Tubes with Infinity IRS Betas

rvito
Tubes with Infinity IRS Betas

When they were first shown in Australia many moons ago at the Amada Conference Room Artarmon, the importer Ceto from Audio Excellence gave the old propaganda speech before playing them.

In that speech before we listened he said after conversing with Arnie Nudell, many will ask why we have the big Audio Research mono blocks on the bass and the (just as big) Threshold monoblocks on the mids and highs.

It was because of the IRS Beta’s impedance curve, it sounded better this way in the mids and highs and the bass was still in control with the tubes on them, with the tubes on the mids and highs there was a distinct lack of hf extension, air and dynamics.

https://www.stereophile.com/images/archivesart/988BETAFIG1.jpg

This is what was said on Stereophile with VTL300’s on the mids and highs " with a rising output impedance with frequency will produce a sound that is much mellower in the treble"
You don’t want this as this is what we got with the AR’s on the mids and highs

And what they got with the Mark Levinson on the mids and highs
" Mark Levinson No.20.5 amplifiers produced a sound from the Betas possessing considerably more HF energy than the VTL 300 tube amplifiers".

I would suggest a good powerfull solid state with high Class-A ability, not the Krell plateau biasing class-A, I’ve never thought that system sounded like it should of.
But set class-A like the user adjustable Class-A Gryphon Antillion or the bigger Pass Labs XA series


Cheers George

You said it yourself "many moons ago"...let’s say customer A has a nice used pair of Beta’s, a fully refurbed Threshold S/500 Series II (of which you’re very familiar) and a 2nd hand ARC Reference 110 with new NOS tubes, where are you going to put the tube amp?

Wouldn’t change anything, if fact back then our hearing was far more acute, still remain the same, as that downward sliding impedance curve
3ohm@150hz
2.5ohm@700hz
1.5ohm @3khz
1ohm@20khz
This would still knock the HF out of the tube amps, on the Threshold s/500 things will remain flat out to 20khz.
And the Ref110 should cope still with the bass tower impedance, it doesn’t go below 5ohms on the Stereophile graph.

Cheers George