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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
 
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
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
axelwahl OP
788 posts
 
Hi Al,

THAT particular cart actually has no such an issue, as for example a 'Dorian' would have BIG TIME!

But now we'd get close to a make disclosure, which I would not like to do at this point. I'm in touch with the manufacturer to see what they have to say.

I can EASILY use this cart with 47k due to it's damping arrangement, in fact it is rather happy with 1k. (NO MORE CLUE NOW). You might be aware that these days there some are actually some quite fine with 47K.
Next I also mentioned the testing with SUT, which is using as low as 13ohms loading on primary. Results were NOT AT ALL influenced (I'm not talking of scope's beam-width variations here!)

There has been a lengthy discussion on that SUT subject on some other thread, say no more...

If a resonance would influence the channel balance being out by a factor of 10 (compared to spec.) we would see this BIG TIME on the scope.
The only res. as mentioned (~100 Hz!)is VERY visible on the scope.

Axel
rauliruegas
13,125 posts
 
Dear Axel: Well, it will be interesting the Winfeld ( I assume is this one ) manufacturer answer and how they validate its specs on each cartridge sample.

Of course that could be really useful and appreciated that other cartridge manufacturers can share with us their " thoughts " about.

Regards and enjoy the music.
Raul.
axelwahl OP
788 posts
 
Hi All,
well, I'll keep you posted on this one.
I’d love to know if some other folk could share some related example(s), good OR bad, just so as to learn something from it.

You can tweak-align you sweet hind off, and NEVER come right if that happens, distortion is programmed for you right in the cart.

Note: an e.g. relatively cheap cart, the DV 20X-L STILL includes a measurement diagram of the cart you bought --- WELL DONE I SAY!

Thanks,
Axel
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