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Audio Research LS15 Stereo Preamplifier  Print E-mail
Home Theater Preamplifiers Stereo Preamps
Written by Bryan Southard   
Friday, 01 January 1999

Introduction
The Audio Research LS15 Line Level Preamp has been in existence since the middle of 1996. It’s an
all new design which theoretically replaces the former LS2B Mk II in the Audio Research line. I say theoretically because although it took the spot of the former, and much-respected LS2, it is very different in many ways.

The LS15 is priced at the midpoint in the Audio Research line at $2995, and comes with a handy remote control, something that was an additional $500 option for the LS2.

Its basic makeup is an all-tube gain using four 6922 twin triode tubes. It incorporates a fully differential zero feedback; balanced circuit with electronically regulated high and low-voltage power supplies.

The LS15 has a large array of input/output options. These options include balanced inputs, as well as direct balanced inputs, for best signal purity. This path bypasses switching electronics, and allows for the most direct and cleanest path for music. When in this mode, no other options other than volume and mute are active.

It has five single ended input options (including tape) for optimal flexibility. The LS15 has two sets of balanced, and two sets of single ended outputs, including a dedicated tape out.

The Audio Research LS15 is a fully balanced preamp which gives you single ended connection flexibility, but has considerable sonic advantages when run in the balanced mode. I found that when I ran the LS15 in its single ended mode, the stage collapsed somewhat, and there was a greater level of noise in the music. There was a loss of detail and the overall presentation quality had decreased. To take full advantage of this preamp, I strongly recommend it be run in the balanced mode, if of course your supporting equipment will allow it.

A removable power cord, which is a new approach for Audio Research, enables you the flexibility to experiment with today's finer power cords if you desire. The LS15 comes standard with a factory set 12dB of gain, which is somewhat lower than that of its predecessor, giving a wider range of adjustment in the volume control. That is if you have sufficient output in you other supporting components. If that becomes a problem, Audio Research offers a factory setting of 18dB of output, at no additional cost. This is also something that owners of the LS15 can have done at their local dealer, at little to no cost, at a later date if necessary.

The front panel has the traditional Audio Research look, which I have grown quite fond of. It has a solid, somewhat industrial look, yet is very simple in nature. Like many AR preamp’s of the past, it has a 5.25 inch high faceplate with the traditional black handles, which run vertically on the left and right edges of the face. The face includes a step attenuated volume control with 70 incremental steps for volume adjustment. The knob turns just a fraction of an inch and electronically steps the volume incrementally. I found the level of adjustment to be adequate. Additionally it has a selector knob, which controls your input source selections.

When receiving any tube gear from Audio Research, you first have to remove the top cover and install the tubes, which takes a total of about 3 minutes depending on your adrenaline level at the time. Myself, I am usually so excited that I am more concerned with dropping a tube in anxious anticipation of playing with, and hearing a new toy.

The preamp can be argued as having a more dramatic effect on your systems sound, than any other electronic component in your system. It can make or break your system. The best sounding preamp is quite possibly the one that introduces the least sound to your system. In addition, one which can deliver your music most naturally, and void of any obvious coloration. Other aspects that would influence my opinion of a specific preamplifier would be the presence of grain, and overall noise floor, which can cloud your soundstage and make your listening less relaxed. There has been much said about the sonic differences between tubes and solid state components. Today these differences are becoming less and less, and the best of both are closer in sound than ever. However, one typical sonic characteristic of good tubes, is very natural and sweet sound.

The basic function of a preamplifier is to provide switching capabilities between multiple sources. If you had just one input source, CD for instance, you would have the option of running your source directly into your amplifier, provided that you have attenuation capabilities, (volume adjustment), in your CD source, or a passive volume control. In most cases running a preamplifier will give you long term flexibility to run everything from theater to additional sources such as tape. The next step is picking the right unit for you.

The Music
Sound is probably not the best way of describing the LS15. In fact, it’s perhaps the lack thereof, that truly defines this component best. I very quickly found the LS15 to be incredibly neutral and void of any considerable sonic signatures at all. I heard an inherent sweetness in the midrange that was extremely inviting.

For me, one of the more important aspects that defines a component and the level of enjoyment that I will experience with it, is its ability to recreate and accurately represent a detailed soundstage. To test this I went to ‘Belafonte’s’ "Return to Carnagie Hall."(RCA) In this test I found the LS15 to deliver a remarkably rich and detailed stage. I found the stage to extend far beyond my loudspeakers, and deliver remarkable depth. The natural bloom of the recording was allowed to develop very nicely. Overall, it did a very good job at recreating the air in the recording. Unlike the reputation that some tube gear can have for being sluggish, and somewhat colored, the LS15 had no such qualities. It has a very natural and very musical characteristic about it that I found to be inviting, especially for a product in this price range.

As somewhat of a departure for high-end component reviews, I thought I would throw some serious rock and roll at it. I went to ‘Alice in Chains’ "Unplugged," (Sony Music) which is very dynamic and recorded quite well. In the song "Rooster," I found the acoustic guitars to be extraordinarily detailed. The detail of fingers sliding up and down the neck of the acoustic guitars seemed alive. The drums were very deep and solid, holding together nicely even at very high volumes. I detected no edginess in this recording, which I have considered to be somewhat bright with other components in the past.

If theater is in your equation, you will find the LS15 will lend itself nicely with the use of any number of high-quality outboard processor products. Connection of these products can be done in a variety of ways, each varying in convenience and performance.

The Downside
You have to dig pretty deep to find faults in this product. I never want to become so tainted that I consider a $3,000 piece of stereo gear cheap, yet I cant help but feel that at this price you are getting performance matched only by gear costing considerably more. If you were to purchase this product, I would challenge you to find any annoying sonic characteristics in its makeup. There are a couple of considerations you might want to make prior to purchasing this product. With any tube gear you have some maintenance that you do not necessarily have with solid state products, such as tube replacement, possible component placement assuring adequate ventilation for the tubes, and warm-up time, should you chose to spare your tube life and turn the unit on before listening. The tubes are estimated to last up to 4000 hours and have a replacement cost through Audio Research of $60 for the set of four.

On a simple note, the LS15 comes with a full function remote that is, although adequate, nothing fancy. If Audio Research offered a more robust version of this remote at extra cost, I would buy it. Call it a remote fetish if you must.

Conclusion
In a world where achieving the ultimate in sonic and musical reproduction can require a second mortgage, or even worse, perhaps equal the first mortgage, it is refreshing to find products which provide 95% of the performance of the industries best and most expensive, at a fraction of the cost. I have listened to countless preamps in my system and considered the LS15 to be my favorite in its respective price range, and for that matter, several over it. I felt strongly enough about this preamp that I purchased it for my reference system.

If you are in the market for a preamp that provides the very best in sonic performance, I strongly encourage you to give the LS15 a run. You just might find that you prefer it to units costing several times as much.
Manufacturer Audio Research
Model LS15 Stereo Preamplifier
Reviewer Bryan Southard





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