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cart measurement vs quoted spec

Hi,
I'm a bit puzzled by some cart measurements performed with the ACOUSTECH test record, using HP oscilloscope and using (differential connection) through ML 326S phono-modules.

No loading (47k), measured on XLR pre-outputs. The following transpired:
Left vs. Right = *- 2dB* @ 1kHz 7cm/s lateral (mono track), *spec = <0,2dB!*
Left vs. Right = on 1kHz 7cm/s vertical out of phase track, clearly NOT EVEN CLOSE to out of phase!
1 kHz left channel only *- 16dB* leakage to right! *Spec = >28dB @ 1 kHz!*
1 kHz right channel only *-10dB* leakage to left! *Spec = >28dB @ 1 kHz!*

This seems a most disappointing showing indeed. Let me hasten to say that all variations with regards to anti-skate, VTA, VTF, Azimuth and Zenith, were attempted for any optimisation.

I shall not yet disclose the make, which is a VERY well known brand, and their TOP of the range offering.

Has any one got some explanation for how such a major variation can be the case?!

There might just be some folks out there trying there darntest by NEVER getting their apparent alignment problem fixed, please note the various threads, ---- and it might be a cart way out of quoted tolerance?

I have also noted that in this instance, MAJOR Azimuth (+/- 2 deg), VTA, VTF, changes had absolutely MINOR measured effects!
The 'biggest' in this case was 'Zenith' by some 0.5mm left turn to compensate for a 'minor' out of centre cantilever (~ 0.25mm off-set to the left).

Tonality and such is NOT really affected, BUT distortion with massed instruments/orchestra etc. i.e. as soon as things get 'busy' the problems start.

Greetings,
Axel
axelwahl
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axelwahl OP
788 posts
 
The full name of the test record that was used is:
"Ultimate Analog Test LP" by Analog Productions.
Axel

Hi Dougdeacon,
phew, now let ME tell you, that this particular main-line manufacturer considers that ~ 0.2 cantilever off-set within tolerance!

+++ For azimuth and VTA (SRA), MAJOR changes always have MINOR effects +++

Listen! I did, as I mentioned, maybe not that it came that clear across. All of this 'tiny' stuff you can HEAR, oh yes, but IN NO WAY SEE ON THE SCOPE, right?

So, I think this measuring is not exactly inane nonsense. Unless I hear from a production cart maker that a 0.2mm off-set is way out of spec. It is a problem that has been noted before by e.g. J.C. how tricky it is to get it right BY HAND, never mind by some tool, jigs or what ever in volume runs.

I do not think for one moment that I'm the only one around trying to get his cart alignment right, whilst the cart itself actually confounds those hyper-tolerance attempts as e.g. preached by DerTonarm...

If you can have such wide spec variations, go tell me 0.01mm starts to count!? No way for the scope, and who can tell for your ear.

Greetings,
Axel
dougdeacon
3,338 posts
 
This post was interesting, until I reached the part where you FINALLY mentioned the off-centre cantilever.

If the cantilever is visibly off-centre, why waste time on performance measurements? The manufacturer did not quote specs from, nor would any reasonable person expect on-spec performance from, a visibly flawed sample. Measuring junk is silly - discussing those measurements is inane. ;-)

I have also noted that in this instance, MAJOR Azimuth (+/- 2 deg), VTA, VTF, changes had absolutely MINOR measured effect
This is true for all cartridges.

For azimuth and VTA (SRA), MAJOR changes always have MINOR effects. These two adjustments have VERY TINY target zones. Once you're outside those zones, further changes have little effect or, in the case of azimuth, even contradictory or unpredictable effects.

Changes to these parameters must be made in TINY increments, lest you swing back and forth past the target zone without ever hitting it. A 2 degree azimuth change is at least 10 times larger than the target zone, so the probability of hitting it with such changes is quite low.

Better sample + smaller adjustments = better results with fewer measurements.


almarg's avatar
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almarg
9,670 posts
 
Hi Axel -- Would I be correct in thinking that this is a moving magnet or moving iron cartridge? If it were a moving coil cartridge, perhaps the large ultrasonic resonant peak that would result from the 47K load would be a factor in these readings.

Regards,
-- Al
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