I'm curious how many other guys out there own B-1's, what work you've had done to it (in particular if you have had some problems), whether or not it's your main amp, and anything else about your experience you'd like to share.
I'll start, short story long . I purchased my B-1 and UC-1 a few years ago from AKer Mark B, who has one of the best Yamaha collections around. At first, I didn't love the sound as much as I hoped I would. I thought it was a bit dry and dark/rolled off. The first minor improvement came when I replaced the original speaker relays, one or more of which was causing me some problems. That seemed to give the sound a bit more "life." Still, there were times when I preferred the sound of an M-4 in my setup.
Not too long afterward, I sent it off to Avionic for a recap and tune-up. This definitely made a sonic difference for the better, not to mention being mandatory from a reliability standpoint. The B-1 runs hot when dialed in, and you have to watch the capacitors which are near power resistors, particularly in the 250V supply section -- if one of those goes, your VFETs will likely go as well. I can tell you that the 10uF/250V capacitor at the top of that PCB gets almost too hot to touch, even after re-positioning the resistors that are helping to heat it up, so 105C ratings are a good idea in as many places as you can put them. But even then it seems that these amps are quite reliable, and I think I'm quoting this from somewhere, the most dangerous thing to a B-1 is probably the tech [or wannabe tech, like me!] working on it -- VFETs are safe to mess with only after all of the bigger caps have been completely discharged, as per the service manual. I'm luck to live near Avionic, who did a great job on mine, and I think that was his first VFET amp. I didn't mind being somewhat of a guinea pig, but if you take yours to a tech who has no VFET experience and whose work you are not familiar with, just be careful! Even EchoWars has expressed reluctance in working on B-1's, if I am allowed to loosely quote him on that.
At this point, I was enjoying the amp on various sets of big Infinities -- it wasn't as transparent as some other amps I'd had, including some of the later Yamahas, but it could fatten up the sound in a [good] way that my other amps could not. Still, I was in a continual debate with myself as to whether the amp sounded good enough to justify keeping, considering how much they can sell for.
Having gained some confidence with various recap and building projects, I decided to tackle my last real concern about the amp: the main filter caps, for which there are no drop-in replacements available. Now, I had no real reason to suspect that mine weren't still performing well, but my previous positive experiences with filter cap replacement pushed me convinced me that it was worth trying here. And at some point, this will be a concern with all B-1s. It wasn't an easy or fun project, and there are some things I'd do differently the next time around, but I'm currently enjoying the fruits of my labor and I think I made the right call. Several items in my system have changed since I had last run the amp before the new filter caps so all of the acclaim doesn't belong with the B-1, but as it stands right now I don't think I've ever heard my system sounding quite so complete, well-rounded, and downright musical. The B-1 is really capable of some incredible dynamics with the right speakers! The sound might still seem a bit rolled off to some listeners, but I think this is mostly due to the distortion characteristics of the VFETs compared to BJTs. Still, I can't deny that the B-1 doesn't have as much "air" as some newer high-end offerings -- for me, its magic lies more in the lower treble on downward.
I'll start, short story long . I purchased my B-1 and UC-1 a few years ago from AKer Mark B, who has one of the best Yamaha collections around. At first, I didn't love the sound as much as I hoped I would. I thought it was a bit dry and dark/rolled off. The first minor improvement came when I replaced the original speaker relays, one or more of which was causing me some problems. That seemed to give the sound a bit more "life." Still, there were times when I preferred the sound of an M-4 in my setup.
Not too long afterward, I sent it off to Avionic for a recap and tune-up. This definitely made a sonic difference for the better, not to mention being mandatory from a reliability standpoint. The B-1 runs hot when dialed in, and you have to watch the capacitors which are near power resistors, particularly in the 250V supply section -- if one of those goes, your VFETs will likely go as well. I can tell you that the 10uF/250V capacitor at the top of that PCB gets almost too hot to touch, even after re-positioning the resistors that are helping to heat it up, so 105C ratings are a good idea in as many places as you can put them. But even then it seems that these amps are quite reliable, and I think I'm quoting this from somewhere, the most dangerous thing to a B-1 is probably the tech [or wannabe tech, like me!] working on it -- VFETs are safe to mess with only after all of the bigger caps have been completely discharged, as per the service manual. I'm luck to live near Avionic, who did a great job on mine, and I think that was his first VFET amp. I didn't mind being somewhat of a guinea pig, but if you take yours to a tech who has no VFET experience and whose work you are not familiar with, just be careful! Even EchoWars has expressed reluctance in working on B-1's, if I am allowed to loosely quote him on that.
At this point, I was enjoying the amp on various sets of big Infinities -- it wasn't as transparent as some other amps I'd had, including some of the later Yamahas, but it could fatten up the sound in a [good] way that my other amps could not. Still, I was in a continual debate with myself as to whether the amp sounded good enough to justify keeping, considering how much they can sell for.
Having gained some confidence with various recap and building projects, I decided to tackle my last real concern about the amp: the main filter caps, for which there are no drop-in replacements available. Now, I had no real reason to suspect that mine weren't still performing well, but my previous positive experiences with filter cap replacement pushed me convinced me that it was worth trying here. And at some point, this will be a concern with all B-1s. It wasn't an easy or fun project, and there are some things I'd do differently the next time around, but I'm currently enjoying the fruits of my labor and I think I made the right call. Several items in my system have changed since I had last run the amp before the new filter caps so all of the acclaim doesn't belong with the B-1, but as it stands right now I don't think I've ever heard my system sounding quite so complete, well-rounded, and downright musical. The B-1 is really capable of some incredible dynamics with the right speakers! The sound might still seem a bit rolled off to some listeners, but I think this is mostly due to the distortion characteristics of the VFETs compared to BJTs. Still, I can't deny that the B-1 doesn't have as much "air" as some newer high-end offerings -- for me, its magic lies more in the lower treble on downward.
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