Valve Amplifier Repair, Modification and Service

If you are lucky enough to own an Audio Innovations valve amplifier, David Wright offers a range of services that might be helpful to you.
He will repair, modify and service the Audio Innovations amps and he is also the UK installer of the BorderPatrol PSU .
He can be contacted by telephone on 01903 715191 or by e-mail davidwright12345@talktalk.net

Below is a list of modifications to some of the A.I. amps. Contact David Wright for prices and time scales.

Modifications

1st Audio & 2nd Audio Amplifiers
A range of capacitor and diode modifications together with some tweaks will make these excellent amps sound clearer, cleaner, and more fluid with a much lower noise floor and better definition throughout the range. Don't forget that fitting a BorderPatrol Power Supply makes the biggest improvement of all. 

Early high sensitivity amps with ECC88 input and driver valves can be modified to the lower sensitivity ECC82 input valves. As well as giving nicer sound - the ECC82 is smoother than the ECC88 with less glare - the lower sensitivity also means that active pre-amps can be used without gain and noise issues.

Owners of 1st and 2nd Audio amplifiers will have noticed that the 8-pin 2A3's have become unobtainable. Changing to the 4-pin types obviously means changing the valve bases and we can provide this modification service. The Sovtek 2A3 is a 4-pin mono-plate design that offers great sound, excellent reliability and freedom from the low level squeaks, pop's and rustles that plagued the Golden Dragon 8-pin. It also does not 'lock up' on switch on and potentially cause damage. For it's combination of sound quality, price and reliability, we recommend this valve highly. 

P2 Phono Stage
There is more than a suggestion that the shunt regulated power supply in the P2 and L2 is temperamental and quickly goes out of tune. Articles by Dutch engineer Peter van Willenswaard (see links below) describe this and suggest reasons for it though no one is completely sure why it happens. In practice it means that a P2 or L2 properly set up with a new 5687 and OA2's will sound great but the performance will not last for long before the sound degenerates and becomes grey and lacking in energy. I experienced this often with the P2's and L2's. The P2 has 2 chokes and a valve rectifier inside it which means it's possible to convert the power supply to a BorderPatrol-style choke input filter type which sounds great, all the time. This, together with some capacitor and heater circuit modifications and a few tweaks, will make the P2 sound clearer, cleaner, more agile and more energetic with a much lower noise floor and better definition throughout the range.

L2 line Stage
Fitting Hovland Musicap, better quality capacitors, rebuild heater rectifier with discrete Schottky diodes, rebuild HT rectifier with discrete diodes, apply some RF reduction/suppression techniques and some tweaks will make the L2 sound much clearer and cleaner with a much lower noise floor and better definition throughout the range.

Series 700/800/800Anniversary/S1000/Classic 25
Modifications comprise: Fitting Hovland Musicap, better quality capacitors, fast recovery diodes, selected resistors and a few tweaks.
Don't forget the BorderPatrol Power Supply which makes the biggest improvement of all. 

We recommend that owners of the Series 500/700/800/800Anniversary/S1000/Classic25 amplifiers replace the EL34 output valves with Sovtek 5881 types before the EL34's do their special internal short-circuit trick and destroy the cathode resistors (those who have seen their output valves glowing like fluorescent carrots before the sound expired on one or both channels will know what I mean). We can supply matched pairs of Sovtek 5881. No modifications are required to the amplifier when changing from EL34 to Sovtek 5881.

Please note:

This site provides information about repairs, servicing and modifications together with a listing of valve types and brief specifications. We do not have stock of new or used Audio Innovations amplifiers and we cannot advise on prices, 2nd hand values, sound quality, age, compatibility or suitability of the Audio Innovations amplifiers so please do not e-mail us about these matters. We do not have product manuals or sales literature. We offer modifications to the amplifier models below only; we do not have a component upgrade pack for the series 500- the internal layout of the Series 500 is very crowded and sensitive and precludes so of the upgrades that can be done to other models- and fitting a BorderPatrol PSU to any of the amplifiers will make a much bigger improvement to the clarity and the dynamics of the amplifier than any of the component upgrade packs, nice though they are.

Some links to other Audio Innovations sites and articles

For information about repairs and modifications by the Audio Innovations Benelux distributor check out  www.dejongsystems.nl

For a users site dedicated tot the Series 500 check out Dmitri's site at  http://musical-ecstacy.nl.eu.org

For information and some circuit diagrams check out Dr.Tubes site at http://www.drtube.com/audioamp.htm#AI

For tweaks to L2's and P2's devised by the highly respected Peter van Willenswaard of Audio Magic in The Netherlands, click here  Modification of Audio Innovations L2 line stage and Modification of Audio Innovations P2 phono stage  Peter is one for cleverest engineers working in audio and if you are confident in your electronic capabilities these are well worth trying.

For some interesting mod's modifications to Series 700's, 800's and Classic 25's http://httpd.chello.nl/~m.heijligers/classic25/