OTL Asylum OTL, Output Transformerless Amplifier User Group.

---

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

---

[ Alert Moderator ] [ Edit ] [ Delete ]

---

Re: Dc Offset Problem

0

Posted by mark on November 9, 1999 at 07:48:55

In Reply to: Dc Offset Problem posted by Dave H on November 8, 1999 at 15:50:49:

I've seen this problem and found some reasons for this behavior. I'm not suggesting
my experience will solve your problem. There may be other reasons this instability
occurs.

First, I'd unplug the inputs and short both the + and - pins of the XLR connector to
ground. This will tell you whether there is noise, introduced from an outside source,
that is causing your instability. If that's the case, your amplifier is just fine and you
need to look for an external solution.

If you still have instability, with the input pins shorted, you may have a noisy tube in
the driver stage (V1 - V3). Do some swapping and see what happens. V4 is
responsible for the bias voltage. It may also be suspect.

Finally, I've found output tubes that meander around a bit. To find the flaky 6AS7,
individually monitor the voltage across all the one ohm plate resistors. All these
voltages should be rock solid. If not, replace the suspect output tube.

I hope this helps.

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

Atma-Sphere Music Systems, Inc.

---

[ 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 ]

---