V1A & V1B Cascading gain

[angelodp]

V1A @ pin 6 V1B @ pin 1 Can those in the know talk a bit about Cascading Gain theory and practice.

[Firestorm]

I don't think I undertand the question.

[angelodp]

I am trying to get a better handle on the language used here and where it stems from. V1A at pin P6 seems illogical except that it was a function of Dumble's ideas on Gain theory. I would like to know more about how Cascading gain works.

[Structo]

Cascading gain in simple terms just means feeding the gain from one preamp tube to the next.

[briane]

V1A at pin P6 seems illogical except that it was a function of Dumble's ideas on Gain theory.

giving that credit to dumble goes a bit too far. its basic tube theory and how they operate. Its like saying fender invented the amplifier.

What dumble did was tune the plate and cathodes, and work with values to provide the tone he desired. He definetly realized they work as a pair, in conjuction with the subleties of the signal coupling components. He also recognized that cascading was a special case of design, requiring a slightly different approach than not.

But he was not the only one doing this either. though in my view he did do it better than most.

anyways, keep on learnin....

[ampgeek]

In very simple glass and vacuum vernacular, gain is the increase in voltage from a tube's grid signal to it's plate. Pins 1 & 6 and 2 & 7 respectively for a 12AX7 (and others) pre-amp tube.

Slap a 50 mV AC signal from a guitar pick-up onto pin 2 and create a 1V AC signal at pin 1 gives you a gain of 20.

Cascade that 1 V signal onto pin 7 and get 20 V at pin 6 and you have created a cascaded gain of 400 from the original signal.

Repeat as many times as your ears can tolerate!

As others have said, this is a tube theory/circuit design gig (not to mention a tremendous over simplification!) and there are many different ways to skin this cat and still keep it musical. Some designers just did it "better" than others.

Cheers,
Dave O.

[Firestorm]

V1A at pin P6 seems illogical

I still don't think I understand the question. Assuming we're talking about a standard twin triode preamp tube, V1A is the first triode of the first preamp valve; V1B is the second triode of the first preamp valve. Pin 6 is the anode of the first triode; Pin 1 is the anode of the second triode. The only thing "illogical" is that the tube industry decided eons ago that pins 6,7 and 8 were the FIRST triode and pins 1,2 and 3 were the SECOND triode. Odd, I suppose, but that's always been the nomenclature.
Was there a specific Dumble-esque circuit you were looking at that seemed unusual?

[angelodp]

Thanks Firestorm, its making sense now. Lots of new nomenclature for me and I want to get the lingo and theory.

thanks Ange