The configuration is like a tube push pull amplifier (not important if the load is in anodes or cathodes resp. drains or sources).
The only thing of interest is that in push pull biasing can be class A or class AB.
The only thing of interest is that in push pull biasing can be class A or class AB.
It is bridged output but the inductive coupling of the two inductors makes it slightly different than two independent amps simply bridged together. Notice the phase dots on the coupled inductor (or 1:1 transformer), running as two separate inductors does not yield the same performance.
Susan Parker's Zeus amplifier illustrates it is push pull. Same configuration. She biases class AB with good amount of class A.
That answers your question Minek.
That answers your question Minek.
An amplifier’s ability to handle dynamics
X made a very interesting observation about class A/ amplifier dynamics
As it was triggered by the sound of the SySuLu, I thought it more appropriate to reply in that thread. If you are interested in amplifier dynamics, you might find it interesting … 😉
https://www.diyaudio.com/forums/pass-labs/373533-susylu-12.html#post6795217
X made a very interesting observation about class A/ amplifier dynamics
As it was triggered by the sound of the SySuLu, I thought it more appropriate to reply in that thread. If you are interested in amplifier dynamics, you might find it interesting … 😉
https://www.diyaudio.com/forums/pass-labs/373533-susylu-12.html#post6795217
A very clever PP A Class
It is well biased and the constant current is a neat idea but, it does seem to run in Push Pull mode, and therefore not strictly SECA design.
A Neat idea.
I saw something similar in the early 1970, one done by Sir Clive Sinclair and a version by Linsey Hood,
The Mr Hood one was published in WW or PE.
It is well biased and the constant current is a neat idea but, it does seem to run in Push Pull mode, and therefore not strictly SECA design.
A Neat idea.
I saw something similar in the early 1970, one done by Sir Clive Sinclair and a version by Linsey Hood,
The Mr Hood one was published in WW or PE.
Yes, PP Class A
Daanve, it is indeed push pull, but Class A of course because neither device turns off.
X can be given credit for the clever Hawksford Cascode which maintains constant voltage across the LU power jfet, and setting the bias with ground potential on the gate relies on depletion biasing of jfets, using the DCR of the dual inductor to achieve the 3A quiescent.
It really is a new version of an old idea and proposed on this forum with Susan Parker a long time ago. She did a beautiful amplfier with an absurd low parts count.
HD
Daanve, it is indeed push pull, but Class A of course because neither device turns off.
X can be given credit for the clever Hawksford Cascode which maintains constant voltage across the LU power jfet, and setting the bias with ground potential on the gate relies on depletion biasing of jfets, using the DCR of the dual inductor to achieve the 3A quiescent.
It really is a new version of an old idea and proposed on this forum with Susan Parker a long time ago. She did a beautiful amplfier with an absurd low parts count.
HD
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Let’s move further discussion of the SuSyLu amp to its proper thread and keep this one for Alpha Nirvana.
Absent the anti-thump turn-off option of the SSR Speaker Protection board, does the AN amp typically generate a turn-off thump?
Good idea, X. (But I think it was you who introduced the SuSyLu amp to this thread?)
I presume you mean "without the SSR Speaker Protection boards, does the AN amp generate a turn-off thump"?
If so, I can assure you ... it doesn't. 🙂 (I had to remove my SSR boards when I had to re-organise the layout of my AN 4Rs, to fix the instability problem I was experiencing. There was simply no room for them. 🙁 )
Andy
Andy, i was specifically referring to the optional turn-off daughter board, but you’ve answered my question thanks. I will use the Speaker Protection board but wont add the turn-off option.
Hi fellas,
I’m gearing up for my next build, and I have a few questions.
Since my supply is set in stone at +/- 24Vdc (ie I can’t do +/- 28Vdc), can I increase the bias a bit? Higher than 1.65A by changing the source resistors from 0.22R BPR to 0.18R BPR (assuming FQA transistors)? My heatsink is a 5U/400, comfortable with 90W dissipation.
For the feedback capacitor, C124, can I use a 330uf/25V cap that I have here in my shop instead of 470uf ?
