AR88D headphones once again

[JanWra1]

Hi again guys

I like to use my AR88D with headphones and I am a bit concerned before plugging my Koss stereo headphones into the AR88.

The manual states that the AR88D require headphones with 20 Kohm impedance.
However, such high Z headphones are hard to find so how have you guys solved this matter for your own "D" radios?

Have you made some kind of adapter from High Z to 32 Ohm (usual value for stereo headphones) or do you just plug the lowZ phones into the radio and let go at that?
Have looked for a high Z/lowZ adapter but not found any so far.

Back in the 60s I had a very simple 20K headphone with my Ar88 but both that radio and the phones are long gone.

Pls comment.

Jan

[dtvmcdonald]

A look at the manual shows that that set is designed for ... get this ... down to about 5 ohm headphones! Its on p.7 of the AR88-D manual under "output tube". Look at the circuit.

Note that it just says that it gives a certain power into 20K phones, not that it expects them. Read the manual carefully. If you don't have either phones or a suitable
(3.2 or 4 ohm) speaker attached, I'd attach either a 5 ohm resistor to the 2.5 ohm terminals or a 1200 ohm one to the 600 ohm ones, to make a load for the tube.
If you use 30 ohm phones either make sure they are plugged all the way in or,
safer, permanently install a resistor.

If the phones are too loud just plugged in, make a simple pad. If you are worried ... make an adapter so you can
measure the voltage across the phones from a known safe source and the radio with a dummy load (as above)
before trying them.

[JanWra1]

Thanks for your explanation, it is most helpful. I have the original RCA speaker attached at all times so no need for any resistor at the speaker terminals, but I'll keep it in mind if I have to remove the speaker for some reason.

Jan

[Station X]

When phones are plugged in a 5R resistor (R56) is connected across tags 1 and 6 of the O/P transformer.

[JanWra1]

Graham, thanks for that clarification

Jan