Matched Power Tubes, How Many MA Difference is Acceptable?

[dead-pan]

When buying matched power tubes, what is the acceptable difference in MA?

 

[mcstinger]

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

May 28, 2024

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...

• War_in_D
• Replies: 22
• Forum: Tech Corner

• 

 

[dead-pan]

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

May 28, 2024

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...

• War_in_D
• Replies: 22
• Forum: Tech Corner

• 

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.

 

[harddriver]

If mine are within 5-10ma I'm pretty happy with that.

 

[Scumback Speakers]

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).

 

[DanTravis62]

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

 

[311boogieman]

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

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

 

[DanTravis62]

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

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

 

[dead-pan]

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.

 

[311boogieman]

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.

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.

 

[psychodave]

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).

Get hum too.

I must have bought 100 tubes from Terry 15+ years ago. Haven't heard his name in a while.

 

[harddriver]

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.

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.