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Digital should not remain a barrier for diyAudio beginners. Before the digital age, diyAudio was about designing a PCB and soldering through-hole components on it.
Nowadays, diyAudio encompasses digital. It requires designing a PCB hosting SMD (Surface Mounted Devices), and it requires creating a DSP (Digital Signal Processing) program. Those are the two new difficulties.
Ten years ago, most diyAudio enthusiasts would have failed building a digital audio system from scratch. The situation has changed. There are more and more hobbyists dealing with 32-bit microcontrollers. There are more and more hobbyists overcoming the SMD difficulty.

Here is a digital audio system built from scratch. Diptrace got used for drawing the schematic and converting it to a PCB.

The PIC32MX2 gets debugged and programmed using Microchip MPLAB ICD 3 ($189.99) . A simple experimental application would read the stereo audio entering the WM8731, apply some processing like filtering, equalizing, splitting, dynamic compression or expansion, then deliver the processed audio on the WM8731 stereo outputs. (continue reading…)

DipTrace remains free provided you don’t hit the 300 pin barrier. From a diyAudio perspective, what are the possibilities within such limit? Here are three different diyAudio boards as practical examples.
The first board hosts a PIC32MX2 coupled to a WM8731 stereo codec.
The second board is a SigmaStudio target, hosting the ADAU1701 the same way as Analog Devices EVAL-ADAU1701MINIZ.
The third board hosts a WM8580 multichannel codec delivering eight analog outputs.
The common denominator of all three boards is a 2×10 pin expansion connector allowing to stack them. A possibility is to stack PIC32MX2 acting as USB-audio device, grabbing digital audio from the PC, sending it over I2S to the ADAU1701 board. (continue reading…)

Things are moving fast. Want to build your own miniDSP? Operated within Analog Devices SigmaStudio Digital Audio Compiler? Try ordering the  ADAU1701 Carrierboard from Audiodesine. Quite surprising, the company presents itself as specializing in “Audio Design for an Analog World”.

Such statement doesn’t imply that Audiodesine people reject or ignore digital. How possible anyway, now that virtually all audio material get recorded, mixed and edited in digital?

“We love analog, but we do not hate DSP, though we do regret the fact that to get into DSP you seem to need SMD soldering skills and a lot of math”.

Audiodesine selected the ADAU1701 DSP because of SigmaStudio (from Analog Devices) requiring no programming. SigmaStudio allows you to drag and drop prebuilt blocks such as “State Variable Filter”. In a few minutes you have a circuit. (continue reading…)

LTspice from Linear Technology operates as schematic entry for the Digital Audio Compiler.
The filter coefficients get manually entered in the audio subcircuits by right-clicking them. The audio sampling frequency gets defined using the .param Fs=44100 directive. An IIR BiQuad gets simulated using two delay lines, each involving a matched transmission line, with each delay automatically defined as 1/Fs in all subcircuit instances.
No quantizer, no arithmetic saturation, no sample/hold. However the Bode Plots appear to be valid. Try it out with the WM8731 Audio Crossovers – Digital XOs downloadable files. (continue reading…)

WM8580 looks perfect for experimenting multichannel audio. Wolfson managed to pack a lot of features in a well structured manner. The S/PDIF Receiver and S/PDIF Transmitter are the most complicated blocks, needing to comply with the S/PDIF standard. Let’s make sure we know what we are talking about.

First thing to point out when dealing with Wolfson WM8580 S/PDIF Receiver, is the high quality of the recovered clock, exhibiting less jitter than some Cirrus S/PDIF designs still used in digital crossovers like Behringer DCX2496. People having got trouble with S/PDIF in the past may feel a positive difference.

Second thing to point out is Wolfson choice to implement a S/PDIF frame management following the Consumer (Con) grade instead of the Pro grade. There is nothing qualitative in this.
A chip adhering to the Pro grade gives full access to a table that gets progressively delivered, one bit per audio sample, along with the audio data. After 192 audio samples the table gets completely refreshed. You can imagine how powerful and flexible it is, having 192 slow serial channels at disposition for conveying auxiliary data. (continue reading…)

Never heard about the C-Media CM6206 7.1 USB-audio chip ? It comes out as the chip used in most 5.1 and 7.1 USB-audio adapters.
Back in July 2010, Adrian Pardini tried to get it understood by ALSA – the Advanced Linux Sound Architecture.
There is a Linux patch about CM6206. Unfortunately there are reported quirks. Eric Lammerts, Clemens Ladisch and Dan Allongo continued working on ALSA CM6206 support.
In April 2011 Wolfgang Breyha and Takashi  Iwai continued on the Android Source Tree.

