Strange low frequency with sv2s, can you ear it?

[inslashout]

Hi everyone !

I bought the SV2S 73 last week. I'm primarily a guitar player, I wanted to have a nice looking keyboard with great core sounds and onboard speakers to play in the living room with no obstacles or friction. I liked the retro look and the front panel without menu diving. This model looked like the perfect match for me, nothing else quite like it on the market.

I was very happy with my purchase, but it didn't take me very long to notice some strange sounds and behaviours... I took it back to the store, thinking I had a faulty unit, but after some testing on another 73 unit (freshly unboxed by the store employee), and on the 88 version on display, they all did the same strange sounds.

Here is wat I noticed : with the default E.Piano sound after powering it on, if i played a middle C note with the onboard speaker's volume at noon I could clearly hear a low frequency/octave appearing, and then cutting after a few seconds, very unnaturally and abruptly. If I pushed the volume between 6 and 7, the same low frequency would appear after 3 or 4 seconds, and then disappear in the same way...
I tested this with headphones and the line outs : no strange low frequency appearing and then cutting, no problems, great sound.

I was able to reproduce this behaviour with other notes around middle c, on the second E-Piano and A.Piano, at different volumes. But it was so strange to me and obvious that it was a defect, I didn't test this much further before returning to the store. I was very surprised to find out that the other units did it as well. I left "keyboardless" and very disappointed.

Playing in my living room is a very quiet environment, and this was impossible to ignore. In the store, with sounds around, it was more difficult but I could notice it with no doubt.
Since it's not showing with headphones or using the line outs, it is not suppose to be in the sound.
My question is : can you reproduce this on your sv2s 73 or 88? Just power on, put the volume around 5 and play a middle C with conviction.
You can also put the volume higher, then play the C and go back with the volume knob, it should appear.
I'm so disappointed, and I need to know if all the units do this, or did I test 3 faulting units in a row?

Thank you in advance for your time, and your help
Cheers