What are you favorite 845 tubes?

More than welcome. Power tubes are, imo, tricky (and NOS ridiculous). I have experimented more with the smaller driver and phase tubes internally. You may find some interesting insights here: https://www.audioasylum.com/scripts/d.pl?audio/faq/joes-tubes.html. I certainly experimented.

For sure, quality never goes out of style. I cannot decide whether to get another pair for bi-amping (bi-wired), a Classic Amp for the same, or seek a new design completely (all Ypsilon?). Nagra service is dependable too (As is Epsilon, btw). That means a lot with this level of investment on components. In truth, I think I'd change the speakers before the amps. I cannot fault them, even against to comparisons I have made (Spectral 300s, Boulder 1060 & 2060, Burmester 956 - probably the weakest here).I perhaps miss the scale of the 2060 - but it's a machine compared to an instrument set against the VPAs...

Have a great day.

I use Psvane ACME 845s...a matched pair in each of my 2 Chalice Audio ' Grail" mono blocks..have tried most of what are called the best of the 845s..

They well be a very good tube. No good for an unmodified Nagra VPA, however as they won't fit. ACME range use a 66mm dia glass enclosure (as do many others nowadays) so these will not fit through the milled opening in the Nagra top plate.

It is (should be) possible to modify the VPAs by shortening the standoff hex fasteners for the tube sockets so that the tube glass "terminates" before entering the opening in the top plate (with just the base cap going through). May even be possible without altering the wiring. BUT, that won't solve for the tube guards or the tube finisher rings. These are technically optional, of course.

With Linlai being a waste of time, Shuguang closed for the foreseeable, KR being out of the original RCA spec (at least according to Nagra), Elrog too big (that again) that only leaves PSvane and Sophia. The latter, I'm told being rubbish and the former increasingly making larger dia. tubes. Add that to international supply chain tensions, and modifying the VPA may become the only choice for tubes. I hear from Nagra 211s can work, if anyone had any sonic experience there. Doesn't solve all the issues, but does allow for a wider choice...

Ovenmitt said:

@Anchorman , thanks for sharing your experience with your Nagra VPA’s and the replacement 845’s you’ve tried. I also have VPA’s and you’ve probably saved me some time and money. I have been thinking about trying some of the Chinese brands - the RCA clones sound especially interesting - but haven’t pulled the trigger yet. Elrog’s seemed like a great tube to try until I learned early on that they don’t fit. It sounds like I’m going to be sticking with the Nagra sourced tubes….. oh well.

I do wonder if you could share more info on the 211 sub? You mentioned that Nagra told you this? Did they give you any further details?

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I need to bring it up with the distributor. My 211 information is based on the old Nagra website from around 2008 when they had a FAQ posted. One of the FAQs they answered related to 211s and the need to re-bias Nagra sourced tubes are/were match to the serial # of the amps requiring minimal biasing.

When I next order a replacement quad, I'll ask the distributor for a technical statement and post it here. I suspect 2008 was a more enlightened time and that now, the response will be don't do it... but I'd like to know myself as well.