Yamaha B-1 Alert

[NumbDiver]

Now back to the Yamaha, lets not get to over board about the B1 being something like the best thing that ever came to audio, there were and are many other amps that I think would better the Yamaha and they don't use V-FET's.

I would argue that the B-1 (and B-2) truly are one of the best SS amps ever. Especially if you consider the price. If we use round numbers and say the rebuilt/recapped/factory spec’d B-2s are around $1k and B-1s are around $2500; there are few amps that will perform better in either category. Sonically, they are reference grade (when refreshed). Yes they are vintage and the switches can be a PITA, and the binding posts are not up to today’s standard. But…

Take a look at the scientific papers (test sheets) that Yamaha released with the B-1 and B-2. The vfets are special indeed. As the only sand outputs that have similar response curves as triodes; they can do things others (bipolar/mosfets) cannot. They are highly linear, very low distortion, AND very fast switching devices. The square wave output of the Yammy vfet amps may well indeed be bettered by a Halcro, but at TEN times the cost. And all said and done, the Halcro* sounds ‘sterile. Not so for the Yammy. There is a reason so few manufacturers give the kind of test info that Yamaha provided with that particular genre of amp. Yamaha knew full well they had something that nobody else could touch. Sadly the vfets were grown in-house and were expensive to produce.

The B-1 uses only one-pair of (huge) output devices for each of the +/- of its push-pull design. They are basically like push-pull triode amp with silicon tubes for outputs. And the outputs perform as such. Lots of protection circuitry, but the signal path is quite simple. Nelson Pass I believe will go one step further and run them single-ended (with the SIT/vfet devices he had manufactured for himself). THAT is the amp I hope to live with, in the future. A silicone SET with a freq response as linear as a tube triode.

If the right guy came along that could do it (as I would assume Mr. Pass wouldn’t do it for me); I would maybe be willing to cannibalize (yes, destroy) one of my two B-1s, to use the outputs in a single-ended version of a vfet amp. I think our own Unda Marais would have the skills to build one. Man…that could well be a world-class amplifier if done right. Thankfully Mr. Pass is going to do it for me, and my B-1s can remain intact.

But I digress…yes; Yamaha’s vfet amps are ‘that’ good and can easily keep up (or trump) more modern designs. Especially at their price.

IMO.

*I haven’t auditioned the big Halcros, but everything I’ve read says they are very analytical in nature

 

[Elroy]

All GREAT and informative posts! I am getting schooled in VFETs! I am excited to see the likes of Mr. Pass re-embracing this technology and the fact that he is bears witness of their relevance and value even today. I for one will be staying tuned to see what he comes up with (even though I probably wouldn't be able to afford it). I pulled the following quote from the Nelson Pass interview Theophile posted a shortcut to (thanks Theo!). In it Mr. Pass touches on what is so special about VFET's:

"First Watt has some cool new toys - a special type of depletion-mode power Jfet known as a static induction transistor (SIT), also called a VFet. Invented in Japan in the early '70's, these were first made by Yamaha and Sony and enjoyed brief popularity in specialized power amplifiers. Subsequent SIT devices have been mostly seen in radar systems.

Where regular Fets have a characteristic that mimics pentode tubes, the Vfet / SIT has a triode-type curve that allows for very good performance without feedback or degeneration. Unlike tubes, they operate at voltages and currents appropriate to loudspeakers without output transformers or cathode heaters. Last year I had a special run of these rendered in Silicon Carbide (SiC) by SemiSouth, and have spent this year evaluating circuits."

I'd advise taking this one at face value, nothing more, nothing less. I don't believe there is any intentional deception, it truly was not tested beyond what was stated.

That's the problem, at face value a Buyer has no other recourse except to esteem it as a parts unit. I personally never meant to imbue the Seller with dishonest motivation rather only to state the only logical conclusion in the matter which is: if a Seller lists an item as "untested" and "sold as is" you have to bid on it as if it does NOT in fact work and because we are talking unobtanium VFETs- to me it makes it pretty much wothless. Other's may need the parts and see it as much more valuable, still others may be willing to gamble that it is a fully working unit. Not me.

