if everything is OK, they'll be functional in amp
or you can test them in test jig for JFets ......... all you need is laptop supply and 15-20R resistor of 50W or so
for P Channel JDet Drain goes to GND, Gate to +19V, Source to one end of resistor, other end of resistor to +19V; measure D-S voltage when power applied
JFet heatsinked
buzz if you need specific drawing for that
or you can test them in test jig for JFets ......... all you need is laptop supply and 15-20R resistor of 50W or so
for P Channel JDet Drain goes to GND, Gate to +19V, Source to one end of resistor, other end of resistor to +19V; measure D-S voltage when power applied
JFet heatsinked
buzz if you need specific drawing for that
Using Ben Mah’ posting of the Sony Service Bulletin, I measure 1.4 volts and 1.7 volts across the source pin and the case, (D), of each respective VFET, and on each VFET, S to G and D to G register as diodes.
So I am going to go with that test and declare these two VFET’s good to go.
This also id’s the Source pin for me.
Thanks to you both for the assistance.
Onward….
So I am going to go with that test and declare these two VFET’s good to go.
This also id’s the Source pin for me.
Thanks to you both for the assistance.
Onward….
The SK60 version is already extremely transparent without, but I have two built PS cards ready for the inputs. I am going to run the amp as is for a while to assure stability over a few more weeks of use and then add the PS input cards. It's going on three weeks of use now, sounds great.
I put the PS noise reduction card on one channel. The second one bench tested output of 36 v fine with a test power supply, but for some reason, I can't get it to work when I put it into the second card circuit. I might just buy a new one and put it together more carefully rather than puzzle this one out with my lousy electronic puzzler.
This thread seems to be slightly orphaned, maybe because of NP's surpassing generosity in gifting the lottery amps and VFETs to the greedeezs, but I'm kind of glad I waited for the SK60 build. These are well used devices harvested from blown chassis. However, they are single die rather than paralleled dual die.
Never having built an amplifier before combined with my possibly delusional desire to put it into the Sony TA4650 chassis, combined with my all elbows techniques, nonetheless, this mostly built amplifier has been holding me hostage for several weeks now. In spite of having several nice amps, including two other SIT models, this one couldbe the most resolving AND musical. It has real specular highlights and dynamic intensity, which distinguishes it compared to its charming and elegant tubed counterparts like 45 and 2A3. Every input I have tried, both SS and tube (It has no front end card in this chassis), sound excellent with it, including the Pass Korg and the TA4650's own 45 year old wheezing FET preamp.
How an 8-10 watt amp does that I don't know. The SK60 might just be an especially good sounding device when graced with NP's circuit.
This thread seems to be slightly orphaned, maybe because of NP's surpassing generosity in gifting the lottery amps and VFETs to the greedeezs, but I'm kind of glad I waited for the SK60 build. These are well used devices harvested from blown chassis. However, they are single die rather than paralleled dual die.
Never having built an amplifier before combined with my possibly delusional desire to put it into the Sony TA4650 chassis, combined with my all elbows techniques, nonetheless, this mostly built amplifier has been holding me hostage for several weeks now. In spite of having several nice amps, including two other SIT models, this one couldbe the most resolving AND musical. It has real specular highlights and dynamic intensity, which distinguishes it compared to its charming and elegant tubed counterparts like 45 and 2A3. Every input I have tried, both SS and tube (It has no front end card in this chassis), sound excellent with it, including the Pass Korg and the TA4650's own 45 year old wheezing FET preamp.
How an 8-10 watt amp does that I don't know. The SK60 might just be an especially good sounding device when graced with NP's circuit.
OK….I Finished assembling my Sony VFET amp this afternoon. It’s been a long time in production, but I got it all wired and the chassis assembled. Now for the testing and setting the bias. Taking a beer break here for a bit. Might wait till tomorrow to actually warm it up etc.
So what I have is a stock, as designed by NP, Sony VFET 2SJ18 Output board, a Scourge front end, a Ship of Theusus PS filter, installed in the DIY Alum 4U universal chassis. I missed on the purchase of the Lottery chassis, so I used the 4U. Looks good to me. I will put a on off button on the front in the future.
I want to express my gratitude for all of the support and help from this community and from NPass for making this amp possible. Without your assistance, advice and designs I could never have gotten this far. Thanks.
So what I have is a stock, as designed by NP, Sony VFET 2SJ18 Output board, a Scourge front end, a Ship of Theusus PS filter, installed in the DIY Alum 4U universal chassis. I missed on the purchase of the Lottery chassis, so I used the 4U. Looks good to me. I will put a on off button on the front in the future.
I want to express my gratitude for all of the support and help from this community and from NPass for making this amp possible. Without your assistance, advice and designs I could never have gotten this far. Thanks.
Attachments
Great work KMF! 
