PowerPhysics Amps as from Burning Amp

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I tested A-414 last night. Wow, I was pleasantly surprised. This was my first experience with Class D amp and I was quite amazed with what that little guy does. Little just by physical size. I completed one channel only, and compared it to my Hafler 9505.

A 414 is 400W @ 4 ohms, if fed with 80V. I had PS that was giving me around 65V. Even with that it was closing on the Hafler with its punch. Quite amazing bass! I need to finish second channel and to give it a full listening test in order for me to report fully, but I will tell you, for the price and what I heard last night, wow.

A few notes for users that have not been very clear from the data available on the site, so I got clarification, and would like to share it with you.

Regarding connectors and voltages:

Connectors J1 and J4 are identical, and only one is used. The other one is used ether to bypass signal to second amp or to add more capacitance to the amplifier (clever idea) So if you will be using J1 to connect your power supply:

First four pins - only two are used. Pin 1 and Pin 3 or Pin2 and Pin 3 or 4. Since we do not need dual power supply for this amp, any voltage between 30 and 80V will do it. Positive supply is connected to ether Pin 1 or Pin 2, or both if you would like to increase the wire diameter. Pin 3 and Pin 4 are ground for that supply.

Next Pins 5,7,8 and 9 are used.
Pin 5 is +15 V
Pin 6 is not used (-15V is there if there is a need to pass through voltage for the preamap)
Pin 7 + 5V
Pin 8 - 5V
Pin 9 A Ground for 5 V and 15 V supply

Current demand on the power supply for 15 and 5 voltages follows:

Voltage Current
+15v 53mA
-15v 0 ma
+5v 67mA
-5v 49mA

One important fact to mention is the info I received from PowerPhysics:

"The potential of the -5V must be greater than or equal to the +5V during the turn off sequence. (|-5v| >= +5v) This issue occurred once with a preamp that loaded the -5v supply from the amplifier with a number of LEDs. The -5 current draw of the amplifier preamplifier combination was greater than that of the +5V and the A-414 did not like this condition. With just the A-414 attached to a power supply there is normally no problem as I5v > -I5v so V-5v > V+5v as the voltages decay during turn off.

This note has also been added to the A-414 specification."

Connector J3
Pin 1 and Pin 3 are used for positive and negative output to the speaker. This is bridged amp and ground Pin 2 is not used. That pin is used if you would like to do shielding of the speaker wire and speaker itself only.

Connector J2
There you only need to use Audio input pins. Those are Pin 1, 2 and 3. Connector with installed ribbon cable is supplied. The rest of pins are used for various monitoring functions, that are great to have, but you do not need them immediately to test the amp. For their usage read the supplied documentation.

I hope this help lucky winners.

AR2 - Vladimir
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A-154 PowerPhysics Amp Modules

I was one of the fortunate winners of a set of PowerPhysics A154 amp modules. They arrived safe-and-sound well packed in an ESD-safe cardboard box. They're beautiful little amps with a surprising component count despite their small size. Everything looks quite robust with the exception of the output inductor which could use a little more silicone to prevent it coming loose.

Connecting the amp is kind of easy and hard at the same time. All connections are made through a 16-pin male, right-angle header. One way to connect it would be to solder wires directly to each pin and adding some heatshrink tubing to keep it clean. Another way is to wire up a 16-pin female header. This is what can be kind of hard. The first 16-pin female headers I found were the type where the wire is "sliced" into the rear of the connector then clamped together to lock it in place. But, this header would only accept 24AWG wire which seemed as if it would limit the 2+ amps of current needed for higher outputs. Next, I found some 16-pin female headers, only these were SMT solder types. I flipped it over and proceeded to solder each wire onto the solder leads. Unfortunately, when I applied some mounting force to the female header, it fell apart. It either has to be mounted to a PCB or soldering it weakened it. Finally, (phew!) I found a more robust 16-pin female header that would accept 20AWG wire, could be soldered and remained solid. Yeah! I briefly considered de-soldering the male headers from the boards, but decided not to in case I introduced damage plus I would lose the flexibility of disconnecting the boards for later projects.

