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Alpha Nirvana 39W SE Class A Amplifier GB

This is the Group Buy and Build thread for the Alpha Nirvana 39W SE Class A amplifier designed by AKSA. The technical discussion thread is here:

Alpha Nirvana 39w 8ohm Class A Amp

PCBs:
795976d1574122101-alpha-nirvana-39w-8ohm-class-amp-0b1b27aa-1350-49e2-a594-304e256b0462-jpeg


Production ones will be 2mm thick, 2oz Cu, ENIG gold finish, and Blue solder mask.

Amp module looks like this assembled:
797233d1574584334-alpha-nirvana-39w-8ohm-class-amp-build-prototype-completed-main-01-jpg


Includes helper snubber boards to allow remote mounting of MOSFETs for flexibility and ease of installation by decoupling the installation of the PCB and the MOSFETs:
797481d1574673293-alpha-nirvana-39w-8ohm-class-amp-sound-00-jpg


Latest Schematics and BOM will be updated soon, but current version (very close to final) is below:

I recommend use of these Fairchild MOSFETs (higher power rating than IRFP's):

FQA40N25 ON Semiconductor / Fairchild | Mouser

FQA36P15 ON Semiconductor / Fairchild | Mouser

The SLB PSU is also highly recommended - proven to work with single SLB and Antek 600VA 24v (AN-6224) trafo. Should work as dual monoblock with dual SLB and Antek 300VA 24v trafos (or equivalent). Also, a ready to run (RTR) solid state relay (SSR) DC protection is highly recommended to prevent turn on thump and provide safety net for your speakers should something fail.

Also tested to work on DIYA Store Dissipante 4Ux300mm chassis. Board is UMS compliant and I did not have to drill and tap a single hole on my UMS heatsink. Chassis temp is 57C at hottest point in 20C ambient. A 5Ux400mm would be much more generous and allow higher bias current.

Pre-Orders are now being taken in my Etsy shop for the GB.

Pricing is $37ea (includes pair of snubber boards - which cost almost as much as the PCB, hence the higher price). Thus, a stereo pair requires two boards. Free shipping in USA. Etsy calculated shipping elsewhere - circa $23 via tracked and insured USPS First Class mail.

If you place a pre-order, please add your name to a running list below with name, qnty, country. Thanks!

A huge thank you to Hugh (AKSA) for the design and JPS64 for the superb professional layout.

Here is the schematic of my amp "AS-BUILT". These values should work and clears up any ambiguous locations where multiple values are possible.
799467d1575397209-alpha-nirvana-39w-8ohm-class-amp-proto-schematic-built-dec-3-2019-jpg


Schematic of snubber boards:
802740d1576585812-alpha-nirvana-39w-8ohm-class-amp-5783c1a2-a042-4257-b3bc-b51a85b88505-jpeg


Edit Dec 26, 2019: AndyR has put together a nicely annotated BOM for both the 8ohm and 4ohm versions here:
Alpha Nirvana 39w 8ohm Class A Amp

Edit June 13, 2020: note that the feedback resistor R126 and R124 could 1% metal thin film or hand-matched carbon film as 1% not available at reasonable price. This needs to be done to get the same gain from left and right channel. It’s more important that they are matched left and right and not for absolute value. Also note that metal oxide thick film should not be used (dominant H3 and high THD). Do not use carbon composition - that is an error in the BOM. Sorry about that. Carbon film will have a slightly higher THD but more H2 vs H3. Metal thin film will have lower THD but relative H3 will be closer to H2 but H2 still dominant. Safest bet is use 0.5% metal thin film for these 2 resistors. But I personally like the carbon vs metal thin film.

