New member steps into the lions' den ..... (Pass v. Ayre ?)

Hello,
this is my first post at diyAudio.com so be gentle with me ...

Has anyone compared Aleph and Ayre power amps? Both use two stage all MOSFET topologies but they differ in two important (perhaps?) respects:
Ayre uses no overal feedback and is differential throughout (as far as I can figure) and Alephs are single-ended with overal feedback.

The objective differences are easily imagined (especially as Pass is kind enough to provide schematics) but what about the sound?

Regards
13th Duke of Wymbourne
 
I posted this question at AudioAsylum and got one useful reply - the link is below for anyone interested.

http://www.AudioAsylum.com/audio/general/messages/167308.html

Arnach - thanks for the enquiry. I don't want to spoil the ethereal possibility that I'm more than noble of thought and deed but also noble of blood.
If you're really interested drop me an e-mail.

As I'm new to the board, how do you become a 'diyaudio Prophet' - does it involve growing a big, bushy beard?

Regards
13DoW
 
Here is a quote from the Ayre Site -

"The audio circuitry must be capable of amplifying the musical signal without alteration. To this end, the Ayre V-1 circuit is a complementary design using no negative feedback. The circuit's elegant topology comprises a cascoded differential input stage followed by a source-follower output stage. This straightforward approach results in remarkable immediacy and musical purity."

This does seem very similar to the X-series.
 

Joe Berry

Member
2001-03-15 6:15 pm
USA
I've not seen the actual schematic, but Bascom King once described the topology in a 1993 (?) review of the Ayre V3 for the now-defunct American magazine Audio. It's essentially an X amp with a fully complementary front end and no signal feedback loop at all. The output offset voltage is stabilized by DC feedback from each output node to its corresponding folded cascode stage. Another difference is that Ayre uses chokes in the front end and output stage power supplies.

I don't recall whether the review mentioned these details but, given the way the DC feedback network is connected, I would speculate that the front end supply for the V3 is regulated, and that it uses resistors rather than active current sources to bias the folded cascode.
 
Whooo done whaat

There are many designs that are based on many other earlier designs, and also many different names for the same basic designs. This is what is called progress. There are actually only a number of ways that parts can be wired together to make a working circuit of a specific design. So it is not unusual for things that act alike to look alike.

Now who gets credit for what? The original designer behind a circuit concept may hardly be known, while others who borrow the concept or parts thereof and make it popularized may become a household name. Thus to make something popular is the key to success.

I can honestly say that all the circuits I have ever designed are based the work done by other individuals in the world of electronics and electronics engineering. And I hope that everyone is able to give credit were credit is due.

Food for thought, nothing else.

John Fassotte
Alaskan Audio
 
AudioFreak, the Ayre's output is balanced, and like some of the Pass X models, it will accept either a balanced or unbalanced input signal.

As for who did what, it wasn't my intention to make this an issue. I see all these designs as variations on a theme, a dialogue of sorts that may well have begun with some obscure microchip designer a decade or more ago. (I would certainly credit the inventor of the balanced folded cascode if I knew who it was!) There have been some brilliant insights along the way -- and certainly Nelson's qualifies -- which is part of what makes it so interesting to follow.
 

Nelson Pass

The one and only
Paid Member
2001-03-29 12:38 am
Having been through the schematic of the Ayre,
kindly provided by Charles Hansen, it is a very fine
product, however, it bears no relation to the
SuperSymmetric design. SS does not depend much
on implementation details such as types and polarity
of devices or topologies of front ends, cascoding,
Class of operation, or output stage type. It does
require a differential input driving balanced symmetric
circuits, but uses the feedback scheme symmetrically
to only make the errors of both sides identical and
cancelling.