PDA

View Full Version : User programmable DSPs



Jan Daugaard
11-21-2008, 03:40 AM
There are some very nice DSPs that not only serve as electronic crossovers, but which, with the aid of a measuring microphone, are also capable of achieving a nearly perfect frequency and phase response.

The DEQX DSP has been previously been mentioned
http://www.deqx.com/
and at a recent hi-fi exhibition here in Copenhagen I heard a demonstration of another DSP:
http://www.holmacoustics.com/dspre1_introduction.php

The problem is that they are so expensive. The 3-way stereo version of the Holm Acoustics DSP thus costs 40.000 DKK (approx. $6800).

Being a computer scientist with some knowledge of DSP, I could programme a DSP myself. I just need a device with suitable analogue og digital inputs and outputs, and with a USB or similar port such that programmes can be transferred from my PC to the DSP.

I would like to hear from members with a knowledge of user programmable DSPs.

boputnam
11-21-2008, 02:47 PM
Jan, there are many. Interfacing with a laptop is possible, with most.

In relative order of increasing cost, worthy candidates include:

dbx Driverack series
Ashly Protea
BSS Omni or Minidrive
Klark Teknik DN9848
xta DP4-series
Meyer Galileo

I've used all these. My favorite is xta - particularly with their AudioCore software. Slick...!

Jan Daugaard
11-22-2008, 01:28 AM
Are any of them user programmable? They all appear to be turnkey solutions, and I would also like to learn something about DSP by writing the programme.

boputnam
11-22-2008, 09:48 AM
I'm not sure I know what you mean.

Many of the devices have library of "presets" - EQ tunings for specific cabinets. However, they do not need to be use only that way.

I use them without presets, and make my own settings - from input to outputs, using Smaart measurements for time-algnment, phase and EQ.

Ian Mackenzie
11-22-2008, 03:26 PM
Are any of them user programmable? They all appear to be turnkey solutions, and I would also like to learn something about DSP by writing the programme.

You can buy some really good software crossover engines.

http://www.diyaudio.com/forums/showthread.php?postid=1592689#post1592689

Jan Daugaard
11-23-2008, 01:59 AM
Boputnam:

Most of these devices are based on FIR filters:
http://en.wikipedia.org/wiki/Finite_impulse_response

I can, and would like, to write the software from scratch.

Mr. Widget
11-23-2008, 08:53 AM
I can, and would like, to write the software from scratch.I don't think any of the available DSPs are designed with geeks of your magnitude in mind. :D There are so few people who are knowledgeable of audio and capable of programming at that level that there is virtually no market for such a product.

You may find a manufacturer who would let you "crack" their box, but short of that I really doubt that the product you are looking for exists.


Widget

mvaldes
11-24-2008, 01:16 AM
Have you tried this ?

http://drc-fir.sourceforge.net/

It's free, it's open source, and (according to what a lot of user say) seems to be one of the best Software DSP.

Michele

Jan Daugaard
11-24-2008, 02:39 AM
Mvaldes:
The site you linked to contains some excellent suggestions. Thanks!

I have also considered processing the digital signal once and for all, i.e. processing the signal from a CD and then burning the corrected signal onto another CD which is then played instead of the original.

johnaec
11-24-2008, 05:58 AM
I have also considered processing the digital signal once and for all, i.e. processing the signal from a CD and then burning the corrected signal onto another CD which is then played instead of the original.What an interesting idea! Of course, then you're tied to the hardware, if I understand correctly, but it takes a complete layer of processing/reprocessing out as I see it. Or am I missing something?

And before you go all detailed, no - I'm not a programmer of any sort, and wouldn't understand what you're talking about. But I *think* I understood that little nugget you just dropped...

John

HOLM Acoustics
11-24-2008, 09:36 AM
I'm sorry to hear you are not inclined to buy our DSPre unit, but as a fellow DIY i fully understand your eager to try on the task for yourself. The trick re-burning a CD with Digital Room correction is to be found somewhere on the internet - i though completely has forgotten the name of it and can't seem to find it again.. If you are not put off by having a PC running at all listening time and the constant hassel of computer breakdowns ect., i would recommend you getting a multiway soundcard and running BruteFIR on it, this way you can make crossover and correction filters from scratch.. Good luck on your filter coding! Remember you need a gain and phase calibrated microphone+hardware, before any of your filters make sense.

http://www.ludd.luth.se/~torger/brutefir.html

Jan Daugaard
11-24-2008, 12:48 PM
HOLM Acoustics:
There is a private message for you (you have to log in to read it).

readswift
12-24-2008, 05:35 PM
I suggest waiting several months.

ESS Sabre DAC chip ( read : best spec ever )

new revision coming next year with independent FIR filters on each of its 8 outputs. You can use your class-a amps. Completely eliminates digital interfacing jitter. Close to theoretical max specification, thdn ranges from -112 to -116 . 50 step digital volume attenuator, isnt sacrificing much because it is right inside the dac chip.


You wont need multiple digital outs with the new Sabre.

Carl_Huff
12-24-2008, 09:46 PM
Jan,

If you are serious about learning DSP programming for audio purposes probably the easiest path would be to buy one of the Analog Devices eval boards. They cost about $500 and include software development tools.
_______________
Best Regards,
Carl Huff

Jan Daugaard
12-25-2008, 01:32 AM
Carl:

I take it that you are referring to these products:
http://www.analog.com/embedded-processing-dsp/processors/en/index.html

Do you have personal experience with one or more of these products?

Carl_Huff
12-25-2008, 10:52 AM
Yes,

Those are the DSPs. I have experience with two of their eval boards. They represent a great way to learn DSP programming for audio purposes.

For the ADSP21262 Processor:
http://www.analog.com/en/embedded-processing-dsp/sharc/21262-hardware/products/product.html

For the ADSP21369 Processor (newer & much more capable):
http://www.analog.com/en/embedded-processing-dsp/sharc/21369-hardware/products/product.html

Both eval kits include the Visual DSP++ development tools. The Visual Audio addon libs can be downloaded from the AD website.

The new Universal Audio DSP product that is getting such great reviews from users utilizes 4 of the ADSP21369 processors.
http://www.uaudio.com/products/uad/uad2quad/index.html
____________
Best Regards,
Carl Huff