mwhouston wrote:
Can someone tell me the advantage of a totem pole preamp like this one.
The entire class of actively loaded (or "Shunt Regulated" as V.J. Cooper put it) amplifiers was developed to drive "difficult" loads with large voltage swings. Usually "difficult" meant relatively low impedance, highly capacitive loads driven at medium radio frequencies. In short, the topology was developed to address some very specific problems associated with high power television transmitters. Even though they are widely used today in certain audio amplifier designs, this is not for what these circuits were designed.
mwhouston wrote:
A hell of a lot of gain.
I'm not surprised by this at all. At your operating point, µ ≈ 20.5 and rp ≈ 8.0kΩ. This puts the amplification at roughly 13.7 v/v or 22.7dBv. Used as a preamplifier, a normal line level signal (+4.0dBu, 1.8dBv, or 1.23v-RMS) is going to be amplified to 26.7dBu, 24.5dBv, or 16.8v-RMS. This output level will need to be heavily attenuated to prevent overdriving most audio power amplifiers.
mwhouston wrote:
And please tell me the output impedance.
The output impedance is simply the parallel combination of the upper tube path and the series combination of the lower tube path and the bootstrapped upper cathode resistor. At your operating point, this puts the output impedance at about 5.46kΩ.
So more importantly, how does she sound?
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