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In Reply to: please advice me what is this driver stage doing ? pictured posted by lovetube on March 24, 2007 at 08:24:02:
Spice output with (red) and without (green) the 0.047/1meg RC combo. Probably specific to Radford's iron.
Follow Ups:
That's what Mr. Texas and Mr. Instruments said to me. It's giving another turnover, but in just about exactly the same place (3.7Hz) as the filter formed by the coupling cap and grid circuit resistor (3.4Hz).Howcum? I mean, it ends up modifying the response very little, and wa-ay in the subsonic.
...What's missing are the subsonic characteristics of the OPT.and maybe the rest of the circuit. Subsonic stability under closed loop conditions is the goal.
Correct. It's not intended as a tone control, its purpose is to nullify the phase shift of the coupling cap at low frequencies inside a feedback loop, and it can be as stable as direct coupling.This technique is used where direct coupling would be desirable but impractical. The resistor potential divider provides a workable DC level for the grid of the next stage, while the shunt capacitor prevents any resultant drop in signal level. You get a drop in DC but no attenuation of AC, like having your cake and eating it!
thanks .
I thought of that .they should put them in for a reason.
Cheers
LT
The network(s) introduce a LF step response for both amplitude and phase. With proper component values, LF stability is improved when the "global" feedback loop is closed (typically).
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