re-bias when changing speaker out ohms?

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ryanburton
Posts: 22
Joined: Tue Aug 12, 2008 6:00 pm

re-bias when changing speaker out ohms?

Post by ryanburton »

must i re-bias my twin 6V6's when i change the speaker outs from 8 ohms to 4 ohms to use a different cab? i'd like to be able to change setups rapidly in a studio environment.

even if it's not necessary, should i re-bias?

OT is 4/8/16 and amp has exterior bias probe outlets and bias pot.

thanks
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benoit
Posts: 869
Joined: Wed Dec 20, 2006 4:44 pm

Re: re-bias when changing speaker out ohms?

Post by benoit »

ryanburton wrote:must i re-bias my twin 6V6's when i change the speaker outs from 8 ohms to 4 ohms to use a different cab? i'd like to be able to change setups rapidly in a studio environment.

even if it's not necessary, should i re-bias?

OT is 4/8/16 and amp has exterior bias probe outlets and bias pot.

thanks
Nope, not necessary.
"I never practice my guitar. From time to time I just open the case and throw in a piece of raw meat." --Wes Montgomery
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Phil_S
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Joined: Tue Oct 23, 2007 10:12 pm
Location: Baltimore, MD

Re: re-bias when changing speaker out ohms?

Post by Phil_S »

Rebias when you change tubes, not speakers. Bias is about tubes, which are inherently inconsistent in characteristics.

Tubes are coupled to the primary side of the output transformer. Speakers are coupled to the secondary. Tubes are not coupled to the speakers, so speakers are not a factor in setting bias.

Just make sure you match the speaker to the correct impedance tap on the output transformer. Failing to do so changes the load on the power tubes and bias won't compensate for that.
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