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Thread: Audio Innovations 500 'Reborn'

  1. #11
    Join Date: Dec 2008

    Location: penzance,cornwall uk

    Posts: 319
    I'm paul.


    brilliant job and well done...be very proud of that
    there's so much talent on this aos forum

  2. #12
    Join Date: Apr 2012

    Location: Southall, West London

    Posts: 37,242
    I'm Geoff.


    Looks great Alan. I'll be interested in how you find the sound. I like EL34 amps.

  3. #13
    Join Date: Oct 2017

    Location: West Wales

    Posts: 60
    I'm Alan.


    How does it sound?
    Excellent, it has been in daily use since I finished it back in September. As you would expect a fluid mid range and sweet treble, but above all real depth and clarity to the bass. You can identify individual bass guitar notes. Not the 'all one note' effect many amps give you. (Speakers are Dynaco A25s and EPOS ES11s.)

    The other thing is it plays the same at all volume levels, low level through to loud enough. It's one of those amps that you don't listen to, just the music.

    I have tried different valves and found the ECC83 first valve make has little effect.
    The drivers ECC88s have noticeable effect on the treble, I've tried Mullards, Brimars and Teslas (original fitting I think) and by far the smoothest are the Teslas. The Brimars hurt the mid to treble region. Might try some E88CC/6922s if I can find a pair in the future.

    For the output valves I started with 5881s, often recommended for the AI 500, and they do sound really good. However they slightly tilt the whole presentation towards the bass, impressive but maybe a little too much? In the end I've settled on an old set of Winged 'C' EL34s as having the most transparent and even spectrum. (A set of Mullards don't really sound much different, anyway they belong in my Radford and a set of JJ are good, but quite as even as the 'C's.)

    I know I built it, but it really is my favourite amp right now...

  4. #14
    Join Date: May 2012

    Location: Dagenham Essex

    Posts: 8,201
    I'm I'mteachingmarcotheartofpishanto.


    Super Job , Much respect , I wish I was clever and could do work like this , However I would end up brown bread
    Music , fills the gaps between silence !

    TAT Sale post Leader " Marcos Mentor "

    Also a pishanto specialist confirmed by Head Daftee

    Real name " Allen " or "Zoomer Nut”, “Numpty Napper”.


  5. #15
    Join Date: Oct 2017

    Location: West Wales

    Posts: 60
    I'm Alan.


    After I built it I used it for a couple of weeks to soak test it for faults. Fortunately no issues other than the heat it generates.

    The 100 ohm dropper in the HT line alone dissipates 9 watts (I see why later models used 47 ohms) that and the other droppers all bolted to the chassis added to quite a rise in chassis temperature after a couple of hours of use. Touchable but not too good for long term reliability. I rather guessed it would run very warm looking at the original steel chassis and its burn marks! So I made provision for a little forced cooling in the original design.

    Perforated ally sheet and a super quiet, slim line PC fan.

    I opened out the holes for the fan intake and sprayed the whole sheet satin black. Then tried various speeds for minimum noise and most efficient cooling.

    In the end the slowest speed the fan would run at was just under 6 volts, that provides more than enough cooling and the noise is only just audible if you stand next to the amp. It is even quieter if I raise the amp up another 1/2 inch or so off the shelf, so is mostly flow noise and not unpleasant.

    All bolted up and ready for more tunes...

    I've run it all day (8 hours plus) on a couple of occasions and the chassis is only just warm. Much cooler than either the Leak Stereo 20 or Radford STA 15 after the same period.

  6. #16
    Join Date: Oct 2012

    Location: The Black Country

    Posts: 4,396
    I'm Alan.


    Although I would prefer natural cooling that is a brilliant solution.

    I have a large OTL amp that gets ridiculously hot, that is going to get re-built eventually.

  7. #17
    Join Date: Nov 2015

    Location: Wolverhampton

    Posts: 6,563
    I'm Oliver.


    They have some really silent CPU fans for pennies now Alan.

    Sent from my EVA-L09 using Tapatalk
    Analogue: Technics SP10 MK2 > Phonomac AT-1010 MK5 tonearm > Ortofon Kontrapunkt b > Bigbottle Jfet MC Valve Phonostage (Telefunken Valves)
    Digital: NONE
    Amplification: Nelson Pass DCB1 with Khozmo 48 Step Series Attenuator & Krell KSA100 MK2 Amplifier
    Cables: Fisual S-Flex Speaker Cable & SPOTFIRE IC Cables & NEW SPOTFIRE Tonearm cable
    Speakers: Pioneer CS-77A

  8. #18
    Join Date: Dec 2008

    Location: Lincolnshire, Home by the Sea

    Posts: 4,128
    I'm Shaun.


    Really seriously loving the look of that and what a fab project to be involved with. EL34 is my fave valve so I'll bet it sounds fantastic. Pat on the back and raise a glass...!

  9. #19
    Join Date: Aug 2008

    Location: Suffolk, UK

    Posts: 1,337
    I'm Paul.


    Fantastic job (no pun intended).

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