A high-end digital amplifier for everyone

[LineSource]

A DSP capable of executing a high-quality 2-way FIR crossover would be very useful addition to your project.

BruteFIR may be useful for code development.

[randytsuch]

Hi guys,
This is a very cool project, and I am looking forward to more information on it.

I kind of quickly looked over your website, and had a few questions.

How do you do volume control? Maybe I missed it, but I did not see if it was in the FPGA, or in the analog amp section.

I also wondered how much the FPGA costs? I know the big Xilinx FPGA's can get expensive, but I am not sure which one you are using.

Also wondered how much free resources are left in the FPGA, for people to add things, if it gets to there. Maybe Xilinx FPGA's are better now, but I had issues with them a while ago, if you have critical timing in them, and you don't have enough spare resources, it can be tricky to compile one that will work write. We got around it by putting lots of constraints on routing.

Maybe these questions, especially the last one, is asking for too much detail at this point, but I was curious.

Anyway, good luck with this project.

Randy

[Gridstop]

The Xilinx Spartan FPGA's like these guys used are awfully cheap, randy. Nothing like the old big Virtex chips.

The two biggest issues for DIY'ers are the 4-layer board and soldering the FPGA. Xilnx FPGA's come in .65 and .5 mm pitch only.

A DIY'er would also have a HARD time checking his circuit out for RF nastiness. (Except by ear of course).


Personally I would love to try it

Assuming a PCB was sold with the SMD stuff pre-soldered, so we wouldn't have to worry about that or the PCB layout, I think something like this could do quite well.

[DAXgroup]

Cause I can't imagine myself developing software for a company which earns money with selling the only hardware (as their property) that the software can work with...

We really don't consider ourselves a company who wants to make money by using other people's work. Most of us are still students whose goal is to design a very high quality amplifier, for you, and for us. This is only possible with a standard hardware. All the work has been done in that direction and that's why we are proposing our hardware. As many people already pointed out, the advanced technologies used in hardware tend to limit the DIY possibilities. This is only true if you want to produce and assemble everything by yourself. We knew from the very start it would not be possible for the usual DIYer to produce its own DAX (short for digital audio amplifier) since many aspects are critical. For us it would be relatively simple to have the printed circuited board produced since we already have the layout completed and a few units are already working. Moreover, since SMT is used for most components of the project (including the very fine pitch FPGA device), it would be wise to have the boards assembled too in order to ensure quality. Every aspect of the production could be discussed later as the interest grows. However, having the hardware in hand is only the beginning. First, as Brian said, because there’s a lot of work to be done on the power supply. This is a field of knowledge where a lot of people in the DIY community can bring something. Second, software coding just like the features to be added are endless and require a lot of efforts. In addition, we are sure there’re a great proportion of people who would simply enjoy to plug-and-play the DAX in their own project (power supply, case, etc.) and follow the development and upgrades.


The XC2S300E FPGA itself retails at US$50 in single quantity. Which is relatively cheap compared to other high-end devices. Furthermore, at 300,000 gates, this device is the biggest supported by the free Xilinx Webpack development tool.

We have no clue how much producing the printed circuit boards would cost. Obviously the price would decrease as quantity grows. By investing so much time and money in the project we lost track on how much “reasonable cost” is. At some point it will be required to settle on the price range for the project, but we are sure it will be a fraction of the TacT Millenium’s US$5,000!

Right now, the FPGA device (300,000 gates) is far from being fully used. We are talking about 20-25% utilisation. However, this is somehow arbitrary depending on the level of optimisation of the code (which is not on what we put the most of our time so far). Furthermore, we have to consider the thing we already plan to change and that would use more resources. Let’s just say this is not a big issue at this moment.

Concerning the license it is just too soon to figure what is best suited for the project, but the designation “world’s first open source amplifier” is exactly what we have in mind.

A DSP capable of executing a high-quality 2-way FIR crossover would be very useful addition to your project.

BruteFIR may be useful for code development.

Digital signal processing is done inside the FPGA eliminating the need for an additional DSP.

From my own experiments, I found that I needed to begin with my focus on digital interfaces and power supplies for the amplifiers' output sections. I'm guessing that you haven't focused primarily on the power supplies.

You are right! Our main focus was to develop a high quality digital system and output stage. However, as you stated, the power supply is probably the most important part of a digital amplifier. We chose not to focus on that as it can easily be changed. But now, it is exactly the kind of things where we want people to share.


Best regards,
Dax Group

[uvodee]

what is all that about being a money issue?

How much are we talking about and what is it for. break it down will you?

Jean-Pierre

[DAXgroup]

what is all that about being a money issue?

How much are we talking about and what is it for. break it down will you?

The term "issue" is maybe a little bit too much. The only thing we were saying is that production of printed circuit boards will have to be considered. In addition, the FPGA device will probably also need to be included/soldered as the pitch is very fine. A group purchase for parts will also have to be considered since all the boards require the same parts and this will be definitively make it cheaper for everyone. Ulitmately, we could have everything assembled and tested, making the project more accessible.

Therefore, there's no way we can answer the question "how much?" at this moment.

Gabriel,
Dax Group

[uvodee]

you want comments, feedback and advice from diy'ers to finalize a project you started?
good luck!

I have been browsing these forums for some 2 years now and I am still astonished everyday that when soemone comes up with a design, someone else will jack it up or crack it down.
It keeps me speechless!!!!!



I thought it was a case of needing funds to produce and sell.
Sorry for the confusion.

Jean-Pierre

[tg3]

Highly interested.

Keep us posted.

[JoeBob]

Don't let other peoples skepticism or criticism get you down, what you're doing is pretty darn cool and alot of people would be interested when you get this out the door. But if you need feedback from us DIYers, I am sure I speek for everyone when I say, you're going to have to make it easy to reprogram, no one is going to want to keep the firmware it was shipped with for long (byt the sounds of it you already wanted to do this), not that your firmware will have anything wrong with it, but everyone's going to want to change things and add other features. Just wanted to give some ideas, in case you didn't already have them...

Oh, and you know, if you need a beta tester that's close *cough* *cough*, you know where to look (if I weren't obvious enough, well, me...)

[uvodee]

===you're going to have to make it easy to reprogram, no one is going to want to keep the firmware it was shipped with for long (byt the sounds of it you already wanted to do this), not that your firmware will have anything wrong with it, but everyone's going to want to change things and add other features.====



my ink wasn't even dry yet ......

Jean-Pierre