... there are no silly questions, only silly answers...
do you have something like this in mind ?
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Thanks for that.
I ended up printing out a PCB that had a bunch of to-3 transistors on it and used that as a layout template for drilling. End result came out ok I think.
Now my only drama is the number of power supplies... so far it's 9? for a stereo pair?
Thanks for that.
I ended up printing out a PCB that had a bunch of to-3 transistors on it and used that as a layout template for drilling. End result came out ok I think.
Now my only drama is the number of power supplies... so far it's 9? for a stereo pair?
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Hi there - Im usually found over at Audiokarma - however I was advised that I could find some better advice here on VFETS.....
I'm looking at constructing something painfully simple based on one Sony 2SJ28 per channel. Would the diagram posted as the first post in this thread do the trick, or alternatively, something like in the attached diagram? - from Audiohobby.com.
I understand that the 2SJ28 needs negative voltages (whereas the now unobtainable 2SK82 used positive voltages). I think I may need it explained to me how this would work in practice, ie: how to wire up these devices.
I have a lot of expereince with conventional amplifier circuits, and have upgraded/restored several amplifiers from leak, accuphase, sansui.
cheers!
I'm looking at constructing something painfully simple based on one Sony 2SJ28 per channel. Would the diagram posted as the first post in this thread do the trick, or alternatively, something like in the attached diagram? - from Audiohobby.com.
I understand that the 2SJ28 needs negative voltages (whereas the now unobtainable 2SK82 used positive voltages). I think I may need it explained to me how this would work in practice, ie: how to wire up these devices.
I have a lot of expereince with conventional amplifier circuits, and have upgraded/restored several amplifiers from leak, accuphase, sansui.
cheers!
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Hi there!
You should be all good to invert the voltages (including the bias voltage) and away you go. You might find it informative to read This as a rather more advanced example of what you're trying to achieve. Edit: That said, I think there's a warning in the document about which grade part works in that schematic. I'm not familiar enough with what the various grades actually mean to make an intelligent suggestion about whether the part you have is suitable
Edit Edit: part 2 of the l'amp articles, Figure #1 shows an adjustable bias version using an inductor as the load for the V-Fet. Keep your lightbulbs instead of the inductor, but build the bias circuit shown in Fig #5. With all the voltages inverted...
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http://harbuch.com.au/doc/INPUTOUTPUT_TRANS_May2010.pdf is a local(ish) supplier of transformers that may better suit my needs after I test stuff out with what I've nabbed already...
Any reason I can't use a 150R:150R:150R:150R instead of the suggested 600R?
Any reason I can't use a 150R:150R:150R:150R instead of the suggested 600R?
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well, actually you´re in the wrong thread....
you should go over to here:
http://www.diyaudio.com/forums/pass-labs/201655-lamp-simple-sit-amp.html
and do yourself a favor and read all of it !!
i know, it´s a long thread, but it´s really fun.(I was through the lot
in 5 days...) you will learn alot about building nice amps with
the lovely VFETs.
...and about wiring up the sj28 with the reverse-polarity-thingy
is discussed somewhere in the last 500 posts.
Thanks a lot guys - look Aspringv - our flags are almost the same! (I wish we voted for the kiwi with laser-beam eyes personally!) BTW, those 2SK's are legit and you are happy with them?
Cheers MBalou, I will go to the right place now. I really want to build the simplest thing possible, and the lightbulb circuit sounds great.
Cheers MBalou, I will go to the right place now. I really want to build the simplest thing possible, and the lightbulb circuit sounds great.
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Lightbulbs may not be the ideal... they're non-linear resistors.
But might sound interesting...
Consider Current Mirrors, chokes and even a resistor instead?
Lots of schematics for SE output stages.
Probably needs a fair amount of drive...
_-_-
Last time I looked, circuitdiy.com still had the 2SK82's. It's the 2SJ28's
that are harder to get. Of course you can make that circuit with the 2SJ28's
by simply reversing all the polarities.
The circuit presented above is likely to have some issues. First off, the
Vgs of the part is usually in the range of -5 to -10 volts for 1 amp @ 20V Vds.
This puts you into several ohms value for the Source resistor, and will
seriously cut into the gain.
You can attach the negative side of the loudspeaker to the Source pin of
the VFET, and that will at least give you the gain back, if that's what you need.
I usually used a 300W light bulb for the load, which was about 22 ohms
in this kind of circuit, and it worked pretty well. Look at the Zen Lite for that.
I didn't find the non-linearity of the light bulb to be a significant issue. The warm
glow of the bulb more than made up for it.
that are harder to get. Of course you can make that circuit with the 2SJ28's
by simply reversing all the polarities.
The circuit presented above is likely to have some issues. First off, the
Vgs of the part is usually in the range of -5 to -10 volts for 1 amp @ 20V Vds.
This puts you into several ohms value for the Source resistor, and will
seriously cut into the gain.
You can attach the negative side of the loudspeaker to the Source pin of
the VFET, and that will at least give you the gain back, if that's what you need.
I usually used a 300W light bulb for the load, which was about 22 ohms
in this kind of circuit, and it worked pretty well. Look at the Zen Lite for that.
I didn't find the non-linearity of the light bulb to be a significant issue. The warm
glow of the bulb more than made up for it.
Hi Nelson, good to hear from you. Im getting 2 pairs of 2SJ28s from circuitdiy - they have been out of the 2SK82's for a while.....so I am hoping to build the basic SIT amp circuit from just 1 x 2SJ28 per channel.
I have seen some Tokin 2SK182s & 2SK180s pop up on sites now and then, that seem to be genuine (new & used) but Im guessing they would need to be used standalone and not paired with the 2SJ28's - suitability & rank and all that.....
How about the Tokin THF-51S - would these be a good choice to build something, if one theoretically got their hands on some....?
I have seen some Tokin 2SK182s & 2SK180s pop up on sites now and then, that seem to be genuine (new & used) but Im guessing they would need to be used standalone and not paired with the 2SJ28's - suitability & rank and all that.....
How about the Tokin THF-51S - would these be a good choice to build something, if one theoretically got their hands on some....?
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I built the amp for my friend, it's use four VFET 2SJ28 with Circlotron topology (it's called VFETRON), the amp running with 23VDC at 1,2A bias. The sound is quite good.
Some images and hope all of you love it
.Some images and hope all of you love it
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