A Hackable Hi-Fi Audio DSP

DSP 01 Hi-fi Signal Processor

 

Audiophiles tend to put analog systems on a pedestal. Analog systems can provide great audio performance, but they tend to be quite costly. They’re also hard to tinker with, since modifying parameters involves replacing components. To address this, [tshen2] designed the DSP 01.

The DSP 01 is based around the Analog Devices ADAU1701. This DSP chip includes two ADCs for audio input, and four DACs for audio output. These can be controlled by the built in DSP processor core, which has I/O for switches, buttons, and knobs.

[tshen2]‘s main goal with the DSP 01 was to implement an audio crossover. This device takes an input audio signal and splits it up based on frequency so that subwoofers get the low frequency components and tweeters get the higher frequency components. This is critical for good audio performance since drivers can only perform well in a certain part of the audio spectrum.

Analog Devices provides SigmaStudio, a free tool that lets you program the DSP using a drag-and-drop interface. By dropping a few components in and programming to EEPROM, the DSP can be easily reconfigured for a variety of applications.

Fully Integrated HiFi Studio Monitor

Studio Monitor and PCB

Have you ever wanted to build a high quality audio crossover and amplifier? [Rouslan] has put a lot of thought into making his dual amplifier studio monitor both high quality and simple to build.

With a concise schematic, a meaningful block diagram, and simulation results to boot, his well-written post has everything you need to build self-powered bi-amped speakers based on the LM4766 from Texas Instruments. It is great to see simulations which verify the functionality of the circuit, this can go a long way when working with complicated analog filters and audio circuitry. For those of you who do not have access to PSPICE (an expensive professional simulation tool), [Rouslan] uses LTspice from Linear Technology. TINA-TI from Texas Instruments is another great free alternative.

Additionally, [Rouslan] goes over the typical issues one has with a bi-amplifier studio monitor, such as phase misalignment and turn-on pop, and then provides a solution. Note that his project is powered by 20VAC, which requires an external transformer to convert the 120VAC in the wall to 20VAC. Be careful with high voltages! In the future, adding a high quality voltage regulator will most likely increase the performance.

His post finishes up with a very clean circuit board, which he ordered from OSH Park. With such a complete design, there is nothing keeping you from building your own. Go out and put that old speaker sitting in your basement to good use!

If you don’t have an old speaker sitting around, check out these very cool DIY speakers.

Audio Crossover Back in Service


Audio Crossovers are an essential tool for any high end speaker system. Because most individual loudspeakers are unable to cover the entire spectrum of audible sound as well as multiple drivers are, it is necessary to split the input signal into low and high frequency parts. When a friend of [Anthony]‘s was about to send off a classic Klipsch AA Crossover to be repaired professionally, [Anthony] insisted it was possible to save some money and do it himself.

The oil can capacitors of the Crossover had gone bad, so a new set of metalized polypropylene capacitors were ordered to pick up the task. After carefully removing the old caps, [Anthony] assembled the new set on a breadboard, and mounted the board to the old Crossover base (along with some tasteful McDonalds straw spacers). The entire process is detailed on his blog, and we are sure his friend saved a good deal by this home repair method. Capacitor issues are a common problem in repairing electronics new and old alike, and always a great place to start looking when devices start acting funny.

Broken laptop recovered using an Arduino

We see Arduino boards used in a lot of projects but we’ve never thought of using one as a USB crossover cable. That’s basically what [Jack the Vendicator] did to get his broken laptop running. When his video card stopped working he found himself unable to access the laptop. Newer machines don’t have a serial connector, which could have been used for a serial terminal, so he was at a bit of a loss since neither SSH nor VNC were installed. But he thought he might be able to use the Arduino as a serial terminal connector over USB. He plugged the Arduino into the laptop, and connected a USB serial converter from his desktop computer to the Arduino’s serial pins. In effect he’s just taking advantage of the FTDI chip, translating those signals back into USB on either end. Once he booted the headless laptop it took just a couple of blindly typed commands to get SSH running in order to regain control.