GKlein - K12A facts & figures and ideas in Class A

[lineup]

Hi!

Anybody tried to build Glen Kleinschmidt new K12A amplifier?
Like K10A this is nice Class A amp with free schematics provide online.
See Glenn's stuff:
Glen Kleinschmidt's Electronic and Mechanical Stuff

dont let the 'Site Under Construction' fool you.
Anyhow, for a creative mind everything is constantly 'under construction'.
Only the very rigid, often older gentlemen, prefer to have 'no further construction' sign hangning on their door. Ideas ran out ...
Hello JC .. where are your new amplifier

GKlein mention his new amplifier breifly in a conversation with Bob Cordell:
http://www.diyaudio.com/forums/showt...31#post1773431

Any facts or figures, images and opinions are welcome.
Let's get together and find out some of the good qualities of K12A here


Regars
as always your - Lineup

[lineup]

some basic details:

Amplifier Module, image
http://users.picknowl.com.au/~glenk/K12A1.GIF

K10A
A hybrid 10W class A amplifier
with a 12AX7 twin triode input stage.

K12A
An
- ultra low distortion
- 12W Class A amplifier of a
- unique fully differential design incorporating
- transitional miller compensation around a
- triple emitter follower output stage.

Regulator Module for K12A
http://users.picknowl.com.au/~glenk/K12A4.GIF

[lineup]

Most welcome
if no other knows very much or can judge K12A
some words from the designer, Glen K.

thanks - i am waiting

[GK]

Oh gee, what else do you want me to say lineup?

[MJL21193]

That's a lot of transistors for 12 watts! My gracious!

I like the regulator though.

[GK]

So what? The designs linearity is an order of magnitude better than I've seen anyone else get from a basic complementary LTP topology.
The basic design can be scaled for just about any power. My latest (bridged) version clips at 120V peak into 2 ohms.

[MJL21193]

You've added a fair bit of complexity (and more than a few transistors) to have current mirrors on the front end.
What are the advantages? Do the advantages (if any) offset the additional complexity and cost?

[GK]

I've explained the advantages in terms of improved linearity and (double) slew rate in the circuit explanation on my website. The addition of the current mirrors only adds an additional (besides the current mirror transistors themselves) 2 transistors (the bipolar current source for biasing; Q3 and Q4).
The allegedly complex biasing circuits at the front is just something fancy I came up with that eliminates power-up thump by symmetrically ramping up all of the biasing currents on power-on as C4 charges.
The few extra diodes around the VAS makes sure the amplifier recovers from clipping cleanly (scope pic shown on the webpage).

What does a handful of to-92's cost?

[lineup]

Good question, and a good answer.
All Class A amplifier do not need to be oversimplified.
We have seen quite a few of them .. the THD shows they are too simple.

Also absolutely true, there are no cost reasnond adding some TO92.
And if we have a premade PCB it is hardly any extra work putting them in.

The big costs in single ens cllass A is transformer + box + cooling.

Your is a push-pull with maybe twice the EFFICIENCY.
Which wouldny make it more expensive to build.

[MJL21193]

The more I look at it, the more I like it.
From your website, I see you have a board layout for this - mind sending it to me? Gerbers are fine or pdf's of the layers is good (better) too.