 

[theophile]

The lesson of this thread,is:

Never purchase a v-fet amp in a locale were the operating mains voltage differs from the operating mains voltage stated on the compliance plate of the model which is for sale.

The reason:

V-fet amps are susceptible to destruction when operated on a mains voltage other than their native operating mains voltage,even and especially if that voltage is lower that their native operating voltage.

I,for one knew that they were sensitive to these problems.However this thread has highlighted for me the great probability that these circumstances doom a v-fet amp to almost certain destruction.

The fact that the mains plug has been altered to match the amp to a lower mains voltage,multiplies the risk a thousand times.Making it guaranteed that this amp has been powered-up at a destructive mains voltage. :nono: :tears:

What a waste of a lovely amp.

 

[NumbDiver]

.
...V-fet amps are susceptible to destruction when operated on a mains voltage other than their native operating mains voltage,even and especially if that voltage is lower that their native operating voltage.
..

Disclaimer:I'm not the mastermind that can figure this out. For that we need Avionic/Echowars/Unda Marais to figure out the circuitry.

BUT...as I sit here reading the B-1 service manual and schematic, I believe (again, I'm just a neophyte) that the B-1 protection circuitry will protect the outputs. On a few different levels as a matter of fact. I'm not willing to dial down my variac to confirm, but I see a few under-voltage situations that will not allow the output stage to be energized.

In your statement there's a big difference between vfets being susceptible to destruction due to under-voltage; and vfet AMPS being susceptible. I'm in no way 'calling you out', as I agree things may go south in the amp by trying to run 110 instead of 220, but it looks like:
1)The red-light protection circuit won't even turn off (it'll stay in protection) since the +B Power Supply Detection Circuit will see excessive voltage drop on the +B (85V) .
2)There is a protection circuit (TR701, TR702, TR703) that watches the -200v clamping supply.
3)When doing step 3-6 of the bias/setup of the amp, Yamaha has you hook a variable transformer (with output vfets installed) to the power and dial it up and down +/- 10% to verify that bias balance remains constant. Granted, they are not telling you to dial down 50%, only 10%.

We've all speculated over the years that under-voltage to the vfet amps will send the outputs into runaway, due to the clamping voltage not being adequate. I'm just not sure if anyone really knows or has tested the theory. I may be 100% wrong here, and would love to be corrected. Either way, I'm not going to attempt it with one of my B-1s. It just doesn't look like a death sentence for the outputs if it happens.:scratch2:

 

[theophile]

Disclaimer:I'm not the mastermind that can figure this out. For that we need Avionic/Echowars/Unda Marais to figure out the circuitry.

BUT...as I sit here reading the B-1 service manual and schematic, I believe (again, I'm just a neophyte) that the B-1 protection circuitry will protect the outputs. On a few different levels as a matter of fact. I'm not willing to dial down my variac to confirm, but I see a few under-voltage situations that will not allow the output stage to be energized.

In your statement there's a big difference between vfets being susceptible to destruction due to under-voltage; and vfet AMPS being susceptible. I'm in no way 'calling you out', as I agree things may go south in the amp by trying to run 110 instead of 220, but it looks like:
1)The red-light protection circuit won't even turn off (it'll stay in protection) since the +B Power Supply Detection Circuit will see excessive voltage drop on the +B (85V) .
2)There is a protection circuit (TR701, TR702, TR703) that watches the -200v clamping supply.
3)When doing step 3-6 of the bias/setup of the amp, Yamaha has you hook a variable transformer (with output vfets installed) to the power and dial it up and down +/- 10% to verify that bias balance remains constant. Granted, they are not telling you to dial down 50%, only 10%.

We've all speculated over the years that under-voltage to the vfet amps will send the outputs into runaway, due to the clamping voltage not being adequate. I'm just not sure if anyone really knows or has tested the theory. I may be 100% wrong here, and would love to be corrected. Either way, I'm not going to attempt it with one of my B-1s. It just doesn't look like a death sentence for the outputs if it happens.:scratch2:

I tried to qualify my post by using such words as:

"Probability", "almost certain" and "risk".

I was basing those presumptions on the fact that these amps are now over 30 years old,and the likelihood of a fault occurring increases with the age of these amps,plus avionic's testimony that in most of the v-fet amps that he has had on his bench have had flaws in the protection circuitry.

