At what point would you consider tubes to be mismatched?

[Audiokill]

I've recently noticed many guitarists, mostly on other forums, talking about mismatching power tubes. Some say they prefer it. Others try to avoid it. But very few actually specify how mismatched they're talking about when they write about it. I used to think that a 3 mA spread was the limit, but a lot of folks out there apparently consider anything less than a 10 mA difference to be fine. I'm confused. I need me sum edjumakayshin!

I know it's probably a big gray blurry line, but at what point would you consider a pair of power tubes to be mismatched? A 3 mA spread between tubes? 5 mA? 10 mA?

And how closely do you Mark owners prefer your tubes to be matched?

 

[mark2boogie]

Audiokill,

For me, matching is +/- 1mA at least. Otherwise it is unmatched. You can run an amp with a delta match of 10mA and do not see real difference in tone or power. I would consider 10mA as a reject point if you need good and consistent performance. There is other parameters to consider about matching, but let's stay simple !

A+!

 

[McBarry]

Audiokill,

10mA is quite a distance apart, especially if one considers what current the tubes are drawing...

I usually am content when the figure is within 3mA but can often get 1mA or less with some fiddling.

But also at such tight tolerances, in a dynamic environment, it's not unusual for me to check one of my amps and find it to be different- only to realise the tubes were not as warm, the planets were not lined up the same, or anything of a hundred other reasons... you get the idea...

Long answer for a short figure - <3mA...
Dave

 

[Audiokill]

Okay. Do you guys notice any difference in tone between a perfectly matched pair and moderately mismatched pair (let's say 4 or 5 mA difference)?

 

[mark2boogie]

Okay. Do you guys notice any difference in tone between a perfectly matched pair and moderately mismatched pair (let's say 4 or 5 mA difference)?

No significant difference at 4-5mA, based on my experience - you may perceive an audible confirmable difference when you reach a delta match of circa 10mA, but it depends more or less on the amp itself (voltage, biasing, 2 or 4 tubes) and your playing style / use of the amp : on some it may be more obvious than others. Less pushed power stage circuits usually allow more mismatch than more pushed ones.

A+!

 

[ChrisYoung]

When the power tubes are significantly mismatched, the amp will produce a hum. Kinda like being around a florescent light or a bad ground.
Personally, with Boogies, when you can hear it, that's when I consider it to be a problem.

-Chris