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Distortion mystery -- MC cart mistracking? / transformer / head amp input saturation??

Could use some input from the experienced high end record spinners here....

Context: VPI Classic 3/JMW 10.5 metal arm (damped w oil)/ZYX R100H --> Audio Note ANS2 xformer (low gain setting) --> Jasmine/Mockingbird modded LP2.5 DU active phono stage on MM 47kohms setting... anti skate off.

Recently switched cartridge over from my Audio Technica ART 9 cart to this ZYX R100H to check it out (bought ’low hours’ from a well reputed A-gonner). On some records, am hearing an occasional distortion in the vocals and mid-upper piano range... usually on transients of increasing volume. I first thought it is mostly at the 1st half of the record... but it seems like it happens throughout the sides of records where it happens (...I know the VPI jig sets minimum tracking error at end of sides). Seems to happen on records that play a little ’louder’... as opposed to audiophile records where volume levels are lower.

Checked ZYX alignment using the VPI jig couple times... am right on. Tracking at 1.9 grams, VTA level. Azimuth good via the balance beam pole on headshell. Tried different tracking forces - up to 2.1 grams, raised and lowered VTA - still distorts. Using Zerostat/CF brush on record, and Zerodust on the cart tip. Record washed with Okki Nokki. Very good hygiene I think.

As an experiment, I removed the AN transformer, and ran the Jasmine in MC mode at 100 ohms loading, and the distortion seems to have lessened greatly. Could the AN transformer be overloading the MM input at the phono stage? But then why just distortion on transients?? Many other loud passages do not distort.

By the way, I have no such trouble in 200-300 hrs with the ART 9 cartridge... just pure musi, clean and gorgeous... just hearing this with the ZYX.

Thoughts/comments/ideas??

Thanks in advance...








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jjss49 OP
6,612 posts
 
to dover and almarg

yes you are both quite right... thank you

almarg - my unit is a ANS2 ’H’, thank you so much for your calculations

i had been using the L setting of the ANS2, which in fact provides slightly more gain than the H setting (counter-intuitive, but I am now clear on this) ... my error -- in due course i will try the H setting on the transformer -- the internal impedance of the R100H is somewhere in the middle of the two impedance ranges quoted for the ANS2 settings... I should indeed run the other and see if it cures the ill...

by the stated ANS2 specs the gain is only +/- 2 db in the 2 settings, so not much, on paper at least, but almarg your calcs make it more obvious that into 47k ohms the gain differential is much greater... thus most likely the root cause of my problem - THANK YOU :)

sidebar -- that Mockingbird/Jasmine 2.5 unit is very very nice... punchy, quiet, big stage... plenty of gain of LOMC... incredible value for an active head amp, very glad I tried it after reading A Salvatore’s notes on it...




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jjss49 OP
6,612 posts
 
Further on this... I have discovered the Zyx cartridges' output is measured at 3.54 cm and the ART 9 output is measured at 5 cm... so measurement standards are in fact quite different.  

So taken at face value, the R100H output is 41% higher than the ART 9, or measured at the higher standard, R100H output is at least 0.68 mv (vs the ART 9 spec'd at 0.5 mv)!

That would explain some input overload at the head amp!!
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almarg
9,670 posts
 
Jjss49, yes, that could very well be a contributing factor to the issue, as 5 cm/sec and 3.54 cm/sec differ by 3 db, **if** the two numbers are defined on a consistent basis.

However that discrepancy, which is commonly seen when comparing cartridge specs, is somewhat ambiguous. In part because the amplitude of a sine wave can be defined on either a peak basis (the maximum amplitude it reaches during any part of each cycle) or on an RMS basis (its amplitude as computed on a root-mean-square basis, which may be thought of as a kind of average value). And for a sine wave 5 cm/sec peak equals 3.54 cm/sec RMS.

For further discussion of this see the posts in the second half of this thread, beginning with the posts dated 7-4-2012.

Regards,
-- Al

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glennewdick
1,533 posts
 
I didn’t read every post here so if I’m repeating sorry. But I has a similar situation and like you when I added more load on the cart is seemed to go away after some talk with my audiophile club friends they recommend more loading. I think you are not loading your new cart enough so you get some issues especially at higher frequencies. If like you mentioned it’s better at a 100ohm load there is your evidence that more load is what you need. The audionote SUTs do not have much load I was looking at the same SUT you have and it was just not enough load for my VAn Den hul cart I'm sure your looking at a similar situation 
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