Vfet / SIT Amplifiers

The TA-N7 is the one to have. It sounds excellent. Very clean and transparent. Different signature than the TA-N8550 which has a lot warmer sound.
I did have a N88, but did not keep it because it had issues and I did not want to spend the time to fix it at the time, so I sent it back. Eventually I will get another one.
My friends who have both, the N-7 and N-88, give the N-7 the edge in versatility and overall sound performance. My understanding is that the N88 could sound good too, but it requires more thought on system matching.

Hi, i'm new...
It's really nice to see people who like V-fet😊
I com from France and the V-fet are not popular, people prefer hegel or rega sound, they never listened to it...
I don't like that sound...
I have a Sony ta-5650 amp (i use the power part) and a "lampizator subminiature" preamp, built by "the polish guru" Lukasz Fikus (SRPP circuit, 6h16b russian valve nos and a 6c4p-ev rectifier valve).
I have a preamp Sony ta-E88, too clear for me, and lack of density, the preamp lampizator is much better, the sound is more realistic!
Lukas Fikus compared it to a Verdier preamp at 20.000€, almost impossible to differentiate!!!

Does the N-7 suffer from the diode issue as the Sony's intergateds did?

Hello PR,
Actually there are a few vfet connoisseurs in France....but I agree that  vfet units are so exotic and very much extinct...unless you find a vintage unit and have it properly restored.
Nelson Pass has some newer offerings, but those are becoming rare as well. 

I agree with you about the using a different preamp and not the one in the ta-5650. The Lampizator is in a different class and I am not surprised you like it so much. I am aware of Lukasz and his creations, but I do not own any yet.
About the ta-n88: I agree it could be a bit too transparent but it is a good preamp, nonetheless for those that like that level of transparency. If you have not had it serviced yet, that could also be a reason why it might sound "dry/sterile". Also, if not serviced, your unit could experience PSU failure (some zener diodes in there are ill-fated) that could take out the transformers.

@kitr,
Yes, the TA-N7 has the veractor "diodes" / death diodes, but it also suffers of problems with fusible resistors. The thermal runaway of those fusible resistors is horrible and over time they drift substantially from the original value. When they drift past a certain point, they will take out a vfet or two.
Also, the BJTs in the final stage need to be replaced as they are also known to fail.
Net, Net, while the TA-N7 does not have the death rate of the n4650/n5650, it needs to be restored nonetheless. The problem is that there are very few techs that fully understand vfet units and even fewer who would take vfet units for service or restoration. This is valid for all vfet units.
Depending of where you are located (I mean on which continent) I could point you to someone qualified to service your units.