output devices on X -X.5 and XA.5

[Stefanoo]

Originally Posted by flg

Also, isn't one a complementary follower ouput and one and version of the Aleph type output?

One is complementary on the X/X.5, I thought the XA had the same topology but more bias, but it makes more sense that difference would also reside on output stage.
I doubt that it is like the Aleph though!

[Zen Mod]

which models exactly are of interest ?

[Stefanoo]

Since I have the X250 and I think it is a very nice amp and I have read that there is a LOT of difference between the first generation X250 and the X250.5 and also that the XA250.5 sounds very different from the X.5 series, I am trying to understand what are the major changes that can be attributed to the sonical difference between these models.
I know there is a different level of Class A to begin with between X.5 and XA. However what are the changes from the X250 and the X250.5 for example and is the XA200.5 the same topology as the X.5 series but given a different bias or there othe major circuit topology differences?

[a.wayne]

XS is the best sounding of Papa amps , we can see the physical differences , is the topology same as XA with bigger hammer ..?

Seeing and hearing the XS models is something else ...!

[Stefanoo]

A little off topic, but I would interested in listening to the XS as well.
I am assuming it is similar to the XA but with a linear regulated PSU, correct?
Does anybody know if it uses a series regulation or a shunt topolgy?

[Stefanoo]

Originally Posted by Stefanoo

A little off topic, but I would interested in listening to the XS as well.
I am assuming it is similar to the XA but with a linear regulated PSU, correct?
Does anybody know if it uses a series regulation or a shunt topolgy?

Just giving more thoughts to it, I am sure it is series regulation as it would be impossible to dissipate an oversized "Class A" power supply for a Pure oversized Class A power amp giving that the heatsinking capabilities are the same as the output power section

[Zen Mod]

X250 - older generation UGS based FE , follower style OS with mosfet bias gene , 4 mosfets in OS quadrant,no SE bias , 2x38-ish Vdc PSU

XA200.5 - newer UGS based FE , follower style OS with shunt reg bias gene,7 (or 8) mosfets in OS quadrant,SE bias , 2x34-ish Vdc PSU

[Zen Mod]

type of PSU is least interesting thing in XS amps .
type of circ , with heavy bias , including SE bias , is preventing use of any reg , except possible for FE (which is pretty irrelevant)

[Stefanoo]

Originally Posted by Zen Mod

X250 - older generation UGS based FE , follower style OS with mosfet bias gene , 4 mosfets in OS quadrant,no SE bias , 2x38-ish Vdc PSU

XA200.5 - newer UGS based FE , follower style OS with shunt reg bias gene,7 (or 8) mosfets in OS quadrant,SE bias , 2x34-ish Vdc PSU

It looks like a lot of improvements have been made which would explain the wide sonic difference.
Thanks for the clarification.
I didn't even suspect that the 250.5 would use more MOSFETs at the OS.

Regarding the latest FE UGS design.
If I don't recall wrong several succesfull attemps were made to design the clone, I am assuming, that was related to the first generation.
Is there any design for the lastest as well?

Moreover, when you talk about SE biasing, I don't quite understand how it is achieved.
When I think of SE Bias I can think of the Aleph style where the curernt source on the top side biases the follower.
I have read the paper you guys have linked but I don't quite get how SE bias is applied to a push pull.
Is there any reference on the DIY to this subject?

Thanks a lot.

[Stefanoo]

Originally Posted by Zen Mod

type of PSU is least interesting thing in XS amps .
type of circ , with heavy bias , including SE bias , is preventing use of any reg , except possible for FE (which is pretty irrelevant)

oh I see. However it is using a regulated PSU looking at the big enclosure deidcated to the supply section.
Also recall Nelson mentioning several time that regulated power amp sound better overall although lack of reservoir.
If you can make the regulator as big as the power amp I would assume you would get the benefits of both world which in my little experience cold possibly make a significant positive sonic difference at a price of bigger heat dissipation and more hardware.