300b vs 845

Regarding the use of 845B's with a Viva amp. The ones I used on my viva Solista glowed a most attractive cherry red colour before they quite rapidly failed. Presumably the voltage on the Viva is a tad too high.

I forgot to say, that i enjoyed this thread immensely, I learnt alot and one day upon replacement, id get a nice pair of 845B or 845M. I missed audiogon for ages, returning back into music listening after spent much time renovating. Actually i apologise for not staying on topic as per subject of the 845 tubes (valves), just noting that sometimes you can get good result on a budget with smaller, less costly NOS tubes thats are drivers if not 'output valves'. but i guess chances are that if a better 845 tube the overall result would be ever better.
cheers

I have a pair of ASL 845 (AQ1006 mono blocks) driving Bottlehead Straight 8's.
nothing wrong with the ASL's you just got to tweak it. Maybe the chinese are bland but also they seem to last a long time. ASL using regular chinese 845 however i took a different approach, instead of chasing the pricy, exotic 845's, I changed the drivers tubes to a 2 pairs of CBS (1956/1958) 5692, a famed 1952 Sylvania 6SN7 tall boy, and also pulled out the stock chinese 6L6 for a near-NOS GEC KT66 in place. It made it really detailed, the bass is strong, no flab, highs just sweet not too bright or harsh in anyway.

I recall "Jack G" from Audio Ayslum apparently had the intergrated ASL 845 "Layla" he had spend alot of time buying and trying out combinations of various 6SN7s, and liked it alot and it seemed that the old valves' esp the high-end of 6SN7 and KT66 taking place of 6L6's responded very well to the ASL (845) topology.
If I still have my amps and need to replace the 845's I'd liken to try these 845M or 845B the deciding factor would be which i can afford.
a guy in my hometown, an audiophille of more experience than me, come over for a visit, and listen he was godsmacked saying my midrange is insanely detailed he has never heard anything like it.

Grummer, I've ordered a pair of the new (vertical) versions of the AQ1006s, so your comments are VERY interesting. Other than tubes, are your amps still original...caps, resistors, etc? I've been thru the schematic for the just-superceded version, and it's ripe for improvement, as someone above said. The almost-1000VDC output-stage power supply presents problems for replacement caps; I believe I'll be using 500V. Panasonic TS-UPs in the 1st pole and a 51/1500 Solen metallized 'propylene in the 2nd. I really like the idea of this amp's tube-regulated front-end powersupply. The rest of the amp is pretty standard in what it will get for parts upgrades. I have hand-written notes and a notated schematic that I'll e-mail to anyone who asks--jeffreybehr(at)cox(dot)net.

Have you tried the more-generic Shuguang 845 tube v. the ValveArt 845 and noticed any differences? The former are a little less expensive, but the latter can be bought in matched pairs, FWTW in mono-SETs, for $80/pr. from Advantage Tube Services in FL.
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Jeffreybehr, no i havent tried the more-generic Shuguang 845 tube v. the ValveArt 845, still running the stock ASL845 tubes. I have no spare 845's so obviously, I would need to read alot these varients. Similar to what you may be saying (correct me if im wrong), sometimes plainer varients can win over because the synergy of the system hold it together better than fall apart in vain with excess open-ness. It doesnt matter of the most exotic is hailed about the most, It's how it would 'open up' or 'enrich the details' or even 'flow it out better' depending on what it is lacking or got too much of in audiabily sense. it will be quite a while before i get to this point :)