Picked some some NOS? Siemens preamp (both ECC83 and E83CC's) and (matched?) EL-34's for my H&KTriamp off Ebay. Of the 11 preamp tubes, two were so microphonic as to be unusable. The rest, while being very musical, were merely average as for microphonics. As for the 3 quads I bought, the first quad had two were matched, one a bit off and the other too far off to use. The other two quads all matched each other. BIG difference from the stock tubes. Rick even pushed the
bias way beyond what H&K states and they really came alive and didn't glow at all. So to summarize, it might have been my bad luck but the preamps were of questionable value sonically and quality-wise. The power amp tubes on the other hand - Look up Siemens on Ebay and grab yourself a pair or quad before they're all gone. At $149USD for a quad BIN, they're a great deal and really wake up and turned what was a pretty good head into something very impressive. However with respect to Rick, his triple channel 100W sounds so much better.
(originaly posted to old forum at an earlier date)