On the heals of Ecowars post regarding the blown V-fet on his 4650 integrated,
I am wondering about a pre amp that also uses V-fets with a channel that drops
out. The description given to me is one channel will come on then off again, because this is a pre amp & not a power amp should there be a better chance
that the V-fets are ok, & the problem lies in another direction, cold solder etc.

I don't think there were any VFET preamps.

Well as ByrdWings has informed me, the preamp in question is not a V-fet. Every day I continue to learn a little more.

Preamp esoterica devices were j-fets.

The Yamaha C1 was fet with Vfet output class A between stages in the signal path.

Nakdoc - Any chance you could post the VFET device number for the C-1 output stages you mention? The TA-5650 has a baby VFET in the preamp, but was my understanding that it is the only use of a VFET in a preamp. The one is the TA-5650 is a 2SK63 and we (VFET followers) didn't realize it was a small VFET until about a year, or so, ago (http://audiokarma.org/forums/showthread.php?t=51718&highlight=2SK63 - see posts #3 & 5). Guess we were blinded by the larger VFETs in the amp(s). And, perhaps by the misnomer of 'vertical' FETs (like Halcro states in their advertising today).

Yamaha B-2- being new to the VFET world & reading your post re the TA-5650 & 2SK63
small VFET, does it then follow that the tae series pre amps would then also use small VFETS ?

Definitely not. Need to look at each preamp schematic to see what is there. We were quite surprised when I discovered the 2SK63 last year. And there were several folks (Axel, etc.) who have been into VFETs much longer than I who had not noticed it, either. Perhaps EW will see this thread and cast his eye on the TAE-8450 schematic (he has mine in for a refurb).

As previously mentioned the only known dedicated preamplifier using V-Fets is the Yamaha C-1 ! It uses two 2SK75 (C grade) medium power V-Fets as voltage followers of the output stage. The circuit used for this application is nearly identically to the rumble filter amplifier stage of the B-1.

The only candidate, which remains, is the JP-S7 preamplifier from Victor, which probably used the 2SK69/2SJ19 complementary pair. The high supply voltage of +-59 V (see k.nisi website) doesn´t allow J-Fets to be used (ordinary J-Fets range up to 50V, some types up to 100V, but with very high internal resistances).

A service manual for these rare Victor V-Fet units would help a lot !

Perhaps EW will see this thread and cast his eye on the TAE-8450 schematic (he has mine in for a refurb).The schematic won't tell me much...there's no special schematic for a VFET since a VFET is just a big JFET. I'd need the datasheet for the part, and finding it will be an exercise in futility.

Several of the vintage Sony schematics have the transistor part numbers on the schematic. Like the TA-5650, for instance. Some are near the transistor symbol in the circuit and others are in a box listing the active devices somewhere near the edge of the schematic, identified by the schematic part number (Q101, for instance) and the device part number (2SK63, etc.). But, not having seen the TAE-8450 schematic, it may well be different.

BTW - just received the owner's manual for the TAE-8450.

The only candidate, which remains, is the JP-S7 preamplifier from Victor, which probably used the 2SK69/2SJ19 complementary pair. The high supply voltage of +-59 V (see k.nisi website) doesn´t allow J-Fets to be used (ordinary J-Fets range up to 50V, some types up to 100V, but with very high internal resistances).

A service manual for these rare Victor V-Fet units would help a lot !Would this be the one? http://www.manuals-in-pdf.com/advanced_search_result.php?keywords=JP-S7

Unda I thought the C-2 was the same as the C-1, but without all the fancy adjusting?

Device number (2SK-whatever) doesn't tell me if it's a FET or a VFET or MOSFET, unless you have a list of such devices.

The driver FET's at the output of the 8450 are 2SK43.

Info used to be available on the Vintage Knob VFET site. Now listed as 'Soon Available'. Google resources give 2SK43 as an N-channel JFET. So, not a VFET. But, Mirko seems to all ready know this.

