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XLH SL-11XS Preamplifier Review

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 XLH SL-11XS preamplifier

In the October Issue, I reviewed the very excellent XLH M2000 monoblocks. This is a review of the XLH SL-11XS line stage preamp (no phono), both with the M2000 monoblocks and with other components.

Preamps I’ve dated (but not married)

I’ve auditioned and reviewed several very good preamps in my various systems: the one-time class A-rated Adcom GFP-750; the tubed Cary SLP 2002 modded with paper oil caps; the surprising EAD TheaterMaster Signature preamp/processor; the Sony EP9ES preamp/processor (still used for my home theater); the very good and extremely functional Mark Levinson 380S and Ayre K-5x; and the really, really good Ayre K-1x and Sphinx Project Eight Reference preamps. I mention this lest you think I’m a preamp virgin – I’m not.

So What Do You Do With a Preamp?
This may sound like a funny question, but I have concentrated on finding excellent synergy between components in a preamp-less system. My “preamp” for the past 2 years has been Electronic Visionary Systems’ Ultimate Nude Attenuators. In essence, the UNAs are a series of manually switched Vishay resistors – one at the input of each of my monoblocks. I have to say that they have worked great in my system. One of the things that this allows me to do is to compare minute differences between preamps that I review.

From a purely functional standpoint, most audiophiles want a preamp to (a) control volume, (b) switch sources; and (c) allow small balance adjustments. If possible, many audiophiles would also like a preamp that can allow gain adjustment for different sources, split the output (for biamping), allow reversal of polarity, provide a home theater bypass option, and provide remote capability, all without degrading the sound.

As I mentioned in my review of the Sphinx Project Eight Reference preamp, from a musical standpoint, I’m looking for a preamp to work with my amps to: (a) improve dynamics; (b) enhance bass “heft” and attack; (c) clarify low level detail; (d) enhance the depth and width of the soundstage; and (e) enhance the placement and presence of the performers. I know people who look for a preamp to create a more “satisfying” sound. A common example of this is the addition of a tubed preamp to an otherwise solid-state system. I have done this myself (with mixed results). However, I think that you have to fundamentally like the way your system sounds without a preamp before you select the preamp. Hence my use of the Ultimate Nude Attenuators.

So What Do You Do With the XLH SL-11XS Preamp?

Well, you do the minimalist thing. From a functional standpoint, the XLH SL-11XS is located toward the simple-is better end of the preamp spectrum. This is a preamp that says: “Don’t screw up the sound of a good front end and good amps!” The front panel has 2 dials and one button. The button is the standby/on button. The two dials are for controlling volume – one for the left channel and one for the right. This lets you control both volume and balance without the addition of additional circuits.

The back panel consists of an AC line input, a on/off power switch, one set of RCA inputs and 2 sets of outputs – one balanced and one unbalanced. The fact that the inputs were unbalanced posed a bit of a problem for me in my review. My main front end is the Esoteric P-70/D-70 redbook transport/DAC combo, which sounds significantly better via its balanced outputs than by its unbalanced outputs. As a result, I ran my listening sessions using my P-70/D-70’s balanced outputs into a Silent Source copper interconnect, then into Cardas balanced-to-RCA adapters, then into the XLH SL-11XS’s RCA inputs. I’m not sure what effect this had, but I suspect there was some degradation of the sound when compared to my usual setup in which the output of the front end went directly into Silent Source Silver Signature ICs and then into the amps.

Two Apples to Bite

This is probably a good time to tell you that I had two of these babies to review – yes two! Though they appeared to be completely identical, Ping Gong of AAA Audio suggested that I try both and listen. He indicated that both were early production runs (the serial numbers confirmed this) and that some adjustment(s) were made between the earlier and later production units. As you will read below, the later production unit was indeed more refined. I don’t know what XLH did, but whatever it was, it worked.

Two Bites at the Apple

I ran both production preamps through the same sequence. First, I listened to the preamp in my own system, and then I substituted the XLH M2000 monoblocks for my Electrocompaniet Nemo monos. The differences were instructive.

When paired with the Nemos, the first SL-11XS unit I tested (without checking the serial number) added some dynamics and provided a bit more focus to the performers. However, it also shrunk and recessed the soundstage. Now you should know that almost every preamp I try in my system shrinks the soundstage at least a bit. I have tweaked my system to how I like it, and most changes detract from the sound. (I did not do it in this case, but I have found that moving my speakers can ameliorate this effect.)

I then substituted the XLH M-2000 monos for my Nemos. Well now…that’s better. The M-2000s are more forward and a bit more detailed than my Nemos, and though I stated in my review that they were world-class amps, I generally prefer a slightly laid-back perspective. Combining the XLH SL-11XS with the XLH M2000 provided a wider soundstage as well as one that was more neutral – neither forward nor recessed. The SL-11XS and the M2000 were obviously meant to be synergistic.

