Single or dual differential?

[hitsware]

Originally posted by Bricolo
would adding a 9.5k between the 2nd input and ground be a good idea? (matching the input impedances)

A little maybe but with mosfets (no bias current) don't make much differance..

[Bricolo]

is it only usefull for bipolars?

[hitsware]

Originally posted by Bricolo
is it only usefull for bipolars?

With bipolars it balances the pair offsetwise. With fets that's not a problem, but there may be some dynamic considerations. Perhaps someone with better understanding will chime in here.

[Bricolo]

I would use it.
After all, it's only one more resistor. And when designing the PCB, it could even make things simplier in some situations. You don't have to make the ground trace go to the 2nd gate, take a resistor to connect the gate to ground

[john curl]

Fred, originally proposed a sophisicated and 'improved' biasing stage. I felt that it was not a 'universal' schematic, because it lacked placement of a source degeneration resistor in the N channel rail. However, Fred is correct in this one specific case with using J109's and K389's. Thanks Fred, I didn't notice the difference between Gm's before, in these two devices. However, if you were using K170's and J75's, the difference would be less, and almost unmeasurable. Personally, in a simple circuit like this, I prefer to use high Idss types and run them as hard as possible. This includes even slightly overbiasing the input devices in the forward direction, under transient peaks. Please think it through, before attacking my comment.

[lumanauw]

As pointed before, I looked at http://www.ne.jp/asahi/evo/amp/J200K1529/report.htm and find many "not-ordinary" designs there. Are they practical design, or just design idea? Has someone have a chat with those Japanese designer, I think they have different spirit about audio amplifier from person like Mr.Pass or Mr.JC.
I learned that Mr.JC is former designer of MarkLevinson. Could anyone give me a brief schematic of what is inside MarkLevinson Ref.No.33 (The 200kg mono power amp)? Does it uses basic schematic like Ref.no.2 or JC-3?

[jam]

I believe that Mr.Curl did not design the Ref.33.

The Ref.33 is not a complementary design and nowhere as elegant as Mr.Curl's work. It looks more like a parts farm, to quote another member of this forum.

Regards,
Jam

[Peter Daniel]

Check this link to _see_ what'sinside ref 33. http://www.marklevinson.com/image_li...6&productID=12

Use this link for technical overview http://www.marklevinson.com/products...=pa&prod=no33h

[johnferrier]

Originally posted by Peter Daniel
Check this link to _see_ what'sinside ref 33. http://www.marklevinson.com/image_li...6&productID=12

The outside certainly *looks* impressive. The "what's inside" pics seem to be dead currently.


JF

[Peter Daniel]

I noticed that occasionally they are inactive, but check later, they'll work fine. Those are high res pics, showing even the print on ICs.

I know that some guys don't like ML, but I was always impressed with their engineering. So recently, I bought myself ML38 preamp board. At $140 it seemed hard to refuse. Finally, I have a piece of a cake too.