5751 taste test (bass preamp).

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My tube adventure started when I needed to eliminate the dry, scratchy highs characteristic of stainless flatwound bass strings (the 12AX7 supplied with my preamp wasn't much better at this than a top-notch solid-state preamp). Many thanks to Joe S's supremely useful 12AX7 FAQ, the one that got me started on the 5751 hunt. Following his advice, I nailed sweet highs and a whole lot more on my first try, one of the Sylvanias.
I tested a mess of 5751 tubes using LaBella M45 (stainless round), Pyramid Gold (stainless flats), and Thomastik nickel flats. These are all well-balanced but very different strings (many popular strings I tried had peaks in the 80-160 Hz range, which helps the bass cut through the band, but creates an objectionable thickness/opacity at the bottom IMO). I went back and forth between tubes working my way through these strings; really tiring, but it's the kind of project that's perfect for killing slack time in a motel room. Testing rig: Maple-necked, alder-bodied P-bass with low-impedance active EMG pickup, SWR Grand Prix preamp, Sony MDR-V6 headphones. There emerged four magic tubes. The winners (in order):
1. Sylvania JHS 5751 (1950s production). Reportedly seen as 5751WA, JG 5751, and other designations. Comes in a white government contract box. Important: Sylvania - black plates - three (3) mica spacers - gold printing on the tube. Same as the commercial Sylvania Gold Brand black plate, three (3) mica spacers, gold printing on the tube, also tested. Amazingly tight bottom. The P-bass' characteristic grunt really shines through. Smoothest highs. Vocal mids. It's a very neutral tube. Every little detail of the sound is present with total clarity, so the tube will not have you vainly trying to tweak EQ to elicit things it's not passing on. For lack of a better term, this tube will give you a three-dimensional sound. In fact, all on this winners' list will (to varying degrees), and actually, their ranking is by degree of three-dimensionality. Call it "wetness," call it "liquidity," whatever it is, for me there are four tubes, then there are the rest. This tube puts forth the vibrant, very vocal P-lows that bassists try to describe in terms such as "grunt" or "a farting sound."
2. GE JG-5751, reportedly also seen as 5751WA and other government designations. Important: GE - three (3) mica spacers - black plate. Equivalent commercial samples share these same indicators, but are labeled GE or GE 5-Star. This tube is a little "thicker" than the #1 Sylvania, but it sounds roughly the same (and shows off its three-dimensionality more clearly, but differently) in my preamp with 80 Hz rolled off 3 to 6 dB (I didn't take time to zero in on this, this was just a quick stab that worked). This tube has a more aggressive, chiseled sound than the Sylvania, although the smoother Sylvania is no less precise (OK, I really don't know how to explain this, this is as close as I can get). There is some artificiality to the three-dimensionality; I don't know what it is--perhaps a phasing thing. It's sonically interesting, even nice for fuzak or techno. But I like the Sylvania's smooth, natural 3D effect better (totally subjective).
3. Sylvania Gold Brand, grey plate, three-mica, gold pin 5751 (commercial model). I lucked into this one. It was relabeled Westinghouse (relabeling is very common and if you're sharp-eyed, you can nail some unbelievable bargains). The GB-5751 etched into the glass and the gold pins were a dead giveaway. This tube is similar to the GE in "thickness," but has the Sylvania smoothness plus some aggressiveness in a subtle yet very different way from the GE. This is a really neat tube, I'm guessing maybe a fretless J-player would like this one best of all (actually, I believe any of these will do a killer job of J-howl, but this one would probably be "more equal than others"). But as an established fetish tube, it may not be worth its elevated price, not when you can get the #1 and #2 tubes so cheaply. I want to say it seems a tad less 3D than the preceding winners, but I think it's probably just that it has so much more other stuff going on.
4. RCA 5751, 3-mica, black plate, "silver clip." There are piles of 3-mica, black plate RCA 5751 tubes out there, an undistinguished tube (well, for a 3-mica 5751, anyway). But a few of these show silver plate retaining clips (8 in all) on the plate stubs that stick through the spacers (above the next-to-top spacer and below the bottom spacer). This tube has a brightness that, in a 12AX7 way, serves to mask flabbiness in the lows (it has less 3D than the rest). Might be your rig wants the brightness as a remedial thing despite the sacrifice, or you're a thump/slap/pop player and this tube just hits you right. But it's better to start with a tube that gives you everything and EQ to suit, rather than just grab the brighter tube. The GE will do slappers better--don't forget popping is less than half of slapping; the greater part is thumping those low notes, and the GE's oddball "hard" 3D effect will really aid in achieving a "robotic" funk sound.
I'm not an audiophile, just a bass player. So the main thing for me (beyond mechanical reliability, which any 3-spacer 5751 will serve up in spades) is tightness in the bottom octave. Detail in that range may seem a strange subject, so let me liken the difference between these tubes and all others to the difference between MP3 and CD. The first time I taste-tested an MP3 file against a CD, I listened to an exposed low tuba passage. In the MP3, the pitch was reproduced faithfully, but that was all. On the CD, I could fairly hear each individual juicy flapping of the tubist's lips. Now there is no way that EQ or speakers or any other device can add what's not there. It can add emphasis to a certain frequency, sure, but not detail. Of course, as a Precision Bass player, I'm a fanatic about "grunt." It's the defining characteristic of the P-bass sound, and one of the reasons that audiences feel so good about the P-sound is (first among other things) the very vocal quality imparted to the bass by "grunt."
As I say, I'm not an audiophile, but there are two themes that recur in Joe S's FAQ that translate into terms useful to the bassist. The first is that of "palpability," and the second is of spaciousness of the soundstage. Because a note from an electric bass is composed of so many discrete elements, each of which must be reproduced with integrity, I think these two measuring sticks relate equally to the production of "grunt." However, the bass grunt test cuts more finely than these. While Joe notes its relative imprecision in hi-fi equipment (compared to the magic tubes), one of the tubes that made Joe's "short list," the Tung-Sol, entirely lacks the three-dimensionality I can hear in the four magic tubes. Of course, the "grunt" I'm so crazy about is probably not present on most recordings, so it may not be a crucial issue in hi-fi tubes, but if it is there, I think it would take these magic tubes to allow you to hear it.
Thanks again to Joe S for his eye-opening FAQ, and thanks to Steve Oda for patiently helping me understand many related things including tube break-in and guitar usage of 5751s (now I understand that bass is an entirely different proposition from guitar; that last octave is so demanding that many fine guitar tubes are unsuitable for bass).

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Topic - 5751 taste test (bass preamp). - Bubba (Kurt Kurosawa) 08:55:15 12/05/00 (4)

Re: 5751 taste test (bass preamp). - steven oda 14:00:00 12/05/00 (3)

Re: 5751 taste test (bass preamp). - Scott T. 08:34:52 12/06/00 (1)

Re: 5751 taste test (bass preamp). - Bubba 15:28:26 12/06/00 (0)

Re: 5751 taste test (bass preamp). - Bubba 20:12:04 12/05/00 (0)

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