Audio Innovations made a number of different amplifiers between 1984 and 1996. The company started near Basingstoke, moved to Brighton and eventually down to Weymouth before the brand was bought by Richer Sounds.
The first products were the 800 power amp (25W class A based on EL34's in push/pull) an a matching small pre-amp which could either be powered from the power amp or be run from a separate psu.
These were followed by the Series 500 integrated, again 25W class A with a phono stage, and the 300 integrated which was 10W in class A using ECL86's.
The Series 1000 Pre, an SRPP circuit based on ECC83's and 6SN7's with a pretty elaborate regulated power supply & passive line inputs and the 50W 1000 mono's soon followed.
Although a few French self builders were following an underground Japanese trend for amplifiers using Directly Heated triodes, Audio Innovations were the first company (in modern times) to commercially manufacture/market DHT power amps when they launched the 6B4G equipped First Audio (7.5W) and Second Audio amplifiers (15W). At that time, in 1987, it was unheard of to be trying to sell amplifiers with such low power output but both models received good critical acclaim often being partnered with the Snell range of loudspeakers the company were also distributing.
A new range of amplifiers in a new chassis followed. The 400 integrated and 200 Power amp were based on EL84's, the 200 Pre was another phono equipped design with passive line inputs. In the same style of casework, 2 line stages L1 and L2 and 2 phono stages P1 and P2 were also released.
The 800 power amp circuit continued to evolve and was also used in 2 line integrated designs, the 700 and Classic 25 kit amplifier.
Finally the company released the Alto, a radical looking transistor amp loosely based on the single rail, output capacitor coupled topology pioneered by the likes of Wharfedale, Sugden and John Linsley Hood 10-20 years earlier. It was accompanied by a matching CD Player with a DAC designed by John Westlake of Pink Triangle/early Cambridge Audio fame.
The models to particularly look out for would include the 300 mk1, the 500, 700, 200 Mk2 power, 800 Mk1 and Mk3 power, First & Second Audio, L1, P1, P2 (preferably unmodified), Classic 25, 1000 Mk3 and the early, UK made Alto amplifier. Also any of the MC step up transformers.
The AI EL34 based amplifiers suffered the same kind of valve failure issues as any other design that runs these valves in Class A. Eventually they were only supplied with the Sovtek EL34's installed as these were found to be the most robust type. (they also sounded good) However many AI amplifiers have subsequently been converted to run using Russian 5881 valves and these generally then prove to be very reliable.
AI amplifiers can be serviced by David Wright (via the Sound Practice) although any competent tech could do it given a schematic. The circuits weren't especially complicated. I have all of the schematics should anyone need one.
