Soundstage!- The Entry Level with Greg Smith


Surrounded by preamps


September 1996

I hate buying things that doesn't last. There are two main reasons people get rid of their aging audio equipment. Sometimes, you get something that breaks badly enough that it isn't worth the money, time, or hassle to try and repair it, so out it goes. But for those that catch the audio bug, it's far more likely that a piece of equipment will become outdated or no longer desirable long before it breaks down. While I've certainly been guilty of this behavior myself, lately I've been trying to lower my total spending, and regular equipment upgrading is certainly not consistent with that goal. There are companies that sell high-end audio that cater to both types of consumers. Look at Audio Alchemy as one style of company. Seems that every month they are either introducing new products or offering upgrades or improvements to their old ones. Getting a bit bored with what you bought six months ago? Here, buy a new power supply. Compare this attitude with that of companies like McIntosh, which seems to aim more at the buyer who buys something new, plugs it in, enjoys it, and stops worrying about it for the next decade or two. OK, so maybe I'm stereotyping a bit here, but the point I'm trying to make is that for many an audio purchase needs to have some long-term value that it delivers above a flash in the pan improvement in sound quality.

Source components like CD players or turntables have a high content of mechanical parts and accordingly wear out fairly quick; I always buy them expecting that at best I'll get three years of problem-free operation before they start becoming troublesome. Thankfully, most of the rest of the audio chain offers considerably more longevity. Barring abuse, a good set of speakers should last a good ten years before there's even a hint of problem. How many people do you know that have had speakers for so many decades that the woofer foam rotted away? If you've had them so long that this becomes a problem, you probably got your money's worth long before that. Amplifiers and preamps sit in the middle between these two extremes. It's normal for one of them to go a good five years without incident, but occasional failures after that are common. Amplifiers have parts like transistors or capacitors may go belly up after a while. Preamps tend to have all the buttons and knobs start to corrode and get noisy as they get older, or break altogether. But as a rule, problems with these two type of components are happily infrequent, and you can expect them to last a while.

I have this figure I've been computing for equipment lately, called the maximum yearly cost. What you do is take the purchase price, divide by the warranty period (assuming that the unit may very well drop dead the day after the warranty expires), and get a $/year figure; that is the most that item will cost you per year to own. This lets you compare brands at the upper end of the spectrum more fairly, since warranty periods for high-end equipment tend to be much longer then the mass-market mid-fi stuff. I've used this sort of argument to convince friends that spending twice as much for the better components was in fact a bargain, based on probable longer lifespans; the better sound you'll get the whole time makes it an even better deal.

The flip side to this is that, in order for these components to continue to be useful to you as they age, they have to continue to meet the performance requirements you have. This is obvious enough; it doesn't matter how long something lasts once it outlasts its usefulness. What makes this interesting is the rapid rate at which things in the audio industry change. It's tough to have enough foresight to be able to pick something out that is going to continue to be a good performer for a long period of time. I started thinking this though a few months back when I started having problems with the aged receiver I had been using as a preamp. For a number of reasons, it seemed to be a good time to finally drop the cash for a new preamp, but the question quickly became what exactly to buy. After all, a good chunk of the industry is moving toward home theater setups, and I've certainly been moving at least some of the systems I deal with in that direction. The question I had to come to grips with is whether my main system was ready to start heading that way, too. There's certainly enough high-end approved surround gear to be had nowadays, but I was concerned that the items in the more affordable part of the market that I prefer to shop from weren't going to be competitive with their similarly priced stereo-only brethren.

Who cares? It's only a preamp, right?

I've got an equipment matching method I've been mentioning here the last few months. You start with speakers, then find a compatible amplifier that balances them out well. Next you get a CD player that doesn't aggravate the flaws in that combination. After that, find a preamp that is compatible with the things it gets attached to. Why wait so long before getting the preamp?

The interaction between an amplifier and a speaker, although complicated, is simple enough to appreciate; the constantly shifting impedance load the speaker presents makes the amplifier's life difficult. While it's a big problem, it's one that is well understood, even if the solution isn't. I maintain that you have the same problem at the interface between any two components in your system. A CD player has to drive the load that the preamplifier presents, and the preamp has to drive the load that the power amplifier presents. Good luck even attempting to quantify these interactions; the specifications for what represents "good" preamplifier input or output impedance is non-existent. If you grab a sample of products from a variety of manufacturers, there's no pattern I can find. Equipment designers work within a broad spectrum of possible loads and make their own designs compatible in ways that I'd have to characterize as being personal choices rather then technically verifiable ones.

