TVJ Portable Headphone Amplifier
• Stepped Attenuator - No cheap volume control pot here. Small potentiometers are notoriously bad - they mis-track, get noisy, and break. So the TTVJ portable uses a microprocessor-controlled analog stepped attenuator. Each of the 32 steps changes the volume level by a precise 2dB, and the gain difference between channels is less than ±0.2dB - compare that to normal pots that at best provide ±3dB! The volume setting is indicated by the color of the front-panel LED. In addition, a switch allows you to select 0dB, 10dB, or 20dB of maximum gain, to accommodate all sources and headphone sensitivities.
• High output power - What's the point of a headphone amp if it can't drive any more than your iPod? The TTVJ portable puts out 3.3V RMS and up to 100mA of output current, so can easily drive any headphones. The regulated power supply guarantees full output power over the life of the battery.
• DC-coupled design - The signal path in most portable amps is AC-coupled, with a single power supply. This requires the audio signal to pass through multiple capacitors, which degrade the sound and limit frequency response. The TTVJ portable has a bipolar power supply, allowing the audio path to be DC-coupled. That means the low-frequency response extends from 0Hz to over 100kHz!
• Long-lasting, rechargeable battery - The TTVJ portable contains a lithium-ion battery which will power the amp for more than 15 hours at typical listening levels. It recharges in about 2 hours from any USB port, or a USB wall charger. You can also operate it while plugged in to keep the battery topped off.
• Frequency response: DC to >100kHz, ±1dB; 20Hz - 20kHz ±0.1dB @ 1V out
• Maximum output: 3.29V RMS into 150Ω; 2.14V RMS into 33Ω
• Output source impedance: Approximately 2Ω
• THD+N: 0.004% @ 1V RMS out into 150Ω or 33Ω
• Broadband noise: <10μV RMS, unweighted, integrated over 20Hz - 20kHz
• Output DC offset: <5mV
• Input impedance: 10kΩ
• Maximum input level: 2V RMS
• Channel tracking (gain difference between channels, all volume steps): <±0.2dB
• Maximum gain: 0dB, 10dB, or 20dB (switch-selectable), ±<0.5dB
• Dimensions: 104mm long x 70mm wide x 12mm thick
THE USB DAC section
The DAC uses a TI (Burr-Brown) PCM2704... TI info is here:
It is a 16-bit DAC, 98dB S/N ratio, 44.1 (or 48) kHz sample rate. Your basic CD-audio-quality USB DAC.
The biggest advantage of using a USB DAC compared to using the audio from a computer is that usually the audio from the computer is very noisy... unless a high-quality sound card is used. Our DAC will solve any noise problems and have you listening to your music in bliss!