How close is close enough when it comes to power tube matching?

  • Thread starter Thread starter War_in_D
  • Start date Start date
What sort of sound difference (if it can be quantified) is there between matched and very unmatched tubes?

I have an amp with two KT88’s and one draws about twice the current of the other, currently have the bias pot all the way down (to avoid runaway and I also kinda prefer the sound of cold bias), one drawing 12ma, the other 25mA (485v at plate)

I know I should just buy a new pair of tubes but it does sound good now, and I am dragging my feet dropping £100 on a pair of tubes that was probably £50 a couple years ago.
 
More even harmonics (I think heard as "warmer"?). If they are far enough off, possibly more hum too.
 
Had an amp tech tell me 3.5 mA or less is industry standard. No idea where he got that. I’ve had pairs drift to around 7 or 8 apart and never noticed.
 
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