70W Class A amp.

[shanx]

Originally Posted by ontoaba

I post it here:Its only need +50V for +/-45V outputs.


Hi Eric,
At least it is working.

Hi Ontoaba, Thanks for the link to you post. It is a very interesting design (further discussions to your Post..when I get a chance..)

Hi Eric, Looks like the mods on the soft start worked Now that the HVKs are happy...next step

[shanx]

Hi Eric, Did you try out the audio test file generator yet?

[ontoaba]

Originally Posted by shanx

Hi Ontoaba, Thanks for the link to you post. It is a very interesting design (further discussions to your Post..when I get a chance..)

Ok.

[shanx]

Originally Posted by AndrewT

we give a strong hint and rather than go and check from another source this one decides to argue.

On what basis does SE ClassA magically produce double the current sunk into the resistor or CCS load?

IMHO: Magic does not exist. It is an effect that is sometimes based on an aberration of perceptions and ,perhaps, a misassumption of what is in fact really happening. Another April Hint(!)

All kidding aside, the published design of the amp did not go into a lot of technical details, and having read the article (in my sometimes limited French) there were (many) issues which needed to be addressed to do a proper build. But I think the article was written towards more of a ''pastime'' hobbyist audience.. there is a bit more going on with the circuit that would be beyond the scope of explanation to their magazine readership. That is definitely NOT the case with diyAudio members!!(I say that with complete respect) as can be seen by the numerous suggestions and comments.

I had a chance to listen to the amp, and (even) at the reduced bias/power level the amp sounds very good (IMHO) and the active current sinks (LMs) do not seem to alter or colour the sound.
I think worth going to the next step of increasing the power level...time for a bigger transformer
That's all from me..I'll leave it to Eric to update everyone on the status and results

[Arick]

A little update,
After "making my own" 1Khz signal, thank you to the following programs.

1) "The Audio Test File Generator"
(Thank you Mr. Taylor)

2) Audacity: Free Audio Editor and Recorder
Audacity was used to cut and paste the 120 seconds signal until I had a 30 minutes version.
Then I burned a CD and Voila! my own home made signal generator!

So, biased at 1,82 Amps the amplifier gave the predicted +- 13 watts. Of course the next step is to increase the bias until we get to the famous 70W. But before I do I have to change my transformer because the one I have (been a recycled one) it is pretty much at the end of it's useful life! Also I will set the LM's as directed in the article because we think it is not only about smoke and mirrors. ShaneX believe there is a little devious trick used in this design to increase the bias in a "automatic" way. And since I have gone so far as making this puppy work, I might as well take the next step upward
Anyway I will keep you updated latter, as It will take a couple of week's until I get my hands on my new transformers.
Eric