Tube Power Amp Reviews

May be JCA could review the new Rotel Michi M8 mono-block amps, 1080 WPC into 8 Ohms and 1800 WPC into 4 Ohms, $14,000/pair :-) ........

The best sound at any show I ever heard came from an AR integrated along with an AR CD9? CD player, paired with Verity Audio speakers. CD after CD played revealed detail and lifelike presentation that no system at any show I've attended has ever matched. I can only imagine how good this combo sounds. I wish I could borrow for a month and call in sick from work for 22 straight days.

Jim - thanks for the great review. Do you have any comparison to other amps? Not that I don't trust what you heard, which you have very good skills at describing. But, in this subjective hobby of ours, it provides tremendous value when you compare it against other options the readers may have or other well-known amps. You have Pass Labs XA60.8, which is another amp known to produce a beautiful sound. How did ARC compare against it in its sonic bliss? You also have PS Audio BHK 300, which has a great dynamic. How did ARC compare against it on dynamic or driver grip? I would very much appreciate it if you can add some comparison. Because without a meaningful comparison, a review can be just too subjective or personal.

... with distortion levels approaching those of the Benchmark AHB2?
If so, would it be likely to exhibit the same sort of "musicality" and/or "tonal beauty" that JA2 has observed from the Reference 160S?

Regarding the "impressive price" of $30K for a pair of ARC Reference 600 monoblocks in the mid-1990s, back then there were other manufacturers offering monoblock amps at that price point - and well above.
Among them were the Accuphase M-100 ($30K), Audire Monarch ($60K), Denon POA-S1 ($40K), Jadis JA-500 ($35K) Krell Audio Standard ($35K) and, last but not least, the Audio Note Gaka-On ($250K).

Hi

"..... amplifiers to allow switching between triode and Ultralinear operation." quoted Jim Austin.

VTL got its tetrode power amps with switchable triode & tetrode operation decades back. How come ARC took so long to do so until now?

Likewise, I consider I have done the best ever sonic upgrade of my vintage Dynaco ST-70 35W+35W power amp by converting it to triode/pentode ultra-linear switchable over a decade ago.

That said, we should know the sonic downside of trioded pentode/tetrode by strapping the screen grid to its plate with a low-resistance resistor, a conventional way used by brandnamed amp manufacturers & DIYers alike since day one decades back. So the grid screen is working at a voltage almost the same as the plate.

I have read many reports criticizing such simple trioding method causing the sound somewhat soft, weak & punchless vs its original pentode/tetrode configuration. Unacceptable to my critical ears, to say the least.

To fix such sonic 'problem', I set the operating voltage of the screen grid, STABILIZED, LOWER than the plate as it were working as a pentode/tetrode. Ite is done by connecting the screen grid to the plate with a circuit of diodes, fast quality capacitors, & resistors.
I would label it as: "plate/screen grid split potential topology".

The key issue is: what is the proper voltage difference between the plate & the screen grid to get the best sound.

After enough trial & error, I finally get the right potential difference between the screen & the plate. It works like a chime: it sounds
fast, punchy & forceful like a pentode/tetrode & beats the latter by being more defined, smoother, & transparent like a real triode.

I have used it first in trioding my Dynaco ST-70 power amp & my ALL other later power amp projects. The trioded Dynaco sounds so good that I have left it switched to triode mode for ever.

Added merit: Such split potential triode conversion does not sound noticeably lower than its pentode mode though its output power is rated only half of its pentode operation !

Listening is believing

Jack L
Canada

...those see thru Meterings.

I've owned large ARC Amps, they look & give off the "I'm a certified audiophile" feeling with publicly claiming "ARC ownership" a Statement of audiophile authenticity but it might be more bluster than ultimate performance. I've heard a few ARC Electronic Based Systems that didn't perform as hoped or expected.

It might be simpler to build around KRELL or PS Audio or PASS gear because they lack tubes. ( and solid state devices last forever-- as claimed by Nelson Pass )

Tube life of 3,000 hours seems rather hopeful. 3,000 hours could equate to a Decade or likely less than 2 years of 5 hour listening days. So, a spare set of Tubes needs standing-by. My experience would predict less than 1,000 hours.

Tube Amp buyers are Brave, I have to hand it to them, especially if they are running those pricy KT150s.

Tony in Venice

ps. those Glass Meters are gorgeous Impulse buyer magnets & so are the Diavialet Amps with their remote control and wall mounting.

The notion that the value and enjoyment of music has anything to do with the expense or sound quality of your playback system is the same as the notion that the value and enjoyment of a movie like "The Godfather" has anything to do with the expense or the resolution of the TV picture that you're watching it on.

JCA could also review the conrad-johnson ART 150 stereo amp ($19,500) ........ About the same power output and about the same price of ARC 160S :-) ..........

From the review:

For a company to design its own internal parts was unusual—and remains so—as was the notion that specific capacitor and wiring choices sound quality. And yet, even though transistors were not could affect the sound of an amplifier.

Two consecutive sentences. Does anyone actually read these?