Aksa Lender P-MOS Hybrid Aleph (ALPHA) Amplifier

[xrk971]

What voltage rails and bias current will you plan on running for the 4R version? The 4U chassis can dissipate 75w per channel. If adding a fan, use a Noctua 120mm PWM mounted outside blowing against the middle of the fins.

 

[Shawnstium]

I am not sure on the bias current at this time, but I am thinking I'll go for a lower setting. I am putting together the SLB power supply with a 22Vac 300VA Antek transformer at this time.

 

[danny_66]

See this post for an Alpha 4R version with lower bias.

- 4R compatible: 1.94A bias + FB shunt resistor of 1.8K
- ground lift for the input signal
- FB divider 50R-50R to double the damping factor, gives a DF of around 50 on 4R speakers, DF 4R = 1/2 DF 8R

Regards,
Danny

 

[xrk971]

1.94A x 48v is 93w. Asking the helper fan to remove an extra 20w is no big deal. It will remove more like 60w so heatsinks will feel quite cool.

 

[xrk971]

There are murmurings of an Alpha BB with built in Smooth Like Buttah (SLB) power supply - the ABBB (Alpha Big Boy with Buttah). Im sure it will be fantastic.

 

[zman01]

There are murmurings of an Alpha BB with built in Smooth Like Buttah (SLB) power supply - the ABBB (Alpha Big Boy with Buttah). Im sure it will be fantastic.

Wicked!

 

[AKSA]

You betcha X, I'm very interested to see this layout. It will do all things for all comers and all in one pcb........

HD

 

[Vunce]

Wicked!

Wicked Good Zman!!

 

[xrk971]

ABBB, the new Masterpiece of JPS64 is starting to take shape...

 

[Vunce]

Fantastic work JP!!

 

[Shawnstium]

Thanks for the info danny_66! To clarify about the FB shunt resistor, that is R111 on the modified 4R schematic?

If I use a Dayton MPT 10uF/250V audio grade cap on C1021 is there still a need for a smaller bypass cap? There isn't much room left if it's need...

 

[xrk971]

Dayton MPT 10uF/250V audio grade cap on C1021

Excellent choice, no need for a bypass on this.

 

[pcgab]

ABBB, the new Masterpiece of JPS64 is starting to take shape...

Is there a dedicated thread for the ABBB?

The render looks awesome, JP always does such great job at layout.

 

[Shawnstium]

Great! I have some left over from passive crossover builds. That guy barely fits as is!

Danny, I found a post where you called out R111 as the FB shunt. There are so many post it's kind of hard to take it all in. A book about this project could be easily written from this forum!

 

[xrk971]

Is there a dedicated thread for the ABBB?

The render looks awesome, JP always does such great job at layout.

No, not yet maybe when we get a bit further along. We asked JP to pause work while Jhofland is figuring out an on-board SSR relay protect and startup delay circuit. We want this to be a true "single board amp". To paraphrase Ron Popeil: "Connect it, and forget it!."

 

[danny_66]

Thanks for the info danny_66! To clarify about the FB shunt resistor, that is R111 on the modified 4R schematic?

Yep, that's it (original 820r, 1k8 for 4R) or the R6 in this schematic,
pay attention to R17 0.33, R10 0.15, R13 885 they set the bias at 1.94A

 

[xrk971]

Thanks so much Danny. This is good stuff, if we can put this in a table format, and then I will link it from post 1.

Seems to be a big source of confusion for builders.

Thanks,
X

 

[jwjarch]

This ABBB is exciting! Great work you guys! Can't wait to see it develop.

 

[sst4270]

Can't wait. I have my BB boards still, but this is really what I want to build!

 

[Shawnstium]

Should R121 and R122 (R19 & R22 in the LTspice one you made) also be changed to 50R?