So while the job of the preamplifier seems to be the simplest of any component, simply adjusting the volume of one line-level input and routing it to a line-level output, you end up with a wide variety of preamplifier sounds because there are badly specified component interactions at either end. Many audiophiles try and control these interactions by changing the cables that make these connections, which is certainly one approach. I prefer to put off the final preamplifier choice as long as possible, so that I can get the match I find best before I start changing cables around. Some even prefer using passive preamps because it removes the component altogether and drops the number of interaction points by one. I don't feel this is a particularly good move, because I suspect that CD player designers are designing their output stages to drive a preamp, not a power amp; regardless, I'm sure there are combinations that work anyway, but it's not the approach I'd take.

The other big factor in preamplifier sound quality is that the signals being dealt with are at a relatively low level. While a CD player typically produces a signal that is a nice 2V or so output, and amplifiers output big gobs of current, the preamplifier is often called upon to accurately produce very small output signals. This means that a relatively small variation in something like the power supply, changing the output signal by some fraction of a volt, can have a much higher effect on the signal on a percentage basis.

Shootout at the preamp corral

So while I would like to believe that preamplifier were simple beasts that should all sound the same, the evidence was accumulating that this was not to be. For your reference, there rest of the system (familiar to those who've been following along in past months) included the Rotel RCD- 940AX CD changer, Proton D1200 power amplifier, and Klipsch Forte II speakers. What I had been using as a preamp was an NAD 7100 receiver, a typical sample that depending on who you ask is either at the top of the mid-fi ladder or at the bottom of the high- end. While I found it to only be a good overall performer when I had been using it as a receiver, I found that when I wasn't using anything but the preamplifier circuitry it sounded much better. I suspect that the big power supply, designed to run the entire amplifier system, meant that there was very stable power for the preamp when nothing else was running. When I started having problem with it, I grabbed sample of every preamplifier I could find in my mid-fi and lower high-end corral and dropped each successively in my system to see just exactly how much of a difference the preamp really made in overall quality.

NAD 7100 ($750 receiver): with accurate response in the context of the rest of the system, this is the reference the other components were working against (although I know it can lean toward harsh when inserted in other systems).

Adcom GTP-400 ($400 preamp/tuner): excellent midrange clarity and realism, but too harsh and the bass seemed weak.

Audiosource SS3/II ($400 surround processor/preamp): not even in the same class as the other combatants, all of the sound had the life sucked out of it.

Proton AP-1000 ($350 preamp): very ragged in the treble and harsh in the upper midrange, but the bass was the best of anything in the group.

Harmon/Kardon PM665 ($700 integrated amplifier): very smooth and even response that extended equally well top to bottom. Possibly even better than the NAD, but itís getting old and problematic itself. Again, this one had a big power supply that I wasn't using because the power amplifier section was not being utilized.

After going through these five samples, with a variety of designs and prices, it was very clear that the preamp was anything but an incidental component. Just by changing the preamp, I could take what had been a system I was very happy with, totally destroy the sound quality, or skew it in any number of ways. Clearly, matching the preamplifier was a major factor; I didn't realize how lucky I had been to have something so compatible with the rest of my equipment before. It was obvious that the choice of preamplifier was not one to be taken lightly, so I started working on narrowing down the market.

What exactly, then, did I want, and how much was I willing to pay for it? I was thinking somewhere around the $500 range, but maybe a bit more if it was really justified or I could get surround capabilities. I looked long and hard at the Audio Alchemy DLC preamp (the going rate on which seems to have dropped to under $300). While what I read about it sounded good, it was just a bit too stripped down for my taste, essentially being only a volume and balance control (I'm also biased against anything that doesn't have a big volume knob I can grab). At the other end of the market, I checked out the B&K AVP1000 and 2000 (~$1000). They had everything I could think of to ask for in both stereo and surround, and were upgradable to boot; at twice my tentative budget, though, I needed to scope out some more products first before I seriously considered them.

A different sort of bill

I took a trip to the local dealer I've been buying from lately to see what they had around. In the stereo only format, I briefly considered the Acurus RL- 11 ($800), another basic preamp that had excellent sound. Unfortunately, that was really more then I wanted to spend, at least on a something that was devoid of features beyond volume and balance. The products from Carver all seemed to have gone too far, with endless goofy features I had no need of (like the questionable benefits from the Sonic Holography circuit). Eventually I found myself looking at the product line from Rotel. Having been very happy with the Rotel CD players I had bought before, their preamplifier line certainly warranted a look.

The model that seemed to be aimed closest to what I was looking for was the Rotel RTC-940AX ($450), a preamp/tuner combination. It had the usual gadgets, like bass and treble knobs, and the tuner seemed like a minor bonus (I really don't listen to the radio anywhere but in my car or at work, that's quite sufficient exposure for me). The other component that caught my attention was the RSP-960AX ($600). This was a preamp that was also capable of surround sound decoding. The question, then, was which of these was a better value.

