How expensive are replacement V-fet's?

[Vinylcafe]

I totally rebuilt my Sony 8550 with the help of Echowars many years ago.
It was totally nerve wracking!!
If for one second the bias voltage is interrupted or too low, you fry the VFETs.
According to Sony service bulletins/service manuals the ranks of the complimentary devices must be within one of each other.
That said, you can have completely different ranks for each channel, as long as you change the large bias resistors to match the rank for each channel.
As for replacements, pretty well impossible, unless you get extremely lucky and wait for a long time.
Even then, how do you know they work and are not counterfeit?
Sony does have a service bulletin on how to test them with a common multi meter.

 

[rottalpha]

Is this a project you would take on if I can acquire the unit?

I work only on my own units.

Do you have a goto tech for vfet work?

I go to my friends for question but do my own work.

Are they really worth the effort?

is the frog's ass water-tight? credit to @avionic

The best thing you can do is look out for another unit to hope that it has some good VFETs in it.

why?
the v-fets in this unit might be perfectly fine. Distortion on one channel is not and indication of dead v-fet(s).

 

[slimecity]

why?
the v-fets in this unit might be perfectly fine. Distortion on one channel is not and indication of dead v-fet(s).

Yes thats true. I just assumed that they ARE dead, but thats hopefully not the case.....

To the OP - there is a sony service bulletin over at hifiengine.com that has a very basic procedure for testing if a VFET is OK, by simply using a DMM.

 

[slimecity]

I totally rebuilt my Sony 8550 with the help of Echowars many years ago.

Yes, having EW drop off the AK scene has been a real shame, especially with his VFET knowledge. He helped me a lot rebuilding an Accuphase P300.

 

[avionic]

Yes thats true. I just assumed that they ARE dead, but thats hopefully not the case.....

To the OP - there is a sony service bulletin over at hifiengine.com that has a very basic procedure for testing if a VFET is OK, by simply using a DMM.

Complements of Glenn aka echowar
Bottom portion of this pdf is VFET testing with a multimeter.

 

[audiomaniac2]

Is the sound from a vfet amp that good that it's worth all the trouble dealing with them?

 

[rottalpha]

Is the sound from a vfet amp that good that it's worth all the trouble dealing with them?

is the frog's ass water-tight?

 

[audiomaniac2]

Could you be a little more specific?

 

[OMGCat!]

Could you be a little more specific?

He means yes. Search for any VFET thread on here and you'll either find someone unhappy that their VFET amp blew up OR someone who's ecstatic about how wonderful their amp sounds.
I haven't had the pleasure yet so can't comment first hand but I'd sure love a B-1 or a B-2. I do my own work and would have no problem stretching the repair out as long as I needed in order to be sure it was done right as there is no second chance if you power it up and something goes wrong. I'm really surprised that no one (aside from the really short run Nelson Pass commissioned) has resurrected these devices. They really do seem to be the audio holy grail.

 

[rottalpha]

I'm really surprised that no one (aside from the really short run Nelson Pass commissioned) has resurrected these devices.

http://www.ippinkan.com/digital_domain_b1a.htm
turn your google translator ON for Japanese

They really do seem to be the audio holy grail.

Yes they are some of the most liner devices ever made. Sound like triode but with SS ballz and lengthy life. Very robust devices. It is the ancillary devices in the circuit or user error what kills them.
Want to learn more about v-fets, follow @ilmzn posts here or on diyaudio.

 

[drumbum]

Just replace the 1000uf 35v with some Nichicon gold 1000uf 65v on the A class board on my TAN-5550 this am. Full refresh, save the main filter caps.

Xtree noice 50 watts.

 

[drumbum]

I keep listening to this Ramsa WP-9110 though. Nice amplifier also.

Getting time to rotate stock

 

[OMGCat!]

http://www.ippinkan.com/digital_domain_b1a.htm
turn your google translator ON for Japanese


Yes they are some of the most liner devices ever made. Sound like triode but with SS ballz and lengthy life. Very robust devices. It is the ancillary devices in the circuit or user error what kills them.
Want to learn more about v-fets, follow @ilmzn posts here or on diyaudio.

