As to a basic 845/211 difference, the 211 grid is high-mu/gain to need a high-current driver stage. The low-mu 845 requires a driver of high voltage swing to often be preceded by a 2A3/300B. An 845 works well with a 6-10KΩ output transformer and 850-900V plate voltage whereas the 211 prefers 15-20kΩ and ~1'100-1'200V. Whilst looking somewhat similar, the 845 and 211 aren't readily interchangeable. The arguably most famous 211 amplifier of all time was the 27wpc Kondo Ongaku from 1989. A famous 845 amp with 300B driver was Cary's 27-watt CAD-805RS. Thomas Mayer, today the man behind German tube brand Elrog, had this on the subject a long time ago¹:
"The only valid comparison between these tubes would be if both were tested in the same amp capable to operate either. Otherwise it's more a comparison between driver stages, output transformers etc. I do have a 211 amp with 211 driver which can be converted to 845 via simple switch to change the bias voltage. The 211 driver is certainly capable of providing enough voltage swing for the 845. Output transformer is a Tango X10S which is also okay for the 845. Surprisingly I prefer the 211. I expected the 845 to be better but liked the 211 more. The 211 were NOS GE and the 845 NOS United Electric."
Looking at this Elrog product page, we see an amplification factor of 12 for their 211 vs. 5.3 for the 845 and a plate resistance of 3'600Ω for the former, 1'700Ω for the latter. To outfit Neptune with this glass would cost €1'620 for a matched pair. It makes another German tube resource called Tube Amp Doctor rather attractive who just then had Psvane 211-TMkII for €275 the matched pair. Given its high plate voltage, we already know that a 211 will run very hot no matter who makes it or what it costs. For the lowest point of entry, the same German vendor sells Psvane-made TAD-branded 211/VT4/CV620 which at time of publication carried a price of €89/ea. Those are the tubes Alessandro captured in his photos. Though soliciting costly review loaner tubes is quite an imposition seeing they can't readily be sold afterwards despite just short-term use, I did ask Thomas Mayer whether he'd like to make available a pair of his premium Elrog 211. To my surprise he was happy to. From Tektron Masterpiece to 211 master tube?
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¹ "I've gained much experience since and of course now make my own 211 and 845. This quote still has a lot of relevance but neglects the change in damping factor when comparing these tubes in the same amp. Depending on the speakers used, this can have a positive or negative influence to cloud any differences heard. Also, the driver in 845 amps becomes more critical to dominate the sound more than with 211 amps. So it's again from difficult to almost impossible to correctly pin any sonic changes on just the output tubes alone."
Here we see a friendly shoulder-to-shoulder rub with Audio Note UK's 211 Ongaku Kensei on two dealer shelves; and a Tektron integrated of their aptly named Heritage range to reiterate the cosmetic step change of the Masterpiece editions. Past November's half time, Attilio emailed apologizing that waiting on certain critical parts to finish 'my' build would delay its shipment. By January 11th, Thomas inquired whether I had finished with his tubes. I still hadn't received the amp. Attilio advised that he'd need another 30 days. So I shipped the Elrog glass back to its maker unopened. I couldn't in good conscience add a second month to his loan. The best-laid plans and all that pain.
By February 16th, FedEx in Sicily had the shipping label. Pickup of my sample pallet was booked for the following Monday. Neptune was finally inbound. Would it—in hopefully no uncertain terms—explain why tube amps remain relevant in 2024? After all, environmentally green 90% efficient GaNFet class D amps switching at up to 800kHz are here already and more around the corner. For tubular fire power, I'd get a factory-matched pair of 211 MkII Psvane and a pair of ElectroHarmonix 6SN7. That's glass from Chinese and Russian current production respectively. Fancy pants insisting on NOS bottles will source their own. Having been out of this game, I had no hot-swappable inventory, only 300B and ER50 for my Vinnie Rossi preamp. I'd drive Neptune stock and would surely live to tell the tale. Just to be difficult, I'd briefly leave our usual Qualio IQ in place crossed out and over at 100Hz/4th-order to an active cardioid subwoofer. My signal path has a surfeit of voltage gain. I was quite certain that Neptune would easily get loud enough on these unconventional 3-ways. The real question was, would it leave anything vital under the table? Obviously our Cube Audio Nenuphar v2 was the real destination. But why not take a prior detour to see what a single 211 might do on a suitably efficient but on impedance probably sub-optimal load? At this point I still hadn't the faintest moolah notion. Neptune was that new. Though the general Masterpiece range had been teased as early as January 2021, Neptune didn't see the light of first production until February 2024. It meant no prior published pricing. Had I unwittingly signed up for a Kondo Ongaku piece of exotica in extremis? Attilio promised that reveal for the day Neptune was to leave Catania. The one vague lead I had on the score was UK dealer Nintronics' webpage. It listed the Tektron Classic range as starting at £1'750 for a CD player tube buffer and topping out at £29'900 for a pair of 38-watt parallel single-ended 211 monos with 6SN7 driver. What would this mean for the by contrast half-power Neptune as now an integrated in snazzier threads hiding still stiffer sonic ambitions?