I then ran this same sequence with the other SL-11XS. (Again – I did not check to see which production unit was which – I simply selected the other preamp without checking the serial number.) This time, the soundstage with the Nemos hardly shrank at all. Rather, it gained dynamics and focus without sounding recessed. I then again substituted the M-2000s for the Nemos and found that the SL-11XS/ M2000 combo provided a very wide soundstage that was neutral in perspective and more transparent than that achieved with the other SL-11XS unit. I then checked the serial numbers. Sure enough, the better sounding SL-11XS was the later production unit. Nice production line tweaking!

Main Impressions

Several things came through loud and clear during my listening sessions:

1) The XLH SL-11XS Preamp and the M2000 amp combo were designed to be dynamic. When I say dynamic, I mean DYNAMIC! I’ll restate what I said about the M2000 by itself. If your hot button is to reproduce the dynamics and impact of live music, the XLH combo must be on your short list.

2) The XLH SL-11XS was meant to be synergistic with the M2000. Together they create a wide soundstage that has a neutral perspective and tons of detail.

3) The SL-11XS is a very good preamp in its own right. If I had just received the earlier production unit I would have had some reservations. Its excellent focus and detail were offset by a sound that seemed to be recessed in a shrunken soundstage and not as transparent as I would expect. The adjustments made by XLH in the later production unit (whatever they were) address this problem. The modified unit was not as focused as the earlier unit, but more realistic and enjoyable to listen to. If XLH could make another adjustment that keeps the wide soundstage and neutral perspective but reinstates the focus of the earlier unit without creating a recessed sound, you’d really get a lot of preamp for your money.

4) It probably does not need to be said, but I’ll say it anyway. The SL-11XS has no trace of glare or metallic hardness. The presentation is transparent (more so on the later production unit). Build quality is very good. XLH has clearly taken to heart the need for solidity in a preamp that is paired with an amp that has the explosiveness of the M2000. My experience has convinced me that heavy, mass-loaded components sound better than lightweight components when music is played at concert levels. I am convinced that the mass of the SL-11XS, which weighs in at 37 very solid pounds, contributes to the very clean sound you hear when playing at high volumes.

The Average, the Downside and Some Comparisons

The main aspect of the XL-11XS’s performance that was “only” better than average (not superior) was that it is not as quiet as a few reference-level preamps I’ve heard. Those of you who have read some of my prior reviews will recall that I am a fanatic for dead silent black backgrounds. It’s one of the reasons I’m not a tube aficionado – background noise that doesn’t bother others drives me nuts. (The M2000 monos are very quiet amps, especially considering what monsters they are.) The SL-11XS is by no means noisy. Most people would probably not notice at all. However, if you compare the SL-11XS to the Sphinx Project Eight Reference preamp, the Levinson 380S or the Ayre K-1x, you will hear what I mean. Now, all of these preamps are significantly more expensive than the XLH SL-11XS (some are more than twice as expensive), so I’m probably not being very fair by making this comparison. However, this should give you a perspective on this aspect of the SL-11XS.

One downside is something I noted previously. The SL-11XS only has RCA inputs. This is not a problem in the vast majority of systems. However, if you have a system that sounds best through its balanced outputs, you risk losing some of the performance you paid for. I would be interested in hearing XLH’s comments on this. The SL-11XS’s minimalist approach obviously enables XLH to give you great bang for the buck, and adding a balanced input might just add too much cost for the price range.

Finally, the SL-11XS has plenty of gain. However, it almost seems to have too much when paired with the M2000 monos. The 9:00 position on the volume dials was already quite loud, and turning the dials past the 11:00 position was insane (although it was also quite cool to have Steve Ray Vaughn playing in my listening room).

The Tech Details

Sometimes I fail to focus on technical data, but it is almost always important to look at such data to be sure that you have a good match with your other components. I’m not a tech guy, so I’m not qualified to say anything about how the SL-11XS’ specs relate to performance. The standard wisdom is that a preamp should have high input impedance and low output impedance. All I can say is that there was no indication that either my front end or the amps I used experienced any strain or difficulty when the XL-11XS was inserted into the system.

Let’s Conclude

The SL-11XS is a very nice minimalist preamp that is an excellent match to the XLH M2000 monoblocks. It is also a very good preamp in its own right, especially if you have a single-ended front end. At $5,000, it falls right into a highly competitive price range for higher-end preamps, and you normally need to spend more to get something significantly better. I’m very impressed by XLH’s first products for the US and thank Ping Gong of AAA Audio for letting me audition them. They exhibit great build and attractive design concepts. I look forward to what’s next.

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