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

Showing 3 responses by lacee

lacee
811 posts
 
I have a Manley Steelhead which I run full tilt into a Lightspeed Attenuator and then into a pair of mono blocks.
I assume everything is phase correct.
Cd is run directly into the LSA and to the amps.
To my ears the cd sound is much fuller,which bothers me, because the lp sound is thinner by comparison.
I am thinking there maybe a phase issue with the phono stage added to the mix.My memory is going, but I seem to remember somewhere in the past that when you have 3 stages, it puts the system out of phase and you need to switch at the speakers.In my case I will try reversing the leads on my cartridge as it is less full and perhaps out of phase.
Any thoughts on this?
lacee
811 posts
 
I sort of figured things out.
Reading past reviews, all seemed to say that running the Steelhead in the fixed output mode into a pre amp( LSA in my case)would be better sounding, so using it as a phono stage minus the volume control is what I've settled for also.
I was running it the other way, because you can't access the mono feature in fixed mode, and I occasionally listen to mono recordings.

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.

So now I am quite happy,thanks for the input.
lacee
811 posts
 
Thanks Ralph for the clarification.
It's great to have the real reasons behind what we are hearing explained.
Noise is something that you never know you have until you do something that lessens it,hence I will be doing more experimentation with loading and capacitance eventhough it's a MC.
What I can say about my experience with loading and the Talisman cartridge was that 100 ohms was a bit rolled off but fuller sounding than running it into Clearaudio suggested 300 ohms, at least with the gear I own.
And that was with low cap Nordost Heimdals from the arm and Heimdals from the phono stage.

And things varied from recording to recording.
I'm not about to tally up what settings sound best for each lp I have, so I've settled for compromises,never the best, but unfortunatly a fact.
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