Given the above,I thought that it was a fair call to presume in the absence of evidence to the contrary, that it was a distinct probability that a v-fet amp which had been powered-up on a lower than native operating voltage would have a high likelihood of being toast.

The presence of the mains fitting for a lower voltage on the amp which is the subject of this thread,increases that probability exponentially.

Just my opinion,of course. :sigh:

 

[Elroy]

One nightmare scenario that could happen because the Seller wont verify function is IF indeed it has been converted to US voltage as has been mentioned to be possible due to the presence of the USA plug, the winner would then plug it into a step-up voltage converter believing it to be 240V when all the while it had been previously converted to US voltage! That would suck! :gigglemad Hopefully, whoever wins this thing has some wits about him and gets it to a damn good tech who knows B-1s to assess its true state before doing anything.

 

[sol7]

It must work, after all, don't you see the Passed inspection stickers on the back and side panel???

 

[theophile]

One nightmare scenario that could happen because the Seller wont verify function is IF indeed it has been converted to US voltage as has been mentioned to be possible due to the presence of the USA plug, the winner would then plug it into a step-up voltage converter believing it to be 240V when all the while it had been previously converted to US voltage! That would suck! :gigglemad Hopefully, whoever wins this thing has some wits about him and gets it to a damn good tech who knows B-1s to assess its true state before doing anything.

When considered in it's totality;The specific amp in question,being a 240v amp in a 120v environment,with a 120v mains fitting,likely to have been plugged into and powered-up with 120v,and as far as we all know no information to indicate that it has been modified to work on 120v environements,plus the fact that it is over 30 years old and the failure rate for the protection circuitry is rather high, the logical conclusion would lead one to presume that the chances of everything being ship-shape with this particular amp is slight at best.

 

[Ken Boyd]

I thougth Avionics had already kind of chimed in? But I personally would not like to own an amp that when it has a problem is a boat anchor. And considering its age the likelyhood of failure, disregarding the fact wether its been plugged into the wrong voltage or not, wouldn't appeal to me, unless I got it very cheap. I think right now the price is pretty low but it still has a long time to go, and I would suspect that quite a few people will take that chance right near the end of the auction. I would imagine that their is still a lot of good valueable parts if the vfets are bad, for other owners that have the same amp.

I didn't know if anyone ever saw this list, I am surprised that the Yamaha didn't make this list, considering everyones impressions with it. This list doesn't claim the list of the best amps but the ten most siginficant amps.

http://www.avguide.com/review/the-ten-most-significant-amplifiers-all-time

 

[NumbDiver]

I didn't know if anyone ever saw this list, I am surprised that the Yamaha didn't make this list, considering everyones impressions with it. This list doesn't claim the list of the best amps but the ten most siginficant amps.

http://www.avguide.com/review/the-ten-most-significant-amplifiers-all-time

I must agree. I can't necessarily call vfets significant. Like other boutique products, they may well best the big players, but if they don't find enough room in the market to remain viable, they cannot 'change the landscape' so to speak. Superb? Absolutely. Ground-changing/significant? Sadly they were not. Hopefully Papa's will be.

 

[NumbDiver]

I asked the ebay seller to pull the top (since he has once already for pictures) and test the two DC test points on power board #2. If they showed -200v and +40v, then we (and all) would know the xformers had been changed out to US spec'd versions.

He said no. He could not do that. Odd that a seller with lots and lots and lots of electronic dohicky's for sale, can't use a voltmeter...

Sure be nice to know, but bid at your own risk.

<and Theophile, once you add in the possible failure rates of the protection circuitry itself, I tend to agree with you>

 

[theophile]

Agree.Despite being possibly the best transistors available for audio, they never registered a 'blip' on the audio radar.

Killed-off before they could make their mark.

Indeed, the interest shown in them in the age of the internet has done far more to raise their profile in the public eye,than all of the (little) ink that was spilled on them back in the day.

Papa Pass' following,and their interest in his praise of them as audio devices, will do much, much more to engender interest in them than all of the ink and internet discussion has garnered over the past 30+ years.

