ExtremA, class-A strikes back?

[SSassen]

Glen,

Not entirely. Unless driven from a differential-output preamp, one of the inputs will need to be tied to ground, thus referencing the other input to ground.

Well yes, if you use this amplifier in a single ended configuration. It however is designed for and targeted at the far less problematic balanced operation as is common in studios and with more expensive equipment. As really, whoever came up with the idea of using GND as a signal reference and a means of equalizing chassis potential probably had an off-day at the office.

Best regards,

Sander Sassen
http://www.hardwareanalysis.com

[SSassen]

Leolabs,

Do the small signal BJTs have to be matched????

As mentioned in the article, only the input pair, which are BC550C transistors. You could go through the trouble of matching all of them, but it will yield just a small benefit as per the comments about the distortion plots. Mostly you'll see a reduction in initial offset, but that's compensated for by setting the DC offset trimpot, hence a non-issue.

Best regards,

Sander Sassen
http://www.hardwareanalysis.com

[EUVL]

Quote :

"this is NOT a project for the novice builder"

http://www.diyaudio.com/forums/showt...06#post1142106

Quote :

"the most Hi-End project"

http://www.diyaudio.com/forums/showt...68#post1142668


Sorry for my poor English, Meneer Sassen, but I do not consider the two description as listed above contradictory.
And I couldn't quite find the word costly or expensive anywhere, could you ?

> you must've fluked math class at school

Oh yes I did, but I still somehow managed straight A's for A Level, 1st honour at University, Ph.D. in Precision Engineering, some 40 patents worldwide. Just lucky I guess.

> So my question to you would be, what have you contributed to this community lately?

Not too long ago, a harmless little circuit.
PCB layout also published, just by pure chance.

http://www.diyaudio.com/forums/showt...42#post1133142


Patrick

[SSassen]

Patrick,

but I do not consider the two description contradictory.

I'm sorry, you lost me, what are you referring to exactly?

Best regards,

Sander Sassen
http://www.hardwareanalysis.com

[bear]

Hi,

Read through ur article and looked at the schematic... very interesting and nice design. The results (graphs) look quite impressive!

Was wondering, have you measured the slew rate, how about the power bandwidth?

Also, wondering what a square wave looks like on a fast scope with a highish speed squarewave input?

How about stability into relatively capacitive loads?

In terms of design, to what do you attribute the rather low distortion figures? I see extensive use of current mirrors throughout the input stages... and asking from a position of admitted ignorance here, is this design idea used elsewhere (like an opamp circuit?)

Oh yeah, what's the DF look like?
No benefit to paralleled outpoot devices in your view?

Do we get to see a jpeg of a real world implementation??

Nice work!

_-_-bear

[peranders]

Originally posted by EUVL
At 75 Euros for 2 PCBs, it is about the most Hi-End project by quite a big margin.


Patrick

The price is very dependent of how many pcb's you dare to order and of course the desired quality.

[peranders]

Originally posted by SSassen
Patrick,
I'm sorry, you lost me, what are you referring to exactly?

Best regards,

Sander Sassen
http://www.hardwareanalysis.com

I'm also lost, I'm afraid.

[bogdan_borko]

1. too many gain stages, too many transistors,too many parts....
2. what`s the output power working in pure class a?
3.Isn`t that heatsing small for class a?
4.one bjt output pair?
5.most hi end? - Don`t get me wrong, I didn`t hear your amp and maybe the sound is great but... "most hi-end" seems funy to me...

cheers!

[peranders]

Originally posted by bogdan_borko
1. too many gain stages, too many transistors,too many parts....

... but the important thing is the end result, not how to reach it. I have great confidence in Bruno Putzeys. I'm sure that he has put some thought into the design. I'm also sure it's possible to reduce the amount of parts but this isn't a commercial research project. It's a crazy idea made real.

[GK]

Originally posted by SSassen
Glen,
Well yes, if you use this amplifier in a single ended configuration. It however is designed for and targeted at the far less problematic balanced operation as is common in studios and with more expensive equipment. As really, whoever came up with the idea of using GND as a signal reference and a means of equalizing chassis potential probably had an off-day at the office.

Best regards,

Sander Sassen
http://www.hardwareanalysis.com

OK, but you are promoting the design here on a DIY board. I'd say most people here drive their HiFi amplifiers from non-balanced signal sources. That goes for those who have built themselves mega-buck amplifiers too.

BTW, I'm not trying the criticise the design. Driven either way, as far as I can see, it will still work very well indeed.

Cheers,
Glen