Best,
Anand.
I’m gearing up for my next build, and I have a few questions.
Since my supply is set in stone at +/- 24Vdc (ie I can’t do +/- 28Vdc), can I increase the bias a bit? Higher than 1.65A by changing the source resistors from 0.22R BPR to 0.18R BPR (assuming FQA transistors)? My heatsink is a 5U/400, comfortable with 90W dissipation.
For the feedback capacitor, C124, can I use a 330uf/25V cap that I have here in my shop instead of 470uf ?
Best,
Anand.
Yes, Anand, 0R18 and 330uF is just fine - no effect on sonics but will increase drive into more reactive loads.
FQAs are fine too, they are rated to 280W EACH, strong mosfets.
I found this very useful for figuring the heatsink performance:
Heat Sink Size Calculator
HD
FQAs are fine too, they are rated to 280W EACH, strong mosfets.
I found this very useful for figuring the heatsink performance:
Heat Sink Size Calculator
HD
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Hmm I’ve been trying to figure out how to build the AN with the same PS I’m planning to use with my Pass/First Watt designs… maybe this is the way!
PF4Ever,
Yes, I was just making sure I wasn’t going to make the design unstable. I’ll likely get both 0.22R and 0.18R resistors and experiment. I have a 5U/400 test mule heatsink and bench supply for exactly this purpose. My speakers aren’t difficult loads per se given how loud they get on the Aleph J and Aleph J Zen. And I don’t think the power differences between them and this AN Nirvana will be an audible difference for me given that my speakers are 96 dB sensitive with an impedance nadir of 4.8 ohms over the narrow range of 100-200Hz.
But I do think the dramatically lower overall THD with decent harmonic spectra and low output impedance/high damping factor will be audible.
It’s important to keep perspective with all of this and realize music is dynamic and changing.
Thanks Hugh for the confirmations.
Best,
Anand.
Yes, I was just making sure I wasn’t going to make the design unstable. I’ll likely get both 0.22R and 0.18R resistors and experiment. I have a 5U/400 test mule heatsink and bench supply for exactly this purpose. My speakers aren’t difficult loads per se given how loud they get on the Aleph J and Aleph J Zen. And I don’t think the power differences between them and this AN Nirvana will be an audible difference for me given that my speakers are 96 dB sensitive with an impedance nadir of 4.8 ohms over the narrow range of 100-200Hz.
But I do think the dramatically lower overall THD with decent harmonic spectra and low output impedance/high damping factor will be audible.
It’s important to keep perspective with all of this and realize music is dynamic and changing.
Thanks Hugh for the confirmations.
Best,
Anand.
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@AKSA: earlier in the thread you intimated you might make a commercial amp based on the AN. Can I ask, do you still intend to do that?
Not yet........!!
Hi Studley,
Not at this point, but from where I sit, a city with temperatures up to 45C in summer and rising with each decade, and some of the most expensive electricity in the world, I'm somewhat discouraged.
I have always found that Class A is a brute force technique to ensure outputs never switch. I have found over decades in this insane field that Class AB is the greatest intellectual challenge and a good AB is difficult to best; but then, I'm an old geezer and the future is probably Class D, like my TV and car entertainment amp.
HD
Hi Studley,
Not at this point, but from where I sit, a city with temperatures up to 45C in summer and rising with each decade, and some of the most expensive electricity in the world, I'm somewhat discouraged.
I have always found that Class A is a brute force technique to ensure outputs never switch. I have found over decades in this insane field that Class AB is the greatest intellectual challenge and a good AB is difficult to best; but then, I'm an old geezer and the future is probably Class D, like my TV and car entertainment amp.
HD
OK thanks Hugh. You need to come and live in the North of England 😉. I couldn’t live with the temperatures in Oz, I don’t even want to visit for that reason.
I own a superb Class AB amp (Neurochrome) but IMHO a good Class A amp does something special that no Class AB I’ve heard can replicate.
I own a superb Class AB amp (Neurochrome) but IMHO a good Class A amp does something special that no Class AB I’ve heard can replicate.
