Muffled sounds on RD-700gx - possibly due to wrong OS ?

[PhilipVDH]

Hi all, I could really use your advice on something.

A couple of months ago, I had the opportunity to buy a second hand RD-700gx, equipped with the additional Supernatural expansion kit. I briefly had the opportunity to test the stage piano at the vendors home before deciding to take it. At that brief moment, I did't notice anything peculiar.

Once home however, I rather quickly noticed that both the piano and the e-piano sounds sound very dull, muffled, low, missing clearness. I'm experiencing this both when i'm using good quality Sennheiser headphones, and when the stage piano is connected to a Behringer piano amp. I'm in music school and there I have the possibility to play on a RD-700sx, and on this sx-piano the same sounds are totally different, much clearer. The strange this is that this is only related to the piano and e-piano sounds, all the other sounds like synths, pads, strings, .. sound good enough.

I have of course been trying to adjust the sound using the 4-channel equalizer, but even though i manage to get the sound a little bit clearer by lowering the low and low mid settings and putting the highs a bit higher, the sounds are still not what I would expect from such a piano. On some forums, I have been reading that some other people complain about a similar problem, but i have nowhere found a real solution.

Something that puzzles me is the OS version. I know from the vendor that initially, he also bought this piano second hand from someone who worked for Roland Belgium at the time and had a huge range of stage pianos for demo purposes. When I check the OS version on my piano, it mentions a 2.1 OS version. Which is strange, because according to the Roland website, the latest official version for the 700GX is supposed to be the 1.6 version.

So i'm wondering, could it be possible that some experiments were done at the time with installing an OS version for a later model on this stage piano, and could this explain the distortion in the sounds ? So would it make sense to reinstall the official 1.6 version ? Would there be any issues when i overwrite with an older version ? Or could this possibly disable the Supernatural piano kit ?

Perhaps someone had a similar experience with muffled sounds on this piano and knows how to solve it ? i'm really looking for advice, as the objective is to use this piano in a band and, but currently, the sounds are so muffled that they don't cut through the mix.