Hi All,
I've been kicking around the idea of a basic DSP group buy. I'm familiar with the MiniDSP product. I'm looking to produce a 2 in x 4 or 6 out DSP with crossover capability and equalization, etc. The idea would be a stereo source to 4 channels of amplification for bi-amped speakers. 6 outs would allow for tri-amped. I'm adept at programming .NET and have researched both the DSP chips as well as an interface between a PC based software and the DSP chip. I can create the software GUI and could probably struggle through the design of the DSP board. This post is to gauge interest in a possible group buy as well as to see if anyone would seriously want to join forces for the design of the board.
I've been kicking around the idea of a basic DSP group buy. I'm familiar with the MiniDSP product. I'm looking to produce a 2 in x 4 or 6 out DSP with crossover capability and equalization, etc. The idea would be a stereo source to 4 channels of amplification for bi-amped speakers. 6 outs would allow for tri-amped. I'm adept at programming .NET and have researched both the DSP chips as well as an interface between a PC based software and the DSP chip. I can create the software GUI and could probably struggle through the design of the DSP board. This post is to gauge interest in a possible group buy as well as to see if anyone would seriously want to join forces for the design of the board.
An interesting project for sure. What about your effort would not be, in essence, a duplication something available through (for instance) MiniDSP? Are you just interested in "rolling your own" DSP crossovers? I know of at least one person who has been working on DSP hardware (using the ADAU1701) and is finishing up the code for an extensive crossover design package that would communicate directly with the hardware. To give you an idea of the scope of the project, he has been working on it for several years now... Unless you REALLY want to, or are doing something new/different, it might not be something that you want to start on your own. Not that I (or anyone else) should tell you what to do, but this can turn into a pretty big project depending on how much and what kind of DSP you are planning on implementing.
Thanks for your reply. Is that person you mentioned doing it commercially or as a group buy? I am interested in DSP technology, so that is the main impetus for the project. I don't think I would do a lot of algorithm creation if not needed. Sigma DSP chips by Analog can be programmed directly from Sigma Studio as one option.
The person in question is a retired EE (I think) who I believe will want to sell the "system" of hardware+software when it is finally ready. I let him know about this thread and he can chime in here if he would like.
If you want to play around with DSP, you might think about getting an eval board from a manufacturer. For instance, so that I could play around with SigmaStudio and for something different than MiniDSP, I recently bought from Analog Devices an ADAU1452 evaluation board. This comes with spdif in and out (toslink), 4-channel analog input, 8-channel analog output, and an onboard EEPROM so that the board can operate "standalone". What happens between the inputs and outputs is all up to you and whatever you create for DSP flow using SigmaStudio. Its a very flexible platform (the DSP functionality is reprogrammable, which I find pretty cool), and I didn't have to do any hardware development!
You can check it out here:
ADAU1452 Evaluation Board | Analog Devices
Yep. Charlie is referring to me. Except retirement is kind of a misnomer, in that I feel like I'm working more now than I did when I was officially employed.
Unfortunately, I don't have a credible business plan at this point. Hardware is either low-volume and expensive with high recurring cost or else very affordable when produced in large quantities. But getting to that affordable stage requires a large investment and a large enough market, and right now I don't have that. So I'd be happy to sell software.
One possibility you might want to investigate is using the 2x4 miniDSP board for your hardware. I made a piggyback board with my own micro that waits for the miniDSP micro to load the ADAU1701. Once the micro on the miniDSP is done with initialization, it no longer uses the I2C bus, so you can "take over" the board. My micro is programmed with a simple command decoder that lets a PC send data to the ADAU1701 Parameter RAM via a "standard" FTDI chip. I've got .NET software that provides a math model of the ADAU1701 for designing crossovers and EQ, and it will send the coefficient and register data to the ADAU1701. So this piggyback board will allow you to program the miniDSP board with your own program (developed with SigmaStudio), and it will update the ADAU1701 in real-time.
The picture shows the piggyback board in place on the miniDSP. I've got an extra board that I could send to you, and I could send you a link to the software that controls this board. It will at least give you an idea of what can be done using the $80 miniDSP board.
Another alternative is an ADAU1701 circuit with built-in amplifiers. One of the lowest distortion class D amps is the SSM3302, and I've got a working board with 2 stereo SSM3302 amplifiers and the ADAU1701. This board is fine for lower-powered monitors, as you can only get about 20W max from the SSM3302 chips. I started an update to this board that would provide a subwoofer output that would make it a nice plate amp for a active 2.1 system (it would actually be a 4.1 amp, with shared woofer and separate mid and tweeter amps). The board is small enough that it could be mounted inside the plate amp and it could take its power from the plate amp supply. It could be a nice product that would be fun to play with. The prototype board is in the picture below. The schematic and PCD files are done in ExpressPCB, and I can send you the links if you are interested. The PCB actually includes two circuits-- one is the ADAU1701/SSM3302 board, and the other is the piggyback board (both circuits fit on one of those Express mini-boards).
An externally hosted image should be here but it was not working when we last tested it.
Could you design a new board using the ADAU1452 (ADAU1452 datasheet and product info | SigmaDSP Digital Audio Processor | Audio Signal Processors | Analog Devices) instead of the ADAU1701? In addition to MiniDSP there is also the Elektor Electronics (mag) board availabe using that chip but only the evaluation board using the new one which is much more powerful and contains also an ASRC.
ADI provides schematics for their evaluation boards, so the design part is easy--it's just a matter of laying out a version of their board without making mistakes.
I'll probably make a variant of the ADAU1452 board sometime in the future, but right now I don't have any application that requires the extra processing capacity or features. The ADAU1701 provides 1024 instructions at 48KHz or 512 instructions at 96KHz. Each biquad only requires 5 instructions, so you can implement over 100 biquads and still do a lot of other processing with the smaller, less expensive ADAU1701. Arrow sells the ADAU1701 for less than $7, whereas the ADAU1452 is around $22, so I need a compelling reason to use the ADAU1452. The SRC and SPDIF features of the 1452 are nice--I would make a board with the ADAU1452 when I have an application that needs those features.
Maybe you should clarify your requirements.
You can hook up additional D/A to the freeDSP.
Are you looking for single-ended or differential output? Inputs? Is 0,9VRMS enough for your application?
Supply structure? all-in-one/modular? Special processing needed? (This is one of the main limitation of the MiniDSP)
For example do you need dynamic processing, extended control functions, limiter/compressor, FIR IIR ... budget ...
For the price, i can recommend the eval board, but does it fulfill your requirements ...
You can hook up additional D/A to the freeDSP.
Are you looking for single-ended or differential output? Inputs? Is 0,9VRMS enough for your application?
Supply structure? all-in-one/modular? Special processing needed? (This is one of the main limitation of the MiniDSP)
For example do you need dynamic processing, extended control functions, limiter/compressor, FIR IIR ... budget ...
For the price, i can recommend the eval board, but does it fulfill your requirements ...
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