Audio Line Out’s Top Secret Headphone Amp Project
Audio Line Out (ALO), based in Oregon, USA, are masters of audio art. Their cables and line-out docks are among the best-built in the industry. Ken, ALO’s head, is always busy with some new project and this time, he is targeting the budding iPhone audiophile market with a top-secret new headphone amplifier – an amp whose spy-shots fell into my hands and whose final product will come to TMA for review! Following the break are a few details about the project.
Part of the secret of this amp is its new-fangle chips. One of them is a new type of digital volume control with two gain settings. Ken explained that the volume chip hasn’t been seen in portable amps before, which makes this new project an even welcomer secret.
Ken had the following to say when I asked why he is targeting the iPhone market with his new product:
The iPhone is really putting portable audio in the hands of so many people that would otherwise have not been into higher end portable audio. So I wanted to cater to them. Besides, with the footprint of the amp [which is still unnamed] it works well with all ipods.
ALO are also utilising dual power sources: two 3,7 volt rechargeable Li-On batteries which should supply tonnes of power for headphones of all flavours, from the ultra-sensitive IEM more power-hungry circum-aural headphones.
The amp’s dimensions will be 2,5 * 0,5 * 4,2 inches of extruded aluminium in a choice of red, black, or silver.
- High output power – a minimum of 5.5V RMS and over 100mA of output current, so can easily drive any headphones.
- The ALO Audio amp has a real bi-polar power supply not a rail splitter…
- Long-lasting, rechargeable battery – The ALO portable contains dual lithium-ion battery which will power the amp for more than 15 hours at typical listening levels. It recharges in about 2 hours from an external wall-wart charger. You can also operate it while plugged in to keep the battery topped off. Uses a proprietary DEDICATED battery supervising / charging IC.
- Frequency response: ±1dB; 20Hz – 20kHz ±0.1dB @ 1V out
- Maximum output: 5.25V RMS
- Output source impedance: Less than 1Ω
- ???THD+N: 0.004% @ 1V RMS out into 150Ω or 33Ω
- ???Broadband noise: <10μV RMS, unweighted, integrated over 20Hz – 20kHz
- Output DC offset: <3mV
- Input impedance: 40kΩ
- Maximum input level: 5V RMS
- Channel tracking (gain difference between channels, all volume steps): <±0.2dB
- Gain: 2X / 5V (switch-selectable), ±<0.5dB
- Dimensions: ~4″ long x ~.5″ wide x ~2.5″ thick
TouchMyApps will be kicking off an amp review section to complement headphone reviews, so stay tuned for all manner electrified cables, from cheap boosters to expensive, hi-grade amps such as ALO’s secret model. As always, that section will be housed under our headphone category. Enjoy!