All this fussing over preamps had led me to realize that there was a large measure of "you get what you pay for" operating. All of the components I was looking at were well engineered and used the best quality parts that the company could afford while still selling at the price point they were aiming at. To compare them, I ended up using what I've come to refer to as the bill of material approach. For those of you who aren't familiar with the concept, a bill of material is a listing of all the parts that make up a product. Add up the costs of each of the parts (including labor), multiply by some mark-up factor for profit and overhead, and you've got a selling price for that product. You can look at preamps the same way. Spend enough time browsing through catalogs to figure out approximate costs for the parts involved, find out a bit about typical labor and markup rates, and you can start to guess at the approximate price breakdown for each of the things you're paying for.

Let's dissect Audio Alchemy's DLC preamp, since I've brought them up a couple of times. By using a small, standardized case, I'd guess that adds less than $50 of the selling cost. Their DLC preamp has some inexpensive LED readouts and a remote; figure maybe another $40 for those. This leaves over $200 of the selling cost to go toward good sound in the form of preamp circuits and a power supply (this is relative to the $300 price I routinely see this item selling for; the other units I mention here rarely get discounted significantly, so I'm using the list price for them).

Compare that with the Rotel tuner/preamp. The standard 17" case I'd guess at $100 or so, with all the cut-outs . The tuner seemed to be pretty good, figure that cost a good $100 (tuners are fairly expensive chunks of circuitry). That big, smooth motorized volume knob? Easily $50; they ain't cheap. The bass and treble controls, along with all the other assorted knobs and buttons, I'd guess adds another $30 to the cost (and, as an unwelcome bonus, some extra circuitry that will degrade the output signal a bit). Throw in $30 for the remote. Add all that up, and out of the $450 you started with I'd estimate there's at best $140 going toward the sound quality. If you want gizmos and knobs, you will pay for them in the form of less money going into the power supply and amplifier circuitry. This why I avoided the Carver stuff; when I started to try and mentally add up how much each of those endless little features had to be adding to the selling price, there was too little left to be buying good components in the parts that effect sound quality.

For the Rotel surround processor, again peg the case at $100. the remote at $30, and the volume knob at $50. Nowadays, surround sound processing is mostly one big chip (the PMI 2126 in this case), figure $50 for it. The front panel has a fair number of buttons, but no other knobs; guess maybe $30 worth. There's some video switching circuitry on a board inside, figure $50 for it. So when you figure the retail price, I'd estimate that $290 of the selling price is going toward sound quality.

Guess what? That's exactly $150 more then what I estimated the sound parts in the tuner/preamp to cost, and the selling price of the surround processor is $150 more. Don't you love it when the math works out? (I didn't fudge the figures, honest!) I did some sanity checks on some of the other numbers by computing what the Rotel tuner unit alone should cost, and that worked accurately enough. These guesstimate figures I throw around certainly aren't exact, but I think they are fairly accurate representations of the balance between how much of a component in this price range is buying things and how much is buying sound. And don't get me wrong, these aren't part costs, which are much lower; I'm trying to figure in the markups along the way as well. I wouldn't want to generalize this to more expensive parts of the market, where external component costs start going up a bunch (those big cases and high- end volume knobs can cost considerably more then the numbers I'm throwing around), but the things I was comparing all had similar levels of part quality on the outside.

It seemed like an easy choice. I had reason to believe the Rotel surround processor would have better sound then any of the things I was comparing it directly with, and the surround capabilities made me considerably happier with the long-term usefulness of the purchase. Since I maintain that you can't guess how a preamp will sound any other way then to put it in a system and find out, there was nothing left to do but get one and try it.

Rotel RSP-960AX

September 1996

$599. Surround sound processor/preamp.

First thing to do was drop the Rotel in the place of the stereo preamp I had been using. From the start, this was an amazing difference. Everything sounded incredibly better then any of the preamps I had tried before. The level of harshness, distortion, and noise dropped considerably. The bass extension was far better, and the top-end was more detailed. I have nothing but good things to say about this unit when used in its stereo mode. Trying it with some different components in other systems, there were none of the incompatibilities that plagued my other preamps. Since this unit appears to be an easy one to drive, I've found that differences between CD players are smoothed out (there were players that I thought sounded very different with other preamps that became difficult to distinguish between with this one).

Now, this broad compatibility doesn't mean a lack of sensitivity to those interfaces. I've found that this preamp is good at resolving differences in the sound of cables, for example. Because of the improvement in the sound quality over my older preamps, I find that now I can hear it more clearly when one of the cables I use isn't as transparent as it should be. This has resulted in a dramatic escalation in my cable budget, but that's a story for a future column.

