Randall valve dynamic

[metalhead]

Randall has something called Valve Dynamic in their G3 series amps (possibly designed by Bruce Egnater).12 AT7 driver(?) tube before MOSFET power section.What is the verdict? is it just a fancy pilot light(ala behringer tube pre-amp), or does it serve a purpose?Does anyone know the operating voltage and the real!! function of that tube? Teemu K, is this valve dynamic in the vain of vox design ,which according to your investigations,i believe, was a "scam". With right speakers the amps sound great(they are intented to be used in metal music)but am i blinded by marketing departments "fairy dust" or fake glow of a makebelieve tube?

[teemuk]

Old RG-series amps and Warhead X2 are the only Randall amps I'm slightly familiar with. Those just used a simple cascade of overdriven FET stages. Randall makes great amplifiers regardless of what technology they use. They seem to be very secretive about this new circuit (and once again it's the best, most groundbreaking tube-like invention in the whole world and blah blah blah). Bruce Egnater, I guess, was the chief designer. As far as I know their invention is not patented (not even pending) so it's likely something quite ordinary. What I could make from all that marketing stuff is that they drive a MOSFET power amp with a valve pre. Doesn't tell much as there are dozens of ways how to do that. I'll try to dig up something... This got me interested.

Most manufacturers actually do use those tubes in other functions than just a fancy light bulb. Since you include it you might as well use it to extract a little bit of gain and some overdriven tones. In many circuits the effect of the valve is pretty subtle because a single valve very often cannot do anything marvellous by itself. For example, In Valvestate (Marshall), Tube Fusion (Laney) and countless of other amps, each half of the tube just make up a single, basic gain stage. Configured this way they have little difference to a similar circuit that would have been built with FETs.

The Valvetronix Valve Reactor circuit is not a "scam". It's actually a quite novel topology that to my great annoyance was marketed in a very confusing manner. Most of that marketing hype was also rather incorrect and the real circuit didn't actually fill all those promises. For example, it doesn't utilize a real transformer. If they wanted to publish something "technical" they might as well have kept the information accurate. You can find links to circuit diagrams of Valvetronix amps from this forum's schematic sections and make up your own mind about them. That circuit is, nevertheless, so far one the most promising hybrid circuits I've seen. Not really because of the tube but due to the rather unordinary way it is utilized. Hopefully we'll see more similar inventions in the future.

[metalhead]

Teemu K. Many thanx for your informative reply. You truly are a master in your field.If you happened to find any additional info on that "valve dynamic circuitry" it would be much appreciated. Really like that sound of RG 150/300 G3 and V2/T2 power section for metal purposes.
Thanx for clearing up my impression of those vox amps. I check the schematics. Personally, not my cup of tea, those vox amps, though.

[teemuk]

"...the key to this power circuit is the accuracy in frequency response of a full 100 watt tube power amp, which results in unbelievable dynamic all tube tone, feel, and response."

The marketing slogans seem to make a very big point about replicating this frequency response of a tube power amp so I suggest that there's simply some current feedback going on. Also, the more I have read the material the more uncertain I'm coming of whether the tube section is preceding the power amp or actually forming its driver section.

"Each Valve-Dynamic power section incorporates a 12AT7 preamp tube which drives the first 2 stages of this new power circuit."

How should that be understood?

Does anyone have schematics?