Some of you will likely be turned off by the very low cost of this kit. Before you pass judgment on this little kit, do note that Audio-Technica uses a JAN 6418 sub-miniature tube in its model AT3060 condenser microphone which sells for about $600US. Music professionals often describe this microphone as having a warm classic tube sound....
Sound
The very first build (stock kit) blew me out of my favorite listening chair. This subsequent (upgraded) build seemed a little restrained. Or is it just better balanced? I did feel the first build was a bit foreword which may make this build sound a little reserved by comparison. Also I had a few hours of listening time on the first build and as any thermionic fanatic knows, new valves can have an extended break-in period. Because of their size I would guess that the JAN6418 needs no more than ten hours of continuous play to "settle" them. They do not have a huge life. Setting the filament voltage at a low 1.2V should give one to three years of hard play with little detriment to sound quality. Higher filament voltages will drastically shorten tube life. The tubes are about $2 each and I bought an extra ten tubes.
Anytime you can dig out micro detail and recorded nuances you WILL get a richer, wider, fuller more detailed sound stage. That's what this preamp can do in spades. Good depth, wide breadth and sharp detail revealing fine recorded detail with no hard edges. Every track I listen to now delivers fine detail previously hidden. Tone and resonance in voice now has an extra layer, finer, breathier than I have heard before. Massed strings sound like the space about them was recorded rather than the instruments themselves, airy almost thin. Oboes don’t sound like I remember and every key touch is transported into the room. Piano is a little more "sweet gong" like than all-out bell like. But no register appears to dominate. Bass / rhythm (left hand (lower notes)) are in perfect balance with right hand melody / lead line (higher notes). The piano sounds balanced-tonally, addictive.
The base kit from Oatley Electronics is well worth the $27AU price tag. The original kit may sound too forward though. For about $20 more you can transform this basic kit into a very tonally balance high performance preamp. Or just build yourself a retro-thermionic portable valve headphone driver to go with your space-age mp3 player, iPod or steam driven portable CD player. For 27 bucks, how novel?
Mark Houston
DIY Convener, Melbourne Audio Club
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