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

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

Dover 4-9-2017
What do you mean by "low gain setting".
The ANS2 has 2 IMPEDANCE settings - L and H.
L is for ultra low internal impedance cartridges and has HIGHER gain.
H is for higher impedance cartridges and has LOWER gain.

+1. Excellent point by Dover.

Also, according to its manual there are two versions of the AN-S2 transformer. The AN-S2/L, which has an input impedance switchable between 3 and 12 ohms, and the AN-S2/H, which has an input impedance switchable between 15 and 60 ohms. Which version is yours?

According to my calculations, and assuming a 47K load on the transformer’s output (as you indicated), the gains of the transformer are as follows:

AN-S2/L at 3 ohms: 42 db
AN-S2/L at 12 ohms: 36 db

AN-S2/H at 15 ohms: 35 db
AN-S2/H at 60 ohms: 29 db

Most of those numbers are MUCH too high for use with a 0.48 mv cartridge. A gain of 20 db would correspond to a voltage multiplication of 10x, which would raise the output of a 0.48 mv cartridge to 4.8 mv, which would be just right for a MM input.

If you have the H version of the transformer the high impedance (60 ohm) setting **might** be ok, depending on the overload margin of your phono stage.

Jjss49 4-8-2017
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.

Sharp transients have substantial high frequency content. RIAA equalization that is present on a recording boosts high frequencies substantially (the boost gradually increasing to about 20 db, or a factor of 10 in voltage, at 20 kHz relative to 1 kHz), while reducing low frequencies substantially (the reduction gradually increasing to about 20 db at 20 Hz, relative to 1 kHz). The opposite equalization occurs in the phono stage during playback. It is therefore quite conceivable that overload distortion is occurring in phono stage circuitry that is "ahead of" its RIAA equalization circuitry, that will only occur as a result of the high frequency content of transients. While not occurring on lower frequencies even though they may be at considerably higher volumes.

As to why this happens with the ZYX but not with the ART9 (which has a similar output rating of 0.5 mv), perhaps the frequency response of the ZYX in the treble region rises a bit, relative to the response of the ART9. Or perhaps the output ratings of the two cartridges are based on somewhat different test conditions (which is not uncommon).

Hope that helps. Regards,
-- Al