..... and PCB with one layer , not finished yet .....
Regards ,Alex
Alex... piece of ART, as usual
You are the man
Schematic updates with minor amendments.
Tube / fets at the input - either / or of course.
Cool thing is that sk117's GDS and bc550's BCE are in the same positions, so BJT version comes "automatically"
C8, C9, C12, C13 in OPS are optional (just in case).
Cheers,
Valery
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Ready to show you finished PCB of the amplifier . Some values of component could be wrong (not updated) ....
Regards ,Alex
Hi Alex,
Looks very cool. Just one question - is there some connection of GND on the right with the one on the left? I don't seem to find it...
Also - can you please do a favor and extend it for the full version with the tube?
It's pretty packed, I know, but it may be a bit bigger, also, in fact - local heatsinks are really required only for 2SA1381 / 2SC3503, cap multipliers (BD139/140) don't heat-up because of low voltage drop - can save some space.Thanks again!
Cheers,
Valery
Initially designed for +/- 70V DC, it will easily work at lower voltages.
Going higher is not recommended, as we are already close to those Lat-FETs' SOA limits.
Also note, that rather high VAS quiescent current is required, as this OPS has got no buffer (otherwise some EF is required for driving FETs' input capacitance properly).
Cheers,
Valery
vzaichenko
That is pice a very good work !!
I am looking forward Yours listening impressions.
I am just wondering if 680R resistors R10 and R16 in DD stge (two LTP's) can be replaced with jumpers ?
The version from post #14 with BJT transistors was sounding very neutral, no sound signature like I am just wondering how latFET's and this super-duper-nice looking VAS will sing in the real life.
One other question, what supply is required for the tubes at the front stage ?? I have 0 eqperience with tubes.
Thanks
Peter
That is pice a very good work !!
I am looking forward Yours listening impressions.
I am just wondering if 680R resistors R10 and R16 in DD stge (two LTP's) can be replaced with jumpers ?
The version from post #14 with BJT transistors was sounding very neutral, no sound signature like I am just wondering how latFET's and this super-duper-nice looking VAS will sing in the real life.
One other question, what supply is required for the tubes at the front stage ?? I have 0 eqperience with tubes.
Thanks
Peter
Hi Peter,
R10, R16 can actually be replaced with the jumpers, however I keep them there just to minimize Early effect influence (though it's not significant with only 1V drop on these resistors).
This topology is actually designed to be rather neutral - high loop gain ensures that what you hear - is mostly NFB network
In case you'd like to hear a clear "tubish" signature - look at this one >HERE< - all the voltage gain is purely done by tubes, plus no global NFB loop at all I tested it with 3-pairs HEX-FET OPS at optimum bias - sounds like a good tube amp.
In this particular design, the only additional supply is heating - 6.3V AC. All the rest is taken from the circuit (12AU7 is capable to work well at rather low anode voltage).
Cheers,
Valery
R10, R16 can actually be replaced with the jumpers, however I keep them there just to minimize Early effect influence (though it's not significant with only 1V drop on these resistors).
This topology is actually designed to be rather neutral - high loop gain ensures that what you hear - is mostly NFB network
In case you'd like to hear a clear "tubish" signature - look at this one >HERE< - all the voltage gain is purely done by tubes, plus no global NFB loop at all
I tested it with 3-pairs HEX-FET OPS at optimum bias - sounds like a good tube amp.In this particular design, the only additional supply is heating - 6.3V AC. All the rest is taken from the circuit (12AU7 is capable to work well at rather low anode voltage).
Cheers,
Valery