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Grounded Cathode Amplifier
The Grounded Cathode amplifier is the most used of all tube circuits; with good cause. It is both simple and effective. With just one triode, four resistors and a capacitor, a perfectly usable line stage amplifier can be built. Whereas, using any other single device would require many more parts to achieve similar performance. What makes the triode a good choice for a single device amplifier is that it will simultaneously exhibit a consistent gain, a fairly low output impedance, and a fairly high PSRR.
Textbook Grounded Cathode
Constant current Draw Grounded Cathode
Current Sourced Grounded Cathode
Inverted Transformer coupled Grounded Cathode
Grounded Grid Amplifier
Although this is one the three basic tube amplifier circuits, it is seldom used in audio equipment, because of its very low input resistance. Still it offer slightly greater gain than the GND Cathode amp and much lower input capacitance and it does not invert the phase of the signal.
Textbook Grounded Grid
Grounded Grid with Feedback
Grounded Grid with Hum-Bucking
Hybrid Grounded Grid with P Channel MOSFET
I to V Converter
An I to V converter performs the conversion of current variations into voltage variations. (Of course, all tube circuits must use a variation in current to manifest a voltage variation, but as this current variation results from a voltage variation at the tube circuit input, the tube does not easily lend itself to I to V conversion; whereas, a transistor, being a current driven
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device, would. Still, a very good tube I to V can be built and variation 2, the improved I to V would be an excellent starting point.) The key point here being that a good I to V converter should offer a zero impedance input that does not vary in voltage and should realize all the current variation fed it across the reference resistor Riv, which will develop the output voltage. A near zero impedance input is necessary for many digital to analog converters (DAC), as often there is a non-symmetrically slewing ability when presented with a high input resistance due the circuit topology internal to the DAC; in fact, some DAC's fail to function at all if their output see a departure from 0 volts greater than .3 volts.
Generic I to V
Improved I to V
Lohoff I to V
Push Pull I to V
Long Tail Phase Splitter
This is the second stage in many power amplifiers. It boasts the advantage of providing both phase splitting and voltage gain. It works very much like a differential amplifier whose first grid is the input and its second is grounded. Does this unbalanced operation result in an unbalance at the output? Yes. Quite a bit, actually. With a low mu triode, such as, the 6BX7, the imbalance can be high as 20% in a typical circuit arrangement. To the extent that the shared cathode resistor approaches infinity, the unbalance approaches 1/mu. Using unbalanced plate load resistors, however, can restore the balance at the circuit's output.
Textbook Long Tail Phase Splitter
Long Tail Phase Splitter with Current Source
Long Tail Phase Splitter with B+ only
Long Tail Phase Splitter with Hum-Bucking
Continued
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