Super Symmetry??
" The super-symmetry topology does not use operational amplifiers as building blocks. It has two negative inputs and two positive outputs and consists of two matched gain blocks coupled at one central point where the voltage is ideally zero. The topology is unique in that at this point the distortion contributed by each half appears out of phase with the signal, and we use this to reinforce the desired signal and cancel noise and distortion. This occurs mutually between the two havles of the circuit, and the result is signal symmetry with respect to both voltage and current axis, and anti-symmetry for distortion and noise. This means that distortion and noise of each half appears identcally and cancels."
(C) 1998 Nelson Pass, Pass Labs
How does this occur in your circuit, looks more like a small amount of coupled feed forward error correction?
" The super-symmetry topology does not use operational amplifiers as building blocks. It has two negative inputs and two positive outputs and consists of two matched gain blocks coupled at one central point where the voltage is ideally zero. The topology is unique in that at this point the distortion contributed by each half appears out of phase with the signal, and we use this to reinforce the desired signal and cancel noise and distortion. This occurs mutually between the two havles of the circuit, and the result is signal symmetry with respect to both voltage and current axis, and anti-symmetry for distortion and noise. This means that distortion and noise of each half appears identcally and cancels."
(C) 1998 Nelson Pass, Pass Labs
How does this occur in your circuit, looks more like a small amount of coupled feed forward error correction?
My Circuit works by utilizing the fully differential nature of the device. The dominating feedback loop is the THS4131. That quite simply is how if becomes SuSy. 
You will have to ask TI how they implemented the technology.
This circuit topology is in fact nearly identical in nature to the circuit Nelson himself proposed. It is just that I am using a fully differential opamp where he used a differential pair with CCS. The result is the same topology from a more complete device.
Look here. This thread should answer your questions.
http://www.diyaudio.com/forums/showthread.php?postid=421299#post421299
Cheers!
Russ
You will have to ask TI how they implemented the technology. This circuit topology is in fact nearly identical in nature to the circuit Nelson himself proposed. It is just that I am using a fully differential opamp where he used a differential pair with CCS. The result is the same topology from a more complete device.
Look here. This thread should answer your questions.
http://www.diyaudio.com/forums/showthread.php?postid=421299#post421299
Cheers!
Russ
The key quote is here:
http://www.diyaudio.com/forums/showthread.php?postid=421450#post421450
So you see, in my circuit it is just exactly the same, just the devices are different. The performance of the cirucit will be dominated by the THS4131(or say OPA1632).
In my circuit you could replace the THS4131 with a differential pair and a CCS add one capacitor to block DC and adjust a few resistors to account for the change in gain, and you would have something that would look shockingly (ok its not so shocking) like what Nelson proposed... I have built that version too, and it is very very good. In practice, I found the THS4131 version better for mostly for practical reasons. They both sound great.
Cheers!
Russ
http://www.diyaudio.com/forums/showthread.php?postid=421450#post421450
So you see, in my circuit it is just exactly the same, just the devices are different. The performance of the cirucit will be dominated by the THS4131(or say OPA1632).
In my circuit you could replace the THS4131 with a differential pair and a CCS add one capacitor to block DC and adjust a few resistors to account for the change in gain, and you would have something that would look shockingly (ok its not so shocking) like what Nelson proposed... I have built that version too, and it is very very good. In practice, I found the THS4131 version better for mostly for practical reasons. They both sound great.
Cheers!
Russ
Russ,
Here is my version of a simple double sided PCB of your design. The board is small measuring only 3.8 by 2.5 inches. Notice that I have included an AD8620 input buffer. I am about to send it out for fab. I am looking forward to building it and then doing some critical listening. It is a very interesting circuit!
Here is my version of a simple double sided PCB of your design. The board is small measuring only 3.8 by 2.5 inches. Notice that I have included an AD8620 input buffer. I am about to send it out for fab. I am looking forward to building it and then doing some critical listening. It is a very interesting circuit!
