[John L Stewart]

Hi Patrick,

OK, this is more like it, I have liked your idea bootstrapping the output tube
grid resistors, by using separate cathode bias networks for each tube, ever
since I conceived of the idea 22 years ago.

Come on John, I've seen nothing conceived by you outside your immediate family. Examples of grid booting are given in RDH4, just go look. If you can show us some evidence of your cct using this pls do. Don't see much done by you on your website, very much unlike Patrick's.

Te problem with providing the signal to drive the grid of V2 in the paraphase,
when the output tube grid resistors are bootstrapped, is easily resolved by
using two additional resistors and a capacitor to implement a floating paraphase
circuit. The down side of this is that it increases the load on the driver
tubes, negating the gain from bootstrapping.

While the LTP is fine for a Leak or Marantz style circuit, I question whether it
can be made to work in the QUAD circuit without a negative voltage supply for
the tail circuit, and a negative supply seems like it would push up the cost and
complexity considerably. The negative supply would have to be half wave unless
you use two 6X5s.

Back in the day you or I or Patrick T or anyone else could have used selenium rectifiers for a -ve supply, many of which were available, before 1950. A rail at -100 volts would help a lot with an LTP. And FW not a problem.

Lots of tubed guitar amps used 6AL5's for OP biasing. Back in the day 6H6's would do just as well, 36 mA from a pair. No problem.

--
Regards,

John Byrns

Surf my web pages

My thoughts anyway, John Stewart who still has some Se rectifiers in his stash. And still likes to see new ideas.