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A New VFET Amp?

Yamaha B-2

Yamaha B-2

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Well, a preamp, perhaps. Was reading through the B-2 owner's manual where it discusses the C-1 and C-2 preamps as the appropriate models to be used with the B-2.

The salient points are, and I quote, "With every stage of the signal path handled by field-effect transistors........, the C-1 offers not only superb performance.........". So, no doubt that the C-1 is a full FET preamp on the signal side.

Now for the kicker. Again, I quote, ".......honed down to the ultimate in simplicity, with the technical sophistication to set new standards in audio reproduction. Specially matched YAMAHA vertical FET pairs and advanced, fully complementary circuitry give the C-2 its inherently low..........".

Wow! Appears that the C-2 is a VFET preamp. Guess you know what that means. Am now going to have to spend some effort going through the one I got a few weeks back with the B-2. Ordered the service manual a few days ago, so should have shortly and can check this out in more detail.

Makes me wonder about the insides of the C-2x. Guess I'll have to order up the manual on it, as well. Inquiring minds and all that.

Axel......something new for TVK? Or, do you all ready have this and I'm the one who is behind on the info side of things?

Either way, will be fun to play with an "all VFET" system.
 
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I would think that's a marketing boo-boo. The vertical construction of a VFET is necessary for the high-current output stage of a power amplifier, but in low-current, low-power applications, such as a preamp, there is no real advantage of a VFET to a FET...they would work and certainly sound the same.

If you find differently, I'd like to see it.
 
If it is true, you surely will when you do a full recap, etc., on mine. But, I'll let you know once I receive the service manual.

Also, I got to thinking about the use of a VFET in a preamp. My mind may grind slow, but it grinds exceedingly fine. Remembered seeing a VFET in another preamp and the only place it could be is in the TA-5650 integrated amp. The preamp portion of the TA-5650 uses a 2SK63 VFET in the circuit. So, while not strictly a preamp, there is precedence for the use of a VFET in a preamp.
 
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I doubt that the Sony integrateds envisioned such a thing, but my old Technics SU-9070 preamp was set up to drive a 600 ohm line, and gets as warm as an amp. It's loaded for bear, Buckaroo. I can see a VFET being used (class A, of course) in an application like that.

Now, would a 30w VFET be strictly necessary? I doubt it, but it'd sure be fun.
 
I never seen bigger-than-TO-3 FETs in the C2/2a or 2x...
But I had the same gasp when discovering the german lit' I have on Yamaha's C-1 which says exactly the same thing, just like the french reprint of the former.
Looking at the C-2x schematic now - no V-FETs in sight or in the parts list.

2SK63 = V-FET?? That would be news!
But, hey, just found this: http://www.aes.org/e-lib/browse.cfm?elib=2415 to which the google preview adds: "ID characteristics and the _ linearity of the 2SK63 small-signal V-FET. ... Application of tion Amplifiers the Small-Signal V-FET Type 2SK63 to Phono ..."

K. Nisi does mention "vertical FET type 3" and "horizontal FET type 2" on his C-1 page - what's type 2 and type 3?
However, I'm sure ilimzn would've noted that in his review of the 5650 (at TVK's) and Sony in its abundant lit', too. From all I have, whatever the country or printing date, V-FET = Sony's 2SK60/2SJ18 and 2SK88/2SJ28, Yamaha's 2SK77 and 2SK76/2SJ26 and NEC's 2SK70/2SJ20.

A french review of the C-2/B-2 says the same thing as the C-1 lit' above but only mentions the 2SK77 and 2SK76/2SJ26 and I see none of them biggies in the C-2. Or in the C-1 for that matter...
 
I was under the same impression.

Indeed I posted about this many moons ago,do a search for Yamaha C2x posts.I don't remember where I read it but I thought the C2X was a V-fet preamp.I was told on this forum that it wasn't V- fet but fet.
It seems the controversy has resurfaced. :confused:
 
You both have C-2s so check if there any in them!
I found no V-FET in the C-2x schematic or parts list and no evidence there would be any in the C-1, C-2 and C-2a, given the fact that when these were introduced only the V transistors quoted above were available - bigger than TO3 which one should spot very easily. The C-2a lit' I have mentions no V-Fet.

