strange SMSL M500 high 3rd harmonic

[AnalogSteph]

I have a hunch that input gain on the onboard line-in may be turned down quite a lot... slowly increase generator levels until you see the prominent "zoo" of harmonics typical for clipping, then turn up input gain for the recording device until the 1 kHz peak reaches the top. I would expect the onboard line-in to clip at around -3 dBFS out, they generally can't take more than about 1.4 to 1.5 Vrms with a following wind and a fair bit of odd-order distortion is to be expected before that.

Besides, switching to dBFS display instead of dB SPL would make this less confusing.

With your measurement setup you are also inviting a major ground loop. You may be able to still make this work cleanly (enough) by wiring up the left balanced output to the stereo minijack, e.g. by using an XLRf --> TRS cable and an adapter 1/4" female to 3.5 mm male. (You ultimately need 1x XLR female to 1x 3.5 mm TRS male, sold ready-made e.g. as Cordial CPM FW-BAL. (*)) You would then have to measure with the "Virtual balanced input" checkbox enabled in REW (for the input device). That basically subtracts one channel from the other, forming a poor man's balanced input. Input level handling should increase by 6 dB, but the same goes for balanced vs. unbalanced output level on the DAC, so it's ultimately a wash. Input noise / dynamic range should effectively improve by 3 dB though.

*)

 

[Allank]

There's one going near me at quite a cheap price. Did it ever get resolved as to what serial number the fix started at?

I'm trying to work out if it would have the issue.. The owner doesn't have testing equipment or knowledge.

It has an LCD issue (vertical lines on one side), but that doesn't bother me (unless it's a noise source) . However it means it will be hard to resell if it's got the issue (was bought in Hong Kong so not covered by Australian retail laws).

This is my last ditch at trying to work out whether to buy it.

Software version is 1.7
Hardware version is 1.3
Serial number starts with 190192

FWIW
This is for studio use where I am running SVS subs (RCA) and Kali In-8 as the monitors (currently RCA but have XLR)

Currently I am running monitoring via a analog mixing console (that's also a 18in 18 out interface).
I want to take that out of the loop for mastering.

I like the M500 variants due to the XLR and RCA simultaneous output. I've found aligning the SVS and Kali's was really easy, so I don't need it to act as a crossover (otherwise I'd get a minidsp flex)

 

[Allank]

Well I ended up getting one from SMSL directly - they were happy to show me the testing results on video with the serial number of the unit they were sending me.....

FWIW that is really good service in the end of this story..

They have a few units left, and if you don't need wifi, and are interested in the higher voltage output combined with great AES17 figures - they are much cheaper than the mk3 (although you could get a c200 cheaper - ---- but the higher voltage is good as it adds potential for use in an analog mastering chain if the gear works better with a higher input voltage) ..