POSITIVE FEEDBACK ONLINE - ISSUE 31
the Pre-11 preamplifier
as reviewed by Lester J. Mertz
LA Audio's Pre-11 is the company's top-of-the-line preamplifier. It is a full-function preamp, and a technical tour de force. I read in a magazine recently that entry-level audiophile electronics like amps and preamps now start at $3000. Wow, where have I been? This seems a tad higher than necessary. It is scary, kids! It's no wonder that the average consumer leaves a high-end audio shop with sticker shock, but don't give up hope. Read on about LA Audio's premium preamp, and note that it retails for less than $3000. And what an extraordinary piece it is!
I'll start with the technical details, and there are many. First, this preamp is virtually handmade, from the best components and materials. LA Audio starts with a polished stainless steel chassis, adds point-to-point wiring and ceramic tube sockets, and tops it off with handmade transformers. These toroidal transformers have custom- designed iron cores and use oxygen-free copper for the windings for wide bandwidth. The chassis is dual-mono, with each channel having its own 5AR4-based power supply (an octal-base full-wave rectifier). This supply includes a pi-type filter, a choke coil in series with the current, and two smoothing capacitors on each side of the coil. The basic supply is also followed up with zener voltage regulation. Metal film resistors and custom-made thin-film capacitors are used throughout. The rest of the tubes include four 6SL7s (octal-base high-mu twin triodes) and two 6SN7s (octal-base medium-mu twin triodes).
There is a full-function smart remote—smart in the sense that it remembers your last settings when the amp is shut down. No rushing for the mute switch while you sort things out. The remote wand controls volume, mute, channel selection (L/R), and the input. The volume control is by a motorized potentiometer, and is very smooth. The phono stage that comes standard with each Pre-11 accommodates high-output moving coil and standard moving magnet cartridges, and has an input sensitivity greater than 50 millivolts.
The output stage is also tricked out with dual outputs, one of which is a traditional cathode-follower circuit, and the other of which is from the plate of the output driver tube. This allows the user a choice of two different sonic characters in one preamp. The second pair has a rear-panel level adjustment screw, which means that if you wanted to take the time, you could match the levels of the two outputs for A/B comparisons. I didn't bother, but the two outputs did sound different in my system. The cathode-follower output was more robust, with a solid, meaty presentation, while the plate output was lighter, with more emphasis on the upper midrange.
The gain of the line stage is the standard 12dB. Input impedance is 100Kohm. The output impedance of the second pair of outputs is not specified, while that of the cathode-follower outputs is less than 1Kohm. Signal-to-noise ratio is better than 85dB according to the website, but 90dB according to the handout product card. 85dB is a little higher than normal for this level of product. When I put my ear next to the speakers, it was dead quiet on the right and had a very slight hum on the left, perceptible from about a foot away. It was inaudible at my listening position, so was nothing to worry about.
The Pre-11 weighs about 27 pounds. It is approximately 19 inches wide, 15 inches deep, and under 7 inches high. It feels very solid, as if it were cut from a solid hunk of metal. It is also strikingly beautiful, with striking, gold-finned tube protectors in high contrast with the highly polished stainless steel chassis, glossy black transformers, and thick, brushed silver front panel. It also has polished towers at each corner that provide stable support. This is a very robust piece of gear. I spent several days playing with footers, wooden blocks, metal cones and what have you. Nothing of these things improved the sound, and most were actually detrimental.
The front panel has machined insets for the many LEDs that indicate your choices. There is even a blue light on the volume control that indicates the level setting. Starting from the left of the front panel, there is a power switch, a remote control receptor, a standby switch. a left/right indicator, a mute switch, the input indicators (phono, aux, CD, tuner, DVD), then the large volume control. All of the indicators are blue except for the L/R, which is red when viewed from the left, green when viewed from the right, and orange when viewed from the center. On the rear panel are five pairs of inputs and two pairs of outputs, with a level pot next to the second pair. To the far right is the IEC connector. There is no fuse accessible from the outside of the chassis.
