My simple class a approach

[jerluwoo]

Most who look at the schematic will see right away that this arrangement has been used with tubes for quite some time.It is very simple with no global nfb, it uses only local feedback in the first voltage gain stage then feeds a phasesplitter for the push pull output. Will build it soon and pass on the word. Under sim i get a nice 10 watts into 8 ohm with a sensitivity of 3volts so a preamp is a must for full output.

[davidallancole]

Just trying to teach us some basic knowledge?
Do you like it?
Does it sound good?

[sawreyrw]

jerluwoo,

This circuit will have a large current through the ouput stage as both transistor will conduct at the same time. This will give you high power dissapation in those transistors.

Rick

[jerluwoo]

Yes about 2 amps idle current so of course I will put a couple in parrallel for the output when I build. This isnt any larger of a bias than any other class a I've seen in the same power range.

[lndm]

Yes, I'm not averse to a couple of amps through an output stage. Of course, with that supply rail you'll need a good heatsink.

[Leolabs]

Just like the old days' power amp.

[tschrama]

Be carefull, I am afraid your circuit wont work..

This input stage looks fine. Allthough it is not obvious, the input impedance is only 12K or about due to the feedback arangement of the two 100K resistors. Besides that the lonely 2n3904 will have to cary 13mA @15Vce = dissipate 200mW.. I only guess but won't it will get warm... wihile it's only rate at 40V, you are running it from a 50Volt supply...

Your output stage is all wrong. You cann't just make a BJT version out of a tube circuit...The output transistor won't be working together in push-pull like this ..This kind of phase splitter /bias arangement is just wrong..You got to look better at your spice programm.
Besides..you're idle current is complete depended on the output BJT current gain.. running of 50Volt at 1A they will get very hot and you'll have a hard time stabilizing the current..

But I do know a good old 4 transistor amplifier design... it's calles the John Linsely Hood 10W Class A amplifier.... scale it up to 50Volts if you need to .. you'll have a great amplifier..

goodluck!

[destroyer X]

A nice idea.... very interesting, and in special a much better product than i was expecting as in your personal informations i could read only Blah, Blah and Blah.

I think you are much more than those things you are trying to make us imagine about you.

regards,

Carlos

[darkfenriz]

I agree with tschrama
check Alex Nikitin's N-channel configuration for better output stage solution.

[jerluwoo]

I couldn't agree more with you on the JLH amps as I have built a stereo pair and love them. It is true that the output isnt exactly push pull but rather more like single ended with a varying ccs load. Resistor values for the phase splitter outputs will have to be determined by measured transistor gain to equalize the current at each emitter of the output trans.

Thanks so much for kind words Destroyer I always enjoy reading your posts. As for my personal info I'm mainly just a music junky that has toyed with stereos most his life. The only background I have in electronics was a rather poor 2 year course in electronics repair at the local vocational school. I find building simple circuits and testing and toying with them great fun, who cares if those cheap ratshack transistors go to pot.