SAS Audio Labs TM
Where Music Comes Alive TM
11A Audio Line Tube Preamplifier Review, and Personal Comments
Bound for Sound Review, Issue #199/200, March 2010
McCormack VRE-1 VS SAS 11A Line Preamplifier ($7500.00 vs $2949.00)
By Martin DeWulf
"But in a direct A/B with the SAS 11A tube preamp into high input impedance power amplifiers (Monarchy SE250 and Clayton M300, both mono amps with a 100k input impedance), the SAS seemed to be slightly more bold in its presentation, as if it went from 0 to 100 just a little bit faster, and with a hair more impact when it got there."
"Further comparisons of the VRE-1 with the tube SAS, revealed the VRE-1 to once again be King of the Hill when it came to tone density, though I felt the SAS to have a subtly wider range of colors, same for the SE PLC and Loesch. The ever so slight darkening that I heard with the VRE-1, lessened somewhat its ability to differentiate ultra fine tonal distinctions in the lower midrange, distinctions that the tube preamps I auditioned were able to make."
"Maybe this boils down to a tube vs. transistor debate, but for me the VRE-1 still clearly outperformed many of the tube preamps I've auditioned in the past, including models from Wyetech, ModWright and ASL (not a bad one in that batch). I also keep open the prospect that it may simply be my personal preferences (prejudice) which cause me to prefer the dynamic contrasts of the SAS to the VRE-1; I own the SAS 11A and I don't own the VRE-1. Still there were any number of ways in which I preferred the VRE-1 to anything I've ever heard. Let's maintain a perspective here."
Since the 11A is the only preamplifier tested using multiple proprietary listening testing procedures to judge for absolute accuracy, I feel the 11A is the standard with the McCormack coming close in sound quality. The McCormack VRE-1 joined active preamplification with a passive transformer based line control.
Bound for Sound Review, Issue #178, June 2007
By Martin DeWulf
The 11A comes factory installed with a pair of JJ 6dj8 line stage tubes. There is also an option for the same tubes, but cryo'd. SAS was kind enough to provide me with a set of the treated tubes, and I found them to sound slightly different from the factory set. They were different in that the treated tubes were minimally airier and a bit smoother. In as much as I have a fairly vast collection of 6dj8 (6922, E88CC) tubes laying around, I did some substituting. The goal wasn't to find the most expensive, esoteric available, but to use a tube of modest cost that sounded great. I settled on the $40/ea. Tungsram that ended up sounding better than either JJ, a set of Philips JAN tubes and a similarly priced set of Teslas.
Peering inside the SAS reveals a preamp that looks distinctly different from others I've seen. Then again, the 10A was a little odd looking too. Compared to other preamps that I have reviewed, the 11A had two of the tiniest power transformers around1. At first, I wondered if everything was going to sound okay with the seemingly small power supply. Ends up there was no need to be concerned, and after listening to the unit for a number of months, it seems possible that some of the unit's ability to cleanly enunciate complex passages (ones that cause others to stumble) may be due to the size of the dual trannies. This unit is quick without being light. No doubt, it benefits from the dual mono nature of the power supply as well as the circuitry throughout.
For the AC, I preferred the 11A with the same set-up as the ModWright: the LessLoss power cord plugged into the Monarchy AC Regenerator. The 11A has an automatic mute circuit that has to qualify as one of the fasted on record. Not only does it mute upon turn-on and turn-off (no pops at all), the 11A has an AC polarity switch on its back panel which can be flipped during operation2! Were it not for the super fast reflexes of the mute circuit, one would expect a substantial pop when breaking and AC on one side then remaking the AC after the polarity was reversed. Instead, silence. The only side effect of using the AC polarity switch to reverse the AC is the momentary mute while awaiting the music to come back on.
The unit provided for review has on the back panel a rotary knob that can be used to optimized the preamps performance into a varienty of power amplifier input impedances. I found that by adjusting the knob, either right of left, I could use the 11A with ultra low input impedance amps such as the Pass, as well as with amps with higher impedances like the Monarchy and Edge. Still, in spite of the preamp's ability to handle amplifiers of all types, I found it to have a preference for the amps with higher input impedances. Therefore, while the Pass X250 is an excellent match for the SAS, a tube amp or hybrid with an input of 100k ohms sounds even better. 3 Advancing the knob fully to the left allows one to use the low input impedance solid state amps like the Pass and PBN. Rotating it to the right makes adjustment for high impedance amps, which would include most tube amps. For me, I found a setting somewhere in between to be best in most cases. Though if I were to err, I'd probably do so by having the knob more so to the right than the left.
