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Bias Requirements for 6550 vs KT88

Musicnut1986

Musicnut1986

Member
I need to retube my ARC Classic 30. Manual talks about the bias setting for 6550 tubes but makes no reference to KT88 tubes. Since I understand that the two tubes are interchangeable will there be a different bias setting if I go with KT88 tubes?

I know everyone has their own opinion but any opinions on running KT88 versus 6550 on an ARC amp?
 
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The bias "range" between the 6550 and KT88 is virtually identical,so your amplifier will be able to accommodate either type. You will need to re-bias the unit after replacement,regardless of type chosen.

Just to say, Audio Research has never endorsed the use of KT88 tubes as replacements in any of their products. When asked (for the models concerned) they will always state that the 6550 is the tube to use.
 
Musicnut1986 said:
I need to retube my ARC Classic 30. Manual talks about the bias setting for 6550 tubes but makes no reference to KT88 tubes. Since I understand that the two tubes are interchangeable will there be a different bias setting if I go with KT88 tubes?

I know everyone has their own opinion but any opinions on running KT88 versus 6550 on an ARC amp?
Click to expand...
Whatever you use the tubes on each side should be matched i.e. having the same bias and Gm measured
at typical operating voltage. Spare tubes from ARC will fulfill this.
 
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