While I’ve had some experience with vacuum tubes in the past, it’s been extremely limited to say the least. I have a tubed CD player (Ah! Njoe Tjoeb 4000) which utilizes two 6922 tubes in the output stage and a tube/solid state hybrid integrated amp (Response Audio RAM 301) which utilizes two 12AU7 tubes for the preamp stage. As for an all tubed design, I was a complete novice when I purchased the APPJ PA0901A integrated SET amp a year ago. This minimalist integrated has only one pair of RCA inputs and a passive volume control to attenuate the output of its tube circuit (6N4/12AX7 feeding a single 6P14/EL84 per channel).
It wasn’t until recently I decided it was time to try some different tubes. Why now? First and foremost, I liked the sound with the stock Chinese tubes and wanted to be completely familiar with the sound quality before swapping them out. In fact, I liked the sound enough that I didn’t bother changing the tubes before the summer heat arrived .. I like to use a cooler running amp during summer.
Over the years I’ve read countless reports of huge changes rolling tubes and, while I know there must be some truth to it, I’ve often wondered if there isn’t just a bit of hyperbole involved. Audiophiles are often prone to such exaggeration when changing anything in their systems citing massive gains in sound quality, veils being lifted, larger goosebumps, etc., etc. Color me skeptical.
So, Christmas present to self:
- Genalex Gold Lion 12AX7
- Mullard EL84 (matched pair)
These 3 tubes cost me just under half of what the amp sold for a year ago and was about as much as I wanted to spend. The result .. massive gain in sound quality, 7 veils were lifted, 6mm goosebumps emerged, and ..
Seriously, the APPJ PA0901A sounds like a different amp. Tone, timber, clarity, extension, soundstage, vocals .. everything changed for the better. Of course I had hoped for a result such as this but honestly, I’m somewhat flabbergasted. This isn’t a subtle change, I actually uttered “wow” during my first listening with the new tubes. To say I’m pleased is an understatement.
While APPJ has since discontinued the PA0901A in favor of it’s newer 1501A model, Tube Depot sells it’s own (re-branded?) version found here: TubeCube | 7 Stereo Vacuum Tube Amplifier. Highly recommended. And roll some tubes!