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. Below is a list of modifications to some of the A.I. amps. Contact David Wright for prices and time scales. Modifications
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 L2 line Stage Series 700/800/800Anniversary/S1000/Classic 25 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. Our Sovtek 5881/6L6GC WXT+ or (6pi3C-E to give it it's Cyrillic designation) recommendation seems to have triggered some debate on the net. Engineers, repair shops and valve suppliers all seem to have an opinion about whether or not this should be done. We recommend it because we have been doing it for over 15 years, safely and without failures. During this time I can count three Sovtek 5881/6L6GC WXT failures, none of which caused damage to the amp. There have been hundreds of EL34 failures during this same period, most of which caused considerable damage. During this period 'new' EL34's have been released from Russian, Eastern European and Chinese manufacturers most claiming to have solved the internal shorting problem. We have continued to see failures regardless of which brand is fitted. In answer to some points that have been posted on the net:
Some Sovtek 5881/6L6GC WXT will draw more current than EL34's
when placed in Audio Innovations amp's and some will not. There are
'hot' and 'cold' examples of each. Neither will fry the power
transformer. Much of this debate springs from the specifications of the valve, which are difficult to validate to say the least. If we are to believe that the Russians copied the original USA made and designed 5881 decades ago and have not uprated the valve or changed it in any way since, then fitting this valve would clearly have been wrong and they would probably have all failed by now. This seems unlikely and is definitely not born out in practice. The Russian spec sheet lists a 250V anode voltage, but this is most likely when used under extreme military conditions. Again, experience shows this valve is perfectly happy at higher voltages and works faultlessly for many years. Regardless of whether the Sovtek 5881/6L6GC WXT are being operated 'correctly' in the A.I. amps they do not fail. Sadly the same cannot be said of the EL34. If you have series 1000mk3 mono-blocks with EL34's it is advisable to check the cathode resistors regularly. Look for blackened resistors and charred or discoloured circuit boards. With four EL34's/mono-block, the amp will continue to play even if some of the EL34's are faulty. These comments relate to Audio Innovations models series 500, 700, 800mk1, 800mk2, 800mk3, 1000mk3 and Classic 25 and the Sovtek 5881/6L6GC WXT or Russian 6pi3C-E *The only instance in which we would not universally recommend the Sovtek 5881/6L6GC WXT sub is if the amp has been triode connected, as was common on series 500's circa 1990, and almost essential on series 800mk2 and series 1000mk2. Fitting Sovtek 5881/6L6GC WXT will reduce the output power to approx 8.5W (17W on the series 1000mk2) vs 12W (24W) with the EL34. This is a substantial drop. In this case we recommend changing the amp back to ultra-linear configuration before fitting the 5881's. The EL34 internal shorting issues remain regardless of whether the amp is triode connected or not. p.s. Some Hi-Fi World kits also use this valve. They have HT voltages >440V, significantly higher than the A.I. equipment, and the valve was perfectly reliable in those amps too. Please note:
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/
|
1st Audio & 2nd Audio Amplifiers
The Audio Innovations series1000mk3 has the same 370-380V HT voltage as
the S500/700/800. It used the same power transformer and 400V rated HT
capacitors. Some very early examples of the (hard wired) series1000mk1
may be different. If you have a very early series1000, or any very early
Audio Innovations model, it would be best to check with David Wright
before doing any valve changes.
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 some
of the upgrades that can be done to other models. 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.