12AU7 vs 6SN7, or other tube based preamps

[jazman]

12AU7..............6SN7????

The debate rages on here, as in other forums. Is it possible that much depends on the design and implementation of the design which makes the diference?

I currently own a 12AU7 based preamp which I consider excellent in it's ability to present the music to me within the context of my humble 2A3 system. I've sat and listended over the last few days, trying to find what I think is missing, if anything in the music I'm hearing. Without the benefit of owning a 6SN7 based preamp, I have no ready frame of reference. To seek some answers, on what may present better "musicality", I will soon inject a different preamp in the system along with using that preamp with a 300B SET amp, also giving my 12AU7 an opportunity to present the music from a 300B tube. The to be added preamp is not 6SN7 but 6080 based. But it's still another reference point.

After doing some online research I found an old review of the Cary SLP94 by that guy again, Art Dudley. I certainly don't know him or believe he's the ultimate authority, but he expresses some of my experience with this 12AU7 based product.

Extracted from Listener Magazine review by Art Dudley.

"But mostly, the Cary is simply musical ­ it gets the notes right. and presents them in a manner suggestive of the real thing. Last issue I described the Audio Note Kit One as a product that lets the music ebb and flow dynamically in a way that very few hi-fi products seem to do ­ and Cary's top of the line preamp is in the same hallowed league. Used with certain basic amplifiers, like the conrad-johnson MV55, the Cary lets that openly dynamic, almost "organic" quality of the real thing pass through unsullied. Used with the Kit One, that effect becomes exponentially more evident: Now the music really breathes. The effect is hard to describe. equally hard to forget.

"Here's an affordable product ­ affordable by perfectionist standards, at least ­ that on some counts goes beyond excellent into unexcelled."

The notes themselves seem well respected by the Cary. There was none of the ponderousness, lack of involvement, or flat-out fatigue that I associate with amplifiers that can't do pitches, pitch relationships, or proper musical timing. Swapping one of Naim Audio's preamps ­ an obvious choice in this regard ­ directly into the system for comparison isn't possible for reasons of cabling/grounding incompatibilities, but while I suspect that the top of the line from Salisbury might wring even more temporal accuracy from my system, nor would the unusually nimble Cary be disgraced by the comparison. Listen to almost any track from the Dead's American Beauty for proof: This is what I think of as a "borderline" recording, one that's pleasant overall but which is especially gear-sensitive, and which can be pushed over the edge toward boredom by gear of ponderous musical abilities. (Maybe it's Phil Lesh's precariously loose bass playing that accounts for this.) Not so with the Cary/Audio Note, though, via which this music never failed to engage.

And timbrally, as I hinted above, the SLP-94 is pleasantly sweet. There's just a touch of midrange warmth here, I think ­ though not so much as with the first "modern" tubed units of the late 70s ­ and to be frank, I like that quite well. The overall spectral balance seems right, though, being neither etched nor egregiously soft at the top end, and with an appropriate sense of bass weight. If I had to find fault at all, I'd wish for a bit more detail and open-ness in that bottom octave, as at least one other preamp and two integrated amps of my experience are more informative as to precisely how such instruments as electric bass and orchestral drums are being played down there. (Perhaps that tinge of warmth works its way into the lower registers after all). Maybe if I tried that oil-filled signal cap option Cary quietly mentions in their brochure... See? This solid, sweet lil' thang already has me playing Owner, even before letting daylight hit a new page in my checkbook. And when last my accountant saw me (Hi, Blaine), I was trying to figure out some honest way to buy one.

What it all boils down to is this: There are lots of at-least-decent preamps on the market, and some are even halfway cheap. But here's an affordable product ­ affordable by perfectionist standards, at least ­ that on some counts goes beyond excellent into unexcelled. It makes beautiful music, it's easy on the eye, and it's always a delight to work with (uh-oh, I almost said "use," which while true to my already overwrought metaphor might surely put me right back on the Tofu Trail). To be in the market for a tubed preamp at any price and not consider the SLP-94 would be like having the phone number of the prettiest, sweetest, smartest girl you've ever met (women: Feel free to substitute handsomest, sweetest, smartest, handiest-around-the-house guy) and losing it in the wash. So don't screw up: Audition the SLP-94 before Cary takes all the praise to heart and plays hard to get. Meanwhile, assuming I can afford it by the time you read this (and I have to admit, I'm already more than pushing the envelope of Listener's self-imposed time limit on review sample loans), consider the Cary SLP-94 my reference preamp."

