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DieterK 28th February 2016 06:51 AM

nice Project! Do you plan to sell completed Boards?

ohdsp 28th February 2016 06:16 PM

Thanks for the comment DieterK. I have thought about selling completed, or part completed, boards if enough interest builds in the project. I did not see the point in trying to do this without any interest.

Ideally I would have waited for a polished/finished system before posting, but as I was making it all free/open it didn't matter much to me. Long term I have more ideas, some I have already started working on, which might make this system a little more desirable. If not I'll just end up with some crazy DSP/volume control system driving my homebuilt speakers, and it would still cost less than equivalent passive commercial speakers+amplifiers, which is fine by me :)

ohdsp 3rd March 2017 09:15 PM

1 Attachment(s)
Been a year since I posted here; My project is still alive and growing (and sometimes working as well!):

Example speaker crossover that is about to get some serious abuse.... I mean sensible testing.

Attachment 602845

more updates and ramblings on my blog:
Open Hardware DSP Platform - Open Hardware DSP Platform Blog

carlos515 3rd May 2017 04:05 PM

I am interested in building the DSP. One question I have is would I need the differencial to single ended active buffer if i am just using the boards as an electronic crossover ?

ohdsp 3rd May 2017 06:47 PM

1 Attachment(s)
If you have a DSP and DAC board you can cheat and connect to the 0V and positive output of each channel on the DAC PCB. Leave each negative output unconnected. (or if you want to have the phase inverted connect to negative and leave positive unconnected). The output level may be a little high for some amplifier inputs.

You would need to add a dc blocking capacitor as the positive and negative outputs sit at around 2.5V. A 100uF aluminium electrolytic (Panasonic FC or other good cap) and 100nF polyester film in parallel would be fine.

A diagram will probably make it clearer; Have attached a sketch with added channel markings and two channels connected to phono/rca sockets.

Attachment 614705


carlos515 6th May 2017 08:46 PM

Thanks ,
I have ordered all the boards and a hot air rework station . This is an interesting project. Will the freeusbi and CYC68013A usb eeprom board work to program your dsp board? Also will I have to disconect the dsp control board from the power supply when programming ?
I have the option of a 1A wall wart or 3.3A wall wart. What would the draw be for , 1 adc , 1 dac and 1 dsp board. I would be using 2 input and 6 output. 3 way crossover.


ohdsp 6th May 2017 09:41 PM

The freeusbi option should work. I have not tested it with this DSP board but it should just emulate the official Analog Devices EVAL-ADUSB2EBUZ.

Also a 1A transformer would be fine; my speaker crossover box I have been testing seems to draw around 170 to 200mA from a 9Vac transformer. My transformer is rated 10VA at 9Vac on the secondary, so around 1.1A.

Edit: I should also point out that the PCM4202 ADC seems to have weak output drivers; I accidentally set my DSP and the PCM4202 to be outputs on BCLK, LRCLK and SDATA and now my PCM4202 is spewing out junk on the I2S interface. Just make sure you have the DSP setup properly before connecting the cable to the ADC!


carlos515 19th May 2017 09:16 PM

3 channels in ?
Hi ohdsp,
I have my boards. All 50 lol . I was wondering if the ADAU 1452 can handle 3 channels in. I would use 2 ADC4202-se boards. I was thinking of my center channel .But i have not looked at the Sigma software. Can the software also handle 3 distinct channels to cross over ? The center channel is a 2way while my main channels will be 3 ways.


ohdsp 20th May 2017 07:59 AM

Hi Carlos,

Good news with the PCBs, at least you won't run out :D

The ADAU1452 can support up to 48 channels in and 48 out through a mix of I2S and TDM interfaces.

The PCM4202 is I2S only though. But you could connect up 4 of these for 8 channels in.

Internally you can pretty much wire up the filters as you wish. Under SigmaStudio there is a routing matrix where you can tell an input to go to the Core, or through an ASRC (really useful for different clock domains).

With inputs routed to the Core, and outputs from the Core, you can "drop" input/output connectors on the main schematic. And then just connect up whatever filters/equalizers or other effects are needed in between.

A good play around with SigmaStudio will help your understanding; not sure if there are any tutorials online.


ernperkins 20th May 2017 08:32 PM

Here's a good place to get started:

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