VTL Tetrode/Triode

Update: Tetrode/triode mode appears to be speaker dependent, too. I recently switched to B&W N802s from N803s, and with the Nautilus 802s, I'm back to tetrode for most of the time. Those babies like power, and triode is fine only if the dynamic swings in the musical fabric aren't too pronounced. Tetrode gives a much deeper and wider soundstage, and preserves all of the waveform; which makes for an unflappable presentation.

Well, anyway, I thought I'd post this, I'm just glad VTL provides both modes. With other speakers, it will be different, no doubt.

Larger woofers to control at the least, and maybe a more difficult impedance, I don't know. The 802 was always my favorite B&W, over the 801, although I haven't really auditioned the N-series. But I never heard one with tubes. Your experience is another bit of evidence suggesting that where tetrode is superior, the extra power may be the main or even the only reason.

Agreed with Hgabert post entirely, in a way the Triode/pentode switch could be a Hi-End Equalizer for audio setups.

Fernando

To the extent the switch may act as a bit of a de facto equalizer, that's exactly what I *don't* like about it. As I probably stated somewhere way up above, the fact that an amp can have two subtly different sounds at the flick of a switch just points up the reality that neither presentation can be trusted as accurate. Of course we already knew that, but with amps that don't offer two different-sounding modes, at least the subject isn't put on a platter for us.

I once owned a DAC, briefly, that offered externally-defeatable 'upsampling', in a choice of three different frequencies chosen from moveable jumpers inside the unit. Objective testing by a rather involved methodology I worked out to help me evaluate the effects showed that performance was most faithful to the signal fed the DAC with the upsampling switched off. However, I couldn't deny that there were disks whose sound I subjectively prefered with one or another of the upsampling rates switched-in, even as I could hear some areas of fidelity being compromised. But I wasn't happy that the machine editorialized the sound at all, and luckily my (non-'upsampling') reference DAC outperformed it anyway and I sold the thing.

With the VTL's, I think the ultimate answer would be to get one of the very high-powered Reference models and run it in triode. Answer, that is, if you're a richer man than I...

On a related subject, I spoke with one the technicians at VTL not too long ago and learned that it's perfectly OK to run the amps with tube pairs subtracted, equally from each bank (same number of output tubes removed respectively from both the left and right sides of the chassis, though it's not important that the tubes be from particular corresponding positions within each of the banks, due to the way the amps are wired). This will simply have the effect of reducing power output, with everything else, like the power supply capacity, held constant.

In the case of my 185's, with their three tubes per bank, I can run them at full power (all six tubes, three pairs), 2/3 power (remove one pair), or 1/3 power (remove two pairs, leaving just one pair in the amps). And I have tried this with no problems at all. But for 450 owners, with four tubes per bank, one of the available choices is 1/2 power (two pairs removed, leaving two pairs in) - a close approximation of the same power reduction you get when switching to triode mode. So a 450 owner could compare tetrode mode with only two tube pairs installed, vs. triode mode with all four tube pairs installed, and the prevailing differences would presumably be entirely due to just the different operating modes, without being confounded by different output powers. Just in case any of you 450 owners are feeling curious and experimental...

Zaikesman: thanks for the above, informative post. I'll try that, as this will be a more "fair" comparison. But in any case, I suspect I will continue needing to run with full banks in tetrode, unless I upgrade to a MB-750, or to the Siegfried (yeah, right!).

I also agree with you that being able to change the sound at the flick of the switch is perhaps "unsettling." But with other amps which don't have a switch like that, the problem just isn't that apparent, but present nonetheless.

Any amp, whether tube or solid state, has a certain sonic signature, let's not kid ourselves. So the VTL amps have two sonic signatures, that's all.