The OPS of VSSA is lateral mosfet, then VAS current must be high to drive gate capacitance of lateral mosfet.
The OPS of CFA-X is triple emitter follower then VAS current can be low.
Well in this case I intend to drive the Slewmonster OPS with this VSSA front end. Do you see a problem?
I feel it will work just fine. The changes bring the VSSA VAS current down to the 4-5mA level OS intended the output stage to run with. When setting it up you are looking for ~200mV across R13 or R14 (assuming 47Ω, Ohm's law for other values of R) while tuning for low offset. Seems to be working fine for me with my current testing at +/- 45V.
Even lower VAS I ...
One of the amps that inspired this "slewmaster" endeavor
only uses TO-92 VAS devices set at 3 ma.
In a more miniaturized IPS , the VAS could also be "face to face"
devices like the IP pair. (MPSA92/42 for example)
I used the TO-126 setup for the "overkill" factor.
The OPS can easily be ported to a reduced (or increased) VAS I
by proportionately changing the Vbe resistor values. I chose
4-5ma because the HK680's VAS operates at this current.
BTW - the original amp that made me pursue the EF3 was
my little Z-5900 "survivor" (Sansui). 😎
OS
One of the amps that inspired this "slewmaster" endeavor
only uses TO-92 VAS devices set at 3 ma.
In a more miniaturized IPS , the VAS could also be "face to face"
devices like the IP pair. (MPSA92/42 for example)
I used the TO-126 setup for the "overkill" factor.
The OPS can easily be ported to a reduced (or increased) VAS I
by proportionately changing the Vbe resistor values. I chose
4-5ma because the HK680's VAS operates at this current.
BTW - the original amp that made me pursue the EF3 was
my little Z-5900 "survivor" (Sansui). 😎
OS
Driving the input of these IPS ? I don't see why not !
If it is unity gain - just a straight "shot" to the IPS input. If
it has gain , the IPS's gain can be reduced easily.
If that is a single tube circuit , a "spooky" sized (76 X102mm) PCB
could fit CFA-X + the tube/passives ... 🙂
OS
It's a single tube designed for the Single Ended Sewa amp which has no gain.Will try to find the link.
http://www.diyaudio.com/forums/tubes-valves/85952-tube-pre-amplifier-sewa-7-watt-classa-mosfet.html
http://www.diyaudio.com/forums/tubes-valves/85952-tube-pre-amplifier-sewa-7-watt-classa-mosfet.html
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I read it. It's just a follower that happens to be a tube. Coupled to the "X"
or the simple (v1.1) "symasui" , either could be on a 76 X 100mm IPS.
The only consideration would be to isolate the HV B+ on a remote area
of the layout ... that's all. As far as actual operation , it would be no
different than buffering the input with a op-amp follower,filter , or invertor.
I actually intend to buffer one of these IPS's with a variable LP filter/variable
phase buffer to integrate into my sub.
OS
5670 and ecc88 are both 2 X triodes ... 5670 has both lower plate
V and I.
How low can they run (voltage) ?
I could most likely adapt after reading some more .... also
the HV electro's and decoupling caps will take up more real-estate.
Quite frankly , this tube buffer would be better as a separate module.
Considering the B+ / large caps (and a large tube - as compared to SS).
PS - I'm sure this would work , a couple "Badger builders" used tube
preamp/buffers ... no issue.
OS
Hi Jason, I'd like to join the party and grab a pair of output boards and VSSA boards to graft onto the front end. Let me know $ shipped to Australia.
That will keep me interested until you lay out / order the Wolverine boards 😉. Will be interesting to see how VSSA performs with 5pr of EF3 on 70V rails
That will keep me interested until you lay out / order the Wolverine boards 😉. Will be interesting to see how VSSA performs with 5pr of EF3 on 70V rails
spooky???
Did anyone tested spooky?
Does it work fine?
Worths to try it?
Any problem with it?
I'd like to try it.
Did anyone tested spooky?
Does it work fine?
Worths to try it?
Any problem with it?
I'd like to try it.
Here's hoping we see some of OS's refinements to the CFA-X from the 'other' thread here soon (the CFA-XH)... I think I'd jump on that right away! A giant VSSA 😎.
Sorry that I don't know much about it; however, it runs from a simple capmulti at +-55vdc split rail on my buffer. . . approximately similar voltages to your amplifiers. Good bass, non-rough treble (not dull either, just not altered), well, really transparent except for perhaps louder low bass. Also long lasting (has run nearly 24/7 for years). Not significantly different from IRF710, except the mos worked better with a little gain and the tube worked easily as a buffer.