 

[theophile]

<and Theophile, once you add in the possible failure rates of the protection circuitry itself, I tend to agree with you>

I considered you too intelligent not to have seen my point. :thmbsp:

 

[Susurus]

Didn't the 240s have a totally different plug than 110/120? So you really have to try hard to screw up?

.

 

[theophile]

Didn't the 240s have a totally different plug than 110/120? So you really have to try hard to screw up?

.

Indeed someone has gone out of their way to make this an absolute f*ck up.

A previous poster may have hit the nail on the head.He suggested that the cord may have been cut-off at some stage.This is my thinking on the matter.

At goodwill stores,charity stores or whatever you may call them, they usually have an electrician test the items before they go out onto the showroom floor.In order that they might prevent electrocution disasters that might render them liable to prosecution on one hand and also to determine that the donated item actually works on the other.When the electrician finds an item that is a risk or doesn't operate, he cuts-off the cord and the item is then either sold for scrap or tossed into the rubbish collection.

My guess, is that this 240v B-1 has been destroyed by some incompetent powering it up on 120v,donated to a charity store, checked by a tech,had the cord removed, sold for scrap, seen by someone who knew what it was, attempted to power-up by fitting a new 120v cord, found to be inoperable and on-sold( with the 120v mains lead) to someone who was stupid enough to buy it. That stupid person sold it to the fellow that Bigears is acquainted with.

Bigears' acquaintance I suspect merely wants to recoup his investment at least,and make a profit if possible.He has no idea whether it actually works,and because the meters and some globes light-up, he states "powers-up" in his auction description.

The seller is a fool. Any prospective buyer is a fool. The seller is a fool because he thinks that saying "sold as is", will indemnify him against redress from the purchaser. The seller is a fool because stating that "The amp is conservatively rated at 160wpc into 8ohms", is fraudulent because Bigears has stated that he doesn't even know if it works. Technically,if you don't know that it works, it has to be rated that it outputs "0 wpc into any load".

Correct?

This seller is a clown, and all of us would do well to remember his eBay ID and to avoid any of his future auctions like the plague.It is misinformed opportunistic flippers like this guy,who give eBay a bad name.

 

[Ken Boyd]

Or who knows some audio repair place might have had it for a trade or repair and found that it was shot, and cut the cord and put it on the dead rack, then at some point threw it out the back dumpster at somepoint. I have read a few post here on AK where people use to go in the dumpsters of audio repair shops and rumage thru them digging out the stuff. Think of all the good parts in the past that were thrown out the back to be taken to the dump. I remember as a kid when we would go to the dump to haul off stuff while my dad would unload the trailer we would go looking for things to play with, we would bring back lots of old tube stereos to set up in our make shift space ships which would be old wood lawn furniture that we would put tarps over and set up all the old stereos as controls for our space ship. I had this thing which I got one Christmas which was a plastic motor that you clamped on a bike, it was a control which made sounds like a motor, I would use that in the space ship to make it sound like we were taking off. Think of all the good tubes in those days just thrown out as people back then were going to SS tubes were at that point considered obsolete old junk.

 

[elrod]

This auction has four hours to go and is at over $800 now. Two bidders with 0 feedback bid it up from $333 to over $800 today. OUCH!

 

[theophile]

My guess is that they are shills for the seller.

Wait and see after the auction.If the 'shills' win, note the date of the ending of the amplifier.There will be no feedback left for the seller on this amplifier for the date of the end of the auction.

The feedback page will be as if the auction never took place

 

[cubby01]

My guess is that they are shills for the seller.

Wait and see after the auction.If the 'shills' win, note the date of the ending of the amplifier.There will be no feedback left for the seller on this amplifier for the date of the end of the auction.

The feedback page will be as if the auction never took place

Just for conversation sake I don't think they are shilling for the seller. One may be an ID another buyer uses to test the waters and see where the current bidder is set. It really didn't matter anyway as there were two 'normal' bidders that wanted it more than the two possible shills did. It only takes two for the price to climb.

According to Watched item there are 84 watchers in addition those that have bid so far. It's setting at $825 currently and I don't think it's done. Craziness.

 

[hugeroost]

just for the helluva it i called my tech and had him pull it up and look, he"s been a full time tech since 1972, he says it aint hurt. But i still wouldnt bid on it, he said he just got done servicing a b2.....Roost