I am very interested in your product Toaster. If all works through, this will make my plan to build a carputer that much simpler and space saving! I really hope you will come up with a final product soon.
I do have a few questions to ask, and I apologize if this has been previously discussed but it's 1 in the morning and I'm too sleepy to scour through 15 pages lol.
1) How will the audio card/amplifier hybrid get its power from? It's safe to say it won't be just from the USB plug so I'm guessing a power cable will have to be run to the battery?
2) Will there be a switched power cable which will turn on or off the card/amplifier unit?
3) What is the RMS output per channel, for the speakers and the sub?
4) What is the projected final price? I am hoping it will be quite affordable, somewhere around 150 or lower.
Thanks for all your hard work Toaster!!
1) Yes you will need a power cable. A dedicated power connection will need to be made using a supplied Anderson connector. This connector is capable of 600v and 100A continuously which is what is required for this amplifier if you run it at the highest output.
2) One of the 4 auxiliary pins on the connector is for the car's ignition cable. Basically any voltage source that goes above 1.2v and less than 30v. So tying it to your car's ignition switched 12v supply is exactly what it is for and it will turn on. It can also be tied to a Fusion Brain output relay to control when the amp turns on and off from an external control or whatever else.
3) Currently 280W to 300W true RMS power per channel for the 4 speaker outputs and around 550W true RMS for the sub. I might be able to increase the output by 10% to 15% but depending on how the board handles high temperatures, I might have to derate it as well. I have not tested this design at those powers yet. It can drive down to 1.5ohm outputs.
4) No way it will be $150 USD or lower. :( Sorry. I can't say final price, but I always work off of designing the best I can. Then once it works, I can find areas to simplify or reduce. These are very high end components and lots of them.
It is also very very large right now. Remember it is a high end audio amplifier that has a high end soundcard in it as well. So it is at least the size of a high quality, high output power amplifier. The version I have now also has some inputs, but I don't know if I am going to keep them in the next rev or not.
USB is a differential digital signal that even meters of cables won't interrupt in the car. Once it gets to the board it stays USB all the way into the physical layer by the FPGA. This then becomes a wider parallel bus into the main processor. This decodes the USB data transfers and keeps the computer happy. At the same time it spits out 3 very very very high speed digital serial communication bus segments into another processor. This second processor takes each of these high speed digital serial lines and splits them into 2 individual serial streams each, a left and a right channel. There are only 5 channels (4+1) so the right side is wasted on the sub line but it makes the physics behind the shielding easier when they are somewhat symmetric, and I have the bandwidth and power to waste 1 channel of digital communication. So now this second processor has 5 serial data streams of 24bit 192KHz music with less than 3ms latency between the PC and the processor and they are all completely synchronized so they are all exactly the same latency, 0 jitter between them. The beauty of the high speed buses. The second processor then interprets the incoming serial stream to an outgoing PWM signal at 32bit resolution. It is 256 times more accurate than the incoming signal so you won't get conversion losses there. These super highly accurate signals are still all synchronized and go into 3 individual amplifiers in the literal sense of the word. What goes in is logic level signals with almost no power. This then gets amplified directly into a signal that gets filtered a few times (distorts the signal at high frequencies purposefully so that any ringing from the digital is filtered out, and leaves the slow audio signals completely alone) by passive components and then to your speakers through a bridge tied arrangement that will produce a +/-48v signal which to the speakers will look like a 96v potential difference.
This isn't your average Chinese amplifier. This is a serious amplifier with serious power and serious thought behind it. :)
I have something in mind but its no where as complex as what you have there, ie it is meant for people who want to build a decent a USB digital amp at home and cheaply with similar power/spec to a good HU.
Let us know the final specs, thd, power out and all. Cheers
Very glad this is still in the works, cant wait to see what it can do. TRUST me when I say the size doesn't matter to me, I've got an amp that literally only fits one way in my trunk, something says we can make it work :)
What about a simple lower power but still fully digital amp that doesn't require a boost power supply? I'm thinking Silicon Labs CP2114EK USB to I2S bridge, STMicro TDA7802 I2S AMP - 28W x 4 channel @ 4 ohm from a 14.4 V supply, large inductor & cap to filter alternator whine, and perhaps a small PLD to fan stereo to 4-ch w/ fade control.
I'm not sure I'd have the time to build up and sell kits, but it would be a purely open hardware design so anyone could build and modify it. It's basically the same type of high efficiency class AB amp in most head units.
Class AB amps suck balls. Very inefficient. Class D profile would be the way I'd go. But then again I'm not designing it.