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BTW, I own the Cary SLP 90L, that happens to be the implementation of the SLP94 product. It's all 12AU7, twin tube rectified, and has the oil cap upgrade mentioned by AD as an upgrade. So, maybe it's not the tube, but maybe the design and implemetation that can produce an excellent product. I certainly look forward to owning a 6SN7 based Pre by JF, whose creations sing of beauty, art, and audio design funtion, all in one package. And yet, even JF seems to be concerned not just with the names on each part, but which parts when put together create the best synergy for great musicality. So I must not, and let us not forget. It's all about the music, not just the tubes and part numbers and names.

The bottom line becomes simple to me. The 12AU7 is doing a very good job presenting the music. That does not mean all 12AU7 based products are the same, or all 6SN7 products are the same. Yet I like many before me, still wonder what it takes to move to the next level, or is there a next level?

A thanks goes to Kelly for spotting my SLP90L and alerting me. As mentioned many times,contact the seller. In my case, corresponding with the seller led to my discovery of the all 12AU7 configuration and oil cap upgrades which made it a wonderful buy.

Klipsch out.

[mobile homeless]

Good post, Edmond. I actually read that review when it came out and have alway thought the SLP-94 a great preamp. My siding with the 6SN7 tube over the 12Au7 is actually based on the air and ambiance, and complete lack of noise I have received from good octal tube preamps. There just seems to be less distortion and a more open, larger sound, more holographic you might say. Dont get me wrong on the distortion front. The SLP-94 is surely not distorted per say...but the octal tube 6SN7/6SL7 seems to really go one step up in this airy, open quality, all this without any hint of grain. It also seems to be amazingly quiet. I think the sound is larger as well... it just has that word I use all too often: Bloom.

When I was living in Chapel Hill, outside of Cary, NC, I got to audition my actual preamp along side the various prototype SLP-90 series preamps they were trying out. Tom and I both preferred my modified SLP-70 to the various SLP-90 prototypes although the tube rectified version was a step in the right direction. We heard one model with 12Au7 but the majority were 12AX7 based. There was one place where the new preamp surely won out with no problem: Beauty! It was really one of the most striking preamps I had seen up to that point. One of the prototypes was in the SLP-70 case while the newest model had that beautiful chrome case with the open tubes and black face plate. Man, did that beast stand out. At the time, I remember wishing my SLP-70 could be put in that new chassis!

Ironically enough, it wasnt till awhile later when they brought out the AE-1 6SN7 pre for their AES kit division did CARy realize, once again, how great the octal tubes were. They ended up going to the SLP-98 which uses 6SN7s on the SLp-90/94 type chassis. The SLP-50 was more along the lines of the AE-3 now but used 12AU7 first. The 6SN7 based preamps just seem to be more warm and atmospheric while STILL providing amazing detail. And the soundstage is HUGE.

Still, I rank the old SLP-94 series to be a GREAT preamp and one of the most beautiful preamps ever. The tube rectifictaion with the twin EZ81 is a GREAT asset as well.

Pat has said GREAT things about that preamp you are getting. I almost got it here for a listen! Let us know how it turns out. Thanks for the words as well.

kh

[Jobman]

Jazman:

Would you be interested in borrowing my Wright Sound WPL-20 preamp? It is out of my system for now.

I currently have some 1950 RCA 6SN7's in there, and I also just received a pair of Red Base 5692's that I have not yet installed.

Plus, mine has the switch for 6SN7 or 12SN7, and the stepped attenuator.

Hey, you can even try the phono section to compare with yours.

You could borrow it for a couple weeks to play with.

Jobman

[leok]

In my pp amp, I used 12AU7s, but replaced them with E88CCs because they are more linear, without feedback, as they were biased. The E88CC specs looked more linear and the tube sounds more linear.

The 6SN7 looks even more linear than the E88CC. And, from my limited experience with the Moondogs, it is more linear.

I would take an E88CC or 6SN7 way before any 12AU7. I think the 12AU7 is most effective in a feedback application, because it isn't linear.

leok

[jazman]

Jobman,

We've still got to get together soon. Let's talk about the Wright then. Such a weieghty topinc definitely deservers fresh suds instead of capaccinno foam. I'll send you an email.

Klipsch out.

[jazman]

Kelly,

My only point is, so much depends on implementation, that the tube and specs alone are not the only consideration. You know that all too well. I'm still trying to learn and experience more about audio designs so I'm definitely not an expert, but want to keep an open mind about things, judge equipment based on what I hear, and not spec sheets. I'm more than certain Pats pre will elevate the presentation to provide another level of knowledge and experience. It will still be hard to part with the Cary though I know I must. Someone is going to get a great preamp.

Klipsch out.