VTL Tetrode/Triode

I agree with your assessment. There are some surprises, however. For example, certain Reggae pieces (Bob Marley, Rastaman Vibration) sounds better in triode, not tetrode (as I originally thought it would). Vocals are a lot clearer, and it sounds more real, live.

On the other hand, take Vivaldi's Four Seasons with Salvatore Accardo on Philips, and it sounds better on tetrode (more liquid, smoother, soaring highs on the massed strings), at least to my ears. Weird.

Hi Hgabert

In my experience (Manley 200/100 Mono's, very similar circuit to your MB's)), in absolute terms, the amps always sound better in triode: much more refined sound, better detail, less grundge, etc., etc. Tetrode becomes advantageous when your system, wether because of your speakers' efficiency, or your preamp's gain characteristics, benefits from the extra power. If your speakers are efficient enough to meet all of the needs of every type of music that you listen to, at every loudness level that you listen at, with the amount of power that triode has to offer, triode may always sound better to you. It sounds like they are not; few are.

I found that in my system, with many speakers, tetrode not only allowed the speakers to play louder, with more bass, but more importantly, it let the speakers unravel complex orchestral passages, it let a string section sound like many individual players as opposed to one large mass of "string" sound; probably why the Vivaldi sounds better in tetrode. Most reggae, while "bassy", is not particularly complex music; so will probably tax the amps less. The problem became that I missed the purity and sweetness in the highs that triode offered. The solution for me was two-fold: get used to listening at slightly reduced volume; this taxed the amps (and my hearing) less, in triode mode, and experiment with the input tubes. I found that with the right NOS 12at's (for me it was W.German Amperex or Tele's), there was enough of an improvement in the detail and treble extension departments, in tetrode, to bring the sound close, if not quite, to the level of triode sound with run-of-the-mill 12at's. This allowed me to enjoy tetrode mode when I absolutely had to have the extra watts. Of course, the sound in triode became that much better also; and this is why it is called "audiophilia nervosa" :)

Good luck.

Hi Frogman,

thanks for your response. I'll try the German Amperex or Telefunken 12AT7, that's a good idea.

But what about the 6350 tube (phase splitter)? Any suggestions there?

And the output tubes (Russian 6550C) are probably ok, right? (I don't think you can change them anyway, even if you wanted to).

Right now the rule of thumb for me is: Anything from solo instrumental, up to seven or eight players, use triode. Anything above, use tetrode (this is also what T_bone mentioned above).

BTW, i use B&W N803 speakers (90 db sensitivity).

The 6350's affect the overall sound less than the 12at7's do. It still pays to experiment, though. This is an American made tube and there are no exotic versions available, to the best of my knowledge. My favorites are the Tungsol's and the earlier RCA's. The RCA's that I have (two different vintages/two different internal construction), sound a bit more relaxed and romantic. The Tungsol's sound a bit more dynamic and alive, with a more prominent top end; this better suited my system. The differences are relatively subtle; but a definite improvement over the GE's that came in the amps. Try "Antique Electronic Supply" as a source of 6350's.

As far as 6550's go, I really don't have an opinion since my amps use 6L6GC's. I will say that the Sovtec 6L6's that the amps came with sound less refined than the NOS GE's that I have. The GE's are not a particularly great tube either, but in my system, a better sound. I hear good things about the Svetlana's; maybe worth a try. By the way as far as the 12at7's go, the Telefunken CCa (a super-premium version of the 12at7) is supposed to be THE tube for these amps. Very expensive, though.

Have you experimented with power cords? My amps definitely benefit from upgraded power cords. I use the old Tiffany "reds". Recommended by the Manley's themselves as the chords for these amps. This is going back several years, however, and I'm sure there are better cords out there for these amps, by now. The improvement over the stock chords was unmistakeable, however. Gutsier sound, with larger soundstage and more refinement. My amps also like to be placed on hard cone-type footers. The soft type makes the same a bit ill-defined and tubby. And finally, VPI bricks on the transformers are a very worthwhile tweak; the tighten up the sound, and make the spaces between instruments cleaner.

Good luck.

Frogman:

whew! I appreciate your insights. Lots of things to try out when it becomes time to re-tube, that's for sure. Right now, I'll enjoy the sound and definitely check out the power cords, and perhaps the other two tweaks you mentioned. Again, thanks!