845 Tube Amps

The greater difference will be found in the typical application of these tubes rather than the tubes themselves. 845s are triods, typically found in lower power tube amplifiers, but relatively highish power SETs. KT88s are pentodes that can be found in amplifiers of all power ratings.

I know better than to answer technical questions, but sometimes I’m overcome by the urge to jump off the porch and run with the big dogs. The KT88 is a tetrode capable of operating in triode and...somebody else take it. I know when to shut up...sometimes.

Phaelon, thanks for your response. My current KT88 Amp can be run in either Pentode or Triode mode. I always run them in Pentode mode bcos of better dynamics and punch. Will I get similar dynamics and punch from 845 amps ? How does 845 and KT88 compare sonically ? Please advise.

If you have speakers that are fairly efficient, then it may be possible to get nice dynamics and punch from an 845 amp. With 845's, you are talking about pretty low powered amps in most cases (usually less then 20 or 30 watts). You would most likely want a speaker rated in the 90 db's and the higher the better.

Wilfredt,

IME, it's hard to answer your question on a "tube vs tube" basis, because so many other variables are changing, too. (I know of no amp that allows the user to swap KT-88s and 845s for an "apples to apples" test.) From the circuit (per Phaelon) to the partnering speakers - the resultant change in sound upon changing from a KT-88 to an 845 may be hard to predict, and in any case, would be hard to attribute solely to the output tube.

I have used both the Cary 805 (w/845, briefly) and the Prima Luna mono 6 (w/KT-88, briefly) with my Verity P/Es and my Merlin VSMs. (Ironically, I ended up ditching both the KT-88 and the 845, using 211s long term in the Cary and KT-66 long term in the PL - see below.)

The best short answer that I can provide to your specific "punch" question is that the KT-88 definitely struck me as significantly "punchier" on the Verity (tho I prefered the Cary, overall). On the Merlins, the delta in macro-dynamics was much less evident.

Overall, the 845 feels like a somewhat darker, more liquid sounding tube than the KT-88 to me, but that observation is subject to all of the caveats noted above.

Marty

Note: My Cary uses the 845 in an SET configuration, which may explain the difference in sound better than the output tube delta. The Cary also allows the user to swap a 211 for the 845 and (with the Verity) this seems to reduce the slightly "dark" character of the Cary amps, so I switched to 211s for long term use with the Verity. Conversely, the KT-66 struck me a somewhat "gentler" sounding than the KT-88 in my PL, so I ended up going that way for use with my Merlins. In the end, all output tube decisions were system driven.