Edit Feb 7, 2020: Pin diagram for Molex quick connects to MOSFETs
815078d1581102749-alpha-nirvana-39w-se-class-amplifier-gb-alpha-nirvana-molex-pinout-jpg


Edit Mar 11. 2020: helpful pin diagram for MOSFETs
824010d1583864664-alpha-nirvana-39w-8ohm-class-amp-a_nirvana-png


Edit Apr 24, 2020 - Dual Monoblock Connection Diagram if using SLB PSU's:
837360d1587747684-alpha-nirvana-39w-8ohm-class-amp-a190389f-cdd0-45c7-8d35-354511cdef86-jpeg
 

Attachments

  • ALPHA-NIRVANA_SCH_001.pdf
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  • ALPHA-NIRVANA_PBA-TOP_001.pdf
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  • ALPHA-NIRVANA_PBA-BOT_001.pdf
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  • ALPHA-NIRVANA_BOM_001.zip
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Thanks X,

I think this is one of my best designs, and X has hugely prototyped, auditioned, measured, and documented it to an inch of its life! It has an even, consistent harmonic profile at all outputs and frequencies, delivering a classic Class A sound with very high efficiency (43%) at full output. It requires no adjustment to get it going, and with a couple of changes you can set it up for 8R or 4R speaker. It will drive just about a rusty nail.

This amp will consume 95W of electrical energy at idle, and at full output. This is a consistent power draw, though it drops the dissipation at audio levels, passing that energy to the speaker. Notwithstanding, the constant power requirement is 190W for two channel, heatsinking is CRITICAL and heavy use of this amplifier will be reflected in your power bill. BE WARNED CLASS A COST MONEY AND YOU SHOULD KNOW THIS BEFORE YOU DECIDE TO BUILD.

JPS's pcb layout is avionics standard, his pcbs are a work of art and his skills are the result of thirty years in the industry. If you build this amp you will be combining SOTA design (it's taken my 30 years to get to this point too!) with professional aerospace layout techniques. It is, in my and X's opinion, as good as any expensive Class A amplifier and in most cases better. You are getting a very high level product at DIY costs; but be aware building yourself is NOT the cheapest option. The cheapest option is always a Class D bought from China, but you choose your poison........

A big thanks to X for bringing my designs to reality, and enthusiastically explaining it to DIYers on this wonderful forum we all enjoy. We three offer this ALPHA Nirvana unreservedly - it is an incredibly good amp with the guarantee of years of music enjoyment for anyone with a bent for the Class A sound with a bit more power, efficiency and ease of build than the majority........... I really hope it becomes a classic into the future!

Ciao,

HD
 
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1) meanie : 1 stereo pair (Singapore)
2) jacques antoine : 1 stereo pair (France) - order placed in store
3) gary s : 1 stereo pair (Australia) - will place order in Etsy shop.
4) mordikai : 2 stereo pair (USA) - order placed in store
5) vunce : 1 stereo pair (USA)
6) spiggs : 1 stereo pair (USA) - order placed in store
 
1) meanie : 1 stereo pair (Singapore) - order placed in store.
2) jacques antoine : 1 stereo pair (France) - order placed in store
3) gary s : 1 stereo pair (Australia) - will place order in Etsy shop.
4) mordikai : 2 stereo pair (USA) - order placed in store
5) vunce : 1 stereo pair (USA)
6) spiggs : 1 stereo pair (USA) - order placed in store
 

Francois G

Member
Paid Member
2004-06-16 8:36 pm
Illinois
1) meanie : 1 stereo pair (Singapore) - order placed in store.
2) jacques antoine : 1 stereo pair (France) - order placed in store
3) gary s : 1 stereo pair (Australia) - will place order in Etsy shop.
4) mordikai : 2 stereo pair (USA) - order placed in store
5) vunce : 1 stereo pair (USA)
6) spiggs : 1 stereo pair (USA) - order placed in store
7) Francois G: 1 stereo pair (USA) - ordered in store, plus SLB PSU
 
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spiggs

Member
Paid Member
2016-12-20 4:53 am
Huntington Beach, CA
Along with the Alpha Nirvana boards I ordered the SLB and SSR boards but having just read through the SSR info again I somehow missed before that these require minimum 24v. I am going to build the Alpha Nirvana as the 20w version which has 20v rails. Am I right in thinking the SSR boards will not be compatible with the 20w build?