Preamp tubes do not need to be matched.
Okay let's qualify this. There's what's called the Class-A or single-ended tube amp, which may require only one large tube. But the class -B amplifiers, which are the usual case with guitar amps (except VOX ata) will have a power amp that has tubes that should come in 2's or 4's. I havent seen a six-tube guitar amp yet, but in theory it is possible, it should come in even numbers. And that even number must be closely matched for parameters.
Kasi po, ganito yan. One tube or one pair of tubes will amplify the upswing (positive cycle) and another tube or another pair of tubes will amplify the downswing (negative cycle). Pag hindi matched ang tubes mo, hindi magpapantay ang up and down swings ng waveform mo and you will get various types of distortion (and I don't mean overdrive, i mean real non-linear distortion inherent in the amp). It will be impossible to get a "clean" sound. Pero kung oks sa yo yun, tutunog pa din ang amp mo, so there's the trade-off with not having the tubes matched.
I got my 6550's at Audiophile and they came in a pair, so pre-matched na sya. If you buy at Deeco, it's best you go there armed with a tube tester so you can measure the parameters of each tube before you buy them. If you don't have that piece of equipment, try audiophile, who carries OEM tubes for Peavey and Fender, kaya lang ang last na tanong ko, the tubes aren't matched din. Without the tube tester, your best bet is to buy from dealers that have matched the tubes. Again, Phasetron Parksquare and those stores at Guadalupe EDSA (near Sogo hotel). There is a good list of dealers who will entertain you at
www.wiredstate.com . Meron pa sa West Avenue. You can also order sa internet, create an account at
www.cedist.com , that's where I get some of my stuff. They offer pre-matched tubes at great prices. Mahal nga lang ang shipping. But the prices are so a-ok. Like a full set (pre-amp plus power amp) tubes for a Marshall 100W only costs like $50. JJ tubes pa, so magandang klase yun.
