The future of preamps

Audiolabyrinth, despite what you quoted in the manual, that idea that somehow tube preamps have DC at their output is a myth! Most tube preamps have a coupling capacitor at their output and so cannot produce DC.

I suspect that is something concocted to sell solid state preamps.

Any tube preamp manufacturer has to contend with the fact that their preamp is going to get used with a solid state amp at some point. There are many threads on this forum to that effect. Many transistor amps have direct-coupled inputs, so any designer knows that if you have DC there it will cause problems for the amp and possibly the speaker too. But fortunately its not something that is a particular concern, as coupling capacitors are very effective and will prevent DC from being a problem at the output of the preamp.

The only thing you have to be careful about (which is true of solid state preamps as well!), is to turn the preamp on first and wait for it to stabilize before turning on the amp.

Charles1dad,

It is interesting to note that personal experience does not always go in tandem with common sense and logic which would define that the shortest simplest path should be the best.

Audio design is indeed as much an art as it is a hard science.

@ Atmasphere, Thankyou, I am glad you told me that a tube pre-amp needs a coupling capacitor at the out-put to protect against DC, that was helpful info, cheers.

Audiolabyrinth, I think I need to clarify that. I think there are maybe 3-4 tube preamps with direct-coupled outputs (Berning made a hybrid called the TF-10 years ago, there was the Messenger and we make two of them. Pretty sure Krell was not talking about us... I think we would have heard about that.

Anyway, the rest of the tube preamps made have either an output coupling cap or they have an output transformer. Either way they won't be making any DC! That is actually a greater danger with a solid state preamp, although most of those have output coupling caps too.

Ahhh, yes, I 'tis remember well when, lo those many years ago, 'ol Steven Stone, reviewing still for Stereophile, told us all that passive pre's would soon take over the earth, that active pre's were not, um, "transparent" enough and that, impliedly, 'ol Ken Shindo should just then pack it up...

Jeez, can one hear an echo around here?

I know, this is hardly dispositive in an empiric sense, but I know of a guy who streams only digital into class D amps - talks a lot, doesn't listen much, cognitively chatters like a monkey - and who says that his is the most "transparent" way, it just has to be, its so, um, logical.

My response? You can't describe the color purple to a blind man...