May your sound test go smoothly and well into the evening. Let us know what you think of the sound.
If another chance to buy the VFET chassis comes up (if there are enough buyers to justify another run), you can always repurpose this 4U/300 for a future project.
Cheers,
Stephen
May your sound test go smoothly and well into the evening. Let us know what you think of the sound.
If another chance to buy the VFET chassis comes up (if there are enough buyers to justify another run), you can always repurpose this 4U/300 for a future project.
Cheers,
Stephen
Congrats. Mine in Sony TA4650 chassis has been working for about a month. It sounds great. Detail, sound staging, intense specular highlights and transients, great attack tones. I don't have the front end gain cards, but every preamp type front end whether SS, Pass Korg, or tube sound great with it. Does sound a bit like what I remember with SIT 1/2, but with more tonal density, nice.
I thought it would sound nice and interesting, but didn't think it would sound so good I am not inclined to go back to my other amps.
I thought it would sound nice and interesting, but didn't think it would sound so good I am not inclined to go back to my other amps.
I ran it a couple of hours yesterday, while setting up the bias. Sounds OK, but to be fair. I need to give it a few days to get used to it. at this point I think my two ACA’s running XLR mono-block sounds better, expecially after I put PO89ZB filter in the mix. But I need to give it some time. To me the Sony VFET sounded a bit softer, lots of detail, but the ACA’s had better attack and dynamics. But memory is unreliable and I will AB the two amps in a couple of days when I get around to installing the PO89ZB filters in the ACA chassis’s and set them up so I can easily switch between the two. I also have the Missouri front end card to swap into the VFET, and it is an XLR card. Supposed to be nasty weather wise here in the next few days so I will have some inside time to fiddle with amps.
I guess soft isn't the word I would use with the SK60 one that I have. It is a current amp only without a front end, so it reflects the source and drivers. It is all dependent on how and what you use them with, as usual.
New stuff takes about 50 hours of use or so to anneal. I have never heard the Amp Camp critters. Mine has the VFET high separation of voices on the stage and surprising intensity to transients and things like horn blasts. Excellent dynamic fluidity in midrange and upper midrange, which seems to be a single ended specialty. Cool.
New stuff takes about 50 hours of use or so to anneal. I have never heard the Amp Camp critters. Mine has the VFET high separation of voices on the stage and surprising intensity to transients and things like horn blasts. Excellent dynamic fluidity in midrange and upper midrange, which seems to be a single ended specialty. Cool.
Mine sounded much better this morning. I have been streaming off of Tidal and Radio Paradise so there might be issues with signal degradation from the internet between early morning and the evening. Will try some CD’s today. Like you say, it will take a while for this to “break In”. Clarity and sound staging were evident this morning.
My sample seems to have broken in nicely so far and has been working as my amp for going on six weeks. It seems to operate a little cooler than at first, though maybe that requires a bias check. It is a source follower, but for some reason it also seems to have picked up a bit of gain over time. It seems to be about the same warmth as commercial First Watt M2, which isn’t a particularly hot class A device. The half of the chassis without the heat sinks stays very cool.
I finally put it through its final torture test with vinyl. Vinyl has a lot more sonic thickness, with intense sustains and intermodulations. The SK60 performed without problem, sounds great. It sounds good with every gain stage I have tried, both solid state and tube, as well as the Pass Korg unit.
I am so pleased with the sound of this amp I am going to build or obtain an outboard linear power supply for it. I really don’t like the little interconnect from the wall wart power supply.
I’ll attach some nice Ukrainian poly caps across the output caps to supplement the little poly cap as an audiophile superstition token.
I finally put it through its final torture test with vinyl. Vinyl has a lot more sonic thickness, with intense sustains and intermodulations. The SK60 performed without problem, sounds great. It sounds good with every gain stage I have tried, both solid state and tube, as well as the Pass Korg unit.
I am so pleased with the sound of this amp I am going to build or obtain an outboard linear power supply for it. I really don’t like the little interconnect from the wall wart power supply.
I’ll attach some nice Ukrainian poly caps across the output caps to supplement the little poly cap as an audiophile superstition token.
LOL! Got a HP 6266b variable linear power supply (40v@5A) for half a C note. The amps both operate together at about 2.8 amps or so. Thing looks bullet proof in spite of age. I'll hook that up to the amp in lieu of the wall wart and see how it goes. It is about the same vintage as the Sony TA 4650, so it will complete the vintage circle.
Now if I could just figure out how to get the little green light in the power button to work, I have the leads, but can't find any info on the specific lamp.
Now if I could just figure out how to get the little green light in the power button to work, I have the leads, but can't find any info on the specific lamp.
Thanks for the answer, I thought that article was specific to the bigger sony vfets, not the J18 K60.
The article for these (J18 K60) does not state bias currrent.