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Yamaha B2 - the "why" and the "how" of a comprehensive rebuild

Pete, l was looking at your post of your new Power Supply boards and have a question. Is the lead spacing the same as the Yamaha board? Asking because I have ordered caps when they were available and will be looking for the other parts also. I do see that some of the caps have multiple mounting options.

Bob
 
Soundslave said:
Pete, l was looking at your post of your new Power Supply boards and have a question. Is the lead spacing the same as the Yamaha board? Asking because I have ordered caps when they were available and will be looking for the other parts also. I do see that some of the caps have multiple mounting options.

Bob
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Hi Bob, are we talking about the regulated PSU board or the Filter Cap / unregulated PSU board? Which caps with multiple mounting options are you referring to?
 
Soundslave said:
I was referring to the regulated PSU board.
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The larger filter caps on the regulated supply(s) should be a drop in from original to the new. For the smaller caps I actually made oval holes so you have more choices without the need to bend legs.

There are actually quite few tricks in this board. I will likely do a deeper write-up on the new boards back into the original post but home are a few quick ones that come to mind:
  • Multiple format footprints for caps, trim-pots, fuses / fuse holders
  • Different markings for PNP vs NPN transistors to eliminate guessing
  • Almost all component values are on the silk screen, so no need to keep on looking at a board layout document
  • Moved from double diode / bridge rectifiers to individual diodes to eliminate parts scarcity challenges
  • Thicker PCB (2mm vs 1.6mm) and 2oz copper
Then, of course we have improvements in circuit layout, better thermal management, better mechanical integrity of the heatsinks attachments to the board, etc.
 
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But these bench performance do not mean anything if the amp does not sound good.
As I stated in the first part of thread, the frame of reference for any changes to the B-2 is another B-2 mule unit that is in excellent original condition, with carefully selected original components that ensure the mule unit is right on the original specs. For the PSU caps for example, I had to go through a box of roughly 50 original original caps pulls from various units to find a set of four caps that were right on original specs. So the mule unit is right in the original spec, with new speaker relays and fully cleaned original front selector with each contact individually measured for resistance, cleaned pots, etc.

To put things in perspective from an audition, musical presentation and enjoyment, the newly rebuild B2s are already performing at a level the original unit can no longer match. As a result, for the regulated PSU board mode and the associated low noise floor and musical dynamics, I stacked the newest B-2 iteration directly against these two amps:
AA9D31A8-438B-4EB9-A99C-FEAB5390E1E4.jpeg
55163635-A75A-400D-8332-065E982B2599.jpeg

Let me say that the newly restored B-2 plays in the same league as these two magnificent amps in terms of fidelity of sound. Power wise, we know the B-2 being a vfet amp, it is limited to about 4 ohm load and about 130-170w depending on load, so in terms of power the B-2 is not in the same league.
 
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Looking to centralize the info from multiple threads so that future readers can find multiple B-2 related topics in one place so going back to the PSU filter caps and any related improvements:

Once we reach this level of musical transparency any improvements are subtle but choosing the wrong part for the job can actually alter performance in an unfavorable direction by a lot.

zaibatsu said:
At the end of the day, unless you've personally tried multiple filter caps in the specific application of the B-2 main filters, you're never going to know the sonic differences.
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precisely and each one's experience and system profile might vary slightly, but what you are saying is absolutely spot on.

ivandezande said:
There is no way the designers in the 70’s had a huge choice of filter caps. These honestly were probably the ones that were big enough and fit, they weren’t staring at the specs. It was probably these or Elna.

Any caps made today are going to be better then what they chose from back then. Literally no way that it’ll somehow change the equilibrium of a hunk of metal and generic rectifier diodes, and if it does - it’s for the better.
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Actually that is not my experience.
CDE, Nippon Chemi-Con, Rubicon, Elna, Nichicon, Riffa all made large and small caps in the 70s and 80s. Nichicon and Riffa made some of the best large cans and still do, with Riffa under the Kemet name. The large can Nichicon caps that are inside the B1, B2, B3 and many of the Sonys were absolutely exceptional for the Audio purpose they were specifically developed for. If there was not for the less than optimal mechanical configuration of the B-2 and the indirect poor thermal management, I would be willing to bet that we would see a lot more of these 45 years old caps still be working well within specs.

