I was musing over the problem of largish resistors (and subsequent large voltage drop) of LTP circuits and the resulting large B+ requirements and wondered whether a choke might help with that problem. In searching the internet I came across this circuit by Boozhound.
Choke Tailed Pair
My thought was to replace the tail with a choke but he makes a good case for using only the cathode bias part with no tail at all.
What do you think of this circuit in general and what about using it in a hifi amplifier input stage (or preamplifier)?
mike
Choke Tailed Pair
My thought was to replace the tail with a choke but he makes a good case for using only the cathode bias part with no tail at all.
What do you think of this circuit in general and what about using it in a hifi amplifier input stage (or preamplifier)?
mike
I just built a Conn organ conversion using the choke and I noticed an improvement over the existing setup, which was not a LTP, however there is no way to add negative feedback from the output xfrmr to the PI.
Mike,
A choke works better than a resistor in the tail, because the AC impedance is high and the DCR is low. However, you can do better (IMO) with a 10M45S constant current sink (CCS). The IC occupies less space, weighs less, costs less, and provides a higher AC impedance.
A choke works better than a resistor in the tail, because the AC impedance is high and the DCR is low. However, you can do better (IMO) with a 10M45S constant current sink (CCS). The IC occupies less space, weighs less, costs less, and provides a higher AC impedance.
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A choke acts very much like a CCS but it has the additional advantage that it allows the supply voltage to swing above B+. Of course this is only useful if your circuit will benefit from this.
The other thing I'm starting to appreciate with chokes - they are very robust.
The other thing I'm starting to appreciate with chokes - they are very robust.
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