Audio Innovations 500 questions.

I've bought a S/H AI500.

1. Can anyone let me know which terminals are 4 and which 8 Ohms (the case has been chromed, and lost its decals).

2. When replacing valves do they all need to be matched?

3. Are 5881's a good replacement for EL34's (If changing the set?)

Thanks for your help

 

1 Can you easily open up the bottom of the case to see if the output transformers are labelled up and then follow the wires to the terminals? Alternatively, try both with your speakers with a range of music and use whichever you prefer the sound of overall.

With my valve amps I prefer the 8 ohm taps on one set of speakers and 4 ohms on the other.

 

Hi,
It might be a god idea to ask the question on one of the other forums such as PFM/Wigwam where Guy posts, since he had a fair bit to do with AI amps.

I'm not too sure whether he pops over here or not.

I hope I'm not speaking out of turn mentioning other places, just trying to help.

Cheers...Dave

 

If the OP has a multimeter he should be able to test this for himself.
On the resistance setting, check each of the two outputs and the one with the lower DC reading should be the 4 ohm tap.

 

The output from a transformer has DC on it

 

I think Robert meant just 'lower reading', after all we're on the resistance setting.

Paul

 

No, I'm suggesting he measure the dc resistance of the secondary winding.
It should be lower for the 4 ohm tap.

I should have said do this with amp switched off.

Just to add, if you find that you get enough clean volume from either tap, listen carefully to the difference.
Assuming it will play your speakers loud enough I always prefer the 4ohm tap.
On all but certain vintage speakers, a lower output impedance is a universally good thing IMO.

 

Thanks folks

Didn't think of measuring the tappings!

Cheers
P