You’ve received many excellent comments above, from particularly knowledgeable members.
I would ask, though, if you are certain about this statement which you made in the initial post:
-- Al
I would ask, though, if you are certain about this statement which you made in the initial post:
The Air Tight is factory-set at 8 Ohms and is switcheable to 16 Ohms but requires removing the base plate and resoldering which I’m reluctant to do — or at least not until listening at the current configuration.Are you sure that it is switchable to 16 ohms, as opposed to (or in addition to) being switchable to 4 ohms? From Stereophile’s review:
The making of loudspeaker connections was only slightly puzzling: Air Tight’s specifications indicate output impedances of 4 and 8 ohms, and the spare but decent instruction manual advises the user to "select the red terminal between 4 ohms and 8 ohms in accordance with the impedance of your loudspeakers"—yet only a single pair of terminals is supplied for each channel, and I found no provisions, inside or out, for switching. In any event, I heard no indications of a mismatch with either my 16-ohm Altec Valencia or my 10-ohm Devore Fidelity Orangutan O/96 speakers.Also, FWIW, the following is stated in the measurements section of that review, although I’m not sure I agree with the statement that the impedance measurements suggest that the tap is "optimized for a 4 ohm load."
As is usual with a transformer-coupled amplifier using a push-pull pair of EL34 or 6CA7 tubes, the Air Tight’s output impedance was high, ranging from 3.6 ohms at 20Hz to 3.3 ohms at 20kHz. This suggests that the single output-transformer tap is optimized for a 4 ohm load, but it results in response variations of ±1.1dB with the magazine’s standard simulated loudspeaker.Regards,
-- Al