Thanks for the links, I'll definitely have to read up. I've missed out on three local B-2s already so I feel that I've got to be close to joining the V-FET party. I've seen pictures of your stash and am surprised/irritated that I haven't been able to land even one.
It looks like the Digital Domain amp isn't being produced anymore. If someone like Pass or especially Yamaha put out a production SIT/VFET amp for less than, say, $8k I'd dump what's left of my collection and jump all over it.

 

[rottalpha]

I've seen pictures of your stash and am surprised/irritated that I haven't been able to land even one

most of my gear is from Japan. It all depends on how bad you want one. B-2 is probably the best bang for the buck out of all V-fet amps...as there are still many around and the prices are not really high for what you get in return. The only condition is that the V-fets are alive and matched...at least for each channel.

B-1s and B-3s are more rare....B-1s were lot more expensive and in a different class. B-3s just did not sale that many but are very good sounding as well.

Listening to some Yello on a B-1 right now...what a bliss!

 

[Onebean]

Units are out there. After all these info, I have kind of decided to walk away from Vfet. Then I ran across a Sony TAN-5550 yesterday in working condition. The knuckle head that has it was priced higher than I liked, I made a lower offer, he turned it down, and i walked away. Later he called me and said he pulled it out, sprayed the controls with cleaner, and fired it up. He said "it's sounding pretty good". He also dropped his price some. I may not be able to resist buying it. Cosmetically it's not perfect, but it's not trashed either. I'm not sure what to expect a trip across a good techs bench to cost, but by the time I ship it to a tech and back, and have the work done, I'll be into it for a chunk.

So before I take the plunge on this, what speakers do these Vfet amps like? Matching up the right speaker with the right amp is always important. Do these Vfet amps play well with ADS speakers that are nominal 6 ohms, with dips into the 4 ohm territory? I have ADS L880/2 and ADS L910. These are both low 90's efficient, which helps with the TAN-5550 only being 50 watts. The other tube friendly speakers I have are Bozak 302 and Klipsch Cornwall (both in the project stage currently), along with KLH Sixes. Is there a favorite full range floor stander to match Sony Vfet?

 

[Onebean]

B-1s and B-3s are more rare....B-1s were lot more expensive and in a different class. B-3s just did not sale that many but are very good sounding as well.

Listening to some Yello on a B-1 right now...what a bliss!

So the B1 is a step up from B2? Where does the Sony TAN-5550 fit in there?

 

[ConradH]

Friends don't let friends buy V-fet amps.

 

[Vinylcafe]

VFETs are fairly robust devices … it's the bias circuits you have to keep an eye on.

 

[vonclod]

Could you be a little more specific?

Yes! they are special!
A shop I hang at sold a B1 to Abbey Road Studio a few years back.

 

[vonclod]

Units are out there. After all these info, I have kind of decided to walk away from Vfet. Then I ran across a Sony TAN-5550 yesterday in working condition. The knuckle head that has it was priced higher than I liked, I made a lower offer, he turned it down, and i walked away. Later he called me and said he pulled it out, sprayed the controls with cleaner, and fired it up. He said "it's sounding pretty good". He also dropped his price some. I may not be able to resist buying it. Cosmetically it's not perfect, but it's not trashed either. I'm not sure what to expect a trip across a good techs bench to cost, but by the time I ship it to a tech and back, and have the work done, I'll be into it for a chunk.

So before I take the plunge on this, what speakers do these Vfet amps like? Matching up the right speaker with the right amp is always important. Do these Vfet amps play well with ADS speakers that are nominal 6 ohms, with dips into the 4 ohm territory? I have ADS L880/2 and ADS L910. These are both low 90's efficient, which helps with the TAN-5550 only being 50 watts. The other tube friendly speakers I have are Bozak 302 and Klipsch Cornwall (both in the project stage currently), along with KLH Sixes. Is there a favorite full range floor stander to match Sony Vfet?

I can't speak on the Sony, but the B1 does not like a 4ohm load!