Matching pre-amp tubes?

[nevusofota]

I know you have to match power tubes, but what about pre-amp tubes. At the tubestore.com they say that for most instances you don't need to have a matching set. They charge $5 more for each matched preamp tube vs. unmatched. In what case do you need matching pre-amp tubes? I have never heard of this. I'm replacing my pre-amp tubes in my 5150III and noticed that channel 3 alone has 3 preamp tubes. Should these be matched?

 

[jet66]

They don't have to be matched. The only time I could think of where you might want a matched set is with a stereo preamp, to make sure both sides are consistent, but that is sheer speculation on my part. I actually prefer to mix and match, with different tubes for my input, clean, dirty, and PI. I have been buying a little sample of tubes each time, and rolling them around to see how I like them in different positions.

 

[steve_k]

I know you have to match power tubes, but what about pre-amp tubes. At the tubestore.com they say that for most instances you don't need to have a matching set. They charge $5 more for each matched preamp tube vs. unmatched. In what case do you need matching pre-amp tubes? I have never heard of this. I'm replacing my pre-amp tubes in my 5150III and noticed that channel 3 alone has 3 preamp tubes. Should these be matched?

A preamp tube is actually made of two identical triodes. The only place this is really important, but not required is in the phase inverter position (the last tube) of guitar amps. This assures that the duet or quad of power tubes are pushing equally. This would be balancing the tube. Matching would try and find preamp tubes of like properties. For guitar amps, definitely not required. Much of the tube business still goes to Hi-Fi audio amps and here it is more important to have matched tubes.

When I order preamp tubes or power tubes, I always order a couple of balanced tubes for the PI.

Steve