Has anyone actually buildt an amp based on the hawksford cascode VA-stage? And if so, how did it sound?
(J10 REDUCTION OF TRANSISTOR SLOPE DISTORTION IN LARGE SIGNAL AMPLIFIERS, M.O.J. Hawksford, JAES, vol.36, no.4, pp.213-222, April 1988).
I got curious and had to try it out in the simulator, and the simulator showed exactly the same distortion numbers as measured in the hawksford publication. Well, I couldn`t just sit and stare at the curcuit (wich I didn`t come up with), so I did some modifications. For better or worse is yet to see...
(Everything I come up with it simulations as usual, since I haven`t got any equipment and components...yet -see signature
. Please don`t consider me an idiot for that reason, eh)
I changed the input (CB), into a diff stage, recalculated the currents, and got even less distortion (0.006%). I probably could have used another topo for the output, but I just wanted to see if my circuit would work.
The circuit uses 50V rails, and delivers 100W@8 ohm.
Distortion 1kHz@100Wrms is 0.084%.
The circuit is shown with single ended input, but 100% balanced input is possible (of course)
Put additional 560 ohm resistors in the right legs of the diff-stage, with additional VA and OPS, and you will have a balanced output too.
I wonder if this thing would work, and if so, would this sound better than an amp with voltage feedback?
(J10 REDUCTION OF TRANSISTOR SLOPE DISTORTION IN LARGE SIGNAL AMPLIFIERS, M.O.J. Hawksford, JAES, vol.36, no.4, pp.213-222, April 1988).
I got curious and had to try it out in the simulator, and the simulator showed exactly the same distortion numbers as measured in the hawksford publication. Well, I couldn`t just sit and stare at the curcuit (wich I didn`t come up with), so I did some modifications. For better or worse is yet to see...
(Everything I come up with it simulations as usual, since I haven`t got any equipment and components...yet -see signature
. Please don`t consider me an idiot for that reason, eh)I changed the input (CB), into a diff stage, recalculated the currents, and got even less distortion (0.006%). I probably could have used another topo for the output, but I just wanted to see if my circuit would work.
The circuit uses 50V rails, and delivers 100W@8 ohm.
Distortion 1kHz@100Wrms is 0.084%.
The circuit is shown with single ended input, but 100% balanced input is possible (of course)
Put additional 560 ohm resistors in the right legs of the diff-stage, with additional VA and OPS, and you will have a balanced output too.
I wonder if this thing would work, and if so, would this sound better than an amp with voltage feedback?
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Hi,
just want to ask if you are going to use exactely those components stated in your schematic, in that case I would look for more linear output transistors than those outdated MJ transistors, I think so at least as the circuit is non FB.
I would suggest for instance 2SA1943/2SC5200 which are one of the best BJT's around at also unbeatable prices.
Cheers Michael
just want to ask if you are going to use exactely those components stated in your schematic, in that case I would look for more linear output transistors than those outdated MJ transistors, I think so at least as the circuit is non FB.
I would suggest for instance 2SA1943/2SC5200 which are one of the best BJT's around at also unbeatable prices.
Cheers Michael
Hej Panzerlord,
you can buy them at: Porfusion PLC
They are O-grade, meaning highest hfe class for these.
Cheers Michael
you can buy them at: Porfusion PLC
They are O-grade, meaning highest hfe class for these.
Cheers Michael
M.O.J. Hawksford, JAES, has authored some of the finest
papers on amp design, i have run them through extended
simulation and the results i have had are in agreement with
the papers, however i have extended his work with much
better understanding of the interrelational mechanisms of
which they are defined (classified)
regards
papers on amp design, i have run them through extended
simulation and the results i have had are in agreement with
the papers, however i have extended his work with much
better understanding of the interrelational mechanisms of
which they are defined (classified)
regards
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