2. amps-preamps
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adjusting the bias on an amp YBA

I have an older YBA Integre Single Transform. It must be 10 years old. About 3 years ago it developed a hum/buzz in one channel that progressively turned into distortion. I thought it was hosed. I sent it in and they said "we adjusted the bias" and sent it back. Now it works perfectly.

I had assumed that something major was wrong (like a cap or something going bad). I don't want to look a gift horse in the mouth but what exactly is "adjusting the bias" and how might it have solved my problem? Are there some screws or something one would turn? Is it a user serviceable adjustment?

Thanks in advance.
eltbee
eltbee OP
6 posts
 
Thank you very much for the responses. Very interesting stuff (to me anyway).

I have another YBA Integre which is an 8 year old Dual Transform model. I have pretty efficient Cabasse speakers. For some reason that old Single Transform has this magical sound with my speakers that the Dual Transform can't produce. It sounds good but just not the same presentation. I'm not that much into audio anymore but I always thought it was kind of counter-intuitive.
asdf7e16
60 posts
 
That sounds to me like there is something amiss with your DT. I'd suggest getting it checked out. Everybody else I know that's heard both, including myself, likes the DT better.
audioengr
3,282 posts
 
The reason it buzzed is that the bias drifted and it was set so high that it made the transformer audibly buzz. This is fairly common. You need a voltmeter, a plastic screwdriver and instructions to adjust the bias (with the case open). There are high-voltages in there, so only attempt this if you are skilled in technicians work.
eltbee OP
6 posts
 
Other than the buzz (which became distortion), would adjusting the bias affect the overall character of the sound presentation?
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