Last of the Yamaha V-FETs, the B-3 makes the separation between the rare and the common V-FET components.
Like the Victor JM-S7 and the Sansui BA-1000, its marketing was restricted to Japan ; unlike the latter two, the B-3 sold very well, despite minimal advertising and no proper catalog (ie. with beauty shots) ever printed.
The production run should be of 5000 units so it remains fairly easy to find today.
The B-3 is a revised B-2, using two pairs of the same complementary 2SK76 / 2SJ26A within a simplified circuit and a very uncommon enclosure which fits with... nothing. It may look like a diminiutive box à la Cyrus or early Meridian but it really is NOT : 20cm height and 40cm depth - big 17kg thing !
The B-3 can be bridged to a monoblock and, slightly potty, has front AND back 0...-20dB input pots (better get rid of them anyway - both pairs).
Sound-wise, of the three Yamaha V-Fet power amplifiers made, this is the best one, adding tonal finesse and delicacy to the strong previous cocktails. Once you have one (or two), there is no need for anything else ever again, no matter the vintage (or absence thereof) : pure musical bliss, like a TA-N7B.
Unlike the later 101M, Yamaha never devised or prototyped an accompanying "C-3" preamp - alas.
Which makes me think the B-3 was a last hurray for the show before moving on to cheaper and simpler things... although Yamaha did make the enormous B-X1 monoblocks in '79 which sold poorly but were advertised at length - sometimes the public taste is right :)
Real B-3s here and here.
Btw, this is the last page I'll ever post on TVK : I found the basic elements prepared a long while ago on a hard-drive.
Instead of junking I did post them with a very basic text as I can't be bothered anymore to do any of the lengthy TVK moves any longer than, say, four or five minutes.
I now OWN a B-3, I listen to the MUSIC through it everyday, and that is much much more important :)