I'm surprising myself - having read Michael's original Luminaria article I think I'm starting to understand this a little!
I know Michael included an optional buffer stage and a volume control on the output to mitigate the high capacitance of the 2SK82 (2500pF). The 2SK60 datasheet I've seen states that it's input capacitance is just 190pF - assuming I'm reading that correctly does it imply that the need for the buffer and output-side volume control is somewhat negated?
I know Michael included an optional buffer stage and a volume control on the output to mitigate the high capacitance of the 2SK82 (2500pF). The 2SK60 datasheet I've seen states that it's input capacitance is just 190pF - assuming I'm reading that correctly does it imply that the need for the buffer and output-side volume control is somewhat negated?
Rumor has it that the 2SK60/2SJ18 (single die) are exactly half a 2SK82/2SJ28 (twin die). The electrical data suggests the same. 2SK60 capacitances should be about half of the 2SK80 iirc.
The attached pics show the internals of a 2SK82 and a 2SJ18 (Not my doing!).
The attached pics show the internals of a 2SK82 and a 2SJ18 (Not my doing!).
Attachments
I was referencing datasheets rather than rumour, however, I suspect that there will be rather more to it than simpling saying one transistor junction in the device instead of two means half the capacitance.
I finished some testing of the 2SK60 the rank is R56.
1. Work piont,VB+=120V,VD=112V,Vgs=26.32V,Chock Load,L=26H(DCR=0.713K),Source Resistor=4.1K
2. THD 0.0876@Vout=1.058Vrms,THD=0.431%@Vout=5.291Vrms,THD=0.862%@Vout=10.56Vrms,THD=1.291%@15.84Vrms,THD=1.71%@21.12Vrms
3. GAIN=14.4db(5.3)
The performance is really good and thanks Mike.I also have listen this preamp,the sound is my cup of tea. Fantastic!!!
attached test some data.
1. Work piont,VB+=120V,VD=112V,Vgs=26.32V,Chock Load,L=26H(DCR=0.713K),Source Resistor=4.1K
2. THD 0.0876@Vout=1.058Vrms,THD=0.431%@Vout=5.291Vrms,THD=0.862%@Vout=10.56Vrms,THD=1.291%@15.84Vrms,THD=1.71%@21.12Vrms
3. GAIN=14.4db(5.3)
The performance is really good and thanks Mike.I also have listen this preamp,the sound is my cup of tea. Fantastic!!!
attached test some data.
Attachments
The frequency response is input 200mv rms.For the FFT picture please ignore the yellow line due to this is the channel B,but I do not hidden it.
Thanks for the info.
I have a resistor loaded Luminaria that I built years ago and I am still enjoying it.
However I have four KP926B that I had been playing with, but that is on hold until I finish my single ended choke loaded 2SJ28 common drain amplifier. Then back to the KP926B which I will hopefully make into a high voltage output gain stage for my follower amplifiers.
I don't want to mess with my Luminaria by choke loading it for higher voltage output. Choke loading would change (decrease) the harmonics, but I like its sound as-is when combined with my amplifiers.
I have a resistor loaded Luminaria that I built years ago and I am still enjoying it.
However I have four KP926B that I had been playing with, but that is on hold until I finish my single ended choke loaded 2SJ28 common drain amplifier. Then back to the KP926B which I will hopefully make into a high voltage output gain stage for my follower amplifiers.
I don't want to mess with my Luminaria by choke loading it for higher voltage output. Choke loading would change (decrease) the harmonics, but I like its sound as-is when combined with my amplifiers.
This looks promising, thanks @Adams_Leo.
I've seen several references to 'rankings' of these Sony VFets - can anyone point me at some information about this - a quick google search didn't reveal anything obvious?
These are my pair of 2SK60s that I bought from Pras1170 - she seems to have a good reputation so I assume they're the real thing but is JA-33 good, bad or indifferent?
I've seen several references to 'rankings' of these Sony VFets - can anyone point me at some information about this - a quick google search didn't reveal anything obvious?
These are my pair of 2SK60s that I bought from Pras1170 - she seems to have a good reputation so I assume they're the real thing but is JA-33 good, bad or indifferent?
Ah, got it, so I need to measure them to get the ranking. I'm feeling a little stupid for asking now but at least I am now better informed.
for the rank,I have only 2pcs 2sk82,but different rank,one is KD33 and another one is JD33.
1. Luminaria schematic,same power and same compoents,the KD33 gain is 8.2times,but JD33 only 6.1 times.
2. the KD33 0.0652% THD+A @1V output,but the JD33 more higher,0.761% @1V.
3. Like Zen Mod said,the vgs is different and current is different.but anyway you can find it sweep splot.
1. Luminaria schematic,same power and same compoents,the KD33 gain is 8.2times,but JD33 only 6.1 times.
2. the KD33 0.0652% THD+A @1V output,but the JD33 more higher,0.761% @1V.
3. Like Zen Mod said,the vgs is different and current is different.but anyway you can find it sweep splot.
The KP926 is excellent part. I mean using to drive the follower output stage.
1. Really high output voltage swing. 32V rms output,but the THD+A only 0.766% and 40.47V rms output,THD+A at 1.984%.
2. Enough gain,very easy to get more than 8.3 times gain.
3. Very low distortion,THD+A 0.0158% @1V rms output and most of is the second harmonic.
4. Ciss is high,Vladimir get from Russia datasheet show 2500pf,but if we add Mikes's org buffer is enought.the buffer output impedance only 33.3 ohm.this is enough for the widely frequency response.
attached two test curve,one is the thd+a at 32V output and another one is the frequency response.the source impedance is set a 30 Ohm.
1. Really high output voltage swing. 32V rms output,but the THD+A only 0.766% and 40.47V rms output,THD+A at 1.984%.
2. Enough gain,very easy to get more than 8.3 times gain.
3. Very low distortion,THD+A 0.0158% @1V rms output and most of is the second harmonic.
4. Ciss is high,Vladimir get from Russia datasheet show 2500pf,but if we add Mikes's org buffer is enought.the buffer output impedance only 33.3 ohm.this is enough for the widely frequency response.
attached two test curve,one is the thd+a at 32V output and another one is the frequency response.the source impedance is set a 30 Ohm.
Attachments
One very bad thing about this KP926 is that it is too discrete and it is very difficult to find a pair. good luck