How does it sound? Fabulous! The Pre-11 has a convincing sound, with body and great soul. This is a preamp that conveys emotion, with a really big sonic delivery that catches your attention and pulls you into the music. When I connected it to my power amp, it seemed to turbo-charge my system. My speakers now had deeper and more defined bass than before. Octal tubes always seem to have that big, lifelike sound. Perhaps it's because of their higher current capabilities, as they usually run almost twice the current of nine-pin miniatures. I also feel that the Pre-11's substantial power supply adds to its musical weight and heft. The tube rectifiers deliver current faster and more quietly than solid-state diodes, which can sometimes be noisy and obscure definition at low levels. Some boutique manufacturers have been singing the praises of tube rectifiers for years, but the claim has not been heeded by the mainstream. I think that attitude is going to change, and may already be changing, as some major players are jumping on the tube-rectification bandwagon.
The Pre-11 is no gossamer lightweight with lots of hyper-detailed highs. Instead, it delivers a rich, full spectrum of sound in a beautifully balanced way. I found it easy to listen to for hours, and always heard things I'd never heard before. Its transient speed and articulation is especially evident on voices, where the Pre-11 brought out nuances that lesser gear just doesn't get right. The subtle vibrato of female singers was abundantly clear. The parting of lips before sounding a word or phrase was well defined, as was the effort to draw a breath without making the sound too obvious. This surprising immediacy was even more pronounced on live recordings.
The soundstage was well behind the speakers, but slightly closer than it had been before. On well-recorded discs, the imaging was almost palatable, within a soundfield that spread from speaker to speaker and sometimes beyond. The sound was utterly non-fatiguing. Some of my listening sessions stretched to six or eight hours (with lunch and other breaks), and I never had the urge to walk away from the music and do something else. This is something that I want in my system. Solid-state aficionados may counter that this kind of sound is too beautiful at times. I won't argue that I am hearing the whole truth and nothing but the truth, but truth is a dish that can be served up in many ways. To me, great music must have a beauty and magic that almost defies logic, but you know it when you hear it.
I listened to the Pre-11 in my system for several months, driving two very different pairs of speakers—my favorite transmission-line models and a stand-mounted reflex design, both using Dynaudio woofers. Both seemed to go lower and sound more powerful than before. The LA Audio seems to dig deeper, with more conviction. It is a better match with my system than my own preamp in this respect. My simple, two-tube, nine-pin preamp has a slightly deeper soundstage, with more delicacy in the upper end. Images really float behind the speakers—both pairs. After switching back to my own preamp for a few days, I put the Pre-11 back in and played some of the same recordings. When I lowered the level to below nine o'clock, I got a deeper soundstage and the beautiful delicacy that I love. Turning the level to eleven and above gave the sound that gutsy delivery that I have described. It was like having another preamp! I don't consider this a fault, and I'm not sure whether it is something caused by the Pre-11 or is a system-matching issue.
Some of you may be concerned about buying tube gear, fearing obsolescence or difficulty in obtaining replacement tubes. I am a long-time tube aficionado (my first stereo was a late-50's, three-tube Montgomery Ward portable), and it seems to me that there are more tubes available today than even fifteen or twenty years ago. Russian, Chinese, and Slovakian tube factories produce all of the basic types. As for the Pre-11, our fearless editor informs me that Upscale Audio has picked up a batch of Pope 6SN7s originally destined for Mullard. These premium tubes are fetching $100 apiece, but you shouldn't feel that you have to make that kind of financial commitment in order to enjoy great tube sound. The currently available brands have gotten much, much better, and when used in modern tube gear, sound wonderful.
Reviews often end with some sort of classification of the piece, letter grades or "good, better, best" and other terms that often go without any real definition. We hear the terms "starter gear" or gear "I could live with". (By the way and please excuse my sarcasm here, but I think this phrase is over used. I wonder if it isn't some kind of code word to the distributor really meaning—please don't call me about returning this piece anytime soon. If you let me keep it I'll put it on my equipment list [advertising] and I'll use it for comparisons to future stuff giving it a mention every other month of so.)
The best class of gear is the kind that once you hear it, you can't go back. The ear is very sophisticated and when the music is cleaner, more revealing, more involving, more satisfying, and more everything—the piece becomes "gear you can't live without." So it is with the LA Audio Pre-11. Les Mertz