[romon86]

I am pretty new to the site.... I just recieved a Marantz 8b and have been told that the A.C. voltage can be measured using the bias meter.... How ??? or what steps are different for measuring the A.C. voltage vs tube bias.. thanks for all and any help...

[Ian Iveson]

romon86 wrote

I am pretty new to the site.... I just recieved a Marantz 8b and
have
been told that the A.C. voltage can be measured using the bias
meter.... How ??? or what steps are different for measuring the
A.C.
voltage vs tube bias.. thanks for all and any help...

This might help.

http://www.triodeel.com/marantz8.gif

cheers, Ian

[David Ginsberg]

You probably mean AC balance, this being an under-chassis adjustment
to balance the audio into both output tubes. There is a small dot on
the bias meter used for this purpose, but I suggest using a signal
generator to put a 1 kHz signal into the amp and measure the signal at
each output tube grid. Do each channel seperately.

On Fri, 27 Apr 2007 06:42:55 +0100, romon86
wrote:


I am pretty new to the site.... I just recieved a Marantz 8b and have
been told that the A.C. voltage can be measured using the bias
meter.... How ??? or what steps are different for measuring the A.C.
voltage vs tube bias.. thanks for all and any help...

[Chris Hornbeck]

On Thu, 03 May 2007 02:45:14 GMT, David Ginsberg
wrote:

You probably mean AC balance, this being an under-chassis adjustment
to balance the audio into both output tubes. There is a small dot on
the bias meter used for this purpose, but I suggest using a signal
generator to put a 1 kHz signal into the amp and measure the signal at
each output tube grid. Do each channel seperately.

Good call that this is what the OP actually meant. I couldn't
have imagined it.

But AC balance is actually done somewhat differently. It's
pretty easy to build an amplifier with predictably stable
balance into the output valves' grids, but the output
valves themselves will drift in balance with time.

The only reason to change an existing adjustment is because
one has available a means of measuring distortion and a
desired operating level in hand. The adjustment is for
lowest second harmonic distortion at that operating level,
and will be (slightly, but measurably) different for other
levels.

Folks with a computer and a good soundcard could use them
to perform the task. A freeware program called rightmark (sp?)
is often recommended. (Don't know personally; stuck in the
70's with antique analog gear; not forever however).

Perhaps Arny Krueger will comment; he's familiar with the
software and will be better able to discuss it.

But the principle remains the same: turn the knob for
lowest (even order) distortion.

All good fortune,

Chris Hornbeck
"If you're doing this as a volunteer, don't."
- Paul Stamler