When being used for stereo, the simple preamplifier circuitry, with no tone controls, balance, or other such controls messing with things, seems to translate into great sound. There are a few oddities. There is a totally useless "bass eq" button that applies an absurdly high boost to low frequencies; it really should be labeled the "cool sound" button, because I can't think of any other useful purpose for it. And the maximum output level from the unit doesn't match some of the competition. I often feel like I'm running out of gain when turning the volume up with some amplifier/speaker combinations; while I haven't actually hit that limit yet (just been close), I could see it being a problem with some systems. Also strange is that at very low levels, there is a bit of a channel irregularity. When turning the knob from off to a slightly higher volume, the right channel on my unit comes on a touch before the left. This doesn't appear to have any effect at regular listening levels (I only noticed it because the extremely high sensitivity on my speakers means that I barely have to turn the volume on to hear things).

What about the surround?

I think it's great that the RSP-960AX works so well in stereo only mode, but in addition to that there's all this fun surround processing available, too. While I certainly enjoy surround for movies, the inexpensive surround receivers I've used before have always butchered any music I tried to play. So I wasn't expecting much when I dragged some more speakers and amplifiers in to test out the surround capabilities. Unexpectedly, though, I actually found myself enjoying quite a bit of the music I was playing in surround mode. The rear channels were distinct, and integration of front to back was far better then any surround receiver I've ever heard. When playing some well recorded CDs with lots of out-of-phase material (like the opening to the Alan Parson Project's I, Robot), the surround effect actually enhanced the music experience instead of districting from it. After hearing the clear, effortless surround processing in this unit, I don't ever want to go back to any of the inexpensive processors I've heard before. In my mind, it's even more of a quality difference than that between a regular receiver and separates in stereo. I was impressed.

You get all the usual Dolby Pro-Logic gizmos. The rear delay is switchable between 20 and 30ms. The center channel can run in any of three modes: normal (bass below 100hz goes to left/right speakers), wide (full-range center), or phantom (no center, all sound goes to left/right speakers). I find a center channel irritating for music, as it tends to break the soundstage into three distinct channels instead of the usual fine gradations. This effect is lessened by using wide mode, but it's still inferior to sitting in the middle and doing without the center as far as I'm concerned. Luckily all this is changeable from the remote, which happens to be very well laid out and easy to use, so it's simple enough to experiment with all these options. There are level control buttons for the relative volumes of the rear and center channels (which happen to default to nothing, so make sure you turn them up a bit before you expect any sound from those channels). The usual Pro-Logic level balancing noise is included. One nifty feature is that there are five red LEDs for the possible active channels. As you switch modes or test, the LEDs bounce around to match what you should be hearing sound from (which is handy to check channel identification on a unit without a balance control). There are some other ambiance modes on the processor, like jazz club or stadium, and while they don't sound horrible, I don't consider them worth fooling with. There is an adjustable subwoofer output, with a level control and several crossover frequencies, but I don't believe the unit removes that bass from the front channels when you use it. There are 2 audio only inputs and 3 combination audio/video inputs with regular and S-video jacks. While there might be a gee-whiz feature or two I would have appreciated, there's nothing I really miss with this processor that I might find on more complicated ones.

Pro-logic? Isn't that obsolete already?

Realize that it could be argued that buying a Pro-logic processor at this point in time is foolish. After all, there are already laserdiscs encoded with Dolby's AC-3 (oops, I meant Dolby Digital) sound. While this is all pleasant enough, I personally don't find this compelling enough to affect my buying yet. With the vast bulk of movies and music, you're lucky even to get Pro-logic. I feel no need to get the latest flashy processor when there will be very little available that utilizes it (after all, most of the new movies and music sucks, anyway). And getting that cutting-edge processor is going to put a big cut in your wallet, too. Don't even get me started on DVD; I have no faith that I can expect my favorite music or movies to appear in that format any time soon with playback units that have the sort of fidelity I expect from a laserdisc or CD player right now. It's just recently I feel those formats are mature enough to justify spending real money on.

Rotel has a much more expensive surround processor that is expandable to handle these new formats, along with being THX certified. The THX program was most notable for marshaling more industry attention on speaker dispersion as being something to control. As a whole, though, I find that the concepts behind what THX surround processors do above what Pro-logic ones handle are obsolete, if they were really desirable at all. Strictly my opinion here, but I certainly wouldn't recommend spending way more bucks on THX right now, whether from Rotel or anyone else. The newer discrete channel decoders render most of the THX sound tweaks obsolete.

I plan on spending the next few years with the Rotel RSP-960AX in my home theater, and at least the next year as a stereo performer (I'm considering spawning off separate audio systems for each, but that's still a bit away). The performance of this unit is well above what I was expecting. Itís high enough that, for most entry level buyers, it erases the stereo vs. surround issue if you can live without some features. Buyers of separates in this price range are not going to lose out on sound quality and get to add surround capability. And those who are solely interested in surround can get much better performance from the combination of this unit and some power amplifiers then they ever would from a surround receiver. Rotel's 5 year warranty means a maximum yearly cost of $120; it's tough to beat $10 a month for sound like this.

.....GS
(Greg has a number of additional ravings about audio and music available on his home page).