Overview

This preamp is the result of many years of planning and ideas. Initially intended to simply provide remote control of volume and input source, the plan evolved to include a 6-channel input for home-theatre use. But this multichannel input couldn't compromise the overriding goal of a transparent audio path; I much prefer music to films! It took some time to find a suitable way of controlling the gain of 6 channels of audio, but luckily the PGA2310 was introduced at just the right time. Note that the 6-channel input is a straightforward analogue input - other than gain control, there is no decoding or processing of any kind. The surround sections are identical to the main stereo channels which should ensure good multichannel performance, and the unit features a wide bandwith (-3dB @ 100KHz), making the unit compatible with high resolution multichannel formats like SACD.

Picture of preamp front panel - click to enlarge..
Picture of rear panel - click to enlarge...

Inputs and outputs

  • Seven inputs, including 1 MM phono stage, 2 tape loops and 1 six-channel input.
  • The MM Phono input can be switched to accept a line-level input via an additional pair of input sockets (sockets or switch not shown on rear-panel image above)
  • Separate record-out selection and dubbing options.
  • Buffered listen source output for use as another record output or multiroom audio distribution system.
  • Dedicated headphone output.
  • Main outputs are low impedance (50Ω) to minimise any audible cable effects over long runs. (Record outputs are 100Ω plus the selected source impedance)
  • Main and headphone outputs are fully protected by muting relays to avoid any damaging noises during mains interruptions and power up/down.

User features

  • High quality, clear and easy to read VF display.
  • Volume control is a high-quality optical rotary encoder.
  • Intuitive operation - all day-to-day functions are simple single keypresses.
  • Simple menu operation of less-used functions like Record-Out or surround level adjustment.
  • Scrolling helptext for menu operation.
  • Control of surround channel levels and a per-input option to send a L+R mix to the LFE output, enabling easy use of a sub-woofer for music sources. For each input that this option is enabled, the level is adjustable. For example, you could choose a lower level for the phono input to avoid problems caused by warped records or acoustic feedback.
  • Full remote control of all functions. Philips RC-5 protocol (responds to some CD player remote controls).

Connectivity

  • An array of 12V triggers to control external devices such as power amplifiers, room lighting, motorised projection screens (as if!), etc.
  • Two buttons on remote (left/right) control 2 triggers for controlling an external device (eg, radio tuner)
  • Provision for future system integration (for example, a matching video control unit or 5.1 decoder)
  • Rear panel connection to program system firmware in situ.

Physical and misc

  • All-aluminium enclosure with extruded front and rear panels (no visible fixings on front panel)
  • Expensive high-resolution optical rotary encoder for long-term reliability and best 'feel'
  • All analogue signal switching performed by sealed gold-plated relays
  • Filtered mains inlet. Twin toroidal transformers - dedicated supplies for analogue and digital sections.
  • Modular design for ease of construction and servicing. Main assemblies linked by a short ribbon-cable 'bus' to reduce internal wiring.