There is no harm in trying either 4 or 8 ohm taps, and likewise either triode or ultralinear operation. You are the only one who can say what sounds the best to your ears and in your particular setup. Are you sure it is an EL 84 amp? With that name I would guess that it is a KT88 amp.
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..
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.
. 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.
This amp runs KT88 as output tubes, EL84s as drivers and 6922s as input tubes. I would guess that it would have enough grunt to operate in triode mode even if that means about half the output of ultralinear. You could also consider operating in different modes for different music/listening conditions. Personally, I don't like to fiddle, so I wouldn't do that, but it is an option.
I believe that the triode setting will enhance the mid-range whereas the UL is more linear in freq response. That may help you to know what to listen for. There again, this is the theory.
Thanks for responding. I should also say that perhaps consideration should be given to my Micro 3000 SVS Sub, related to the Triode vs. UL switch? As some will know the Sub settings are “ on the fly now with SVS installing their App on your phone?
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.
(On a different amp) I was expecting to like triode better the UL, but that was not the case as the bass was thin. But the vocal were more airy in a nice way using UL.
(the beauty of a switch is it is easy to try it.)
Maybe another amp driving the woofers would be a thing for me to try.
I once had 6 ohm, 88db speaker with an impedance dip down to 3 ohms. Naturally I kept the amp on UL mode because that sounded better on most music and hooked the speakers up to the 4 ohm taps.
It sounded great! Listened to it for more than a year like this before trying the 8 ohm taps for kicks.
Well, the mid and upper band frequencies had more 'air'...and no discernable change in bass response.
Who would have thought. I wasted a year listening to the 4 ohm taps.
Not usually a huge deal either way. I have Rogue Apollo with the triode/UL switch, and it still sounds like mostly the same amp in either mode. Different amps sound different by a lot - these 2 modes sound different by a little. Triode is a little smoother cleaner in the midrange. UL has a little more dynamics and slam. These amps being 250 Watts / UL (150 Triode?) and my speakers 96dB means the power loss in triode isn’t very meaningful in my case. For a long time I’ve preferred UL, but that might be changing as I age lol. Tone is the same either way - a tube roll effects more change, especially in tone.
Likewise, the 4 and 8 ohm taps both sound good, and it sounds like the same amp either way. I haven’t spent much time trying to parse out the nuances here, but I've run the Apollo amps a lot from either tap over the years. You’ll usually sacrifice some power by mismatching the tap to your speaker, and the distortion can go either higher OR lower, depending on the amp. For example, the Rogue M180 was measured by Stereophile with lower distortion (at below peak levels) from 4 ohms tap into 8 ohms, than it was from 8 ohms tap into 8 ohms. They also measured the Triode vs. UL modes, and some distortions are a little lower and others a little higher in each mode - which matches my listening. It just effects some minor trade-offs but is still the same amp.
Simply not true. There is no way this is a universal decision. You have to take time and actually listen to all of the various setting options.
Charles
I read it more like start with UL and 8 ohm.
I tried both UL and Triode and 4 and 8 ohm.
That 2x2 matrix ended up at UL and 8 ohm… so the OP might as well start there and deviate off of a known place of success.
I also have those options on my tube amplifier. In addition to output tube types, and variable feedback/damping. I view it as a wonderful opportunity to explore my personal preferences. Other than the fact that the output tap used will likely be more driven by the impedance of the speaker across the frequency range.
Utralinear uses a very specific point on the primary winding where the screen tap is placed in order to get the best linearity- in which case the linearity curve looks like any DHT triode.
For triode operation the load on the tube changes (usually has to be lowered) since the plate resistance of the tube decreases. The chances that the correct load is present for triode operation and the correct location of the screen taps is present at the same time seems unlikely- I would expect one or both to be a compromise.
So I don't think you can say with any accuracy that one or the other is better in some sort of general way. You'll simply have to listen and see for yourself. But if you like what you hear with the triode setting, I would consider getting an actual triode amp.
So I don't think you can say with any accuracy that one or the other is better in some sort of general way. You'll simply have to listen and see for yourself. But if you like what you hear with the triode setting, I would consider getting an actual triode amp
Agree and this is exactly what I ended up doing. 😊
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