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OK to use unmatched or different brand tubes?

My preamp has 2x 12AX7 and 2x 12AU7.
I am thinking of trying different tubes.

Would it be OK to use a pair of tubes with the same brand without testing their current levels?
How about using a pair of tubes from different brands with matching current levels?
How about using a pair of tubes from diffenret brands without testing their current levels?

Overall, if a new pair pair of tubes make improved sound, the mathing of current or brand does not matter?
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creativepart's avatar
creativepart
154 posts
 
Power tubes are much more sensitive to matching than pre-amp tubes. But, still it would be nice if they were in the same ball park. A tube tester that can give you a reference number for each is good but not mandatory.

But in general, unmatched pre-amp tubes have not been a problem in my experience.
rodman99999
6,170 posts
 
As long as the tubes are of the same family(IE: ECC83, 12AX7, CV4004, 12AX7A, 12AX7WA, ECC803S, E83CC, CV492, 6681, 6057, M8137, 5751, 12DT7), you can mix and match pairs to your heart's content. You won't hurt anything.
jimjoyce25
215 posts
 
The difference that matched tubes made on early-production Atma-Sphere MA-1s was like night and day. Roger Modjeski of RAM Labs was extremely helpful in this regard.
rodman99999
6,170 posts
 
My original post was based on the thought that you were trying out different small signal tubes to compare them. If you are planning to use them in the system: By all means buy closely matched pairs, of the same manufacturer. Your balance, imaging, etc. will suffer otherwise. They also must be very low noise(tested) for use in a pre-amp.
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