Mounting it should be pretty straightforward, but I'll post on that when I get there.

Thanks again for the generous donation. I will continue to post as the amp's construction continues.


P.S. I still cannot view the A-154 pinout pdf. I can view all others on the site, but the A-154 is black. This is the case on both my home and work PCs.


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A-154 Project Advancement

Just a quick update. I've made some more advancements on my A-154 stereo amp project. It's coming along nicely and now I've bent up an open-frame chassis out of 1/8" aluminum. 1/8" aluminum is tough stuff to bend without a proper brake, but thanks to some big clamps and an assortment of vice-grips, I managed. Next, I mapped out and drilled all the holes for the connectors and switches. Finally, I installed the switches, connectors, jacks, power transformer, power entry filter and fuse holder. It's looking pretty cool!

I have the schematics done for the filter and power supply PCB as well as the op-amp designs for the stereo/bridged selection. But, they're not entered into a CAD program yet, so I won't be posting them at this time. My next steps are additional hardware fabrication for mounting the modules, rectifier, PCBs, etc. I'll post more pics as I progress further.

As always, feedback and questions are always welcome!



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Amp Project Update

Hi There,

It's been a while since I've posted an update, but I have been working and making progress on my cool little Class-D stereo A-154 amp project.

The first attached pic shows the progress in wiring the transformer primary and power switch. It also has the two A-154 modules mounted to a small aluminum bracket I bent from some thin material I had laying around. I also cut a piece of copper-clad board to use as my power supply board. I wired up the rectifier too and added some small film caps to bypass each diode junction.

The next pic shows the completion of the filter board with the large filter caps for the +/-40VDC plus the regulators and filters for the +/-12VDC required by the preamp and the A-154's signal section. Because +/-40VDC is too much for the LM78/7912 regulators, I had to add a voltage divider to the rails which is what the extra resistors are for.

The small circuit board next to the filter board is the preamp. The preamp is very basic consisting of just two NE5532 op-amps. The first op-amp is a stereo buffer between the input jacks and the power amp. The second device is set up with one channel being a summing-amp and the other channel serving as an inverting buffer. The second stage gives me the option of bridging to the amp to a mono output. The DPDT switch on the front panel will allow me to connect the two power amp inputs to either the stereo buffers or the two, summed, out-of-phase signals. Simple and clean! Plus, it will let me push the A-154 modules to their impressive bridged power level: 500W!

In case anyone's wondering why the circuit boards look strange, it's because they are not manufactured boards, but are simple boards made with a Dremmel tool. For low parts count projects, I simply draw isolating "traces" onto the board with a pencil and then Dremmel out the copper leaving isolated planes. These isolated areas then become the interconnecting traces. It's a method that works great for low parts count projects and for one-offs.

Almost there! It's getting close to the listening stage.


Note: I could not load my first pic. The file was small enough and the right type, but simply would not load. ???


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Power Physics

mmm how to they get 96% efficiency with music????

We have a JLAudio HD750 using this technology and with sinewaves at 1% THD into 4 ohms (Yes each half bridge runs at 2 ohms) we get just under 90% efficiency.

With Pink noise at just below clipping efficiency drops to less than 70% and with average music it is less than 60%.

These measurements do NOT include the switching supply
Done Assembling!

I finished building my PowerPhysics A-154 Class-D power amp! Yeah! It's taken a while, but actually went pretty smooth. Attached are two pics showing the completed unit. The next step is careful and thorough bench testing. With that, I will measure and verify noise, stability, bandwidth, gain and of course, power output both stereo and bridged. This is usually fun and progresses pretty quickly. Yet, it can be a bit nerve-racking the first time cranking it up to full power into a minimal load pushing the limit of the whole system. But, this can also be very satisfying when the amp performs well and remains stable and cool while belting out gobs of power. Sadly, this can also be the moment when countless hours of hard work and toil can go away in a silent wisp of smoke or a gruesome cacophony of melted wires, trembling transformers and shorted outputs.

Assuming all goes well, the final step will be the best part: the listening test. I'll report back to DIY when this step arrives.



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