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To bias or not to bias

After making the switch from solid state to tubes and now having three tube systems, I spend a fair amount of time biasing my amps to obtain peak performance as recommended by many enthusiasts.

As I was doing this one day I thought back to my youth when many people had tube equipment (Yes, I am that old) and it dawned on me that I don't remember anyone biasing their equipment back then. I had a college roommate that had McIntosh tube equipment and he never biased his rig. It always sounded fantastic. I remember my Dad having Scott tube amps and tube radios, playing them for years and other than replacing a bad tube every now and then, never biasing his gear. Again, they sounded great.

So that led me to thinking, why do we pay so much attention to biasing today? Is it because the equipment requires it or is it audiophile tweaking run amok?

Your thoughts on the matter would be much appreciated.
catama
apachef1
164 posts
 
Bigger tube amps require biasing more so than smaller amps
When you have 8-16 power tubes per amp getting that many numbered tubes matched will be a challenge. Even if you have a matched group of 8 or 10 power tubes, larger power tubes tend to drift and one tube will be pulling more of the load. Biasing allows you to make everyone play nice on the power tube grid.
Examples would be ARC ref 300 and 600 amps
my mcintosh mc-225 just requires a quad of closely matched 7591s and she is good to go
thorman
1,262 posts
 
I just do my Thor Monos once a week ( Takes 30 seconds each side )never had a problem and maybe that is one good reason.......
atmasphere's avatar
atmasphere
12,039 posts
 
If you are adjusting the bias more than once every 6 months I would regard that as 'tweaky':) Seriously, the tubes should be able to hold up that long without adjustment.
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