Boozhound Choke Tail Pair for HiFi

[mashaffer]

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

 

[doctorfixit]

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.

 

[Eli Duttman]

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.

 

[Bigun]

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.

 

[ray_moth]

however there is no way to add negative feedback from the output xfrmr to the PI.

.
Yes, there is - add NFB to the second (grounded) grid, using a low-value resistor between grid and ground.