Hello
I'm wondering if I should try out the benefits of class A operation. The thing is, if I decide to keep what I build, it needs to be medium powered and moderately efficient, which implies P-P operation.
One special case is Douglas Self's class G design, of which I have heard that it's possible to run the lower supply voltage in class A.
So basically I have two and a half questions:
1. Are there any nice and small passively cooled class A P-P designs with +/-16 to 25 V power supplies?
2. Has anyone built the Self's class G amplifier, and then run the smaller supply in class A?
I'm wondering if I should try out the benefits of class A operation. The thing is, if I decide to keep what I build, it needs to be medium powered and moderately efficient, which implies P-P operation.
One special case is Douglas Self's class G design, of which I have heard that it's possible to run the lower supply voltage in class A.
So basically I have two and a half questions:
1. Are there any nice and small passively cooled class A P-P designs with +/-16 to 25 V power supplies?
2. Has anyone built the Self's class G amplifier, and then run the smaller supply in class A?
Preferably something less powerful, because I'd use it also during our moderately hot summers and I have no air conditioning. The A40 has +/-32 V rails. Even getting down to +/-25V would be nice.
I've heard that the Self's class G amplifier has the advantage that one can switch easily between A and AB classes for the lower supply.
The A40's peak output is calculated as 25.3 V into 8 Ω, which is 3.16 A (the bias times two), also 80 W (for 100 W dissipation per channel). Now 25 V rails would maybe give 18 V peak output, which is 2.25 A into 8 Ω and therefore 40 W. Requiring a 1.2 A bias, resulting in 60 W dissipation per channel.
With Self's class G amplifier I could use +/-21 V from a +/-15 V transformer and have the other rail for peak needs.
Have a look at the Hiraga 20w amplifier, it is very good and can be build using very cheap and readily available parts, on this site or on the 'class a amplifier site': The Class-A Amplifier Site - Hiraga 20W Class-A Bad english translation, but the original french article is also available there.
You could try this one
Hifisonix kx-Amplifier
PCB’s are available (double sided, THP and gold plated with silk screen).
There’s also it’s earlier brother here
Ovation sx-Amplifier: A High Performance 15 W Class A Current Feedback Amplifier
The kx-Amp is a better performer spec wise. It’s my go to amp for classical and jazz.
Also with high quality PCB’s available.
Another good one is the JLH but you will have to hunt around for your own PCB’s
JLH 10 Watt Class A Amplifier
Hifisonix kx-Amplifier
PCB’s are available (double sided, THP and gold plated with silk screen).
There’s also it’s earlier brother here
Ovation sx-Amplifier: A High Performance 15 W Class A Current Feedback Amplifier
The kx-Amp is a better performer spec wise. It’s my go to amp for classical and jazz.
Also with high quality PCB’s available.
Another good one is the JLH but you will have to hunt around for your own PCB’s
JLH 10 Watt Class A Amplifier