What we have today is high performance, heavy duty caps made for switching power supplies and industrial applications. Besides the purposely built for audio caps from Nichicon and Mundorf we actually have a lot less choices than there were in the 70s, 80s and 90s. Once in a while we ran into an all-purpose large caps type that perform very well in a vintage audio power supply such as some of the series from Riffa / Kemet and TDK / Epcos, but who knows for how long these would still be around. It was not too long ago that Epcos made the Sikorell and Panasonic made the THA series caps, the later still used in the DartZeel amps as special order, but those are also now gonne from retailers with the rest of the good Audio caps from the earlier decades, so no, we are not in a better place when it comes to big cans we can use in vintage audio linear PSUs.
 
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Vint Age said:
What would also be interesting for comparison would be how a B-2 measures in before anything has been done to it ...
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rottalpha said:
Read my description of the mule unit. That selector is fully cleaned and each contact individually tested
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Right , but Vintage said in the above quote, that I also quoted previously, that before anything is done to it. I'd take that as cleaning switches as well, unless he meant differently ? :dunno:

Nashou
 
rottalpha said:
Looking to centralize the info from multiple threads so that future readers can find multiple B-2 related topics in one place so going back to the PSU filter caps and any related improvements:

Once we reach this level of musical transparency any improvements are subtle but choosing the wrong part for the job can actually alter performance in an unfavorable direction by a lot.


precisely and each one's experience and system profile might vary slightly, but what you are saying is absolutely spot on.



Actually that is not my experience.
CDE, Nippon Chemi-Con, Rubicon, Elna, Nichicon, Riffa all made large and small caps in the 70s and 80s. Nichicon and Riffa made some of the best large cans and still do, with Riffa under the Kemet name. The large can Nichicon caps that are inside the B1, B2, B3 and many of the Sonys were absolutely exceptional for the Audio purpose they were specifically developed for. If there was not for the less than optimal mechanical configuration of the B-2 and the indirect poor thermal management, I would be willing to bet that we would see a lot more of these 45 years old caps still be working well within specs.

What we have today is high performance, heavy duty caps made for switching power supplies and industrial applications. Besides the purposely built for audio caps from Nichicon and Mundorf we actually have a lot less choices than there were in the 70s, 80s and 90s. Once in a while we ran into an all-purpose large caps type that perform very well in a vintage audio power supply such as some of the series from Riffa / Kemet and TDK / Epcos, but who knows for how long these would still be around. It was not too long ago that Epcos made the Sikorell and Panasonic made the THA series caps, the later still used in the DartZeel amps as special order, but those are also now gonne from retailers with the rest of the good Audio caps from the earlier decades, so no, we are not in a better place when it comes to big cans we can use in vintage audio linear PSUs.
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What are your thoughts on using a capacitor bank instead of one large cap? I have been considering a pcb design to accomplish this for M-80/85.
 
Asmodeus2112 said:
What are your thoughts on using a capacitor bank instead of one large cap? I have been considering a pcb design to accomplish this for M-80/85.
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Multiple caps would lower the circuit resistance, hence might change the balance of the LC and R tank. At the very minimum you would need to do some tests and likely consider an in-rush current limiter which should be no issue with the M80/85. I can't recall if the amp has one already.

The man to provide a much better assessment of your proposal would be @avionic and I would not be surprised if he did not brewed that thought already.
 
Nashou66 said:
It be hard in units that have the switches acting wonky.
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True and then there's also the protection relay that can cause some grief if their contacts are dirty.

Just thought it would be interesting to see how a B-2 in working condition as it comes in the door measures up verses the mule B-2 verses the beautiful Aletier HiFI premium B-2 ...
 
Vint Age said:
True and then there's also the protection relay that can cause some grief if their contacts are dirty.

Just thought it would be interesting to see how a B-2 in working condition as it comes in the door measures up verses the mule B-2 verses the beautiful Aletier HiFI premium B-2 ...
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Right , I for one would be reluctant to push an all original B-2 to its limits though, all you need is one cap or transistor in the wrong location to yell UNCLE and toss its oats and those V-fets are gone!

Athanasios
 
Nashou66 said:
Right , I for one would be reluctant to push an all original B-2 to its limits though, all you need is one cap or transistor in the wrong location to yell UNCLE and toss its oats and those V-fets are gone!
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Not even in the interest of science? :biggrin:
Just joking of course. You're absolutely right in that there's a high risk factor.
 
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