Sons of VHex

OK, I have performed a few simulations. The jFETs are running at constant voltage (set by Vbe + 2 x LEDs) and virtually constant current (set by CCS), enforcing their operating conditions. 2SK209, 2SK170, BF862 are all showing very good performance.

BF862 is showing slightly higher transconductance and wider bandwidth than the others, resulting in the lowest 20KHz THD (0.003% 50W @ 8 ohm, 0.009% 90W @ 8 ohm).
 
That means with BF862 it could be a little bit better sounding amp- more Breth (airy)
and shininess in top end?
Juma has done a good choice, after homework, to use the BF.
My interest is more waked up.

BF862 is a good one no doubt, plus it's currently in production. However in the design with relatively high NFB loop gain, like this one, I'm not sure if you will hear the difference between, say, 2SK209 and BF862 in a proper blind A/B test.
You can try though, if you like - it would be interesting to know your impression.
 
i am hooked

[QUOTEBF862 is a good one no doubt, plus it's currently in production. However in the design with relatively high NFB loop gain, like this one, I'm not sure if you will hear the difference between, say, 2SK209 and BF862 in a proper blind A/B test.][/QUOTE]

Hi Val,
so i am hooked and must remitting other from bench and wait for Layout,
but will play too with Eagle- tp learn.

Regards. :rolleyes:
 
Layout

Progressing ;)

Single-sided, etching-friendly - as requested.
 

Attachments

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VHex+CP docs

OK, here we go. See attached.

Important note!
Do not connect GND1 and GND2 under the board.
GND1, GND2 and speaker return must be connected to PSU main ground with separate wires.

Let me know if you will have questions ;)

Cheers,
Valery

P.S. Version for BF862 will come soon.
 

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  • 00-VHex+CP-Sch-1.0.JPG
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  • 01-VHex+CP-PCB-BOTTOM-1.0.JPG
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  • 02-VHex+CP-PCB-TOP-1.0.JPG
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  • 03-VHex+CP-Sch-1.0.pdf
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They will work as is, but it's likely only a couple minutes work to change the hole size. Pick a pad and select all similar in the drop down window. All pad of the same pattern will change with one alteration. You've only got a few pad sizes there.

Edit- This doesn't work as well in the latest Diptrace.
 
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