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
Axel,

Have you verified your measurement procedure with another cartridge?

If I had captured those numbers, they would seem to be suspect to me. I'm not saying that they are but I'd sure want to know that I can at least verify the results/technique with a different cartridge to be sure it's not a measurement error.

Dre
[b]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. [/b]

Are you saying that a measured 12dB peak at 80-120hz is inaudible?

dave
Hi all,

Dave,
that res. ~ 100Hz showed a 'lift' of 2.25 times signal level compared to the rest of the measured band level.
I would NOT think it is a faulty test record... And as I stated, it is not audible with normal listening.
Why? I have no idea, other than at ~ 40Hz I have some 'room lift/lock' --- and it might just all fit together. Who knows.

Dre_j,
in being proper and decently scientific what you suggest aught to be done. Alas I have not another cart of same make and build to do this. THEREFORE, in all fairness my measurements are not 'valid' according to scientific method. What is valid is that I get distortion at high vinyl levels with massed instruments / orchestra / fortissimo, and it *seems* to tie in with the channel imbalance. At medium level, and less complex music it can not be easily noted, if at all.

Larryi,
it sounds contradictory and you noted that correctly.
Yet --- if I compared the two carts, not factoring in the problem area of the one, it is my finding. Since at the time of comparing I was still assuming that 'some' as yet un-detected alignment issue was causing this distortion with massed instruments, fortissimo, etc. It is NOT affecting tonality, detail, and such at more normal levels. So, the 'assumed to be defective' cart still sounded a good second to what I had listened to. The Orpheus is yet more detailed, yet a bit clearer, yet a bit more balanced, simply better. I incidentally also had the lesser "Transfiguration AXIA" in my system and of course given taste and all such it was not my preference, with a type of slightly more refined Dorian sound i.e. it has a slight edge on a Dorian - AND if you like that sound presentation. It is VERY open sounding and a bit tilted towards the top i.e. not at all as neutral as the Orpheus.

The point is, that the cart under question is NOT breaking up all over the place!! It might just be yet so much better if it were in spec. --- an assumption of course.

Part of this enquiry was to get some feedback on similar 'encounters' AND NOT to categorically insist on a scope beams width measurement finding.

There is e.g. one track that puts left to right channel out of phase so as to cancel them. All being at it's best next to nothing should be heard during play-back.
I instead get 1kHz 'screaming' at me. A pretty clear indication that the preceding measurements of channel leakage and imbalance found were correct.

Greetings,
Axel
Hi Dave,
some dB correction.
I just veryfied the 100Hz res. level. It was 2.5 times signal level. BUT that makes it ~ 7dB and NOT 12dB. Sorry, for this misstatement.

It appears to fill in the upper bass 'floor bounce' related dip in that area of the speaker, and is therefore not actually noticable.

Axel
I meaured channel match + crosstalk on PC1, ultraeminent and titan I. All performed to spec. L & R less 1db difference (assuming phono stage gain is matched). Titan I was best in channel separation with 34db crosstalk on both channels tested with Analogue test LP (track 2 and 3) while mounted on the Phantom. On the Davinci with no Azimuth adjustment, still a manageble 29-30db. The azimuth sweet zone is tiny and easy to jump thru.

I did not measure the frequency response of the cartridge.