Some people don't like dual volume controls. Having to adjust for balance with every change of volume can be a test to a person's patience. There are, however, two reasons to welcome the use of two pots instead of one. First, it's the sonically superior way of attenuation. In a circuit similar to that of the 11A, the music signal passes through only one pot instead of the two when there is a volume control as well as a balance control. Additonally, one can make minor adjustments to a shifted soundstage due to uneven tube wear, or room dimensions. Sometimes it's nice simply to be able to center a vocalist on a recording where the engineer didn't take the time to get it right the first time. The pots look to be Nobles, though Steve took some time to black-out identification marks and model numbers.4
Sound and Operation:
Of all the active preamps auditioned to date, the only one that I clearly prefer to the SAS 11A is the ultra sophisticated, ultra extreme, ultra expensive PBN Olympia-L with outboarded MPS Dual power supply. Other than the PBN, there is no other preamp, tubed or solid state, that I'd rather listen to. Direct comparisons to my old friend, the Symfonia Opus 8, revealed the SAS to be cleaner, more transparent and more organic through the midrange. The Symfonia wooped-up on the SAS in terms of pure bass depth and power5. But in other ways important to the critical listener, the SAS is a bit of a wonder-kid in affordable audio. Remember, it was the Symfonia Opus 8 that went toe-to-toe with the exalted CTC Blowtorch. There, the two exalted solid state designs traded punches throughout the mids and highs, with the CTC edging out the Opus on points in the deepest bass. The fact that the SAS bested the Opus in some important respects, especially in the midrange, says volumes about the quality of this preamp from Steve Sammet.
In terms of the music and nothing but the music, perhaps the better comparison for the SAS 11A would be the Sonic Euphoria PLC passive attenuator. Yes, it is an eggs to apples comparison, one being active and the other being based on a passive autoformer, but the end result for both is remarkably similar. It's the coherence, lack of additive distortions and dimensional transparency that makes these products as special as they are.
The 11A is a simple design, the circuit complexities found in ARC and Krell components are not found here. And Yet, I'm tempted to say that it's no simpler than it needs to be. Peering inside, one can tell that Steve Sammet is a bit of a capacitor nut. He uses some of the finest foil and film types around, and then for good measure by passes even those. The wiring is point to point and is neat to the extreme. After the power cord, the design is clearly dual mono through the power supply, volume attenuation and the gain stage. Wonderfully clean is this circuit as well as being deceptively straightforward. And it sounds exactly that way.
Tube sound is no good if it gets in the way of the recording. At the same time, tube preamps have a way of capturing and expressing the natural and the organic aspects of a recording. The 11A by capturing all that is natural in the music without adding a smarmy layer of artificial warmth goes beyond the typical description for tube sound to something truer, less voiced for euphony. The 11A does not possess a "formula" sound or a sonic character created for the purpose of selling tube preamps to people that expect a certain overlaying personality to each song played through it. It changes as the music changes.
I liked this preamp enough to purchase it. Because of its flexibility, unfailingly honest approach to the music and its organic honesty, I bought it. But it's more than a reviewer's tool. It's a music lover's companion as it is able to express the finer, the more subtle aspects of a performance, without resorting to proven audio gimmickry. It took an industry outsider of sorts to put into place a different set of sonic priorities, one that got us closer to the music and away from the bottom line.
Yes, on an absolute basis, the PBN Olympia-L line stage is a degree closer to the truth and a bit more transparent than the SAS. But at what cost? The comparison to a product costing three times (actually 4 times) as much is not an injustice done to the 11A. It serves to put the 11A in some very classy company."
1. The 11A preamplifier is operated true class A. In pure class A operation, the average plate voltage and current are constant, so no regulation issues to deal with. The transformer only has to have good frequency balance, handle the current and remain cool. If a large transformer is necessary, with its artificial fullness, there is a problem with the design.
On the other hand Class AB and B operation have plate current swings, thus plate voltage swings. A huge transformer is necessary to keep the plate voltage regulated. But using a high resistance rectifier tube negates the low resistance of the huge power transformer.
2. Although the mute function is extremely quick, I do not guarantee one will not hear a "click" upon turnoff. It is always good protocol to turn the amplifier off first, then the preamplifier. When powering up, turn the preamplifier on first, then the amplifier.
3. "The Moscode hybrid power amplifier sounded superb with the SAS preamp." This preamplifier seems to sound nice with both tube and solid state designs.
4. Not a biggy but although I do blot out component part values and manufacturer's names, the potentiometers come the way Martin saw.
5. What Martin heard between the preamplifiers in the bass was correct. The difference between solid state and tube preamplifiers lies in the fact that DC coupled stages actually excentuate the bass because of the circuit to power supply relationship. So solid state DC coupled preamplifiers may sound fuller, have more punch, but are not as accurate by the inherent design. (To understand this though, one needs in depth research into electronics design and sophisticated listening tests; 3 1/2 years on the 11A to make sure the Bass is accurately reproduced.) I use proprietary multi-method listening tests to check my preamplifiers for absolute accuracy.
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*copyright©: 11-06-2006 Updated 09-03-2012. All contents of this page article (except Sovtek and Svetlana Tubes) are copyrighted. All layouts of all our components, term "lead to lead wiring", "lead to lead connecting", "we make music come alive", "we make music truly come alive", "the last watt is as important as the first watt", and any and all designs and schematics are copyrighted. All rights reserved. No portion of this article may be reproduced without written permission from Steve Sammet at SAS Audio Labs. SAS Audio Labs is registered with the state of Illilnois.