A Re-Introduction to Two-Channel Stereo (Part 5: Amplifier)

Time to get serious by placing the amplifier, or power amplifier, in its proper context. As the final electronic component in the chain from original recording to loudspeakers, the amplifier’s job is to increase the power of the signal, or simply, to make everything louder. For better or for worse. Better: high quality original recording, high-quality turntable / cartridge / phono stage or CD player, pre-amplifier, and high quality interconnection cables running between these devices. Worse: the inadequacies of the weakest link are amplified, too.

In the previous article, we discussed a $999 Rotel pre-amplifier, the RC-1570. Happily, this component was designed to pair with the same company’s RB-1552 Mk II, also $999. (Each can be used with a component from another company, but they look and sound good together—and they’re available in a choice of silver or black.). The RC-1570 is a 130 watt amplifier—a 200 watt version is available for $600 more as the model RB-1582 Mk II—useful if your loudspeakers require more power.

Here's a look inside the Rotel RB-1552 MkII with the large transformer common to power amps.

Here’s a look inside the Rotel RB-1552 MkII with the large transformer common to power amps.

How much power do you need? The answer depends upon several factors. The first is the size of the room—think cubic feet, not square feet. A small room—let’s say 10 feet by 15 feet with an 8 foot ceiling—that’s 1,200 cubic feet would require about 50 watts per channel, more if you’re driving a pair of speakers with a special power-consumptive design (the Magnepan series of flat panel speakers are an example). A good-sized living room (20 x 20 x 10 feet = 4,000 square feet) requires about 100 watts per channel—more if you play your music loud. Bigger room, more power required. However: if your room’s acoustics are “dead”—tapestries on the walls, lots of soft absorbent furniture, thick carpeting, few exposed reflective surface—you may need more power. And if your room is very “live,” you may need less power.

If this seems complicated, trust your ears. Ask your dealer to arrange an in-house test so that you can listen to the prospective amplifier and loudspeakers in your listening room. You will learn a lot about the relationship between the amp and the speakers. (More about listening rooms in the next article.) Be sure to listen to your own records, your own CDs—music whose sound you know from past experience.

Start with the low register: the bass, the drums, the bass section of the orchestra, the lowest vocal sounds. If the amp is suitable to the room and the speakers, the bass will be clearly defined—and thrilling. If you sense some straining, or graininess, then the amp is insufficient for the speakers’ needs (this is why your in-home demo ought to include a test of an amplifier beyond what you believe you need). Now, listen for the soundstage—the placement of the instruments, the sense that you are listening to a full group, ensemble or orchestra. When the music becomes complicated, does the amplifier keep up, or does the soundstage begin to decompose? Start at a lower volume, then gradually increase. If the music sounds very good at a low level, you’ve got a good match between speakers and amplifier. If the music doesn’t sound as good when the volume increases—is the higher register smooth or does it become edgy (and, perhaps, headache-inducing)? Don’t be afraid to go louder than you might listen to under normal circumstances—you want to push the system near its limits (preferably under dealer supervision so you don’t blow out the speakers). Listen to a variety of recordings in order to expose both strengths and weaknesses. And by all means, step up to a better amp in order to understand what you are and are not buying.

For most listeners, most of the time, the Rotel RB-1552 Mk II will be an ideal choice, but it’s considered an entry level amplifier for high-end audio, as is the competitive Parasound A-23 Halo (also $999) for comparison. If you were to increase your investment to about $2,300, and your room, listening preferences and/or loudspeakers require the additional power, you should certainly consider Parasound’s 250-watt A-21 Halo. And, take note, there is a sister pre-amp ($1,095), the well-reviewed Parasound 2-channel P5.


To learn more about any audio component, download the owner’s manual before you buy. (Click on picture.)

Here, we begin to understand the passions of an audiophile: the resonances of the cello, the timber of the piano, the breath behind the vocals, the feeling of warmth and presence, all of these indescribable factors come together to more than justify the additional investment. It’s tempting to read the engineering background, and to refer to the design of the transformer, or the capacitors, or the overall approach to technology, but for me, none of that matters much. Most equipment in this price class is well-made, and most benefits from sophisticated engineering design, but it’s very difficult for me to understand these technology discussions. And besides, what I hear—and I do spend a lot of time listening, as you should if you’re making this kind of investment—and I’ve learned to trust my ears, my brain’s ability to process the information, and the holistic feeling that each recording seems to offer. I think the Rotel sounds very good, and the Parasound A-23 sounds even better—for all of the reasons described above. They also sound different from one another, but I cannot fairly detail the differences because I listened to these models in different rooms, with different loudspeakers.

img_0903Too theoretical? Maybe. We can shift back to the practical side of technology. These amplifiers—typical of their class—offer both RCA and XLR (“balanced”) inputs. It’s best if your pre-amp and your amplifier are both equipped with balanced connection. In the high-end community, there is no clear consensus in favor of balanced connections, so try both to determine which approach you prefer.

The other big decision: tube vs. solid state design. Certainly, tubes can sound sweeter, but solid state may seem less, well, scary. This is a longer discussion for a future article. My short-form recommendation: a tube pre-amp paired with a solid stage amplifier—but there’s lots more to discuss.

img_0902If you’d like to dig deeper into the world of amplifiers, that’s a good reason to buy The Complete Guide to High-End Audio by long-time Stereophile writer Robert Harley (now in its fifth edition. Some of the information in the book is fairly technical, but most of it is written for the same reason I’m writing these articles—to help select the best listening equipment.

