KT150s For PrimaLuna’s DiaLogue HP Integrated Go For the Gusto!

By Jeff Dorgay

If you’re the kind of person that’s on the phone shopping for upgraded wheels, tires, suspension and brake components the minute you bring your new superbike or sports car home from the dealer (possibly even before you take delivery…) then this brief article might interest you. However, if you like things as they come from the factory, then turn the page.

It’s no secret we love the PrimaLuna  DiaLogue HP integrated amplifier. My relationship with PrimaLuna goes back to day one – the original ProLogue, which I reviewed for The Absolute Sound, and subsequently purchased. That little amplifier is still in my family on it’s second set of tubes, chugging away, nearly 14 years later without as much as a burp. That’s awesome reliability as far as I’m concerned.

As PrimaLuna expanded from their ProLogue series to the DiaLogue series, with bigger transformers and even better components, building on the core values that made them great, the resolution just kept improving. Their Adaptive Auto-Bias™ makes all the headaches associated with biasing tubes a thing of the past. In 14 years of using PrimaLuna amplifiers, I’ve only had one tube failure, and the  Adaptive Auto-Bias™ did its job safely and efficiently, shutting the amplifier down without bother. On a few other “big name” tube amplifiers I’ve owned, this would cause at least a blown fuse, and on occasion, led to a blown resistor; once bad enough to scorch the circuit board beyond repair, and once a mini mushroom cloud. Fortunately, I was sitting close by, jumped up instantly to pull the plug and spray a little bit of Halon on the culprit. But I digress.

A tube rolling dream

To make this perfectly clear, all of the PrimaLuna amps come from the factory sounding great. Kevin Deal is the undisputed Jedi master of vacuum tubes, and he takes great care to voice the tubes in your PrimaLuna. If you don’t want to fiddle, sit back and enjoy, these are the world’s easiest tube amplifiers to live with.

But if you’re that guy or gal that has to wring a bit more performance out of everything, consider the KT150 option in your HP. Out of the box, the HP delivers 70 watts per channel with EL-34s and 73 per channel with KT-88s. No big deal there, the KT88 choice is more of a tone control, but swapping to KT120s takes you up to 89 watts per channel and all the way to 96 watts per channel with KT150s!

However, a set of KT150s will set you back $800. As Patrick Starfish likes to say, “That’s crazy talk SpongeBob!” But who ever said big fun was cheap? It’s still cheaper than a set of Michelin Pilot Super Sports for my BMW, and the way PrimaLuna runs their tubes, I guarantee you’ll go through about four $1500 sets of Michelins before you ever wear out those KT150s, so it’s a bargain. While I’m spending your money, grab a pair of super duper 12AU7s from Kevin to replace the two driver tubes too. You only live once.

Viva la difference

Some speakers responded to the upgrade more than others, and depending on your listening tastes, you may even prefer the EL-34s – they sound lovely. When driving my Graham LS5/9s, I honestly like the sweeter sound of the EL-34. That Adaptive Auto-Bias™ makes it a snap, just plug the new tubes in, push the bias switch on the right side of the amp and go. Best of all, considering how gently the PrimaLuna amplifiers are on tubes, should you have some mega-expensive NOS EL34s, they will last forever.

If you really like to rock out, that nearly 30 extra watts per channel does comes in handy. Recently I used the HP to break in a set of $45,000 Sonus faber Il Cremonese speakers and with the KT150s installed, this little (but heavy) $4,500 amplifier was giving the five-figure stuff a run for the money.  Where the HP equipped with EL-34s struggled a little bit to drive the massive MartinLogan Neolith speakers, just reviewed in issue 79, with the KT150s it was smooth sailing with plenty of headroom.

The biggest surprise and joy is driving the Quad 2812s with the HP/KT 150 combination. These ESLs don’t really need a lot of power to sing, however they do benefit from an amplifier with a lot of grip, and the HP is one of my favorite amplifiers for driving these speakers at any price. Swapping the KT150s felt like I added a pair of subwoofers to the Quads. The only time these speakers have demonstrated this kind of low-end grunt is when they are connected to the Pass Xs 300 monoblocks. ($85,000/pair) To get this kind of sound out of an amplifier just tipping the scale over five grand with a complete set of KT150s is unbelievable. In every other instance, the KT150s are a to-taste option, but if you are driving a set of Quads, the KT150 upgrade will change your worldview.

Am I crazy?

Probably. One of the most fun aspects of a PrimaLuna is the ease by which you can swap tubes, offering an almost infinite level of fine-tuning. This may drive some of you to insanity, but if you can approach this with a bit of prudence with a specific goal in mind, it’s exciting indeed.

Though spendy, keep the KT150 option in mind for your HP. Considering my original ProLogue went almost 9 years before I had to retube, this isn’t even a latte a week. Like I said earlier, it’s a bargain.

If you call Kevin Deal at Upscale Audio, to get a set for your HP, you won’t be disappointed. Highly recommended.