If I can't get a matched pair......does it mean a lot?
It is a follower.........so gain will be same for both channels.
It is a follower.........so gain will be same for both channels.
Pras don't stock 2SJ28, if you are lucky, she may sell you Yamaha 2SJ20, but only in pairs with 2SK70. Not matched. But that is not neccessary for this kind of follower, no gain.
Unfortunately I don't know the sweet spot for this V-Fet.
Unfortunately I don't know the sweet spot for this V-Fet.
@ Meper
Yes by email or PM on the forum Sell thf-51s 2SK182ES NEW NOS to-79 SIT v-fet, from Japan TOKIN
Yes by email or PM on the forum Sell thf-51s 2SK182ES NEW NOS to-79 SIT v-fet, from Japan TOKIN
No, it is not a real issue. I provided parts with matched Vgs because it was easy to do.
Thank you!
Then it may be easier to get some.
My have 84 written on them.
Can I relate this to a value I can measure if I get a few new VFETs?
Then it may be easier to get some.
My have 84 written on them.
Can I relate this to a value I can measure if I get a few new VFETs?
Excellent work and 42C is cool in my books (after all 57 watts / chan heat dissipation is easy to work with). As for linear power supply, 24 VAC is fine in full wave rectification.
I would be keen to find out if others have explored the linear power supply option and have found there's an audible difference?
I would also be keen to hear this.
Plus from anyone who has rolled the input coupling cap.
Here's my finished franken-beast.
Very happy, velvety-smooth & detailed sound.
Thanks so much Nelson and everyone else involved who made this happen!
Attachments
Thanks both!
Dammit - considering the principle of convection cooling; I did think of doing that at some point, then I totally forgot about it.
Yes thats a very good idea.
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^ That chassis turned out quite nicely. 
A linear supply will need to start with more than 25V secondaries from the power transformers. 28V secondaries will probably work if you have good low Vf bridge rectifiers. I used a pair of Triad 160VA transformers with 30V secondaries and single rail SLB CapMx boards.
Note:
The linear PSU will require some effort to reduce the hum to a level that is as inaudible as the kit SMPS. I suggest a CLCRC filter or the SLB.
A linear supply will need to start with more than 25V secondaries from the power transformers. 28V secondaries will probably work if you have good low Vf bridge rectifiers. I used a pair of Triad 160VA transformers with 30V secondaries and single rail SLB CapMx boards.
Note:
The linear PSU will require some effort to reduce the hum to a level that is as inaudible as the kit SMPS. I suggest a CLCRC filter or the SLB.
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I still have 2 outstanding mods on my side...
- The bypass caps at the 10000uF output caps, hopefully next week time permitting (it is very quickly done but I am overloaded since 4 weeks)
- The SMPS filters in front of each output board, likely to take a bit more time as I want them quickly removable to carry out quick tests with and without it
Argh, need really more time, but, err... isn't this just a hobby to waste some time, so... 🙂
Will of course report as ever once done
Claude
- The bypass caps at the 10000uF output caps, hopefully next week time permitting (it is very quickly done but I am overloaded since 4 weeks)
- The SMPS filters in front of each output board, likely to take a bit more time as I want them quickly removable to carry out quick tests with and without it
Argh, need really more time, but, err... isn't this just a hobby to waste some time, so... 🙂
Will of course report as ever once done
Claude
I got info from Prasi that she has 2SJ26 (and 2SK76) but those are probably not "drop-in" replacements for 2SJ28?
I don't have the data sheets.......
I used the Yamaha 2SK76 for a L'Amp, realy nice, even nothing knowing about the sweet spot. I have to lern to measure distortion.
Thank you!
I probably better find a 2SJ28 and not try to experiment with 2SJ26 ....which is a Yamaha?
I wonder who actual produced these? ......Toshiba? or had Sony their own silicon factory? ......I guess Yamaha did not?
If I get the full PDF data sheet for 2SJ28.....can I in there see the difference between KF-33, KE-33 etc.....?
Nobody produced actually these V-Fets, the Yamahas are also obsolet.
I guess, you will be sucessful with your search for 2SJ28, it may take time. Think of looking only for 1, may be easier and as far as I remember you have only in one channel strange noises. Matching is not important.
I guess, you will be sucessful with your search for 2SJ28, it may take time. Think of looking only for 1, may be easier and as far as I remember you have only in one channel strange noises. Matching is not important.