after exchanging lengthy PM's with Rafft regarding the subject matter, I decided to share this to those interested to tread the path of class A amplification, applicable in vacuum tubes(Common in single ended triode SET) & solid state (JLH, Hiraga, Nelson Pass, Flavio DeLLepiane, Rod Elliot...etc). A short summary:
Selling point in class A:
Sonic Qualities- Typical of a class A amp, subjectively, they seem to approach nearly the warmness of tube amp while maintaining the dynamics & speed of the solid state.
Durability- provided with a generous heatsinking, they can last a very loooooooooooooooooong time
The setbacks:
Efficiency- only 25% goes to audio, 75% is wasted as heat, very inefficient indeed. My 5watts per channel Dellepianne amp use a heatsink for 200watts per channel class AB amp.
Power Supply- as a rule of thumb, a regulated series pass or a capacitance multiplier is a must plus a big heatsink for the power transistor. Unregulated B+ degrade sonic qualities considerably, introduce hum in the signal path that is quite irritating and "audiophiles" #2 in the hate list
the setbacks all translates to a builders " pain in the neck " owing to the extra space needed. But once you've heard it "sing" you'll surely forget the setbacks
Some old pics for the Dellepiane amp. I have also built the Hiraga & JLH, but after my wife complained about the unusual heat in the room & the unexplained sharp rise in electric consumption, I opted for Dellepiane, a flea power class A amp, but not an issue since i'm using a high efficiency loudspeaker 95dB typical, more than enough in a 4meters X 6meters room. idling at 700mA the heatsink can be touch w/o the "ouch", compared to JLH idling at 3.5A, is enough to cook an egg in the heatsink
I almost forgot the pix....
pardon the fuzzy celfone pix
driven by a tube pre-amp for that "warm & sweet sound"
a fellow E-lab member, honestly I have no idea what his thumbs up means, Probably he likes a shot of whiskey i gave him before listening to the amp
I'm looking forward to sir Rafft project pics being posted here, he is currently building his Dellepiane amp
here are some links about class A topology:
http://www.tcaas.btinternet.co.uk/http://redcircuits.com/Page80.htmhttp://sound.westhost.com/project10.htm
