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Alpha Nirvana 39w 8ohm Class A Amp
Alpha Nirvana 39w 8ohm Class A Amp
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Old 26th September 2021, 12:05 PM   #1771
andyr is offline andyr  Australia
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Quote:
Originally Posted by xrk971 View Post
Letís move further discussion of the SuSyLu amp to its proper thread and keep this one for Alpha Nirvana.
Good idea, X. (But I think it was you who introduced the SuSyLu amp to this thread?)

Quote:
Originally Posted by Studley View Post
Absent the anti-thump turn-off option of the SSR Speaker Protection board, does the AN amp typically generate a turn-off thump?
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
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Old 26th September 2021, 12:31 PM   #1772
Studley is offline Studley  United Kingdom
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Andy, i was specifically referring to the optional turn-off daughter board, but youíve answered my question thanks. I will use the Speaker Protection board but wont add the turn-off option.
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Old 26th September 2021, 06:35 PM   #1773
poseidonsvoice is offline poseidonsvoice  United States
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Alpha Nirvana 39w 8ohm Class A Amp
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.
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Old 27th September 2021, 12:38 AM   #1774
AKSA is offline AKSA  Australia
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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
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Last edited by AKSA; 27th September 2021 at 12:41 AM.
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Old 27th September 2021, 01:37 AM   #1775
pinkfloyd4ever is offline pinkfloyd4ever  United States
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Alpha Nirvana 39w 8ohm Class A Amp
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!
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Old 27th September 2021, 02:30 AM   #1776
poseidonsvoice is offline poseidonsvoice  United States
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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.
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Last edited by poseidonsvoice; 27th September 2021 at 02:33 AM.
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Old 27th September 2021, 07:10 AM   #1777
Studley is offline Studley  United Kingdom
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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?
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Old 27th September 2021, 09:49 AM   #1778
AKSA is offline AKSA  Australia
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Default 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
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Old 27th September 2021, 10:41 AM   #1779
Studley is offline Studley  United Kingdom
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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.
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Old 27th September 2021, 04:14 PM   #1780
pinnocchio is offline pinnocchio  Canada
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Winter in Canada... Bring all the Class A you want! I'll use as baseboard heater! LOL
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