Marc Mickelson
May 1996
"Tubes are cool," a person I know said to me after I had given inventory of my audio system. I knew immediately what he meant: the glow, of power tubes in particular, is seductive--especially to non-audiophiles. On the other hand, those of us who take the reproduction of music way seriously know the real truth: tubes make music, especially with digital. OK, and the glow is cool too.
But audiophiles also know that tubes mean inevitable replacement, and really high-quality equipment (the somewhat temperamental CAT Signature, for instance) doesn't take kindly to anything less than superlative tubes. I never received a decent pair of 12AU7s for my CAT's linestage--this includes the original pair and factory replacements. Each pair would work for a few days or weeks and then start spluttering--an intermittent hiss that signals the end of the tubes. To the company's credit, CAT shipped me a number of replacement sets, and Ken Stevens, the man behind the mighty feline, was always helpful and willing to send new tubes. Still, it's situations like this that make me wonder why I go through it all.
So: I own tube equipment (in addition to the CAT, I also own a pair of Quicksilver M135 mono amps, which can use EL34s, 6550s, KT88s, any pentode power tube), I've done lots of research and rooting around to find the best tubes for my equipment, and I want this month to share my treasure with you. Beware, however, that your satisfaction with the tubes I mention will vary according to the circuit in which the tubes are used and your own level of tolerance for the hunt. Also, this survey is not all-inclusive; I haven't experimented with 6550s, KT88s or any small signal tubes that I don't mention below, and I don't have the vast amount of circuit and specification knowledge of other reviewers (and others on the Net). I'm just a guy who loves his tube equipment and has experimented to improve its sound. And this is my story....
Tesla E34Ls, the designation given to premium Tesla EL34s available from New Sensor Corporation and Gold Aero (among others), are wonderful--relaxed, resolving, the antithesis of forward. And they're NEW, not NOS--and correspondingly cheap. I'd love to get some Siemens or Amperex EL34s in my Quicksilvers, but the Teslas sound so good that I feel no great urge to seek out these rare and expensive replacements.
As I've mentioned, my CAT is hard on 12AU7s, and this makes evaluation a breeze: the CAT lays bare all deficiencies. I had only good success with low-noise RAMs (decent sound, short life), and no luck with any other new tubes. A pair of NOS Amperex 12AU7s sounded fine, but they made the CAT a microphonic mess. Without a doubt, the best 12AU7s I've used are the NOS Telefunkens. They cost anywhere from $30-$60 each, and of course they're not easy to find, but the sound is splendidly natural--music itself. I also understand that they usually last longer than new tubes, so you may pay more for tubes you'll have to replace less often. "Things nowadays just aren't made the way they used to" is one of my dad's mantras. You mean he's been right all these years?
The German RFT 12AU7s that Ken Stevens now uses in the CAT SL-1 Signature Mk II preamp, and available through Gold Aero, are also worthy of consideration. My CAT comparison of a few months ago called attention to these tubes, and none other than Dick Olsher endorses them. They are NOS, not made for 10 years, but they probably won't carry the standard NOS price. I'd still recommend the Telefunkens if you can find them, but the RFTs may be just as good.
The Yugoslavian EIs are getting harder to find but are worth the hunt. They have explosive dynamics and a smooth overall character; their effect on the CAT is like that of the Telefunken 12AU7s, although to a lesser extent. Again, some NOS Amperex 12AX7s were very microphonic and hard-sounding. I wonder if the NOS Amperex tubes, so sought-after, are drying up and all that's left are rejects.
The CAT uses a single 6DJ8/6922 as a cathode follower--not exactly the most critical position in the circuit. The Sovtek 6922s are cheap, plentiful and as good as any others I've tried in the CAT, including an NOS Amperex. If you have an Audible Illusions Model 3A or other preamp that uses these tubes throughout the circuit, you will definitely want to experiment. I've heard really good things about NOS Amperex 7308s, a premium equivalent manufactured for use in medical equipment.
I've saved the best information for last: two terrific sources for not only the tubes themselves but also information and advice.
Andy Bouwman at Vintage Tube Services is personable and sells a variety of meticulously graded NOS tubes. He also offers a 100% satisfaction guarantee on the tubes he sells--although you'll pay for this luxury. Andy's tubes are not the cheapest around, but it seems he's always willing to scare up tubes he thinks you'll love. He's full-service--sort of the Nordstrom's of tubes.
Kevin Deal at Upscale Audio sells the best new tubes, a wide variety of NOS tubes and (here's what really hooked me) almost NOS tubes--which Kevin admits are not new but test within the parameters for new tubes, even for expected in-circuit life. The ANOS tubes cost roughly half that of NOS, but if you really want a bargain, Kevin also sells used tubes that again test well but are dirt cheap--usually a quarter of what his NOS tubes go for. These give you the opportunity to try some of the more esoteric and expensive tubes and not pay premium prices. However, as Kevin explained to me, and I wholeheartedly agree with, he's not in the business of renting tubes, so you have to know what you want before you order. All of his tubes are tested, graded and guaranteed; and I've gotten nothing but the goods from him. You can call or e-mail him and he'll send his current price list to you by return e-mail.
You can reach Vintage Tube Services at (607) 454-3467 (CST); Andy has a nice printed catalog and may even include a packet of tube information and vintage magazine ads that will make you wish you were older and could've seen the future. E-mail Kevin Deal at kevin@upscaleaudio.com , or call him at (909) 931-9686 (PST). Both Andy and Kevin are a blast to talk with, but Kevin's e-mail address makes it easy and cheap to pester him about minute differences. What more could an audiophile want?
Please e-mail me with any tube news you think deserves reporting--especially replacements and combinations that improve the sound of your equipment. I'll compile it all and publish it in upcoming months. And who knows? With all of us working together (in harmony?) we may just end the tyranny of solid state for everyone, everywhere. SA-LUTE!
...Marc Mickelson
marc@soundstage.com