A Re-Introduction to Two-Channel Stereo (Part 4: Pre-Amplifer)

Just to review: an integrated amplifier combines two functions, pre-amplification, and amplification. A pre-amp accepts  incoming signals of varying strength–from the CD player, FM tuner, and phono system–and makes the necessary adjustments on the way to the amplifier. Your volume adjustments are made on the pre-amp, too. In theory, a pre-amp should do little more than equalize the signals, and allow you to switch between the devices. In practice, your choice of pre-amplifier will greatly affect the way your system sounds, so it’s worth experimenting with several models before you make a decision.

A good pre-amplifier will cost over $500. You can spend a bit less, but you won’t get much for your money. You can spend many thousands of dollars on a pre-amplifier, and we will cover more expensive models later in this series of articles. For now, let’s have a look at what $1,000 will buy–and for that exploration, I often turn to a long-time favorite manufacturer in this price range, Rotel.

Specifically, let’s explore the Rotel RC-1570 ($999). And let’s have a look at the front and back panels of this pre-amp because we’ll be referring to the various features in a moment. (FYI, there’s a black and a silver model.)


As with any pre-amplifier, you’ll find a power button, a volume control, an input selector, and, on mid-priced models, a headphone jack. This particular pre-amp offers a whole lot more–a trend that is gaining favor. On the left, there’s a USB connector so you can attach a mobile device (an iPhone, etc.). There are a lot of other inputs, discussed below, and there is a visual display that provides a remarkable range of technical information. These features are uncommon, but all are welcome.

In fact, the back panel is the place to go for a clear understanding of capabilities. Let’s take a closer look.


On the left, there are two rows, one for the left and the other for the right channel. First up is the phono input–this pre-amp includes an equalizer for “Moving Magnet” or MM phono cartridges (some pre-amps do, others do not). You can also plug in a CD player, a tuner, and two other devices. All with RCA-type plugs. Then, there’s the output–both via RCA plugs and also via XLR connectors as “Balanced Output” (a different way to connect components that often reduces background noise and adds considerable clarity). There is one Balanced Input pair of jacks, too. There are some additional digital inputs useful for connection to a TV set top box, or a Blu-Ray CD player–in addition to the basic two-channel experience that is the principal purpose of a stereo preamplifier. And there’s more–but now we’re getting way beyond the typical operation of a pre-amplifier. (Perhaps that’s why Rotel refers to this model as a “Control Amplifier”–it does a lot!

It’s easy to get caught up in features, but before we move on, I’ll mention two ideas that aren’t typical of pre-amps, but make this device a pleasure to use. First, the volume control comes with a kind of memory–when you listen to a CD player, for example, it will remember the most recent volume setting, even if you turn the power off. It’s smart enough to recall the most recent setting for each of your devices, so the next time you play a record, it will remember the most recent volume setting for that device, too. Pretty cool! Second, you can attach a USB receiver so that anyone (with a password) can wirelessly connect and play music through your stereo system. Nice!

I am not an engineer, but friends who know audio engineering design are often impressed with the “build quality” of Rotel products. Often (but certainly not always), good design translates into a good listening experience. We can speak of particular transformer designs or the specific qualities of the Wolfson D-to-A converter, but that’s beyond me and most other people. And now is a good time to set expectations: this is not a high-end stereo pre-amplifier, but it is a very good mid-priced pre-amplifier. The difference is explained in a review of this device, and its paired amplifier, by The Absolute Sound, a leading audio journal:

The sonic question for components in this price range is not whether they can produce a fool-you facsimile of the real thing. Unfortunately, barring a technological revolution, they can’t. The more pertinent question, then, is whether they get enough sonic elements right—and whether those strengths are not overly compromised by the inevitable trade-offs—to convey music engagingly. “Engaging” is a word we high-enders use as shorthand for the cumulative effect of a multitude of sonic factors, but I believe that chief among these are the elements that most directly impact musical expressivity. Speci cally, I look for good timing, tonality, and dynamics.

As someone with a similar system in one room of my home, and a bona-fide high end system in another, I can attest to the difference. That said, listening to the RC-1570 is a pleasure, especially when paired with the RB-1552 Mk II Stereo Power Amplifier, and the sister CD player, the RCD-1570 CD Player. Each of these components costs $999–add a good turntable with an equally good cartridge for another $500 (the Rega RP1 with a Rega Bias 2 phono cartridge is on sale for $445 from Audio Advisor). And you’ll need loudspeakers. Total system price: about $5,000, but if you needed to come down a bit, I would probably cheat on the CD player (a $500 unit from Cambridge Audio or NAD would probably be fine.)

Gee, does that sound like a lot of money? We’ve only just begun. For most people, a $999 dedicated preamplifier is a major step forward, the beginning of a serious two-channel stereo system. And yet, $1,000 is considered a modest investment in high quality sound. As this series of articles continues, we’ll get into more costly gear. In fact, the next article, which is about power amplifiers (or, if you prefer, amplifiers) will begin to explain the virtues of a larger investment.

I should mention that Rotel makes an even more versatile pre-amplifier, the RC-1590. The step-up adds a lot of features and technology. See it here.


Be sure to explore more than one pre-amplifier. You’ll find different features and a different sound. One of the most popular is the Parasound Halo P7 7.1, which costs $1,699 and comes with a very wide assortment of RCA and XLR inputs and outputs. The phono input accommodates both a Moving Magnet and a Moving Coil cartridge. There are home theater capabilities, too.

If you’re seeking something simple–fewer features, more of a focus on sound–you’ll likely jump up into a somewhat higher price range, and you’ll be encouraged to explore the various advantages of tube vs. solid state pre-amps. Again, a topic for another day.

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