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The Alpha Big Boy with Buttah (ABBB) 52w Class A Amp GB
The Alpha Big Boy with Buttah (ABBB) 52w Class A Amp GB
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Old 12th June 2019, 10:18 PM   #1
xrk971 is offline xrk971  United States
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The Alpha Big Boy with Buttah (ABBB) 52w Class A Amp GB
Default The Alpha Big Boy with Buttah (ABBB) 52w Class A Amp GB

This amp is the evolution of the Alpha BB amp bit combined with the popular Smooth Like Buttah (SLB) active bridge cap multiplier power supply all integrated on board. The amp uses the wonderful Aksa Lender front end with the superb hybrid P channel Aleph output stage. In combining the Alpha BB with the SLB we have essentially simplified one of the most time consuming and difficult aspects of building a Class A amp: making the power supply and connecting it. We have also decided to include a custom solid state relay (SSR) speaker protection and delayed start circuit designed by jhofland. The SSR protection is really new - so testing it on veroboard remains to be done. In the mean time, JPS64 has not wasted any time and has come up with the following layout.

Click the image to open in full size.

Click the image to open in full size.

Click the image to open in full size.

Notable features of the ABBB amplifier:
  • 52w into 8ohms
  • Remotely mounted power transistors with Molex quick disconnects
  • 400VA to 500VA 32v power transformer (per channel) with dual secondaries is recommend to achiev about +/-37v rails
  • Designed to be used with cost effective CPU coolers
  • Built in ground loop breaker using NTC and 22nF cap
  • Bias current is circa 3 amps

This is about as close as we can come to a single-board Class A power amp. All that is required is to connect the transformer secondaries (4 spade FASTONs), connect speaker +ve and +ve (2 spade FASTONs), audio input (2pin JST), and chassis GND (1 spade FASTON).

Of course, the 2 TO-264 BJTs for the cap multiplier need to be connected to a heatsink capable of removing about 10W to 15W each. The two TO-264 IXYS MOSFETs need to be connected to suitable heatsink or CPU cooler capable of removing about 100W. Note that many CPU coolers have a large enough pad to accommodate both BJT as. MOSFET size by side. We recommend Noctua PWM fans for silent operation.

The nice thing about mounting the actives to the heatsinks is that they are on flying leads with 4pin polarized Molex connector. So the amp board installation and actives heatsink installation are separate operations. And you can pull the amp board out of the chassis without removing the transistors from their heatsinks! How convenient is that?! We tested this on the SLB ans another one of Hugh’s amps and found that it works superbly. Very convenient.

The addition of an on-board DC protection circuit and power on time delay will help to prevtndameg to the speaker and eliminate turn on thump. It is a small and unobtrusive circuit near the output FASTON terminal.

Here are the preliminary schematics:

Click the image to open in full size.

Click the image to open in full size.

We still need to test the DC speaker protection circuit - so I will post that schematic once it has been verified to work.

I want to acknowledge the circuit designs by Aksa and Jhofland used in this amp and JPS64’s superb layouts. Without their help - this amp would not be possible.

For now, if anyone is interested, please put your name and number of boards you would like in a list below. Once we have enough critical mass, I will open up a new GB preorder listing on my Etsy shop to collect funds. The Etsy interface should help me with the logistics for efficient GB order fulfillment.

EditJune 22, 2019: Pre-Orders for the ABBB GB can be placed here: ABBB Amplifier PCB | Etsy

Edit Aug 27, 2019: Mouser Shopping Cart here (please save as your own project before modifying)
Mouser Electronics


Edit Sept 3, 2019: Joshua43214 put together a compressive BOM and corrections in this post here. Thank you Joshua!
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Last edited by xrk971; 3rd September 2019 at 12:42 PM.
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Old 12th June 2019, 10:52 PM   #2
gary s is offline gary s  Australia
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Hi X, very nice work. Put me on the list for 2 of these ABBB PCB's thanks.
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Old 12th June 2019, 11:18 PM   #3
jwjarch is offline jwjarch  United States
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Sign me up for a pair, X!

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jwjarch - 2 boards
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Old 12th June 2019, 11:20 PM   #4
jwjarch is offline jwjarch  United States
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What is the 3rd DIP-8 on the lower middle of the board? I don't see it in the schematic anywhere??? Also, can the KSC3503 be a D for Hfe or do we need to find E's by some miracle?
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Old 12th June 2019, 11:21 PM   #5
Vunce is online now Vunce  United States
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The Alpha Big Boy with Buttah (ABBB) 52w Class A Amp GB
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gary s - 2 boards
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Old 12th June 2019, 11:56 PM   #6
AKSA is offline AKSA  Australia
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Jwjarch,

That DIP is a dual comparator which is used to control switch on and DC sense for the speaker. It's not included in the circuit yet.

A 'D' version is not needed. High beta does not define high open loop; you can use any cooking pot KSC3503 here. What is important is Cob and ft, and that transistor is very good.

Magnificent coordination, layout and design to XRK, JPS64 and Jan - this is really stunning work. But to builders, remember that each output, two for each channel, will need forced air cooling using a CPU cooling tower. This will dissipate a lot of heat.........

Hugh
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Last edited by AKSA; 12th June 2019 at 11:58 PM.
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Old 13th June 2019, 12:35 AM   #7
jwjarch is offline jwjarch  United States
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Thanks for the info Hugh. That's a pretty slick DC protect system. Very hi-tech! Well done you guys!

Good to know there’s no unobtanium parts once again.

I have 8 of these guys to put to use. I've posted this info on the Alpha thread before, but if anyone needs a cheap cooler here you go. They were made to dissipate at least 130W on Xeon servers and have large copper pads on the bottom. Should be able to handle one mosfet per cooler I would think. Need 4 for an ABBB. I used these to test out my Alpha 20 build and they worked really well.

HP ProLiant CPU Heatsink DL580 DL980 G7 LGA1567 570259-001 591207-001 | eBay
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Last edited by jwjarch; 13th June 2019 at 01:02 AM.
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Old 13th June 2019, 12:54 AM   #8
xrk971 is offline xrk971  United States
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The Alpha Big Boy with Buttah (ABBB) 52w Class A Amp GB
Thanks for the tip on the heatsink - the copper pad looks big enough for both cap Mx and MOSFETs. I just ordered a pair from different seller for $10ea shipping included. Last 2 though.

But this part number looks like a good heatsink for our purposes.

LGA1567 570259-001 591207-001
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Old 13th June 2019, 12:55 AM   #9
meanie is online now meanie  Singapore
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gary s - 2 boards
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Old 13th June 2019, 02:44 AM   #10
asuslover is online now asuslover  Romania
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The Alpha Big Boy with Buttah (ABBB) 52w Class A Amp GB
Quote:
Originally Posted by jwjarch View Post
Thanks for the info Hugh.

I have 8 of these guys to put to use. I've posted this info on the Alpha thread before, but if anyone needs a cheap cooler here you go. They were made to dissipate at least 130W on Xeon servers and have large copper pads on the bottom.
Are these heatsinks suppose to work with a fan?
Thanks
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