1. Things you need to know about the new ‘Conversations’ PM system:

    a) DO NOT REPLY TO THE NOTIFICATION EMAIL! I get them, not the intended recipient. I get a lot of them and I do not want them! It is just a notification, log into the site and reply from there.

    b) To delete old conversations use the ‘Leave conversation’ option. This is just delete by another name.
    Dismiss Notice

Audio Innovations Valve amps

Discussion in 'audio' started by BlueYeti, May 11, 2008.

  1. BlueYeti

    BlueYeti pfm Member

    Hi folks - does anyone know anything about "Audio Innovations" old valve amps from the late 80's and 90's? They had a perspex acrylic top and the valves sat behind. I think they were the 500 and 700 series, but I'm not sure.

    Are they a possible good used buy for a first dalliance with glowing tubes?

    Any experiences would be welcome!


  2. pure sound

    pure sound Trade: manufacturer/distributor

    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.
  3. Mr Underhill

    Mr Underhill pfm Member

    What a GREAT reply!
  4. hifi_dave

    hifi_dave Hi-Fi Retailer

    Guy, can you please be more precise. :D
  5. Robert

    Robert Tapehead

    Guy, did you hear the Alto amp and CD?
    They got slated in the audio press but the designs looked interesting.

    Used to hear AI the S500 driving Epos ES14s quite regularly and it worked surprisingly well.
  6. pure sound

    pure sound Trade: manufacturer/distributor

    I don't know about 'slated'! It was quite well regarded by Choice & What HiFi.



    It was/is a very interesting design & sounded very different to the other similarly priced amps of the time majoring heavily on tone & timbre.

    The CD Player was more of a joint venture with Audio Partnership (Richer were selling the Alto) and used the Yanion mech that was in the Cambridge CD4 & CD6 and the nice sounding if OTT Westlake DAC.

    I still have one of each. When Richer Sounds (AP) took over they changed the amp design to something more 'conventional', included a Tuner and gave it a remote control that would also operate the simplified CD player.

    If someone wants to try the amp, go for the non remote controlled UK made one. They do turn up on ebay often for less than £100.
  7. bottleneck

    bottleneck pfm Member

    I couldnt help but comment.

    My first experience of audio (ever) involved the Alto (mk1) solid state amp, some Epos ES11's and a Rotel amp.

    It was that system in a demo room that made me buy my first decent hifi.

    I 'fell in love' with the perspex covered audio innovations amps of the time, but at my age at the time and income, it was a pipe dream.

    I've since owned an L1, and had some experience with a P2.

    Coming back to the better AI stuff, makes you wonder if things have really moved on that much..
  8. anubisgrau

    anubisgrau pfm Member

    i'd happily lived with AI 300 for some 15-16 years. sometimes i wish i've never reinvented my interest in audio again, those were the happy days.
  9. BlueYeti

    BlueYeti pfm Member

    Interesting stuff - thanks for all of the info so far folks - especially the really detailed history from Puresound (Guy?). Much appreciated.

    When I was still in college in Brighton I had a basic system (Rega P3, Nytech 202, Monitor Audio 252) and I was thinking of upgrading (modestly) and I'd heard that a chap had set up a small bespoke type HiFi dealership in his own home - literally round the corner from where I was sharing a house.

    I made an appointment and duly spent a really interesting evening listening to the combination of Voyd turntable, Audio Innovations valve amps and very big Impulse speakers that he had set up on one side of the room where another customer had had a previous dem. I do remember being blown away and very impressed with it at the time and vowing to revisit that type of set up when budget would allow - hence my recent posts about Impulse and Audio Innovations kit as I'd remembered all these years which manufacturers gear were making such an interesting sound back then.

    In this dem I listened to more modestly priced kit that was available to my budget (Systemdek TT etc) but felt that the stuff was either similar or just a little better in sound quality than I already had and the next level was a big jump in price as this chappie was aiming for high end bespoke solutions.

    The dealership in question turned out to be Definitive Audio right in the first few months of trading! :eek:

  10. pure sound

    pure sound Trade: manufacturer/distributor

    A 300 would still sound nice with your current speakers!
  11. davidsflee

    davidsflee New Member

    Hi Pure Sound

    I am a first timer looking to this forum, looking for schematics for Audio Innovations Series 800 Mk2b which I have recently purchased off ebay. The tubes 4 EL34s, 2 12AY7s and 2 other unmarked ones - not sure where to plug these ones on the amp. Can you anyone please tell me what the 2 switches at the back of the amp are for? One appears to control the EL34s.
    Thanks very much
  12. pure sound

    pure sound Trade: manufacturer/distributor

    That amp does sound as though it has been modified. The 800 Mk2 originally had ECC82s and PCC88's. Perhaps the 12AY7's (aka 6072) have been put in later.

