I received my Ah! Tjoeb 99 yesterday that I bought on Audiogon. I let it sit inside and acclimate until this afternoon. I let it warm up for about a half hour before listening. The mids are not as lush as with the Njoe Tjoeb 4000, nor is the bass as deep, but it has a decent sound. You can tell this is a first-generation product - opening up the unit, the fit and finish is not as good as with the 4000. I'm certainly not complaining, given the money spent.
I notice that another Tjoeb 99 appeared on Audiogon today at approximately the same price point... and was gone within hours.
Tonight I decided to install the upsampler in my Njoe 4000. I'm a fat-fingered clumsy oaf, so I proceeded very slowly. It's not too tough of an install, other than the cable from the upsampler did not want to fit into the socket on the main board. You have to be REAL careful with the long pins that fit into the old opamp sockets. I did a bit of a head-scratch when it came to installing the heat sink as the last part of the upgrade process. My player already had a heat sink installed in the exact position that I was supposed to place one. I think I remember reading that the first Tjoeb 4000s did not come with the heat sink installed, which resulted in some skipping issues, so I think they started adding the heat sink on all stock units at some point.
This is easily the most audible upgrade I've ever done, even moreso than adding an outboard 2-channel amplifier to my system. The difference before and after is mind boggling! As other people have written, it's as if a "veil" has been lifted between me and the music. The clarity and level of detail that is revealed is astounding.
I would go so far as to say that they really should not sell this player without the upsampler. The difference is that stark. If you have a Tjoeb 4000 and do not have the upsampler, you are doing yourself a disservice.
I read over at audioasylum that many people prefer upsampling to 96kHz rather than 192kHz because of the introduction of noise. The one exceptiion to this seems to be the Tjoeb, supposedly because the filtering algorithm used is leaps and bounds above other that are out there. I don't know what the physics and mathematics are; I just know it sounds f--king awesome!
Time to go drown in some music... :D :D