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What Do You Hear When Your Amp Needs Biasing?

Hi, Everybody,

I was listening to my rig the other day and noticed that some (but not all) closely miked recordings of female singers (Diana Krall on some of the cuts on "When I Look in Your Eyes" comes to mind) sounded a bit edgy or harsh. I checked the bias on my Manley Mahi amplifiers and found that some of the values on the multimeter, which should have been at 250, were as low as 240. I made the bias adjustments and, lo and behold, the vocal tracks sounded better. So I'm wondering what, in general, is a tipoff that a to be of a fire needs to be biased?

Thanks!
rebbi
stanwal's avatar
stanwal
3,147 posts
 
Your amp need bias if it is sounding too neutral and uncolored. I recommend playing Rush's show to increase the bias on the right channel but since Keith is off the air I don't know what to use on the left channel.
samhar
1,048 posts
 
+1 Stan
doc77
47 posts
 
More often than not I'll think I hear something off, check the bias and it's still dead on. There was one time however that a certain piano concerto I'm very familiar with sounded a bit zingy, so checked the bias and one of the power tubes was way off.

Most of the time though I think it's pretty hard to hear the small wanderings that are common.
minorl
1,016 posts
 
What does the manufacturer recommend as to when you are suppose to recheck bias on the amp? That is the criteria I would use.

enjoy
rebbi OP
1,326 posts
 
Minorl,

All Manley says in the Mahi manual is that the number should be 250. On average I've been checking them about every other month.
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