Go googling “revision 8129e79ed7932bd11d60518d62434a0b687e5771″

ALSA: usb-audio – Terratec Aureon 7.1 USB ID as C-Media cm6206 quirks
This patch adds support for the Terratec Aureon 7.1 USB which uses a C-Media cm6206 and needs all the quirks already found in the past.  (continue reading…)

LabVIEW from National Instruments (NI) is a renowned PC-based instrumentation system, specialized in signal analysis and measurement. LabVIEW became available on the Windows PC platform in 1992.
Since then it pervades the academic world, generating plenty R&D applications as spin-offs.
Many universities and tech schools impose LabVIEW tutorials to their students.

Back in 1992, an average PC was clocked at 33 MHz or so. One year later, thanks to the first i486 cores clocked at 3 times the external bus speed, the Windows PC performance got a big boost – when running on cache. (continue reading…)

Digital Audio Compilers are getting user-friendly nowadays. No more programming. Creating an audio application only consists of dragging and dropping blocks, interconnecting them, for defining digital audio signal flows. Let’s read the descriptions of three of them:

- ANALOG DEVICES – SigmaStudio
- FREESCALE – Symphony Studio
- DSP CONCEPTS – Audio Weaver
(continue reading…)

Most soundtracks you are listening to, actually depend from Steinberg VST. Such technology is at the heart of digital sound creation (the VST instruments) and sound processing (the VST effects). From a diyAudio perspective, it is worth knowing a few VST basics, especially when experimenting with Synthmaker or Flowstone.

Here follows a neutral compilation of covering most important VST aspects. Worth visiting, is the Steinberg website, where it shows how VST has deeply penetrated all compartments of the sound industry.
Steinberg is currently promoting the The Art & Science Of Sound Recording video tutorial series on music production, presented by multi-platinum producer Alan Parsons. In more than 10 hours of footage, more than 40 fellow professionals join Alan Parsons in this guide to modern recording, including Erykah Badu, Jimmy Douglass, Jack Joseph Puig and Simon Phillips. This 10-hour DVD set applies classic, old-school recording experience to the modern recording scene and will be a standard work on the subject for years to come. (continue reading…)

Active crossovers are a popular diyAudio topic, however only a few hobbyists managed to build a home-brew digital crossover on a kitchen table, for less than $99 all inclusive, software included.

This is going to change with the recent arrival of the PIC32MX1/MX2 family (twin I2S), and the NXP LPC4330 (twin I2S and possibly more through the SGPIO). I2S stands for Inter-IC Sound, Integrated Interchip Sound, or IIS. This is different from SPI and I2C. I2S is a 20 year-old standard, still widely in use, for connecting a µC on an audio ADC, DAC or Codec. On top of this, the PIC32 and ARM Cortex chips feature a fast 32-bit x 32-bit multiplier delivering a 64-bit result. This enables computing audio with a 192 dB dynamic range, about 50 dB more than the best available ADCs and DACs. Quite a headroom would you say.

The PIC32MX1/MX2 has Flash memory and runs at 40 MHz. This is a nice single chip µC, easy to use. Like all PIC32 chips, there is a MIPS M4K core inside, 32-bit of course. The PIC32MX1/MX2 is fully supported by Microchip MPLAB ICD3 programmer and debugger. Call it a one-stop-shop solution.  The PIC32MX1/MX2 is a nice recent addition (early 2012) to a mature µC architecture. We need experimenting with the PIC32MX1/MX2 in first place. Back in 2008 most µC programmers got intimidated by 32-bit µC, thinking they were expensive, complex, requiring C for programming, and always short of RAM with Linux as background. Lucio Di Jasio from Microchip did a great job in optimally introducing the PIC32 to people having started their carrier more than 25 years ago, writing firmware for 8-bit µC like the Intel MCS51 one-chips or Motorola 68K CPUs back in those times.

(continue reading…)