In article ,
Big Bad Bob wrote:
On 05/20/11 03:22, Patrick Turner so wittily quipped:
Baxandall's amp isn't real bad, but the first input pentode must
produce a voltage large enough to drive one 6L6 grid in beam tetrode
mode with fixed Eg2. The other input pentode operates as an inverting
anode follower with unity gain, but any THD generated in V1 is passed
on to be reproduced in V2. In effect, driver amp distortion is double
that of a single tube, and this defect also occurs in any amp using a
paraphase driver.
I hadn't heard the term 'paraphase' until you mentioned it, so I did a
bit of online research, found out that I've seen things like that before
and I never liked it done 'that way', but yeah, using PENTODES just
makes everything worse for distortion and potential imbalance. Relying
on the circuit gain characteristics of a tube for your design, or
requiring a balance adjustment to make it work, is just silly.
I prefer the floating paraphase phase inverter as it has many advantages over
other forms of phase inverter. If the inverter tube has sufficient gain,
balance is excellent and no balance adjustment is necessary.
--
Regards,
John Byrns
Surf my web pages at,
http://fmamradios.com/