Alpha Nirvana 39w 8ohm Class A Amp

Here are some more sims like Hugh did, but at 20vp (40vpp)
Green is the current over N-channel
Blue the current over P-channel CCS

Original AN8R with 8R load
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Original AN8R with 4R load, running out of current(clipping) on N and P-channel
1743444574840.png


New ANxR with 8R load
1743444720860.png


New ANxR with 4R load, only clipping of current on P-channel CCS
1743444806574.png
 
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Anand,
From Danny's graph it does appear the SJEP looks very good.
I do see that the current range on the nmos is not so low as with the hexfet, but it works very well and you might expect results. You could force a greater differentation by using 0.27/0.10 however.

Myles,
Yes this change of source resistors will work just fine with FQA40N25 and FQA36P15. These devices are my first choice for this amp. Good luck with the completion of your Alpha Nirvana!

Hugh Dean
 
I seem to talking with Anand about this some years back, Vunce, and I think we decided on 100R. He highlighted Nelson Pass' design using the same SJEP from memory....... His post was at #2218 at page 111 of this thread in fact.
In fact, Anand, did you swap out your hexfet for the SJEP? If so, did you use a 100R stopper and did you measure ANY voltage across it, showing a finite gate current?

Hugh
 
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Anand, did you swap out your hexfet for the SJEP? If so, did you use a 100R stopper and did you measure ANY voltage across it, showing a finite gate current?
Not yet Hugh! Too many projects! I will be building up the Alpha Nirvana’s in their own monoblock enclosures though and all these goodies we are discussing will be added in!

Best,
Anand.
 
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Hi Nikos,
Yes, at 2.6A it's even better, if you can handle the heat 😎
With 2.1A 2x25v 105w my 4U 400mm passive heatsinks are 25°c above room temperature.

I just listened to Daniel Pemberton - Escape From East Berlin
Never heard it this good, AN is really a very very good amplifier, excellent !
 
With 2.1A 2x25v 105w my 4U 400mm passive heatsinks are 25°c above room temperature.
2.6A 2x 21.5V =111.8W piece of cake for CPU Fan 12cm P12 Arctic .Very very quiet, temp on cpu heatsink 44-47C, body 54-57C, room temp 30C.
 

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A quick question if I may:
Will a transformer change from 22V secondaries I have on the stock AN39 be required. If so, I was thinking that 18V secondaries would suffice assuming that the SLB will drop approximately 3V. This should give approximately 22VDC to work with if my calc's are correct. Thanks for the help.
MM
 
Myles,
No. 18vac will give you an idling rectified voltage of just over 25Vdc. Loaded with this Class A amp would drop around 10% to just 22V then less the 3V of the SLB which is 8V shy of the required design AN39-8 voltage of 27V.
However if you are building a 4R amp 18Vac trafos would still be unacceptable as you still find up with a little less voltage of 19V.
I would always go for the 22Vac trafos. Better to have more than less as removing 5-10 turns off the toroidal secondaries is doable!
Hugh
 
Thanks Hugh,
I was thinking of possibly building the amp with the different source resistors 0.22 and 0.15 ohms. Danny66 post #3751, indicates:
25v 0.22-0.15 8Rload
2.12A 107W
vpp: 47.5202
power_output: 35.3979

So using 22Vac with the SLB's should be around 27V, so maybe a bit less biasing applied and should be OK.
Does this make sense ?

Or, I just build the 8ohm version with the 0.22 ohm source resistors and not worry about getting fancy 😉

MM
 
Thanks for the info Hugh. I was trying to think and manipulate the V and the bias to keep the dissipation around the 100W number. I will keep my eye on this thread for future tips before I get back to working on the AN39. Right now enjoying a month in Mexico.
Cheers,
MM