So the buffer I showed here
http://www.diyaudio.com/forums/pass-labs/269379-live-lab-hangout-1-1-posted-50.html#post4333515
seems to work fine. The voltages in real follow the values Spice showed.
Hearing with the buffers all softness was gone, shocking clarity…. so I took immediately the screwdriver und tuned in for more k2…..
you know we are never content…. now too dull.
I managed to find a position that combines both the clarity and the softness.
Heating up these values shift and I had to rearrange the value after half hour.
That is the real "sweet spot" for me, the percussive elements in the same line with the melodic elements.
And that is so easy with this SIT amps, you dial simply the bias voltage until you get the right mix of k2 and k3 for your taste with your speakers.
Next days I will hear Mikes depletion Mosfet buffer in comparison with the shown J-Fet buffer.
In SIT-1 and 2 Nelson uses a J-Fet buffer as he writes in the owners manual,
maybe the J-Fet sweetness against the Mosfet body emphasis…..?
I will see.
http://www.diyaudio.com/forums/pass-labs/269379-live-lab-hangout-1-1-posted-50.html#post4333515
seems to work fine. The voltages in real follow the values Spice showed.
Hearing with the buffers all softness was gone, shocking clarity…. so I took immediately the screwdriver und tuned in for more k2…..
you know we are never content…. now too dull.
I managed to find a position that combines both the clarity and the softness.
Heating up these values shift and I had to rearrange the value after half hour.
That is the real "sweet spot" for me, the percussive elements in the same line with the melodic elements.
And that is so easy with this SIT amps, you dial simply the bias voltage until you get the right mix of k2 and k3 for your taste with your speakers.
Next days I will hear Mikes depletion Mosfet buffer in comparison with the shown J-Fet buffer.
In SIT-1 and 2 Nelson uses a J-Fet buffer as he writes in the owners manual,
maybe the J-Fet sweetness against the Mosfet body emphasis…..?
I will see.
Hello all. Using upgrade curve tracer of Michael I have measure all THF51 I own (a lot of dady and some mine) and some 2sk182es (thanks Tim) near operation point (3 or 4 A). I have found there is a lot of variablility between them. I printed all curves and selected pairs. From these pairs I have used one for mount in resistor loaded amp. Well, using spectrum analyzer I have get this pair have 0.8% of THD at 1Wrms and 8ohm load. And both channels working similarly.
But I have select a pair between a lot, using its curves near real operation point. And curves shown all devices not working similarly, and with some we can reach 10Wrms with lower THD, but this it is not possible with others (lines are not equally spaced and parallel).
All of us have some pieces, but it is possible not have good pairs.
It might be a good idea share devices and search good pairs for all of us.
Any comment?
But I have select a pair between a lot, using its curves near real operation point. And curves shown all devices not working similarly, and with some we can reach 10Wrms with lower THD, but this it is not possible with others (lines are not equally spaced and parallel).
All of us have some pieces, but it is possible not have good pairs.
It might be a good idea share devices and search good pairs for all of us.
Any comment?
Attachments
Sharing and swapping is a good idea. I don't have THF-51S, but I have 3 pieces of 2SK182ES that are available for swapping, with their curves attached. As I've decided that for my target power level, 2SK180 is more suitable for me, so if anyone having spare 2SK180s is interested in a swap, kindly send me a PM.
BTW, two of these 182ES are matching particularly well (see the last graph).
Attachments
It's easy to get excited by the curves and such. I have ended up testing the
parts in the target circuit, adjusting only the Vds against distortion at a given
wattage (1 watt usually). I also note gain, Vgs, noise, Vds and gate current.
Assuming that Vds and Vgs aren't out of bounds and that the Gate current
and noise are sufficiently low, they are then matched by Gain.
The result is very consistent matching of performance, that is to say the
distortion curves are very similar.
As I said, the adjustment parameter is Vgs for a target distortion number.
parts in the target circuit, adjusting only the Vds against distortion at a given
wattage (1 watt usually). I also note gain, Vgs, noise, Vds and gate current.
Assuming that Vds and Vgs aren't out of bounds and that the Gate current
and noise are sufficiently low, they are then matched by Gain.
The result is very consistent matching of performance, that is to say the
distortion curves are very similar.
As I said, the adjustment parameter is Vgs for a target distortion number.
I have ended up testing the parts in the target circuit....
@ Nelson Pass
Very interesting this sit's are 2SK180 or others ?
What is target circuit for this test ?
Dozen on my bench untested
Best regards
Attachments
Last edited:
100 subscribers today! Yay!
Congratulations, if memory serves me well, I believe I was among the first 30
.BTW, LuminAria work in progress .... it's using TL431 voltage reference instead of the original self bias, but will need to wait a month for the back-ordered components to see if it'll work.
Attachments
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