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 6 responses by atmasphere

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, we have had that feature in our preamps for the last 22 years. Its the least used switch on the preamp- by far!
Recording engineers do not take note of whether their mixing board or recorders are inverting or not. Nor does it show up in the manuals for such.

The simple fact is that a recording may or may not be absolute phase inverted. There is no coin, no decision, the issue never comes up. When you send the recording out to be mastered (in the case of LP) you have no idea if the result will be inverted or not. For example the manual for my Westerex stereo cutter system does not mention a thing about it. Neither does the manual for the Masterlink (a digital setup that can do mastering) or the various recording programs we have on computer. Its not a consideration in the studio. Neither does it show up in the manuals for our analog recorders. Its just not a consideration.

So you can be assured that 50% of all recordings are in phase and the other half are not.
Kirkus is right in that in some ways the phase is preserved- but I think if one looks into the equipment the interest of the designer will not be seen to preserve the absolute phases of the inputs.

I've used a lot of boards over the years and serviced them as well. What I have found over and over is that while they maintain certain standards, for example pin 2 of the XLR might phase non-inverting, that they are not so interested in what the ramifications of that fact is beyond the idea that all the channels get the same treatment.

IOW the unit may well be phase inverting from input to output, but no provision for that is guaranteed by assuming that pin 2 of the XLR is indeed noninverting relative to the input. It can only be assumed that the relationship will the same with *all* the inputs. Its a tricky nuance!

Some equipment uses a modification of the original balanced standard, in which pin 2 is non-inverting. Sometime in the 70s or 80s, European equipment went to pin 3 non-inverting. This practice has shown up in some Japanese equipment as well. This stuff is all over the industry! Unless someone has taken the time to make special cables that convert from the pin 2 convention to the pin 3 convention, the result is there is simply no way to know what is up.

Since it is reasonable at this date to assume that this equipment is everywhere peppered through the industry, its very safe to assume that 50% of all recordings are out of phase and the other half is in phase.
Lacee, if you are running a preamp already you certainly don't need the passive volume control after it. I would have to imagine that is messing with your bass!

Check the setup and loading on the cartridge. Absolute phase won't make the system should thin: something else is up.
Also, running the cartridge(Clearaudio Talisman V2 gold)thru MM stage and not the transformers in MC also has sonic merits.Experimenting with loading, so far 100 ohm sounds good, less cartridge ringing.

I guarantee that the load had no effect on ringing! If you look at the inductance of the cartridge, you will see that it is so slight that the load could not possibly affect it at audio frequencies.

The reason it is making a difference has to do with the apparent fact that the Steelhead is sensitive to Radio Frequency Interference (RFI) at the input of the phono. The RFI is generated by the resonance of the inductance of the cartridge, in parallel with the capacitance of the cable- the two form a tuned RF circuit. The energy of the cartridge sets this circuit into resonance- and that is the source of your RFI. By adding the load, you are detuning the RF circuit so it can't resonate.