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
11,629 posts
 
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.
nick_sr
263 posts
 
I see a black ground wire going in the bottom of the tonearm, but I don't know where it is connected to.

The black wire is connected to the aluminum arm wand by the screw that hold the arm wand into the pivot assembly. At the arm board PCB it is connected to the green tonearm wire, the ground return of the red interconnect as well as the ground wire. The blue wire is only connected to the ground return of the white interconnect and nothing else.

I hope this helps. If needed I can upload a photo of the arm board to my system page. Let me know.
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.
atmasphere's avatar
atmasphere
11,629 posts
 
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.
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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