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Old 14th January 2016, 07:45 AM   #1
freedsp is offline freedsp  Germany
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Default freeDSP main thread

This thread is a place for links to other threads that are related to the freeDSP project. Feel free to post with these links and a brief comment on what the thread discusses. Occasionally the moderators will consolidate them into fewer posts.

Please create individual threads (and link them from here) to connect with other people working with the freeDSP for discussion and to support each other. Please keep in mind that freeDSP is a spare-time project and not a commercial product. If you want to get a freeDSP you need to build it yourself (manufacture board, order parts, …) or organize centralized buying with other DIYers.

The freeDSP is a low-budget open-source digital signal processor family, which is published under a creative commons license. It allows the unrestricted use and modification of the modules. The applications range from active loudspeaker concepts and room equalization over advanced musical effect processors to car audio signal processing. We would be happy if you join us and improve or extend the project.

GitHub is used for file exchange. If you want to join the development team, just send us a private message with your ideas and your GitHub user name. Most freeDSP PCBs will be designed using KiCad. Some guidelines were defined to make future freeDSP development and extensions as compatible as possible. These layout guidelines can be found in the freeDSP-Wiki.

In the following you’ll find a summary of the current freeDSP plans:

green = sources tested and available,
black = work in progress,
gray = on the wish list

freeDSP motherboards:
freeDSP CLASSIC (ADAU1701 / 2 x In & 4 x Out Analog via RCA) freeDSP thread, SigmaStudio AutoEQ
freeDSP CLASSIC SMD (ADAU1701 / 2 x In & 4 x Out Analog via RCA)
freeDSP INSANITY (ADAU1452 / 4 x In & 4 Out Bal. Analog via Jack, alt. 8 In x 8 Out Unbal. / 1 x In & 1 x Out SPDIF via RCA & Toslink)

freeDSP compatible motherboards:
PiDSP (ADAU1450 / RasPi In + Out / 3 x I2S In + Out ) PiDSP thread

freeDSP programmer:
freeUSBi + EZ-USB

freeDSP IO expansions:
freeDSPx AES/SPDIF IN (1 x In AES/EBU via XLR / 1 x In SPDIF via RCA)
freeDSPx SPDIF IO (1 x In & 1 x Out SPDIF via RCA & Toslink)
freeDSPx BAL OUT x16 (16 x Bal. Out Analog via SUB-D)
freeDSPx ADAT IO x3 (3 x In & 3 x Out ADAT via Toslink - maybe even 4 IOs)
freeDSPx BAL IO x4 (4 x In & 4 x Out Balanced Analog via Jack, alt. 8 In x 8 Out Unbal.)
freeDSPx UNBAL IO x2 (2 x In & 2 x Out Analog via RCA)

freeDSPx AMP

freeUSBi kits and freeDSP classic kits are almost always available - please use the contact fomular on our website :-)

Last edited by freedsp; 7th March 2017 at 03:48 AM. Reason: freeDSP & freeUSBi kits still available
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Old 29th June 2016, 07:56 PM   #2
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Location: Regensburg
Default Quick start Thread for 2-way crossover with FreeDSP

Hello FreeDSP friends,

if you need some help to have a first 2-way crossover design with FreeDSP (Classic) have a look to my thread. You find there also information how to include volume control (with buttons and IR control) and to prevent power on/off noise.

You find the link here:

Have fun!
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Old 6th January 2017, 05:43 PM   #3
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Default aes/spdif pcb and free USBi board's


I ordered an aes/spdif board, but because transport was the major part of the costs, I ordered some more.
Please contact me if you're interested in the pcb. They are 9 euro each, send by standard post in Europe.
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Old 25th May 2017, 07:48 PM   #4
Mayday is offline Mayday  Sweden
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Any advice on how to set up a 2-way x-over with dipole compensation on the Low pass?
I've played around a bit with Sigma Studio, but apart from using behringer dcx2496 I am a complete novice when it comes to DSP.
I'm refering to what filters or other tools to use.
The High pass filter, I'd like the signal to go "unaltered" to the passive x-over in the mid/high part of the dipole speakers.

I will try to use the FreeDSP classic with IS in via an audio-widget board. And once I have it working, use two es9023 DAC's as output via IS from the FreeDSP board.
The more you learn, the more you realize how little you know...
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Old 26th May 2017, 10:37 AM   #5
Mayday is offline Mayday  Sweden
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Does this look like a decent starting point?
(attached screenshot of SigmaStudio)

I do have two fully populated (and tested as far as that they take programming), so I guess I could use one FreeDSP Classic/channel, allowing for more complex filters etc.
I've also made a measuring mic with amp according to the info on Linkwitz site, including the modifications to the mic.

When the system is up and running enough for me to measure it with REW, I'll need to read up on how to use REW etc with SigmaStudio to get the best sound quality possible in the room.
Attached Images
File Type: jpg FreeDSP_2_way_xover_test_1.jpg (111.7 KB, 28 views)
The more you learn, the more you realize how little you know...
Revived my blogg
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Old Yesterday, 01:55 PM   #6
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Location: Regensburg
Hello Mayday,

if you have measuring capabilities I would first to start with a measurement of the different loudspeakers. It is crucial to understand the frequency response and SPL levels each speaker is providing.
From that you can choose/plan the filters and level adjustments you need.
Important to know is also which amplifiers you use. Are they identical? Or do they habe different output power and amplification?

For a first implementation I would go for the infernal DACs and one Freedsp as it offers sufficient computing power for many solutions.

Good luck!
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