Unda I thought the C-2 was the same as the C-1, but without all the fancy adjusting?A quick look at the C-2 schematic shows no FETs of any sort in the preamp, other than a couple in the power supply. Everything else is a few ICs (probably the Yamaha specific modules) and discrete BJTs.

Every year, just before christmas a nice (but more or less senseless) V-Fet discussion starts. I´d like to have more V-Fet discussions all over the year !

EW:

I wished shipping from Germany to the U.S. would be easier, then I could send you your 2SK60.

To ship a VFET to here would cost a Euro or maybe two at the most. I sent a whole bunch of ceramic IF filters to a AK'er in Germany a year or so ago, and I think I spent about $1.75 US to do it.

Every year, just before christmas a nice (but more or less senseless) V-Fet discussion starts. I´d like to have more V-Fet discussions all over the year!

EW: I wished shipping from Germany to the U.S. would be easier, then I could send you your 2SK60.Maybe they don't have a postal service in Germany. Or, if they do, it doesn't go out of the country. :D

Since Germany is the country with the highest export rate in the world, this would be very strange ... :lmao:

I´ll check ...

As previously mentioned the only known dedicated preamplifier using V-Fets is the Yamaha C-1 ! It uses two 2SK75 (C grade) medium power V-Fets as voltage followers of the output stage. The circuit used for this application is nearly identically to the rumble filter amplifier stage of the B-1.

The only candidate, which remains, is the JP-S7 preamplifier from Victor, which probably used the 2SK69/2SJ19 complementary pair. The high supply voltage of +-59 V (see k.nisi website) doesn´t allow J-Fets to be used (ordinary J-Fets range up to 50V, some types up to 100V, but with very high internal resistances).

A service manual for these rare Victor V-Fet units would help a lot !
Yup, Nakdoc and Unda Maris know their stuff. Take off the cover of the C-1
and the 2SK-75's are staring you in the face. I had the C-1 on the closet shelf
while dabbing around with the likes of tube pre-amps, Parasound Fet preamp
and having fun just changing stuff around. I put the C-1 back in, driving
the B-1 and B-2's(two main preouts and one switchable pre-out makes this
easy) and Wow, I'm not straying again. Maybe there's a reason the C-1 cost
$1800.00 way back then. Maybe it's the super smooth sterling sound, Ya
think? Ssuperrob, grabbed the latest one on Ebay, Congrats! Long live
V-fets. :yes:
http://i127.photobucket.com/albums/p158/Klipschornman/picture005-1.jpg
http://i127.photobucket.com/albums/p158/Klipschornman/picture004-1.jpg
http://i127.photobucket.com/albums/p158/Klipschornman/picture003-2.jpg

I had the C-1 on the closet shelf
while dabbing around with the likes of tube pre-amps, Parasound Fet preamp
and having fun just changing stuff around. I put the C-1 back in, driving
the B-1 and B-2's(two main preouts and one switchable pre-out makes this
easy) and Wow, I'm not straying again. Maybe there's a reason the C-1 cost
$1800.00 way back then. Maybe it's the super smooth sterling sound, Ya
think? Ssuperrob, grabbed the latest one on Ebay, Congrats! Long live
V-fets. :yes:

Very nice system Klipschornman!

I would like to hear that :D

Since Germany is the country with the highest export rate in the world, this would be very strange ... :lmao:

I´ll check ...

Not for much longer! A very quick mental inventory of hardgoods purchased this year indicates that China is closing in :yes: .

