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tiefbassuebertr 11th March 2010 01:30 PM

New Amp "ULTRASYMMETRY" from Nelson Pass - still a Concept Amplifier?
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From anywhere on the web I have found some photos from prototype of the brand new amp "ULTRASYMMETRY" (as I recall right from the CES).

Are there any news?

If I guess right the sizes of heatsinks, then the idle current for each channel must be in such aera to reach 1 - 2 KW power (heat) loss. Thus this must be an ultimate sounding amp under all encountered conditions - even by full range ribbon loudspeakers.

currently I found only this:
*֤jU :: View topic - Ultra Symmetry *Ŧeũj

Which topology is in use there?

Zen Mod 11th March 2010 01:57 PM

wensan is also member here

rest of the questions ........ maybe Papa will answer , but - do not expect miracles ...... in any meaning


analog_sa 11th March 2010 03:03 PM

May be a great amp but i wonder if aluminium is indeed such a great conductor?

Andrew Eckhardt 11th March 2010 03:42 PM


Originally Posted by analog_sa (
May be a great amp but i wonder if aluminium is indeed such a great conductor?

can you measure microOhms in your lab?

tiefbassuebertr 11th March 2010 04:40 PM

Front end PCB "Concept FE R0"

Originally Posted by analog_sa (
May be a great amp but i wonder if aluminium is indeed such a great conductor?

because of the large thickness of the material the disadvantage to copper is negligible - I think.

I read by the first article about the single ended power amp "ZEN" this:

There are two most essential principles to audio amplifier design. The
first is simplicity. The second is linearity.
Einstein said, "Everything should be made as simple as possible, but no
simpler." Simplicity is a common element of the best and most subtle
designs. It is preferred for purely aesthetic reasons, but also because
fewer elements color the sound less, and lose less information.

This rule is observed by all me known commercial and diy amplifier topologies from Mr. Nelson Pass since the ZEN/Aleph topologies. Consequently, even here.

This circuit from the PCB seems by first look a bit more complicated, because there are various soldered and unsoldered jumpers to test different topologies and 6 pieces dual jFETs 2SK389 and/or 2SJ109
Abbreviations: G-S-D = gate/source/drain, CAS = Cascode. PAR unknown for me - perhaps power amplifier right?
1) setting jumpers each half: 2x "G PAR" 2x "S PAR" 2x "D PAR"
2) jumpers, not in use, each half: 2x "G-CAS" and 2x "D-CAS" (there are no "S-CAS" mentioned)

There are still following: at both halves:
3x 750 ohms/3watt sky (heaven) blue resistor from Matsushita
14 variable cermet resistors "4x BIAS, 4x CASCODE, 1x "+ CASCODE" 1x "- CASCODE", 1x Gain and 3x without advices
10 TO220 MOSFETs for each half mounted on black anodized small heatsinks
10 TO247 MOSFETs for each half mounted to the main outside heatsink
4 pieces of blue KP foil caps and various resistors in brown colour.

The most likely topology for the voltage gain stage here is a mirror symmetric double differential cascode, i. e. an ensemble of normal and folded cascode.
And for the power buffer pure class-A stage (I think push pull true complementary) there are two various modes: Cascoded buffer (cascoded power source follower) and normal push pull source follower (in last case the twice of the paralleled output MOSFETs in use).

I try to create in the moment such topology in a CSPP (Circlotron) arrangement to get more symmetric behavior. Unfortunately I need therefore 4 power supplies. But one advantage I note already by the SRPP output stage by simulation:
no difference regarded THD values between cascoded and not cascoded version. In this respect there is already an (actually always wanted) simplification again.

analog_sa 11th March 2010 04:58 PM


Originally Posted by Andrew Eckhardt (
can you measure microOhms in your lab?

How is this relevant? At very least aluminium oxidizes. And it reminds me of those coat hangers from the famous joke.

tiefbassuebertr 11th March 2010 05:20 PM


Originally Posted by tiefbassuebertr (
I note already by the SRPP output stage by simulation:

An typing error from me. It must mean of course CSPP instead SRPP in the last paragraph of post #5 from me - sorry.

Parasonic 11th March 2010 05:25 PM

Excellent works of art
Such a high build


Nelson Pass 11th March 2010 06:20 PM

The concept amps were just that - experimental circuits and
chassis for evaluating potential future product.

We have already gathered most of the information we wanted
from them, and one pair currently graces my listening room
while the other pair is disassembled, waiting for revised circuits.

Actual product is scheduled for later this year.

These are unrelated to Wensan's excellent design, which I
hope he will develop further.


tiefbassuebertr 11th March 2010 07:28 PM

about Wensan's excellent design I have found this:
translation in english isn't possible, but amazingly in German:
Google Nachricht
unfortunately with much translation loss

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