But if 2SK63 is a "newly" discovered V (and not a pre-MOSFet or Power-Fet or whatever) and there are some in the Yam' peramps, then... I guess... Cs are V preamps using single-ended Vs like the B-1 used only 2SK77s :)

The AES paper I posted the link above is dated april '75 and the google description would prove that the 2SK63 dates from april '75, too... But then how come none of the lit' ever mentions this "small-signal" V-Fet?

ilimzn, are you reading this?
 
I've seen marketing mistakes like that before. I doubt VERY much that you have VFETs. My guess is that some marketing guy with no technical background put this document together, and simply copied much of its content off of an older document that referred to the VFET units. This guy saw the word FET, and had no clue that the Vertical designation was particularly important.

I have an advertizement for an old Sony TC-766-2 reel to reel that claims that it features a direct-drive capstan, when it is actually a 100% belt drive unit! It also claims that it features phase correction circuitry, with is also not true. Obviously some marketing bozo simply read an add for the TC-880-2 and recycled much of it's content for the 766-2, even though it was entirely inapporpriate to do so.
 
theophile said:
Indeed I posted about this many moons ago,do a search for Yamaha C2x posts.I don't remember where I read it but I thought the C2X was a V-fet preamp.I was told on this forum that it wasn't V- fet but fet. It seems the controversy has resurfaced. :confused:
Click to expand...
I sort of recall this and think I was an 'unbeliever' at the time. Do you have the schematic and parts list for the C-2x? If so, check for the 2SK63, as in the Sony TA-5650 preamp section. Symbol for a VFET is, unfortunately, the same as a standard FET. But a google of 2SK63 brings up a number of listings for it as a VFET device.
 
If it is, was it possible then to make a V-FET in smaller enclosures than the ones used in the B-2/B-3 and Sony's units?

2SK63 isn't listed in the C-2x parts list: only regular transistors, FETs and Dual FETs.
 
Manual for the C-2 just arrived. No VFETs. Input is a pair of ICs with dual FETs, but nothing special. Pair of 2SK30A's in the PS, but is just a canned FET. Oh, well. Just more marketing BS.
 
It is not a new thing, 5650 manuals clearly says for it to have 10 vfets, of which 8 are 2sk60 and 2sj18, and the missing two are somewhere to pass all fantastic microinformation that gives the charm, a shocking experience, through external adapter1 input, which is the shortest and purely hi-end path that makes this 30 year amp sounding silky smoother than anything, VAC resaianance valves, radford sta-25 series III, PM-94, quad II, Bryston 7b-st, krell ksa-50, ......that i compared A/B. 5650 is not a simple vintage gear. Feed it with true signal like from XA7,meridian 508.24, X707es, cary audio, not with marants cd63 KI etc. And connect a good speaker, fast and smooth enogh to get differences. vfets dont have missing punch, have better deeper heavier bass from monitor audio pmc702 than B&W802 connected to bryston 7bst. Have power to kill anything around with serious instant attacks. Trebles are not cut or missing, more airy and natural than many valve amps, if you compare to SS trebles with unable sources and speakers, those are liquid nitrogene to freze the world not the trebles. I dont know any instrument TiiiiiIIIISSSHHHHHing. At AER fullranges, radford trebles are tiny bit better but not as detailed, natural and airy. Bryston 7bst is faster, plays sounds in realistic periods but no other things. Get the microinformation from vfets, all those truth, thus the shocking vfet difference, the Sound. Timing, unbelievable depth, true defined extensions, true windows through midband, musical focus, sprayed spatial endless stage are bonus.

-I need help on upgrade of parts that will not interfere with current result.
-Is it possible to safely bypass also mute switch, filters, gain stage and thus make preamp consisting of only a volume controlled, external adapter1 input selected buffer to hardwire power input? Any tries simplifing pre stage correctly?

Best Regards.

Mesut B.
 
Welcome to AK, Mesut.

If were me, I would not do the bypassing, etc., you ask about in the TA-5650. I would find one of the VFET power amps from Sony or Yamaha (see Axel's The Vintage Knob for VFET info) and then use a preamp that either does not have these controls or the ability to bypass them with the flick of a switch. Or, get a passive preamp such as a Placette or a Mod Squad, etc.

But.....the question remains.....is the 2SK63 a VFET device?
 
