ZYX Universe - Unipivot or Dual Gimbal arm

Thom,
I'm following your azimuth posts with interest, though I won't have much time to experiment or post for the next few weeks. We have (non-music listening) house guests and I'm interviewing for jobs.

One correction: Wally's azimuth measurement does not equalize output levels between channels. That method would indeed be fraught with errors. Wally's method minimizes crosstalk.

I presume minimal crosstalk occurs when the coils are positioned to move symmetrically within the magnetic field. Depending on the accuracy of the cartridge's construction, this position may or may not align the contact edges of the stylus precisely with the groovewalls. If the cartridge is not perfectly built (and I assume that none is truly perfect) then "perfect" azimuth adjustment is in fact unattainable.

FWIW, adjustments of < 1 degree do indeed produce measurable changes in crosstalk. I too have noticed what you call "null" zones, where adjustments have little effect or even reverse effects.

The main thing we hear when azimuth is just right is the tightest L/R imaging available from that particular cartridge, a reduction in image "bloat".

Best regards,
Doug

Hi Doug and Thom,

Continuing the azimuth discussion, there appears to be two different methods of "minimizing crosstalk". One is where you measure crosstalk and adjust azimuth until the crosstalk measures the same in both channels. The second method is described here

http://www.audioasylum.com/scripts/t.pl?f=vinyl&m=138751

In this second method "The aim of adjusting azimuth for minimum crosstalk is to achieve the lowest figure for crosstalk in whichever channel gives the worst result. For example –29db left and –35dB right is a better result than–26dB left, and –26.5dB right, despite the fact that the difference between the left and the right is greater in the first case."

I have been using this second method to set azimuth initially. I then make small adjustments left and right around this point to see if my ears can pick a better point. My ears tell me that my initial point is usually very close to the best point.

However, if there are several null points, how does one find all of these points without spending hours and hours adjusting and listening, adjusting and listening?

Best Regards,
Roger

Hi Roger, Doug ...

The fascinating revelation for me was the discovery of multiple null points (false nulls) which brought me no comfort in the least. I believe I described this in a recent thread (this one?).

Failing instrumentation, we're left with starting out with a headshell that's parallel to the record surface (in the azimuth plane), and beginning our adjustments from this point.

The is a leap of faith that the cantilever/stylus assembly is within reasonable manufacturing tolerances so that the null you hit (by ear) is the real one. The thing we have going for us is that minimal crosstalk will also yield the lowest distortion, because the stylus will be sitting squarely in the groove.

If you're troubled that perhaps you are one null away from the truth, then you can always go counter clockwise by one null and also clockwise by one.

Rather than reiterate Brian Kearn's brilliant post you pointed the group to, I suggest that everyone take a moment read it. Even if the math confuses you, I suggest you read it and file it away for future reference. Come back to it from time to time. You'll be amazed at how things like this begin to make sense over time.

One key point to focus on is midway into this post, where Brian hits the nail squarely on the head:

"I disagree with this method of calculating crosstalk. It does not take into account the effect of channel imbalance on the crosstalk measurement. In effect this method assumes that a cartridge has perfect channel balance."

Cheers,
Thom @ Galibier

Hi Thom,

Before I start measuring crosstalk, I play a test tone thru both channels and use the balance control to make the measurement the same in both channels. Once I have equal output in both channels, then I measure the crosstalk using the left channel and right channel test tones. I assume that is the coreect way to do it. Yes???

Wally's method does not assume perfect channel balance, in the cartridge or any other component. He specifically designed to avoid that assumption.

He starts by measuring output on each channel. Any imbalance is allowed for in the calculations that follow.