers ruin music by CHOICE or by ORDERS from above to 'liven it up'....???

If they do it by choice, they all need ear exams, but if by orders, you could sort of understand them wanting to stay employed.
kirkus
502 posts
 
Tbg - dunno how many or which players invert polarity. I dunno why either, but I don't think they do it on purpose. Maybe they are like recording engineers and just donl;t think about it.
There are three reasons why a consumer audio product would invert phase:

1. Ambiguous or no standardization on hookup of balanced interconnections (i.e. the XLR pinout conventions that Atmasphere mentioned)

2. Error in design, manufacturing, or nomenclature

3. Preference for circuit design topologies/combinations for which inversion is a side-effect. An example would be a two-tube line preamp where the first stage is a plate-loaded voltage amp, and the second is a cathode follower . . . the signal will come out inverted, unless another stage is added to flip it back around. These types of circuit designs are increasingly eccentric and anachronistic in modern equipment . . . and pretty unusual even in the field of enthusiast audio where eccentricity and anachronism is widely respected.

Reason #3 is especially uncommon in CD players and DACs, given that the overwhelming majority of high-quality DAC chips have balanced current outputs and/or on-chip signal inversion capability . . . meaning that the designer can just as easily preserve signal polarity regardless of the design of the output stage. That's why I used a CD played from a Pro Tools recording/mastering process as my "good bet" example.
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