Sons of Vhex ver.1.2 2sk146GR
Another surprice.
Picture 1 version with unmatched 2sk117
Picture 2 version with dual fet
Another surprice.
Picture 1 version with unmatched 2sk117
Picture 2 version with dual fet
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Better overall DC balance leads to lower distortion, especially below 1KHz.
Interesting result 🙂 One more proof that matching really makes sense, especially in the input LTP.
The other interesting find is that matching input fet ONLY is enough for 0V d.c offset IN THE MIDDLE OF TRIMMER.
I've been doing a quick match with a cheap meter for all the VHex input transistors. I rarely need to adjust DC offset at all. They all seem to run nicely within 3mV.
i'm guessing the 2sk146 having a lot more transconductance at the operating current probably helps the distortion too.
Folded cascode is helping mitigate distortion increase as frequency increases, in spite of much larger capacitance of 2sk146. It's a large geometry part, famous for large gain, very low noise and high cost, when you can even find them.
🙂
mlloyd1
Folded cascode is helping mitigate distortion increase as frequency increases, in spite of much larger capacitance of 2sk146. It's a large geometry part, famous for large gain, very low noise and high cost, when you can even find them.
🙂
mlloyd1
Yes - this is cool.
It's a pity that many good pairs are not manufactured any more.
2SK389 for example.
Do you mean ARTA STEPS at the higher amplitudes,or the rise time measurements at a higher level?
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I actually mean this kind of picture for the rise/fall time. If you can see it at higher amplitude - like 50Vpp or so - you will get more precise measurement.
Look at your 20KHz square wave - it makes around 35V in less than 1uS.
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Do you not think the lsk389 is not equivalent? and now they offer dual p channel lsj689 to go along with lsk489, expensive but available.
Bob Cordell did a talk, (utube video avail) at Burning Amp on his app using a symetrical push pull IPS & VAS... lateral mos ops, so many designs, joining Terry's club 🙂
Ah! You're right - I should try these ones.
So far we're using 2SK246/2SJ103 for symmetric IPS, but they are also getting hard find.
Sons of Vhex ver.1.2 2sk146GR
Today Sons tested using capacitance multiplier for input and vas stage but i can't see any further improvement.
Today Sons tested using capacitance multiplier for input and vas stage but i can't see any further improvement.
PSRR is good enough
It's like trying to zip a jpeg - it doesn't compress any more 😛
Terry,look these pictures.
It is from a commercial amplifier to be compared with the sons of vhex
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