The great aspect of owning tube equipment (apart from the fabulous sound) is the ability to alter or ‘tune’ the audible output via a process known affectionately amongst tubaholics as ‘tube ‘rolling’.
Simply it entails changing out the stock tubes for a superior replacement, or patiently trolling through countless forums on-line in search of a tube with a specific aural characteristic. Current sound too bright and harsh – look for a tube with a more ‘mellow’ personality from comments and opinions on the web.
Apart from the desire to alter the sound quality of your tube gear there is also the finite lifespan of tubes to consider, because they won’t last forever – especially the high-current power and driver tubes found in amplification.
I decided to change the tubes in my Jungson Moon Harbor CD player. These haven’t been tinkered with since I bought it and although I hadn’t noticed a deterioration in sound quality, the drop off in performance is more of a subtle degradation over time. In a nutshell, the tubes could have ‘gone off’ without me necessarily noticing it.
But where to buy these things? Luckily up here in Auckland there are a few retailers that stick true to the calling of the tube.
One outlet that isn’t part of the Hi-Fi establishment is Freedom Music in Avondale. Ryan has a vast selection of mainly musical instrument tubes, but also a whole heap of product specifically designed for Hi-Fi.
It was simple: I needed 3 new 12AU7’s, and after once I’d arrived and listened to Ryan’s advice regarding long plate vs short plate tubes (long plate = better dynamics but possibly more microphonic than short plate types), I walked away with a trio of JJ long plate 12AU7’s and set off towards home with a purpose.
The Chinese-made Moon Harbor is an exquisitely built and great sounding CD player – in fact it deposed my Raysonic CD128 a few years ago which really surprised me. Both players use the same D/A converter and transport mechanism, the real differences lie in the power supply and analogue output areas, and for me the humble Jungson gave me just a little more warmth and involvement. A good looking player, it is clad in solid aluminum and strengthened with a baseplate made of solid copper – this also aids in the rejection of spurious RF noise (it’s also known as a Faraday shield). So it’s a CD player I want to keep a hold of and maintain, thus the tube replacement.
After turning the player off (and waiting a couple of minutes in case of a stray electrical discharge) I started off by loosening off the 8 copper screws that attach the top cover to the main chassis. The top cover holds the main transport buttons and is connected to the rest of the player by 2 umbilical cables, so I was careful not to ‘yank’ this top plate off and just placed it to one side giving me enough access to the tubey bits.
I remembered to be careful about handling the tubes, touching them with bare fingers can create hot spots when they warm up. shortening the lifespan. Armed with an excellent German-manufactured dust cloth I was ready to pounce.
The tubes were easy enough to locate, and after a bit of wiggling I had them out of each socket. Interestingly they weren’t Chinese tubes as I’d suspected but GE ECC802 long plates, and this may have accounted for the long life and generally excellent sound quality. Replacing them was a breeze, but I had a bit of a fright when I saw how tall each tube was – with the cover back on there would only have been 3 or 4mm’s of clearance between the cover and top of each 12AU7. Phew.
Once I’d squeezed the new tubes into each socket I fired the player up with a CD to check: it was sounding great, and I hadn’t electrocuted myself.
I wrapped the old GE tubes and slotted them into the JJ cartons, they were probably still ok and could have quite a bit of life left in them, so into my HiFi cupboard they went for a potentially early retirement.
So there we have it. There was no biasing of course, these are preamp tubes after all, so the process couldn’t be easier – try rolling transistors in your average solid state CD player – I dare you.
After an hour of warm up I noticed a touch more detail while listening to Tori Amos’ The Beekeeper via the Moon Harbor, and I’m keen to find out just how the player sounds after a proper burn-in.
Watch this space…