Hi-Fi Preamp - Overview:

After much research, planning and building, I can reveal details of the product that is almost built! Shown here in a NAD colour scheme - a remote-controlled hifi preamp:

The main requirement of this preamp was to provide remote control of volume and input source, and to provide a 6-channel input for home-theatre use. A simple and transparent audio path was the main priority as I much prefer music to films! Note that the 6-channel input is a straightforward analogue input - there is no decoding or processing of any kind. The surround sections are identical to the main stereo channels, making the unit compatible with future multichannel formats like SACD.

Inputs and outputs:

• Seven inputs, including 1 MM phono stage, 2 tape loops and 1 six-channel input.
• MM Phono input can be switched to accept a line-level input via an additional pair of input sockets (sockets or switch not yet shown on rear-panel image above)
• Separate record-out selection and dubbing options.
• Buffered listen source output for use as another record output or audio distribution system.
• Dedicated headphone output.
• Power amp outputs are low impedance (50Ω) to minimise any audible cable effects over long runs. (Record outputs are 100Ω plus the selected source impedance)
• Power amplifier 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)
• Connections to program system firmware in situ.

Physical and misc:

• High quality all-aluminium enclosure with extruded front and rear panels (no visible fixings from 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.

On to the next section - read about the user-interface and facilities...