Not sure I get you, do you mean suitable to build a clone? Or repair?
Or do you mean a DIY VFET design?
If the latter, then the Sony 2SK82/2SJ28 were available until recently, but they have all been snapped up by DIY-ers.
The nice thing with the Sony devices is that they can be run at high voltages so you can build a circuit in the manner of an old school valve amp. My testing tells me that they like this approach (choke/transformer loading) - they really are similar to triodes in this respect. The commercial designs tend to use them as followers which kind of misses out on the benefits of the triode-like characteristics and IMO, they’re best used as common-source elements.
Not been able to find any of the Yamaha VFETs, at least at prices I wanted to pay and be sure they’re not fakes.
Some of you will have heard the one I build for PMAC, which also uses 2SK79s (think solid state ECC88) in the front end or the hybrid ones I build for Dave, which use a tube for the voltage gain).
Interesting. DIY, as it happens. Idle curiosity, as I don’t see me ditching the J2 any time soon, but wondered if the ongoing interest had compelled anyone to produce something new, SemiSouth-style.
TBH I don’t have the skills to design a circuit that uses them properly, sure we can sort something out like fixing a rather annoying japanese 300B amp in exchange
This talk of an old sit/other unobtainium amp does interest, but I’m really looking for something fit and forget and not worry about it going up in smoke one day.
if you want to go full bonkers SIT without the risk then Digital do Main are still making SIT amps (given the name and SIT used it’s probably a copy of the Yamaha B-1)
They use the Tokin 2sk77b for 150 Watts of Class A
Price might be a think of a number, double it and add a few zeros though.
Pretty much. They can fail and that leads to losing bias and toasted VFET devices which, unfortunately, are unobtainium these days.
Happy to do this for you.
Just don’t let Adam near it as he’ll remove the wrong devices and put them back in the wrong order then have to sell it for £50 because it doesn’t work properly.
