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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
axelwahl OP
788 posts
 
Dougdeacon
afore we're all gonna ride real high on that one, a little supporting help for all those imperial/inch folks.
0.254mm or 2.5 tenth of a millimetre = 10 thousands of an inch! (I hope this will help some)

I'd be little surprised if there aren’t some (or more) folks that would not even trust themself to see that difference...

As a trained Engineer (Mechanical) I can, thank you.
But that needs some training, and then some…
Axel
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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rauliruegas
12,890 posts
 
Dear Axel: That's why I " love " those vintage MM/MC cartridges and maybe one or two of today cartridges that come with real test diagrams of some of its specs even some of them comes with a " certificate " for its specs.

Other that your recording maybe is not right on its specs what you find it is no surprise at all. It is easy to write specs on product manuals/brochures where we read it and almost never we ask for a test on it that can validate those specs: we trust on it.

That happen not only on products like cartridges or TT but in electronics/speakers too.
Any one can read through Stereophile reviews the manufacturer specs and the real measurements that JA makes where you can read that almost always are " differences " , sometimes and more often that we like " severe " differences.

Regards and enjoy the music.
Raul.
axelwahl OP
788 posts
 
Hi Al,

It is an MC as I surely stated, all of 3.5$ of it.
We also measure it by switching channels, and stepping up and down the alignments parameters mentioned AND using an SUT just to see. NO DIFFERENCE AT ALL!

There is a resonant peak ~ 12dB --- can you believe it, at between 80Hz - 120 Hz!
But it does not translate into hearing it... The main issue it that whacked out channel balance.

Hi Raul,
I think you put your finger right on it!
+++ ... what you find it is no surprise at all. It is easy to write specs on product manuals/brochures where we read it and almost never we ask for a test on it that can validate those specs: we trust on it. +++

SO, PLEASE CAN WE HAVE SOME SHOWING OF HANDS WHO MEASURED HIS CART WITH OSZILLOSCOPE AND TEST RECORD!

How about Dougdeacon, who thinks it is 'inane' to measure a 10 thou out-of-centre cantilever cart?!

Axel
almarg's avatar
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almarg
9,670 posts
 
It is an MC as I surely stated, all of 3.5$ of it.
We also measure it by switching channels, and stepping up and down the alignments parameters mentioned AND using an SUT just to see. NO DIFFERENCE AT ALL!

There is a resonant peak ~ 12dB --- can you believe it, at between 80Hz - 120 Hz!
But it does not translate into hearing it... The main issue it that whacked out channel balance.

Hi Axel -- I had looked pretty closely at the original post, but I didn't (and don't) see a reference in that post to whether it is mc or mm. In any case, as you are no doubt aware, a mc working into a very high impedance or open circuit will have a pronounced resonant peak at ultrasonic frequencies, perhaps even approaching radio frequencies (e.g., 100kHz+). So I'm wondering, considering the miniscule distance between coils, if radiation of those frequencies between coils could account for the poor channel separation numbers you measured.

This may be of interest:

http://www.hagtech.com/loading.html

Regards,
-- Al
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