    Not sure about the switches. Some AI power amps had an earth/isolate switch which kept the chassis grounded while allowing the audio circuitry to float. But that would only be one switch.

    The 800Mk2 was a not altogether successful attempt to make a zero feedback pentode amplifier. it was very load sensitive. It sounds has though someone may (wisely) have altered it to incorporate some feedback. (perhaps the additional switch relates to that?)
  13. stevec67

    stevec67 pfm Member

    My pal has an AI valve pre in mint condition that I think he'd sell, he bought it from a dealer's closing down sale without really having a use for it "because it was a bargain" and apart from the odd plug in now and again it's never had a run out. PM me if anyone's interested and I'll pass on his details. I don't stand to gain anything from this, it's just that every time I speak to him he lists everything he's got to sell and frankly the list is getting long enough to be boring :p, if I can get an item off it we are in front.
  14. per-Sony-fied

    per-Sony-fied Me in another jacket

    Well I have a P2 phonostage with the MC step up transformers & I have to say I think it's marvellous (with changed valves).

    Theres only one think I hate about it tho', it hums quietly with the MC transformers implanted in the unit; they come with thier own seperate case but sound is improved if placed in the P2.
  15. davidsflee

    davidsflee New Member

    Hi Pure Sound,
    Thanks for the quick reply and information. I purchased the AI Mk2 from ebay and the amp arrived with all the tubes bubbled-wrapped. I have tried to get information from the seller without luck.

    At the back of the amp states the model to be MKII and since the seller sent 2 sets of tubes (and 4 EL34s) I assumed it has to be the AI MK2b. No problems with the EL34s. The other tube sockets on the amp - 2 pairs with each pair looking different from the other. I found from a web search that the Mk2b's uses 4 EL34's, 2 ECC88's and 2 ECC82's. Still puzzling me why the vendor included the two 12AX7's as they are compatible to ECC83 which is not part of the Mk2b.

    As you indicated, one switch may be for earth/isolate? I worked out that the first set of switch is for powering on and off - couldn't resist the temptation to power on. If you can kindly provide a schematic diagram it would be greatly appreciated as I can trace and work out if it has been modified and mostly importantly whether I have received the correct tubes. Will tell you the results of my endeavour and the modification done if any. Thanks again.
  16. Dowser

    Dowser Learning to bodge again..

    Any reason you don't recommend the L2 pre-amp? What were the differences between L1 and 2?

    Thanks, Richard
  17. pure sound

    pure sound Trade: manufacturer/distributor

    The L2 and L1 shared pretty much the same audio circuit with switchable feedback around the stage to offer higher & lower gain. The L2 had Jensen PIO coupling caps and also had a buffered (another ECC82) tape output. The L2 also had the shunt regulated power supply used in the P2 but without the valve rectifier & chokes. That does need to be set up to dump the right amount of current down each leg. It may need a tech to do it if the valves involved are tired and need changing.

    They are both nice enough sounding pre-amps perhaps hobbled a little by the need to keep the gain sensible and the output impedance lowish. I recently heard an L1 converted to point to point wiring instead of using the PCB which sounded very good indeed.

    Per. It was always difficult to get the MC transformers satisfactorily quiet inside the P2. As you'll know there are some substantial wound components in that case. I used to recommend that customers bought the stand alone T2 transformer if they could. I do have a wiring diagram if you ever do want to build them into an external case. They are very good transformers, it might be worth doing.
  18. Dowser

    Dowser Learning to bodge again..

    Many thanks - looking at a possible L2...your lack of inclusion had me worried!

  19. Alex M

    Alex M pfm Member

    One of my seminal audio experiences was at Audio South in Farnham, many years ago. I was interested in moving on from my Exposure X integrated and had a feeling that valves were the way to go.

    Their setup was a Voyd Reference with Cyalene and Goldring Eroica, through a stepup transformer into a little AI Series 300 integrated, and this drove Snell Js, if I remember correctly. The 3-D imagery and presence from this sytem astonished me - I had never heard anything like this before. In retrospect I should have asked to hear some big orchestral music or rock, as it probably wouldn't have suited the system nearly as well as the small-scale music they were playing through it at the time. I don't know how much the quality of the Voyd front end affected the overall sound, but I really was surprised by how transparent the little AI integrated must have been.

    In the end I went elsewhere and bought a Croft pre with a Quad 306, the latter in due course giving way to a Croft 5, and this suited my tastes much better.

  20. martin-logan

    martin-logan New Member

    I also have bought a 800 amp MK2, and the tubes seem to be wrong... (the small ones...)
    I don't find any schematic of this model...
    MK1 and MK3 have ECC 82 and ECC83...

    Pure sound tell that on the MK2, there are some PC88?

    Does anyone knox exacly which tubes we have to put and where we must put them?

    Thanks a lot!!!

Share This Page


  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice