VTL Tetrode/Triode

One thing I've been doing lately is to use different input tubes for each mode with certain types of recordings. For triode mode, the brighter, more incisive Telefunkens make a good match, while in tetrode the darker, fuller Mullards complement nicely. I agree (I think it's agree) that the Shelley Manne intros to those SR tunes generally sound more natural in triode, but when Ray Brown kicks in the pendulum swings toward tetrode...space is also presented differently in each mode, but there I tend to prefer whichever mode I'm listening to at the moment ;^)

Even if your input tubes display no audible microphonics, I urge everybody to try some sort of tube dampers here (I'm using Herbie's); for a nominal investment, you'll probably hear the amps cope better with stuff like vocal sibilants, plus truer tonality and more stable imaging, with 'quieter' spaces between performer images. Everything gets a bit less edgy and a bit more listenable, especially at higher volumes (not that transient impact is smoothed out - actually, HF transient tracking fidelity is increased, because there's less tizz and overhang). The improvement isn't huge, but neither is the cost or hassle.

Zaikesman: Isn't that a pain? Flipping a switch on the back of the amps is one thing, but unscrewing the covers, pulling out the two input tubes, and replacing them? Or do you leave the covers open? Maybe, in that case, it is not too bad.

Well, anyway, that's an interesting thought. Enjoying the music is what this is all about.

he probably leaves the tube cages off as I also do

Yep, I leave'em off, if for no other reason than I like to check the bias more often than I want to deal with the covers. But playing with input tubes is a more fun reason.

I'm also just paranoid enough that I prefer an unobstructed view of, and access to, the tubes in case one should give a hint it's beginning to act up; a few times in the past (not always with these amps) I've caught stuff out of the corner of my eye which likely saved me bigger headaches within moments - including smoke wisps emanating from around transformers - that you're not going to notice as easily with covers on. Have you ever done the jump-up and across-the-room-sprint when a tube started in with a light show? :-) And although I think the amps look better with the covers in place, I assume that heat dissipation - and therefore tube life - probably gets slightly improved running naked.

Update: I just replaced all tubes (input, output, and driver) and I must say that now, triode is a lot better than it used to be. In comparison, tetrode is a little hazy and distant. But triode is crystal clear, and now, for example, the the above mentioned Brahms trio is unbelievable, with fantastic rythm to boot. Also, piano is fantastically present. Take Richter's performance of Beethoven's Appassionata sonata on RCA. You can hear every tap, all the hidden gems, counterpoints, etc. Amazing! And now triode (with new tubes installed) has the power to preserve the waveform, as that piece has incredible dynamics, from ppp to fff.

So, maybe this is what happens over time: as the tubes age and lose power, triode loses its magic, at which point tetrode sounds relatively better. Could it be that simple?