Tentlabs Volume Control

Designer Jos van Eijndhoven set the concept for this DIY module. It fills a gap by combining high-end sound quality with ease of use: Volume can be set in 64 steps of exactly 1.0dB by rotating the encoder. Additionally, 4 inputs can be chosen by pushing the encoder. Philips / Marantz and Sony remote controls will be able to fully control the unit as well. The attenuator is a passive design, hence long cables and low impedance power amplifiers cannot be driven. To solve that, a high performance, discrete design line amp/buffer will be introduced soon. 

64 steps of attenuation are achieved with 6 Omron G6K relays, controlling 12 Dale RN6 resistors in a parallel configuration. This is a fundamental difference compared to other attenuators, which usually have more contacts or resistors in their signal way. The relays are controlled by a microcontroller. A second microcontroller onboard the display section takes care of remote control decoding and controls the other micro to achieve correct volume and input settings. It also displays these settings. The power supply consists of a low drop 5V regulator. Onboard rectifiers and decoupling capacitors assure proper functioning of the whole unit, is powered by either AC or DC. Additionally, a power on/off signal is present to directly drive an external relay which in turn can switch a power amplifier, or fulfill other functions. In power-off mode, the controller of the volume control remains active, with very low standby power. 

Specifications:

Electrical 
Input impedance: > 40 k-ohm (actual value depends on volume setting) 
Output impedance: < 8 k-ohm (actual value depends on volume setting) 
Power: AC or DC, 6 to 10V max, current max 150mA DC, 225mA AC (power connector supplied with module) 
Volume setting: 64 steps of 1.0 dB 
Channel imbalance: < 0.15 dB 
Inputs: 4 
Input / Output connectors: Cinch / RCA (can be supplied without connectors on special order) 
Remote control: Not included, can be programmed by Philips / Marantz models and most Sony types 
Power on/off output: Open collector 
Display colour: Blue

Mechanical 
Main PCB size: 120*58*28 mm (W*L*H)(excludes connectors) 
Hole pitch: 111*49 mm (symmetrical) 
Display PCB size: 120*20*8 mm (W*L*H) (excludes control shaft) 
Hole pitch: 111*11 mm (symmetrical) 
Display PCB size can be reduced to : 80*20*8 mm (W*L*H) (excludes control shaft) 
Hole pitch: 71*11 mm (symmetrical) 
All hole diameters 3.2 mm 

Price (1 off)
£203.66 +vat +p&p