In an earlier post, I talked about how I entered the world of low-voltage audio and my commitment to delivering the best possible performance subject to that constraint. In this post I’d like to consider some strategies for generating power.Continue reading “Joys of Low-Voltage Audio: power strategies”
It turns out the world of low-voltage audio is a lot of fun, and I’d like to start sharing some of my journey through it.
I suspect everyone has a different reason for entering this world, lending each story a different color and set of priorities. Mine goes something like this.
A recent chassis redesign project I undertook for Audio by Van Alstine is now in production.
This project pushed “constraints as creative resource” to the limit. The client specified that the design language and elements from the product’s predecessor be maintained—down to the knobs, faceplate treatments, and typography.
The project brief revolved around electronic and industrial design work to bring the client’s preamplifer platform up to functional parity with current market offerings within a framework that fits with the client’s existing manufacturing capabilities. The result is a platform that is significantly more capable than what it replaces yet easier for the client to manufacture. It is also amenable to comprehensive appearance changes if and when the client deems the timing is right.
So while it might not seem there’s much innovation on the outside, there is a lot of innovation for the client on the inside.
The Verge has an interesting writeup on Native Instruments’ Stems, “a new audio format that stores up to four different tracks in a single audio file.” I (and I am sure others) had this idea back in the late 80s but based on multitrack cassette and synced MIDI control of mixing parameters. It’ll be interesting to see where this goes!
As part of my Open source audio remote control initiative, I’ve just published Volume-AlpsRK16814MG, an open source hardware design that integrates a high-quality Alps motorized quad potentiometer with an H bridge. The design lets you control the motor’s direction using two logic-level signals: VOL_UP and VOL_DOWN. The fact that it’s a quad pot means you can use it to control regular stereo volume by ignoring one of the dual gangs or a differential stereo signal.
I’ve also modified the remote control receiver to better support motorized pots. There is now a compile-time option that lets you latch and unlatch the VOL_UP and VOL_DOWN signals rather than produce repeated VOL_UP and VOL_DOWN pulses—which makes control of motorized pots more fluid.
*Subject to change!
I’ve started a FLOSS remote control receiver project for DIY audio preamplifiers. I think it’s just about good enough to make public.
Remote control is one of the more challenging things for an audio DIY person to implement, so I thought having an open source hardware and software platform for doing this would be useful. It uses our good friend Arduino for brains and works with the Philips RC-5 protocol. I like RC-5 because its the closest thing I know of to a universal, well-documented, brand- and model-agnostic protocol.
The IR command decoding is done using Guy Carpenter’s excellent RC5 library. I also considered using Ken Shirriff’s multi-protocol IR library. Ken’s library works with a large number of protocols, but I thought its larger memory footprint might preclude porting this thing to tiny AVRs.
Last week I finished delivery of a custom 6-channel DAC for mastering engineer Greg Reierson at Rare Form Mastering. It uses three stereo DAC cards I designed previously for Audio by Van Alstine, Inc. (currently used in their production DACs) and six custom dual-differential gain/filter cards. I designed the gain/filter cards to use an absolute minimum of active stages—something I have consistently found to help subjective performance.
Greg reports that the new DAC is dead silent and delivers noticeably better LF control than his previous setup. We hope to do some gain-stage device (that’s opaque-speak for “opamp”) comparisons down the road to see if things can be improved further. He will be using the new DAC for general monitoring and also to drive his newly acquired Neumann VMS 70 cutting lathe.