i am happy to announce that the Megapixy design files are now available online for your viewing/modding/hacking pleasure. this took awhile. it turns out, when many of my design files are over a year old, i need quite a bit of time to organize them! Megapixy is an adventure in sourcing parts. you will probably struggle to find the PCB receptacle for the IPEX micro-coaxial cable , as well as the…
i ended the last update with these two problems: the chassis is stupid. the wood warps when wet, the design wastes material, and the bezel bends under my fingers when i hold it. the LCD panel is mounted unevenly, causing backlight bleed . these are both chassis problems, which require chassis solutions. solutions i built in parallel with Giger board - such is iterative design. at this point, i was…
let's detour into visual design - did you notice this on the previous update ? it's the Megapixy logo! i like Megapixy, and i like making logos. go figure. in the infinite possibility space of logo (and not-logo) design, some reason must be provided for why anything looks like anything. the Megapixy logo exists because: Megapixy uses the embedded Displayport video interface. Megapixy has the same…
let's revisit that photo from my last post : why is the bottom-right footprint not like the others? in my last post, i got the Retina iPad LCD panel working. but it was buggy & small & rather underwhelming. although! that is just one LCD panel in a world full of LCD panels. my approach should work with any panel which communicates through embedded Displayport (eDP). what other eDP panels are…
in my last update , i assembled a mediocre monitor using an AU Optronics LCD panel. it required an LCD control board to act as an HDMI -to- LVDS converter, for LVDS is the language of most LCD panels. old-fashioned LCD panel requiring an LVDS converter to connect to a computer. but LVDS is losing popularity. as our phones & tablets keep shrinking, how can anyone make room for that LVDS-converter…
to write about Megapixy is to write about the last 2 years. this project has tested my patience and perfectionism and pursuit of beauty as few have. Megapixy was an adventure in sourcing parts. it was my first self-directed surface-mount PCB design, my first try at soldering QFN & DFN packages, my first attempt to route high-speed differential signals, my first non-Analog system design. Megapixy…
i built the µENA for a job. it worked but lacked political backing (perhaps for good reason), and was ultimately abandoned. i feel bad for it, as i feel for all neglected projects. so here i am, telling its tale beyond the grave. what if you were trying to take a measurement which needed all this equipment? an electrical network analyzer (for which the µENA is named ) two digital multimeters an…
in the previous update, i fretted about the 146Hz node in my listening room, and wondered if i could fix it. you can't just fix it by turning up the gain at 146Hz - it's like pouring sand into a black hole. the problem has to be fixed acoustically, so it's time to try bass-trapping . bass-trapping is the process of shoving huge amounts of foam and/or fiberglass into the edges and corners of a room…
i think i've hit the point where electronics and speaker design can only do so much. it's time to talk about acoustic room treatment. two weeks ago, i was having sidewall-reflection problems. this means i was hearing too much reflected sound that had bounced off of the sidewalls of my listening room. this sound was interfering with the direct sound which traveled directly from the speakers to me.…
i built the DSP 01 as a platform for my audio projects. so now let's use it for something. here's a speaker which i designed & built almost four years ago. i didn't know what i was doing back then, but the pair came out alright regardless. it's a 3-way closed-box design, built to minimize distance between tweeter and (dual) midrange drivers. with a midrange-tweeter crossover at 2kHz, the off-axis…
the chassis which holds the DSP must do these obvious, practical things: it must be dead silent. it must keep itself cool. it must accept 24V DC power. it must have six amplifier outputs. it must accept digital & analog audio inputs. it must have controls for volume, input mixing and other programmable features. it must also do these less-obvious practical things: it must not waste. it must…
in my last post , i established that the CP2114 doesn't work. so how are we going to solve the synchronous clocking problem, and build a working digital input for the DSP 01? there's always the brute-force approach - use a high-fidelity asynchronous sample-rate converter . this is a circuit which doesn't care what sample rate (and sample clock) the source is using - it will resample the signal to…
if you're playing music from your computer, and it's coming out of amplified speakers, the signal chain probably looks like this: the music is stored digitally in your computer. it gets converted to analog audio by the digital-to-analog converter (DAC) which is in your soundcard (or external). the analog audio is embiggened by the amplifier, which then pushes your speakers. When you stick a DSP in…
i've decided to make DSP 01 an open source project. you can find all the files here. this is not one of those open source projects where i misdirect you to an indecipherable Github folder. i've organized my files in a clear way. i want you to be able to see exactly what i did, how i did it, and how to do it yourself. i've put all my design files on an open source page where you will find…
there's a bunch of different ways for ordinary people to transmit wireless audio. nope! i'm kidding, you're stuck with Bluetooth audio. it is awful for these reasons. way too much transmitter hardware. you need a.. smartphone? or something smarter? complicated pairing process. way too much latency (time delay in transmission). you can only connect one thing to one other thing. proper wireless…
the last post was far too long, so here is something different. hi! here is my belly. no don't put me in the chill-out room nooooooo Tshen2 2014
i appear to have a DSP. time to set it up! first, the basics: do the two inputs (ADCs) work? do all six outputs (DACs) work? do my knobs and clip-indicator lights work? does it self-boot off of EEPROM? here's the architecture again: DSP architecture, version 2 (final) as you can see, both ADCs and four DACs are built into the ADAU1701 itself. they communicate directly with the DSP core using…
analog signal processor, front panel, circa 2013 the single biggest difference between 'hacky' and 'solid' audio gear is the box it comes in. this isn't just vanity. well-constructed equipment lasts, which justifies its cost in cash and time. you won't worry when you move it. you won't worry when you touch it. the interconnects won't wiggle out of place, the volume control won't crackle or…
DSP architecture, version 1. here are the goals i set for the DSP: stereo inputs with clip-detect lights. DSPs are notorious for gain staging problems, so i wanted the user to give it the largest possible signal without clipping the inputs. six outputs to support stereo triamplified speakers or stereo biamplified speakers + subwoofer. modular user interface for an arbitrary configuration of…
analog signal processor, circa 2012 four years ago, my favorite programming language was solder. i drew a BJT on my badge at job fairs. i'd just designed my first op-amp. it would soon be on Digikey. like most analog nerds, i called myself an audiophile. unlike most audiophiles, i called myself a scientist. my speaker designs used Class-D amplifiers . active crossovers, biquad bass boost, baffle…