Tube Amp settings: Triode vs UL; 8 ohm vs. 4 ohm ?

They run KT88. EL84s and 6922. 87% efficient. They can run out of gas with a low efficiency speakers with yours at 90% they should play just fine. UL. If you can use 8 ohms valves will like it a lot better. Loose the bass duty it will be a one up, again.

Tubes amps don't do really well trying to control larger VC drivers. 4 ohms is even worse. KT88s will take up a little slack though.. Learn to bias correctly.. Best thing you can learn right now... UL, bias cool, try 8 ohms, loose the bass.. :-) Cary is fun.

I'm looking for another V12R (Red). I have a pair of SixPacs too. 6V6, 6L6, KT66, 6550, EL34, KT77, KT88, KT90, KT99 all work in both units. The V12 will work with 4, 8 or 12 valves. They work very well from 17 wpc to over 100 wpc. Great amps..

Regard

If you select the 4 ohm tap, you will be selecting a higher turn ratio for the output transformer of the amp.  This should tighten up the bass and reduce frequency response variations caused by the amp’s interaction with the varying impedance of the speaker.  But, there is a cost to using this tap instead of the 8 ohm tap, which is the amount of power that can be delivered to the speaker is lower.  Generally speaking, the best tradeoff would be to use the 8 ohm tap for speakers rated at 8 ohms and the 4 ohm tap with 4 ohm speakers.  However, the ratings are somewhat loose, so it doesn’t hurt to try the ‘wrong” tap.

A lot of people prefer triode operation over ultralinear for sound quality (smoother, less brittle sound), but the cost is lower output.  I have only heard a few amps where such a switch can be made for a direct comparison and I don’t recall liking triode operation that much more than ultralinear.  Again, give both a try.

I owned this amp in the past. You need to try the different settings and listen for yourself with your speakers to determine which settings and speaker taps work best.

With the Fortes you will more than likely prefer the 8 ohm tap.

Almost without fail, every switchable amp I have owned has sounded better in the UL or Pentode mode. Most manufacturers voice their amps in UL and add the triode setting as a marketing tool. But every ear is different. Try both and see what you prefer.

Oz

. But every ear is different. Try both and see what you prefer.

This is the simple truth.  +1 The recommendations to try both triode/UL mode and 4 and 8 ohm speaker taps. Purely an individual case by case preference as to what will sound better.

Charles