Want Better Tone?

Braciola

Gold Supporting Member
Messages
6,167
For years I would play it safe and bias my vintage Marshalls between 60% - 65% plate dissipation.
A few years ago I decided to crank up my '72 metal panel 100 watt Marshall and play through it while biasing the amp without a meter.
I took my time dialing it in, just to where it was preforming properly...... then slightly goosing up the bias to a spot where the amp was just singing with warm juicy harmonics.
Just to see where I was at, I hooked up a meter and the tubes were reading between 70% - 75% plate dissipation.
My ears have really developed over time and I never use a meter anymore to dial in my Marshalls.
Yes, you will go through power tubes more often, however the improvement in tone is well worth it.

* also to note - wall voltages in most homes are much higher than they should be to power vintage Marshalls.
Therefore I highly recommend a variac to bring the voltage down to run your amps safely and have them sound/ preform at their best.

.
 
Last edited:

56Tweed

Ge Fuzz-o-holic
Gold Supporting Member
Messages
2,756
I didn't think 70% would really eat them up that much quicker. For the lengths that some of us go for that last 1% of tone, I'm not sure it should be a problem to change power tubes a little more often.

I found the video by Uncle Doug interesting recently...
 

GT100

Member
Messages
3,833
For years I would play it safe and bias my vintage Marshalls between 60% - 65% plate dissipation.
A few years ago I decided to crank up my '72 metal panel 100 watt Marshall and play through it while biasing the amp without a meter.
I took my time dialing it in, just to where it was preforming properly...... then slightly goosing up the bias to a spot where the amp was just singing with warm juicy harmonics.
Just to see where I was at, I hooked up a meter and the tubes were reading between 70% - 75% plate dissipation.
My ears have really developed over time and I never use a meter anymore to dial in my Marshalls.
Yes, you will go through power tubes more often, however the improvement in tone is well worth it.

* also to note - wall voltages in most homes are much higher than they should be to power vintage Marshalls.
Therefore I highly recommend a variac to bring the voltage down to run your amps safely and have them sound/ preform at their best.

.
Sorry, but this certainly isn’t one size fits all.
People have different tastes and different internal plate and screen voltages on their amps...
 

TP Parter

Member
Messages
1,154
Sorry, but this certainly isn’t one size fits all.
People have different tastes and different internal plate and screen voltages on their amps...
Pretty sure the OP's point is not 'hey everybody bias yer Marshalls at 70-75% plate dissipation', but instead 'hey next time you bias yer Marshalls don't just use a voltmeter, use yer ears too'.

Makes sense to me. After all we aren't making math, we're making music (which can be expressed mathematically of course). I use my eyes and ears when doing setups and tweaking pickups, not just calipers and guages. I know what I like regardless of measurement, I only measure to fine tune and define to others what I reach mostly with my eyes and ears.
 

gulliver

Silver Supporting Member
Messages
10,210
FYI ... externally adjusting AC to lower voltages will lower the bias %. Are you saying; lower the voltage first, then set the bias high? If so, the amp would be running super hot if plugged in normally, without a voltage changing device. Kind of impractical.

I tried different settings when I had a 2204. I didn't think the tone differences were enough to worry about ... I just set to spec.
 

Marshall_SLX

Member
Messages
246
I usually go 75% but my SLX currently is running 65% and sounds great... pretty sure Marshall actually recommended 90% around the time the jcm 2000s came out... what a bad time to be recommending that with all the bias issues they had at first.
 

Jchrisf

Member
Messages
1,949
For years I would play it safe and bias my vintage Marshalls between 60% - 65% plate dissipation.
A few years ago I decided to crank up my '72 metal panel 100 watt Marshall and play through it while biasing the amp without a meter.
I took my time dialing it in, just to where it was preforming properly...... then slightly goosing up the bias to a spot where the amp was just singing with warm juicy harmonics.
Just to see where I was at, I hooked up a meter and the tubes were reading between 70% - 75% plate dissipation.
My ears have really developed over time and I never use a meter anymore to dial in my Marshalls.
Yes, you will go through power tubes more often, however the improvement in tone is well worth it.

* also to note - wall voltages in most homes are much higher than they should be to power vintage Marshalls.
Therefore I highly recommend a variac to bring the voltage down to run your amps safely and have them sound/ preform at their best.

.
What variac do you recommend?
 

drbob1

Gold Supporting Member
Messages
27,873
First off, be CAREFUL with variacs, the difference between these and a bucking transformer (ala the Brown Box) is that a Variac CAN produce more than wall voltage. Be very careful about how you set it. Even better if you put in a pin or screw to prevent it going above 125v.

That out of the way, if you're going to use one, plan to use it all the time. Not only will the bias point change with a change in voltage but the sound will.

As to the idea of using 70%, that's where I often end up, but there was a long thread last year about how 45 was a much better number and 70 was just abuse, so it's very much a YMMV kind of situation.
 




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