Home Tubes Asylum

Questions about tubes and gear that glows. FAQ

[ Follow Ups ] Thread: [ Display  All  Email ] [ Tubes Asylum ]
[ Alert Moderator ]

Now we are talking...

I measured too...
Try my bias points with my circuit, not with anemic tubes... I found practically unlimited bandwidth from the driver side. The real limitation comes from the output stage and my hunch would be the output transformer. 12 Hz to 80 KHz 3 dB bandwidth from input to 8 ohm output is what I measured. Incidentally, the 12 Hz directly corresponds to the time constant of the phase splitter and that 0.1 cap. The theory does work :-)

Two comments:

While all those dual-triodes work for low level signals, only a few would swing the full dynamic range required for full output, hence my choice of a 12AT7.

A diff amp design will develop symmetrical (phase-inverted) drive to the final stage under feedback only if the open-loop gain is extremely high (basic FB theory leads to this standard "opamp" concept).
This required that I use at least two gain stages (for around 5% asymmetry, which I consider acceptable) which raised the amount of NFB beyond a "good taste" (that's MY taste!) and you can hear it!

This post is made possible by the generous support of people like you and our sponsors:
  Atma-Sphere Music Systems, Inc.  

Follow Ups Full Thread
Follow Ups
You can not post to an archived thread.

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2024, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]