DC biasing of line o/p xformers

[Kev]

and people say I'm cryptic at times ... :wink:

I think zmix is referring to the
large object like a 0.5uFd cap, closely surrounded by a metal body
and the VERY high impedance at the plate
so
when you wave you hand over the lot you may get the oscillation

good, good, good, good vibrations ...
:green:

 

[volki]

ah. thanks. - well, that would make sense actually. the circuit i'm referring to (schoeps 201) was divided in two for reasons of miniaturization of the mic - one half - tube and some resistors - placed in the actual mic housing alongside the condenser capsule, then a few feet of cable, and then the other half - the bulky parts, like xformer and 'lytics - placed in another enclosure. so if the cap were before the xformer, the cable indeed could have been subject to what you described.

the observation would also apply to the akg c60 small diaphragm condenser mic which has the same arrangement of cap & xformer, here they're even placed in the psu itself. obviously the cathode follower design with it's lower impedance than the CC designb of the schoeps made it posssible to drive a longer cable.

 

[clintrubber]

from zmix:

One possible side effect of DC throught the primary is that the core will have a magnetic polarity. This can lead to the core becoming saturated asymmetrically. This can cause even harmonics to be generated... hmmm sound like a Neve??

and from Kev:

I'm having a little trouble finding the guts of the original question.

DC is on the trafo ...
because the preceding circuit happens to have a DC bias
or
DC is deliberately applied to the trafo for a specific reason

and are we to talk specifically about the BA283 or keep it more general ?

So what's the general concensus:

Is DC-through-the-primary essential for the sound of circuits like the Neve BA283 ?
Or would it have been 'just as nice' with no DC through a non-gapped TX and using AC-coupling ? (w.rt. 'sound' - so apart from efficiency and or certain smaller side-effects)

Or in other words (and as far as this could be judged separately):
Is it the class A & a sweating TX in general -or- the core becoming saturated asymmetrically ?


Thanks,

Peter

 

[zmix]

[quote author="clintrubber"]

Is DC-through-the-primary essential for the sound of circuits like the Neve BA283 ?
Or would it have been 'just as nice' with no DC through a non-gapped TX and using AC-coupling ? (w.rt. 'sound' - so apart from efficiency and or certain smaller side-effects)

Or in other words (and as far as this could be judged separately):
Is it the class A & a sweating TX in general -or- the core becoming saturated asymmetrically ?


Thanks,

Peter[/quote]

Very good questions, all. Has anyone run any tests?

 

[clintrubber]

Anyone ?