Matched Power Tubes, How Many MA Difference is Acceptable?

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dead-pan

dead-pan

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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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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
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Same. Most places will send you matched sets. All the ones I've bought recently from Eurotubes were only 1mA off at most.
 
311splawndude said:
Same. Most places will send you matched sets. All the ones I've bought recently from Eurotubes were only 1mA off at most.
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For new tubes I like using Mesa's matched sets, and same. Most of the time even the quads are exact but at most 1ma off
 
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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