Audio Innovations PPP 2A3

 

Here we have the famous Mr Peter Qvortrup again, unless i'm not well informed he is the man behind this company that went bust.

And what did they do, they had a PP EL34 stereo amp, so they used the same chassis, omitted 1 output tranny and ordered custom made 2A3's with octal sockets.The schematic is probably the same except that they needed a big power resistor to cut the excessive high voltage.

What kills me is that they probably had a new power tranny made as this one uses 4 3volt windings to get 2.5vdc rectified. One can recognise this design filosophy as being tvery close to the Audionote UK products, use of quality holco resitors, use of jensen aluminium paper in oil caps and especially many cheap electrolytics as bypass.

However this one was supplied with ecc88 tubes and that works fine but gain is way to high, backtracking learnt me that originally it uses ecc82 tubes, the µ = 20 and not as high as ecc88 so gain is much lower.

At switch on, the full high voltage is on the poor 2A3, and no cathode bias yet working.

Even after installing 25A 800volt bridge filament rectifiers the amp still developed some problems, the main one is that very often a diode in the bridge just collapses.10A100v schottky types are no option due to the way it starts up and bridges with higher voltages are no exactly on my shelf either. So i resolved the problem by adding a small choke, know the filaments burn at a meager 2.2 volts . Beurk.

Not a great amp by any standards, i still have a full set of replacement tubes ( octal 2A3 )

Original Schematic :

In case you want to check the handdrawn original :

Some pics of the insides ( shame on me )

 

After the MOD:

Its a good amp for testing microphonics on ecc88 tubes!

 

 

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