Tuesday, June 2, 2009

How to Sound Like Tube Guru 101

How to Sound Like Tube Guru 101

Common Cathode CC is name as such because its Cathode is connected to the Common Ground.

The CC is good at Voltage amplification, i.e., magnify signal; this is generally the strength of glassware.

It has high input impedance of easily a few hundred thousand ohms; in plain English, it is very sensitive to input signals and very easy to drive.

Fairly high output impedance, which means it is not so good at driving difficult or less sensitive loads such as Solid State Amplifiers and Loudspeakers without some neat tricks but its sufficient to drive another tube stage.

Biasing, to get the tube into operating condition, we set the DC bias or quasient state, its like getting your car on idle speed; When AC signal (yes, signal can only be AC, that includes noise signal too) is applied, its like stepping on the accelerator, and the engine will respond accordingly to how hard you step on it

There are 2 biasing methods in general, Fixed-Bias and Self-Biasing. My emphasis will be on Self Biasing as IMHO they are easier to tinker with and better sounding too.

Self Biasing means we put something (resistor, LED, Diode, Battery or Constant Current Sink) between the tube’s cathode and the ground so that it can generate the required bias voltage by themselves, hence Self Biasing.

Input signal, lets consider CD player output signal of 1Vrms, that means 2.83V peak to peak. V max of +/-1.414V.

You don’t need an input capacitor solder in your circuit as CDP already has an output cap to do the job.

Output coupling. We are going to use Capacitor coupling. This capacitor will ensure only signal voltage is delivered to the next stage. That’s all you have to know for now.

Recite the above to your pal is enough to impress your tube ignorant buddies.

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