Matched Power Tubes, How Many MA Difference is Acceptable?

dead-pan

dead-pan

Well-known member
When buying matched power tubes, what is the acceptable difference in MA?
 
War_in_D

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

Recently picked up a used original Maximatcher and I've been going through a bunch of my power tube stash to see what's up. For consistency, I've been running the Maximatcher through my AmpRX Brown Box and testing all tubes at 120v-121v. I read that the Maximatcher can read differently based on how many tubes you test at any given time, so I've been testing my like branded tubes in pairs, even if I have a full quad. I've discovered that I have a lot more pairs of like branded tubes than I have quads, so I figured by testing them as pairs I could conceivably mix brands if needed as long...
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mcstinger said:
War_in_D

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

Recently picked up a used original Maximatcher and I've been going through a bunch of my power tube stash to see what's up. For consistency, I've been running the Maximatcher through my AmpRX Brown Box and testing all tubes at 120v-121v. I read that the Maximatcher can read differently based on how many tubes you test at any given time, so I've been testing my like branded tubes in pairs, even if I have a full quad. I've discovered that I have a lot more pairs of like branded tubes than I have quads, so I figured by testing them as pairs I could conceivably mix brands if needed as long...
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Click to expand...
The last post there says the mentions the possibility of 3.5 being the industry standard.

I guess I should add that I am referring to the difference when purchasing a matched set.
 
Generally I like mine around 3-5 MA spread max. If you get tubes too far out (10 MA +) they tend to produce wild overtones (according to Tube Tramp/Terry Kilgore).
 
I try to keep them 5 max

Obviously if you get them closer that's awesome, but I haven't noticed a significant difference in sound, as long as it isn't above that range.

It also depends on the amps power section to a certain extent
 
DanTravis62 said:
I try to keep them 5 max

Obviously if you get them closer that's awesome, but I haven't noticed a significant difference in sound, as long as it isn't above that range.

It also depends on the amps power section to a certain extent
Click to expand...

Same. Most places will send you matched sets. All the ones I've bought recently from Eurotubes were only 1mA off at most.
 
Appreciate the thoughts.

All of sets I have purchased prior were very close.

Just purchased a NOS matched pair and the are over 8 ma different. Felt this was a bit much but wanted to see if there was an acceptable range.
 
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dead-pan said:
Appreciate the thoughts.

All of sets I have purchased prior were very close.

Just purchased a NOS matched pair and the are over 8 ma different. Felt this was a bit much but wanted to see what if there was an acceptable range.
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Depending on the amp, there is a rule of thumb for this. Matching pairs together, but you probably already know that.



And Dan - I'm going to start using the Mesa color chart to find the range for my Mesa amps and then just buy within that set range. To save a little mainly and also because it always erked me that Mesa wanted people to buy their tubes - even though I get why they say that.
 
Scumback Speakers said:
Generally I like mine around 3-5 MA spread max. If you get tubes too far out (10 MA +) they tend to produce wild overtones (according to Tube Tramp/Terry Kilgore).
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Get hum too.

I must have bought 100 tubes from Terry 15+ years ago. Haven't heard his name in a while.
 
dead-pan said:
Appreciate the thoughts.

All of sets I have purchased prior were very close.

Just purchased a NOS matched pair and the are over 8 ma different. Felt this was a bit much but wanted to see if there was an acceptable range.
Click to expand...
If this is in a 100 watt amp you can match up the tube pairs that are closest to each other that work together to balance things out in a class A/B power amp.

In a 100 watt Marshall the two outer pair of power tubes work together and the the two inner power tubes work together in the class A/B push pull circuit. I am fairly certain most class A/B power amp sections are designed like a Marshall amp. The Mesa Simul class is different.
 
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