There is even no fet rather than known ones at poweramp section, then at the rest all the other fets around are 2sk23A. Sony says there are 10 vfets, but mentions about vfets and LEC transistors at 5650 manual page15 implying vfets are at the poweramp section and lec transistors are at phono amp. If 2sc1636 is a LEC type than we may trust sony that 63 is another vfet. What about at other sony TA manuals? Is 2sk63 always common unknown missing vfet? Or does sony add lec transistors(implied as so important) to number of vfets of 10 at manual?

I dont have turntable to use possible vfet phonostage but original 5650 preamp throgh external adapter1 input(without this a worthless amp, poweramp is not one over the top) is better than simple ALPS stepped pot as volume control, sony XA7es player variable output, Audio research LS25 and LS7 and than all others that I tried in terms of everything. Only alps pot seems tiny bit faster but after 5 minutes it looses everything, no detail, no air, no drive, no punch, no balance, and as usual no microdetails,...... Lec, vfet or not I know noone tring it throgh external adapter1. Phonostage (2sk63 is vfet or not) through usual pre path is worthless, however overall as integrated with mentioned input...

http://www2.ocn.ne.jp/~applen/V-FET.1.html (?)
http://www.patentstorm.us/patents/5783970.html (may be there are pages for LEC transistors)

http://www.guangdongdz.com/indexpage/2product/chanping_657197.html

http://www.guangdongdz.com/2product/pro_grade_05.asp?iscanid=656707&scanname=场效应管 2SK60

there are 8 types
 
Are there unknown Vfets?

I can categorically state,I do not know.Anything I've stated in this or any other thread about the Yamaha C2x having V-fets,I've seen on the 'net somewhere;and I can't recall where I saw it. :no:
My experience with the Yamaha B-2 now I've owned it for a month is that it's an awesome power amp.I use my C2x as a phono preamp,with the power switch on the front panel switched off .I take the signal to the preamp from the C2x's tape out sockets,which bypasses all of the front panel controls except tape-out selector and source selector.The Yamaha B-2 has emphatically made it clear to me that in my system,this is the best sounding option.
So are there V-fets in the C2x?I don't know and to be quite honest I don't care.There's an academic interest,but in the end I'm quite happy to simply listen to the result and leave the investigation to others.I've taken the bottom off my C2x a coupla months ago and marvelled at the build quality.I spotted a couple of Black Gates,which confirms that rumour.The build quality is in a different league altogether to the C2a.I don't know enough to say whether they altered the circuit between the C2A and the C2x.I'll leave that to others to determine.
Up until I purchased my Altecs I was a"turntable,integrated amp and speakers" kind of guy.I haven't played around in the big boys league of equipment.Therefore,I'm not able to make sweeping statements about the ultimate ranking of what I own vis a vis what was available in the past or what's available new.I am happy to share my observations of what I hear in my own system.I would say that vintage gear enables folk like me who haven't unlimited or sufficient funds to get a taste of what it's like to own top-notch gear.I have to thank people on this forum and AA for giving me recommendations of great vintage pieces which have more than lived up to the accolades they were accorded. :thmbsp:
 
The C-2x was many years removed from the v-fet days. It has none.
I own a C-1. The signal path is 100% fet, and cascode loaded v-fets are used in the output of each stage (the C-1 has about 100 stages:))The v-fets run class A. The C-2 is a simple version of the C1, but they sounded dark and somewhat compressed. C-2a was an attempt to fix the sound. One reason NS1000 speakers were so bright was to balance the C-2. The C-1 sounds much better, but it is tough to keep running.
V-fets are not intrinsically better than FETs, but they can conduct more current. A v-fet preamp could drive low impedance loads at high levels, but would not sound better than a fet pre running higher impedance loads. Parts have something to do with good sound, but not everything.
 
theophile,
glad to know you do like the B-2!

Nakdoc,
So the C-1 does have V-FETs indeed? In a smaller box than Yamaha's 2SK77/2SK76/2SJ26? Is the 2SK63 a V-FET like we mean Sony's 2SJ18/2SK60 are V-Fets?
And how come that (smaller?) V was never photographed like the others that were displayed at length in the ads, catalogs, posters etc?
 
Nakdoc - What VFET device was used in the C-1? Do you have the schematic? If not, are these devices easy to see when the case is removed? If so, you should be able to read the device number on top of the can.
 
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