SURE 4 Channel Multi-Channel Amplifier
2x TA2024 AA-AB32155












This is being used in a spare bedroom with a smaller TV and 3 older Infinity speakers. Absolute loud volume is not needed and this puts out a very comfortable volume in the smaller room compared to a living room


This design uses 2 seperate TA2024 powered boards to create a multi-channel amplifier. The boards are supplied by individual 15V regulators. I used Texas Instruments TL780-15 high precision regulators. These are pin compatible with traditional LM7815.

I originally tried to use a 15V laptop power supply by itself and daisy chain the units since there are DC/GND connections on both sides of each board.

But I encountered a strong amount of noise whenever both boards were used at the same time. If only 1 board was being used at a time it was fine.

I then tried branching out to both amps from the same starting point. From the DC plug of the laptop supply, then to each board.

This cut the noise down quite a bit, but the noise was still there none-the-less


DIY Audio Thread Looking For Help

Regulators and Standby Switching


Next was deciding how to get clean power. I decided on giving each board it's own dedicated voltage regulator. I decided to use the TI TL780-15. This is fed from a generic 18.5VDC laptop supply. The regulators just need anything 2 volts greater then 15V


The TL780 is also rated at 1.5A instead of the 1A most LM7815 are rated at. I did use my Fluke multimeter and measure the current used by each board and to my surprise the boards each only pulled 0.065A at idle and at most 0.085A at comfortable levels. Probably explains why these generate almost no heat. As shown in the video at the top the system pulls 20mA in sleep mode. 160mA at idle. 180mA at high volume.


I used a Electronics Salon/Audio Wind PCB-SP2-1 regulator PCB I bought on eBay for the regulator circuit. This is a really well made PCB that only cost several dollars from China. The PCB is normally supposed to provide +/- volatge from a transformer and LM78/79 regulators. But with some simple modifications, I was able to put 2 +15V regulators on the board and have 2 seperate DC rails.


I also used an additional LM7805 5V regulator to provide 5V for switching the amps into standby mode instead of just cutting power.




The biggest change is swapping the positions of 2 legs on the negative side of the regulator (since an LM7915 has swapped legs).






Here's the parts I ordered from Digi-Key




I was able to fit some large TO-220 heatsinks on the board, but had to trim them just a little to clear the capacitors and other close components. I used a grinding wheel and Dremel cut-off wheel (the larger EZ-Lock 1.5" kind).




Once trimmed I painted with flat black spray paint to make it look better (though putting tape over the spot the regulator would mate up)




Here is the leads out to each amplifier. I used one of the extra grounding holes for another ground wire.




Bottom view of PCB.




ON/OFF & DC Trigger


To handle the on and off, I wanted to incorporate a DC trigger to shutdown the amp when not in use. This uses a 2 switches and a relay. A switch on the back chooses between front panel and DC Trigger.

The amp doesn't actually turn off. I am using the SLEEP function. It works by applying +5V to the "Sleep" pin on the board. That mutes the board and puts it into a low power mode (still on, but less then idle)

I actually didn't understand the function at first as it is not explicitly documented. I thought I had to apply +5V to the +5V pin on the board. But that is a +5V supply that you could jumper over to the sleep pin.

I had already built the additional +5V LM7805 circuit, so I kept what I had as it works just the same


I added pins to the boards to make easy to use connections. The AudioWind SP2 has extra connections on the +voltage side for an adjustable voltage regulator. This gave me a nice interface sending the 19V input over to the ON/OFF board





I do not know the actual name of this type of pin, but they fit the jumper cables that are common in computers. I bought them at Tanner Electronics in Carrollton Texas

Here is the schematic. A 5V LM7805 creates +5V which is used to power the Sleep pin on the Sure boards. If "DC Trigger" mode is selected, then this 5V is supplied by default, muting the amps. The 12V relay gets triggered by the reciever and cuts off the 5V supply to the Sleep pin and the amps come alive.




I made the 5V circuit by hand, so it wasn't as nice looking. I then painted it black to make it less obvious




Chassis


The chassis is a BUD Industries AC-424 Aluminum Chassis, 12" Length x 8" Width x 3" Height


I measured the distances between the RCA terminals and used Avery 15663 Laser Printable Shipping Labels to make markers for drilling


What I did was put the Amps on top of a hobby PCB to simulate the thickness of aluminum bottom of the chassis. I then measured how high that was (in milimeters) and used Microsoft Word to make a rectangle the fit the dimensions of the RCA spacing between each other and from the ground. I printed the label and drilled out the holes.






I did similar for the binding posts since the ones I bought had built-in spacers.






I used JB Weld to attach the stand-offs. Tighten the stand-offs to the boards. Slater on the some JB Weld to the bottom of the stand-off and then place it where needed. Use a toothpick or similar to spread the JB weld up the sides of the stand-offs and around the chassis.






Covered the tops of the stand-offs with painters tape and then painted it white using spray paint from auto store (its better quality then Krylon, but not as thick per coat).






I again used the laser shipping labels to print out labels for the terminals. I applied a clear coat after applying the labels to protect them and prevent from peeling




I had a glass top cut for the lid. It was $16 at a glass place called Ajax Glass. They also drilled holes in the glass to line up with the holes in the chassis and they rounded the edges of the glass


I used speed nuts or U-nuts to attach the glass to the chassis. I also painted a 1" border on the underside of the glass (using painters masking tape) to hide the speed nuts and top of the chassis. The thickness of the speed nut also raised the glass slightly off the chassis so that air can exchange with inside the chassis to vent off heat.