What's a Triode configuration?

Hmm...in 25 years in this insane obsession...er...crazy hobby, I've seen only one tubed preamp, NOT an ARC, with a pentode in it. Said another way, ALL active tubes in ALL tubed preamps (but this one) were all triodes. I wonder why your suggestist even mentioned this.

Just to be confident, I suppose you could ask if the preamp you're considering is all triode.

ARC makes great stuff. Conrad-johnson and others, too, do.

Understand that some tubed preamps have much-higher-than-normal output impedance. This will somewhat limit your choices in length and types of IC and poweramps driven. Ask about that, too.
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"...what makes a Triode configuration different from say a Pentode?"

Tiodes and pentodes are different kinds of vacuum tubes. A triode has 3 active parts, a pentode 6. A pentode has more voltage gain than a triode, but, GENERALLY, triodes sound better. (Some triode fans say that pentodes sound more like transistors.) GENERALLY, triodes are used in Voltage-gain situations such as preamps and the frontends of poweramps, while pentodes and beam tetrodes are used in the output sections of tubed poweramps.

But lots of us prefer triodes all around, the most-extreme execution of that being the SET or Single-Ended Topology (or Single-Ended Triode). ('Single-Ended' means NOT having amplifying devices in push-pull configuration.) I have a pair of Antique Sound Labs Explorer 805 SET poweramps that I love. To confuse the issue, pentodes and beam tetrodes can be wired into triodes. They then have less Voltage gain and (maybe) they sound better. Triode-wired pen- and tetrodes are used in poweramp output sections or as output-tube drivers and NOT in Voltage-gain situations.

So, again, if you're considering a tubed preamp, simply ask the manufacturer if it's all triode.
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Thx, Doc. Obviously didn't think about THAT one!
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