Unison Research Pre and Power Amps


These Unison Research pre and power amps are currently in the workshop for servicing. The power amp is the hybrid valve /solid state model. Repairs included the input selector and a choke for correct earthing and hum.


Rose RV23 Preamp

This preamp dates from the early 90s when it had a reputation for great sound quality. It stands the passage of time well and still sounds very decent. It had had various mods and servicing over the years, including main electrolytic capacitors, valve sockets etc.Someone had also replaced the ribbon connector with some Cat cabling.It is a hybrid valve /solid state design, with transistors used for the phono stage and valves for the line stage.

My work was to upgrade the coupling capacitors, and add a choke power supply by adding a choke and additional smoothing capacitor. Once this work was complete it transpired the original main smoothing capacitor was pretty spent, so that was replaced too.That took a while to find as it broke down after around 2 hours use, but was fine up until then.

The result was very worthwhile, performance has been lifted to a very pleasing level. The pre operates with a much quieter background, displays subtleties better and is more dynamic to boot.


WAD Pre2 /PSU 2 For sale

I’m selling these on behalf of a client who’s upgraded to my KT150 amps and preamp. These have been converted to cathode follower design as an improvement over the original hummy WAD design. These have been converted to cathode follower design as an improvement over the original hummy WAD design. The build contains every possible upgrade including: Tocos carbon pot in shunt mode with Vishay naked foil resistors, Vishay naked foil grid resistors, Jupiter beeswax signal caps. The power supply has an upgraded 30 Henry choke, Schottky heater diodes, and Hexfred HT diodes.*The valve is an ECC88 gold pin Mullard. Excellent sounding line pre in daily use. Front panels in good condition, some scratches on sides of black chassis.

AD Audio Announces New Amplifier and Preamplifier

AD Audio is pleased to announce a licensing agreement with Oddwatt Audio to build their amplifiers and preamplifiers. The first two products are the Cannonball KT150 Monoblocks and the Satchmo preamplifier.

For full details visit the AD Audio Sales Site here

WAD 300b Stereo, Pre2 and Phono 2 Upgrades

I’ve built four WAD 300b stereo amplifiers and serviced many more. One of my own amps is a WAD 300b stereo too, so you can tel I love the sound. img_4137An upgrade for the Wad 300b stereo I’ve now done on six 300b stereos is to add an additional choke to the power supply for the input section. This improves an already great amp, providing more bass slam, detail and dynamics. The owner brought along his Pre2 and Phono 2 for upgrades too.

The Pre 2 had been converted to a cathode follower already, which overcomes the original design’s hum issues. So this time I increased the size of the power supply choke and converted the power supply to a pseudo mono set up. For phono 2 I added cathode bypass caps to the first valve.

Overall results are a very nice improvement in SQ for the system.

Perreaux SM3 Upgrades

The picture below shows the completed upgrades. All electrolytics have been replaced. There’s 12 alone in the power supply, and many more across the pre and phono boards. Elena Silmics have been used where space permits, otherwise Panasonic FC and Nichicon Muze. None of these is in the signal path. The main input and output capacitors-originally metallised film have been replaced with foil /film types. All components were mounted as in the original preamp, with the exception of two in the phono stage which were mounted slightly above the board to allow for nearby warm running resistors.