Permanent Bias Meters

by SoundBound Sun Jul 31, 2011 10:31 pm

SoundBound: Posts : 13
Join date : 2011-07-31

Post n°1

Permanent Bias Meters

by SoundBound Sun Jul 31, 2011 10:31 pm

Hello,

New to the forum, first posting.

I am currently refurbishing a set of Mark IIIs and about to install the VTA driver board for these lovely puppies. On my wish list, possibly, is the installation of a permanent meter(s) for monitoring the tube bias.

There are two ways to do this;
1. A volt meter wired across the bias measurement resistor(s). Scaled 0-2V at best.
2. A milliameter wired in series with the bias measurement resistor(s). Scaled 0-100 or so mA.

Question, is this an ok thing to do and which method is preferable to monitor the bias, voltage or current. I know that you can set the bias by either method but will either approach have negative effects on the Mark IIIs ?

If anyone has any comments in regards, glad to hear them.
SoundBound

by **Bob Latino** Mon Aug 01, 2011 5:51 am

Bob Latino

Bob Latino: Admin; Posts : 3272
Join date : 2008-11-26
Location : Massachusetts

Post n°2

Re: Permanent Bias Meters

by Bob Latino Mon Aug 01, 2011 5:51 am

Hi,

Your choice # 1 is the best method. It is basically the same way as bias is now measured on a Mark III except you want a permanent meter to constantly monitor bias.

Since a VTA driver board on a Mark III has TWO bias measuring points, you will need either two meters for each Mark III or some type of switching device to switch the meter between the two output tubes on a Mark III.

Bob