Very nice system Klipschornman!
Thank you, Mark B. Sometimes you don't know what you had till it's gone!
It was so clear after I reinstalled the C-1 back in its rightful place. I suppose
some people think that it's too cluttered with controls. Talk about versatile.
Can't believe it sounds that good with all of that stuff in the way. Have you
had any progress on your B-1's? Next, I'm gonna let the C-1 push the Sony
TA-4650 and see what happens. I love AK. If more people spent time here,
half of the world problems would dissappear. :yes: Cheers.
K-man

If more people spent time here, half of the world problems would dissappear. :yes: Cheers. K-man:lmao: :lmao: :lmao:
If not on AK, then at least listening to good music on their vintage rigs.:thmbsp:

I would like to hear that :D
Hi Stoffie. Actually, I was thinking the same thing in reverse. Would love to
hear your Sony TA-E88B driving your TA-N7B. I'm not going to rest until
get my fill of Sony v-fets as well. Not greedy, just love the V-fet sound.
If you're ever over this way, shoot me a PM and I'll have my wife do her out
of this world fried chicken thing and chocolate pie.:D Then, we can get to
the serious thing of listening to the music. LOL. Happiness always,
K-man:thmbsp:

You betcha K-man. I was planning on doing a road trip in the US in a few years, or as soon as I can afford it (I do go to the US regularly, but always Oregon/California).

So it's only a matter of time !

Same for you, if you are ever in the neighborhood, my door is always open :)

I am really in love with the sound of my setup, but I do think the current cd/dvd player is a limiting factor. Will see how much of a difference the PS-X75 turntable is going to make. Can't wait :D

I am already considering putting together a Yamaha VFET setup for my study, hmmm, going to have to rob a bank or something...

...The only candidate, which remains, is the JP-S7 preamplifier from Victor, which probably used the 2SK69/2SJ19 complementary pair. The high supply voltage of +-59 V (see k.nisi website) doesn´t allow J-Fets to be used (ordinary J-Fets range up to 50V, some types up to 100V, but with very high internal resistances).
A service manual for these rare Victor V-Fet units would help a lot !

I just got a used Victor JP-S7 preamp from Japan. I have removed the cover but no VFETs inside.

sandawa we demand pics :)

Interesting unit, here in Europe it is called JVC JP-S7.

K-man...I think with all those Yamaha Bs and Cs and those VFETs at your place, there is a slight gravitational shift in the Earth's axis...can you feel it? I can certainly hear it!

The Vintage Knob calls the JM-S7 / JP-S7 a v-fet combo, but only describes the JM-S7 as having V-FET's:


From The Vintage Knob

Victor JM-S7
Victor JP-S7
(1975 - 1977)
The other V-Fet combo... Japan-only, unfortunately.
The JM-S7 uses 4 pairs of NEC's V-Fet (2SK70A / 2SJ20A) while the JP-S7 preamp is a magnificent piece of forward design, adorned with Victor's staple S.E.A. graphic equalizer.

sandawa we demand pics :)
Interesting unit, here in Europe it is called JVC JP-S7.

Here are some photos:

a.) from back w/o the cover
b.) top-front w/o the cover
c.) the board underneath
d.) fully covered

http://img251.imageshack.us/img251/9079/99760059qd1.th.jpg (http://img251.imageshack.us/my.php?image=99760059qd1.jpg)http://img250.imageshack.us/img250/2844/10144499vp1.th.jpg (http://img250.imageshack.us/my.php?image=10144499vp1.jpg)http://img251.imageshack.us/img251/7616/68053629wd9.th.jpg (http://img251.imageshack.us/my.php?image=68053629wd9.jpg)http://img251.imageshack.us/img251/1733/15870390ky6.th.jpg (http://img251.imageshack.us/my.php?image=15870390ky6.jpg)

Nice; I like the diagram on top, It reminds me of older pro units where many brands also printed the block diagram on top.

Hi V-FET Fan's

I used to have a TA-5650 until my wife made me throw it away ....20 years ago!! :cry: Probably I need my head examined :tears:

Anyway, here's some interesting info on V-FET's. Sony Service-Bulletins and the schematic for TA-4650 where it clearly shows the 2SK63.

Have fun,

Kind regards,

/tri-comp

Tri-Comp...
Thank You a lot for the cool Infos and Schematics :-)

Cheers!

Darko

tri-comp: how do you host .pdf files so that can be opened by anyone through the posted link? Thanks.