Tube DIY Asylum Do It Yourself (DIY) paradise for tube and SET project builders.

---

[ Follow Ups ] [ Post Followup ] Thread: [ Display  All  Email ] [ Tube DIY Asylum ]

---

[ Alert Moderator ]

---

DC Filaments for EL-34s?

Posted by JimWayner (A) on January 2, 2010 at 15:35:39

I'm going to re-do my Eico HF-87 for about the fifth time and was wondering - should I consider going to regulated DC for the output tube filaments? I've dug thought a bunch of forums and searched the internet and looked at some schematics of high end gear, but pretty much all the power amp output tubes seem to be run on AC filaments.

I want to make the amp quieter, and getting the AC away from the signal path seems like a smart thing to do. There is no hum balance pot on this amp, and I wonder if that is some of the problem. And if I do convert to DC, should I float the filaments or ground one side?
'
I did find something interesting while poking about underneath the amp. The amp has a twisted pair of about 22 ga. wire running from tube to tube and there's about a half volt drop at the far end, so that needs to be fixed anyway. The filament voltage at the high end runs about 6.4VAC, which seems pretty much OK.

Comments/opinions/speculation appreciated.
Jim W.

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

VH Audio

---

[ 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 ]

---