Home Tubes Asylum

Questions about tubes and gear that glows. FAQ

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

Re: Experiments with "UltrPath" connection

The explination for how the circuit works was described to me by thorston at the london show last year, I will try to relay my understanding of it.

If the B+ rail falls, either under dynamic signal or ripple conditions, then an unwanted AC voltage will form across the OPT. To correct for this an error signal of amplitude reduced by the gain of the output stage and inverted in phase has to be fed into the grid of the output tube. A convinient way of removing the need to invert the signal is to add it into the cathode circuit so it is subtracted from the input. Since the AC conditions of the cathode are determined by the cathode by-pass capacitor, it is easy to inject this signal using a capacitive divider made with the cathode capacitor as the lower leg and an additional "ultra-path" capacitor connected between the cathode and the B+. To get the correct cancelation the AC voltage divider needs to have the correct ratio, the ultra path capacitor should therefore be the gain of the stage minus one times smaller than the cathode by-pass. Also the "ultra-path" capacitor should be of a similar construction type and characteristic to maintain this ratio over wide operating conditions.

If the value is severly wrong then positive feedback on the signal will occur, but since the dynamic impeadence characteristics of the PSU are frequency dependant, the amount of positive feed back will also be frequency dependant, causing a rise in the bass response.

HTH

Chris


This post is made possible by the generous support of people like you and our sponsors:
  Sonic Craft  

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

[ Top Top of Page ] [ Contact Us ] [ Support/Wish List ] [ Copyright © 2025, Audio Asylum, all rights reserved ]
[ General ] [ Speakers ] [ Tubes ] [ Vinyl ] [ Digital ] [ Hi-Rez ] [ Video Asylum ] [ Cables ] [ Tweaks/DIY ] [ Music ] [ Films ]