Help Needed

[Tea24]

I have two turntables playing through a Beresford TC-4270 Audio Router to a Graham Slee Jazz Club Phono Stage and then to my pre-amp.

Tonight a problem has arisen.

Suddenly on one turntable only I find that if I switch the Jazz Club to mono I lose almost all volume. On the other TT no loss of volume!

(When it is switched to stereo all is fine)

BUT I STRESS THIS ONLY APPLIES TO ONE TURNTABLE ONLY: not the other, so presumably it cannot be the Phono Stage.

Yesterday I did not have this problem.

I am assuming that it must be a connection issue but I don’t know where to start.

I intend to play with connections, but tomorrow when I have time, not now.

Any help gratefully received.

[jaym481]

Swap the cables from the arms to the switchbox and see if the phenomenon follows. If it does, it's somewhere in the direction of the arm, if not, it's probably something in the switcher.

If it's in the arm direction, basic troubleshooting - check connections from the cartridge back. If you can swap headshells, do that, so you can further isolate it.

[Tea24]

Well, problem solved I think.

I discovered that someone (guess who!) had wired the cartridge up out of phase:doh:.

When I switched the phono stage to mono it cancelled out and gave virtually no output.

I have read of this phenomenon somewhere before to do with setting up azimuth but don't really understand it; can someone explain in words of one syllable?

[walpurgis]

If you've wired a cartridge out of phase you will get sound in stereo as you've found, although it won't sound right, but you are still operating two separate channels. But, if you then switch to mono you are more or less combining the two discrete channel signals into one, unfortunately they will be opposed in phase and each wave of the signal in one channel will largely cancel the signal on the other channel, basically one channel mopping up the energy of the other. The only information left as an audible signal will be the stereo difference between each channel, mainly ambient stuff, added effects and differences due to microphone positioning. You can achieve much the same effect by wiring one of your speakers out of phase and putting them face to face with a gap of a few inches. The sound will largely disappear due to cancellation, especially noticeable at lower frequencies where the wavelength is longer. Acoustic in this case and electronic in the former, same principle though. Its an interesting experiment.

[Tea24]

Wow! Walpurgis, that is about as succinct and understandable as it gets.

Thank you!

Even this little thick boy can get that!

It strikes me that it is a good check on whether the cartridge is wired right, apart form any thing else.

I knew I could count on the serious expertise of those on AOS.

Thanks again.

[DSJR]

I've heard tale of a VERY expensive phono stage being hoiked round dealers that actually played in mono. Only one dealer noticed it and yet others actually placed orders on it's mono performance and didn't hear the fault ;)

Wiring a cartridge out of phase and playing a mono recording may actually aid setting up I reckon?