Posted: Sat Feb 02, 2008 3:59 pm
Fair enough. I thought you were being oblique
It's possible to have a solid-state inverter, so I looked around to see if anybody could say for sure what this amp is using its 12ax7 for... phase inverter or traditional 2-stage preamp. There are tons of user comments that take one side or the other, apparently based on plain hearsay.Right here are some "reviews" by people that have opened their Super Champs up and looked inside. And so far the most definitive answer is... it's doing both. Half the tube is warming up an otherwise digital preamp, while the other half does the phase inverting.
Absolutely right.... overdrive is solid-state. And as another amp-opener on the same page says, the tone stack is all-digital too.The phase inverter uses half of the 12AX7, the old concertina style, which doesn't have gain. It has a slight bit of loss, in fact. The other half of the 12AX7 comes before it, and it's a standard Fender preamp gain stage. It takes the signal from the digital stage and boosts it to drive the PI. The fact that they did this with a tube instead of a transistor tells me that they wanted to add some tube warmth. I haven't gone in with a signal generator and a spectrum analyzer yet to see how much harmonic content gets added, but there must be some--it's a fairly high-gain stage.
But all of the tone that matters--breakup, distortion, etc--comes from the DSP. The SCXD does not depend, as far as I can see, on the tubes for distortion, just overall warmth and graceful compression as you approach maximum power. Since the 6V6s operate below their maximum rating, I doubt that you'd ever hear power tube distortion from this amp.
Then again, power tube distortion is actually somewhat uncommon in most amps, despite what people think. Most of the time, they're hearing preamp distortion or even distortion in the phase inverter.
On a positive note, there's a bias pot for the power tubes inside the amp. Nice to have.