Bear,
Does the mac and/or quad having the cathode windings use the cathode windings phased to oppose the gain or to go along with it? I must not have noticed, or I forgot.
I had very good and very linear results using the 25V center tapped widing to make negative feedback windings for the cathodes. (The 0-4-16 taps could have been used as well).
The iron was already as large as a hi-fi amp on the amp in question. I changed the tubes from 6L6 to 6CD6 to allow more current and also lowered the G2 supply from ~400 to ~200V.
Pls look at the schematic, I'd be interested in your opinion on the section around the output transformer.
The feedback there is only for the purpose of making the transformer behave as though it cost more. <snip>of the tubes in a manner to counteract the 'error'.
What do you mean by current dumping? Do you have a schematic for an example?
Fast answer version, since it is OT for this forum, but might be of interest in terms of building modulator iron or applying it!
They draw the McIntosh output stage "funny" so in all probability the cathode is out of phase with the plate. It is a
unity gain stage, which is why it is problematic at higher powers - the driver stage needs to go "greater than 100% modulation"!!
You can find Quad schematics online and in the Radiotron Designers Handbook, iirc. It's a variant to get around the McIntosh design...
The problem with "flattening" the response of not so good iron is that you can get the response flat, but at the expense of ringing, which translates to not that great sonics (if ur critically listening, if not, no worries!). The cathode feedback method, or using the secondary (see early Audio Research - not Acoustic Research, the speaker people - schematics) is "one way to do it". In some respects it is a good idea.
To get a really full discussion of this idea, go to
http://www.diyaudio.com and search and/or post ur schematic and thoughts there - you'll get a pretty high % of good information back!
_-_-bear
