"Making Mono" for checking Azimuth

I need to update my system! Now I've got a Technics sp10ii with an SME312S tonearm and an Airtight PC-1 cartridge. Thanks.

You don't need mono... or test records.

Fact: inaccurate azimuth increases crosstalk between channels.

Fact: increasing crosstalk "fattens" sonic images, making instruments/vocalists sound wider or fatter than they should.

Fact: our ears are most sensitive to the directionality of upper midrange sounds.

Therefore: we can best hear azimuth changes in live instruments and voices (because we innately know how big they should sound) in the upper registers (the range our ears are most sensitive to).

So, choose records with a well-recorded female vocalist and/or prominent, upper-range acoustic instruments (flutes, clarinets, oboes, acoustic guitar, etc.). Listen for the tightest imaging. A vocalist should sound human sized. A flute should sound flute sized. A guitar should sound like a small, hand-held instrument, not a billboard.

Technical note: azimuth adjustments must be made in VERY TINY INCREMENTS, the smallest possible adjustments your tonearm allows. Start by making the stylus appear vertical when viewed from the front whilst playing, then listen for the above and adjust in tiny steps. Try both directions until the image sounds as tight as possible.

Thanks Doug. I'm sure you are right, and will give it a try. It's a bit intimidating with the SME 312S. It has a detachable headshell, and they instruct you to just grab the headshell near the tonearm and apply rotational force to it. Hard to imagine making small changes that way.

That said - I wonder what the easiest designs are for adjusting the azimuth?

Any advice with the SME?

If you want to supplement Doug's typically excellent suggestion with the test record method, it would most likely be ok to use either of the y-adapter approaches you asked about. The one circumstance in which I would be hesitant to do so is if the output impedance of the phono stage is particularly low, meaning significantly less than perhaps 50 ohms, especially if the tracks being played may have significant content that is off to one side (i.e., mostly in one channel). In that situation I would seek the manufacturer's opinion before shorting the two outputs together.

To the extent that the output signals of the two channels differ at any given instant, the output stage of one channel will have to drive a load impedance equal to the output impedance of the other channel, resulting in current flow that is much greater than under normal circumstances. The lower the output impedance the greater the current. With most and perhaps nearly all designs I would expect no harm to result from that, even if the output impedance is very low, but better safe than sorry IMO!

Regards,
-- Al

Peter,

I haven't used the SME and from your description I think truly fine tuning azimuth may be difficult. The adjustments needed are on the order of 1-2 degrees at most.

The easiest and most repeatable designs I've used are of two types:
- TriPlanar, Kuzma Airline: loosen two set screws along the armtube; adjust azimuth with a third, finely-threaded screw that rotates the armtube (1/24th of a turn makes an audible difference); retighten the set screws.
- Durand Talea: rotate a finely-threaded screw that moves a magnet toward/away from a second, fixed magnet that's located above the arm pivot; the opposing magnetic fields hold the armtube at a fixed angle, varying with the distance between the magnets.

The Talea's is the best I've used and unique. It's the only arm I know of that allows azimuth adjustment on-the-fly. This lets you hear exactly what you're doing, a great feature. It's a great arm generally, sonically head and shoulders above either the TP or the Airline IME.

Good technical advice from Almarg, as usual. I tend to avoid technical measurements if listening will do, since for me listening to music is more fun and I can perform most adjustments that way... but as always, YEMV (Your Ears May Vary!).