The next DIY project - what is it?
- Thread starter mr_phil
- Start date
martin clark
pinko bodger
The JLH Class A design is a classic for good reason - it does sound good. Simple, too, with only four transistors in its original design. Tremendous bang-for-buck. I'd like to try a Hirage 'Le monstre' too for similar reasons.
I've not tried any of the various Pass designs but there are loads to choose from.
I've not tried any of the various Pass designs but there are loads to choose from.
I was thinking of a scaled back version of this i.e 1/10 of the power, but with regulated/gyratored front end psu
http://www.amplimos.it/images/krell_ksa-50_mk2_original_schematic_2.jpg
Although I like the idea of minimal component count style amps, such amps can often be fussy of load in terms of impedance. Would be cool to make a giant killer like this I think.
Ian
http://www.amplimos.it/images/krell_ksa-50_mk2_original_schematic_2.jpg
Although I like the idea of minimal component count style amps, such amps can often be fussy of load in terms of impedance. Would be cool to make a giant killer like this I think.
Ian
I just did a quick capture of the voltage going to my Kensai at an average background listening level. peaks around 1.5V. The Kensai has a minimum impedance of 6 Ohms so that is about 0.5watts.
Funny though, because I have tried some low power amps like the Project 'Box' amp and they sound dynamically constrained. Perhaps an amp which is power limited by the output devices rather than the power supply would sound a lot better than one limited by the PSU.
Funny though, because I have tried some low power amps like the Project 'Box' amp and they sound dynamically constrained. Perhaps an amp which is power limited by the output devices rather than the power supply would sound a lot better than one limited by the PSU.
I would avoid having intentional "limits" in either output transistor or PSU.
So, I would think go for supplies between 15 to 20v, but with plenty of current capability, say 200VA per channel. Maybe use medium sized output devices, T0220 size max, with plenty of hfe, and bandwidth. Although care would be required to avoid stability problems. Perhaps try multiple output transistors.
The "limit" would be the gain, which would be lower than normal, by the feedback. This would mean if you had a high gain pre amp you would be able to get more than the required few watts but if you were building this that would not be your aim.
Also avoid unnecessarily limiting the bandwidth at either end.
Ian
I would be looking at 15W max to give a peak output of 105dB with my mids ,have thought about a JLH type amp with separate front end supply ala Voyager there used to be various boards out there.
Check out the ESP site lots of class A stuff there
There is also the class A website itself which covers the history and later versions of the JLH amp
neiljadman
Senior Member
I need to get off my *rs*, contact PD again - after the success of the B4 I still hanker after the PD PowerAmp, the circuits are all drawn up and ready to prototype and still to resolve the phono stage too....