Attachments
Super symmetry?
You are missing my point, If you look at the internals for the THS4131 it uses a form of super symmetry useing a voltage controled differential amplifier for the cross cancellation to acheive the signal symmetry and anti-symmetry for the distortion and noise components.
By feeding a portion of the NFB back to the input you are reinforceing the input signal component with the feed back circuit, basically achieveing a feed forward effect , not cross differential cancellation.
The chip itself will see any reinforced distortion component as signal applied as forward feed compensation, not differential nulling.
If not can someone show me useing the actual super- symmetry circiut how yours works, because I've got to be thick.
You are missing my point, If you look at the internals for the THS4131 it uses a form of super symmetry useing a voltage controled differential amplifier for the cross cancellation to acheive the signal symmetry and anti-symmetry for the distortion and noise components.
By feeding a portion of the NFB back to the input you are reinforceing the input signal component with the feed back circuit, basically achieveing a feed forward effect , not cross differential cancellation.
The chip itself will see any reinforced distortion component as signal applied as forward feed compensation, not differential nulling.
If not can someone show me useing the actual super- symmetry circiut how yours works, because I've got to be thick.
Re: Super symmetry?
A portion?
The power stage is in the TSH4131 loop. The performance of the amp is dominated by THS4131.
Would you say that Nelson's proposed circuit is also not Super Symmetrical?
How is my scheme different from his? The THS4131 is no less a differential device than a differential pair. And I am applying feedback identically.
Cheers!
Russ
tiltedhalo said:
A portion?
The power stage is in the TSH4131 loop. The performance of the amp is dominated by THS4131.
Would you say that Nelson's proposed circuit is also not Super Symmetrical?
How is my scheme different from his? The THS4131 is no less a differential device than a differential pair. And I am applying feedback identically.
Cheers!
Russ
So, I have my prototypes running (single-ended at the moment), and they sound fabulous. Working on getting a TwistedSibling going for SE->Balanced to hear that. Should be tonight.
I have seen some smoke signals coming from Russ' cave, so I think he will be emerging (now moved in to new house) soon
I have seen some smoke signals coming from Russ' cave, so I think he will be emerging (now moved in to new house) soon
Hi Max. I am on my laptop this morning working on finishing touches for the first version of this PCB we will be making available as well as a couple of others which will be ordered very soon.
We may need to order a few prototypes for beta testers since I always like to test a new layout before we get them in quantity.
Cheers!
Russ
We may need to order a few prototypes for beta testers since I always like to test a new layout before we get them in quantity.
Cheers!
Russ
Hi guys,
Just wanted to note that I have received a few requests to be beta testers for the PCB I will produce for this amp.
I will post again when I am about ready to order with my cost to get protos made. If you want a couple prototype amp PCBs we will all share the actual cost equally to be fair. I don't think it will cost much probably less than $20 each per pair, but I will post the actual cost.
This actually should be a fairly small PCB. The PS will be a seperate PCB. If people do not want to make their own PS I will include that in the bundle.
I will post the layout here soon. I hoped to have it done today, but it was a crazy day at work, and now that I am home, the real work begins! Unpacking!!!
At least at work I occasionally have a spare moment.
Cheers!
Russ
Just wanted to note that I have received a few requests to be beta testers for the PCB I will produce for this amp.
I will post again when I am about ready to order with my cost to get protos made. If you want a couple prototype amp PCBs we will all share the actual cost equally to be fair. I don't think it will cost much probably less than $20 each per pair, but I will post the actual cost.
This actually should be a fairly small PCB. The PS will be a seperate PCB. If people do not want to make their own PS I will include that in the bundle.
I will post the layout here soon. I hoped to have it done today, but it was a crazy day at work, and now that I am home, the real work begins! Unpacking!!!
At least at work I occasionally have a spare moment.
Cheers!
Russ
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