Integrated Amp Reviews

In the 1960s, my dad gave me a Panasonic receiver with two cube speakers, just in time for the advent of FM stereo radio in the San Francisco Bay Area. Out of the blue one night, he just walked in with it. The receiver allowed me to plug in a record player, though I only had a few LPs. Later, when I went off to college, my mom took me shopping for a new stereo. I chose a Kenwood integrated amplifier—without a tuner but with the capability to plug in a tape deck, which I did. During my undergrad years, it served me well. Later, I switched to an NAD receiver, which allowed me to listen to the radio again.

When it was time for my sons' high school graduation, I gave them identical pairings of Peachtree integrated amps and Nola loudspeakers, bought at the late, lamented Lyric Hi-Fi in Manhattan. That's where I first heard the term "Swiss Army knife" applied to audio. The Peachtree boasted an internal DAC and a USB input for a CD transport, but no phono stage or radio.

For a long time, my hi-fi life was integrated. More recently, it evolved to include high-quality separate components.

AVM (Audio Video Manufaktur) is based in the small town of Malsch, Germany. Company owner and designer Udo Besser explained his priorities for their new Inspiration CS 2.3 integrated amplifier—a true Swiss Army knife—like this. "Once upon a time, in order to have dynamic, engaging music in the home from a number of sources, a whole stack of gear was needed: preamp, power amp, phono preamp, DAC, streamer, and on and on. That was then, this is now, and AVM's all-in-ones can provide genuinely engaging sound using any source imaginable—all from a single, elegant box."

Lately, I have rearranged the deck chairs, assembling three audio systems, clustered in three price categories. The Upstairs System is all separates, and the Downstairs System is centered around a McIntosh integrated amplifier. For the Apartment System, I have been using another Peachtree Nova integrated—that makes three I've purchased! It was in the latter rig that the AVM Inspiration CS 2.3 ($6995) seemed most appropriate, as I realized immediately when Stereophile Editor Jim Austin first described it to me.

Honey, I shrunk the amps!
Describing the appearance of the AVM Inspiration CS 2.3 is easy. Much harder is explaining everything this small box contains. Measuring just 13.3" wide (skinnier than a standard "rack" unit), 12.8" deep, and 3.6" high including three nice metal feet, you can fit this unit pretty much anywhere. Thanks to the use of class-D amplification and clever implementation of everything else, the 2.3 runs cool enough that other things can be stacked on top of it. I even put a turntable on top, gaining some vibration isolation with IsoAcoustics footers. In such a configuration there's a risk of hum due to electromagnetic coupling—but I heard no hum. If I had, I would have abandoned this setup immediately. Bottom line: The CS 2.3 is apartment friendly; you could use this thing in a camper van!

The design aesthetic of the Inspiration CS 2.3 is minimalist. The top, sides, and front are handsomely finished, available in black or silver metal, plus custom options. On the left, a modestly sized screen, which is partially a touchscreen, displays various operating parameters and provides access to various functions. In the middle is a slot for feeding a CD drive, then three small, multipurpose buttons and a 1/8" miniplug headphone jack. On the right is a single large knob for adjusting volume. Besser described the volume control to me as "ballistic": How fast you turn the dial affects how fast the level changes; turn it slowly for small, precise changes, fast for larger adjustments.

The back panel is packed, with connectors for two antennas—Wi-Fi and Bluetooth antennas—two coax S/PDIF, on RCA; a USB-A connection for flash drives and hard disks; a LAN/Ethernet port; HDMI; two sets of analog inputs on RCA; one phono input on RCA (yes, there's a phono preamp inside), and two more RCA inputs for phono loading plugs. (Yes, that preamp can handle MC cartridges.) The outputs are two TosLink; a stereo pair of preamp outputs on RCA that can be used for a subwoofer; a single line output on RCA (a single stereo pair); and a pair of small binding posts for loudspeakers. Also on the back is the AC power switch. The CS 2.3 is designed to make extensive use of standby mode, accessed from the AVM RC X app (about which more momentarily) or front panel control buttons. Standby power consumption is a single watt.

The CS 2.3 runs unbalanced, so there are no balanced inputs or outputs. Analog signals remain analog; there is no internal A/D conversion.

Besser and his AVM engineering team wrestled with the trade-off of size versus audio quality, because compact size was a central part of the CS 2.3's design brief. Besser believes they won the battle. "The CS 2.3 may be compact and light in weight, but it's no lightweight in its performance or versatility," he told me. "Keep in mind all that would be in that single box: a stereo power amplifier producing 140W per channel, a line stage, a phono preamp, a headphone amp, a streamer, and a CD transport. Trial-and-error prototypes made it clear that effectively utilizing the available space would require the latest in 3-D modeling and simulation software."

Though the AVM CS 2.3 is as close to being a universal audio tool as any component I've experienced, a few tradeoffs were made in relation to space and cost. There is no USB-B input, which means you can't easily use your computer as a source of music data—unless the computer has an HDMI output, which many do. The loudspeaker posts were too small to handle the hefty spade lugs on most of my speaker cables. "In the predecessor model (the Inspiration CS 2.2), you could only use banana plugs," Besser told me. "Then we found these cute little terminals that you can use with smaller cables." Cute is one word; flimsy is another. The solution here is cables with banana plugs, which worked fine. I left my stripped-wire days behind me in the college dorms.

Not so long ago, class-D amplification was a hot-button topic in the audio world. Some loudspeakers seemed to sound better than others with certain class-D amplifiers. As with certain high-output-impedance tube amps, but for different reasons, the sonic balance depended on the impedance curves of the loudspeaker in use. Speakers with rising impedance at the ends of the audio spectrum interact with some class-D amps, in a negative way. Tinny, harsh digititis in the upper audible frequencies could result.

As Udo Besser said, "That was then." This is now (footnote 1). Two companies based in Denmark, Purifi and Pascal, provide most of the modules utilized by class-D audio amplifier designers worldwide. The Inspiration CS 2.3 utilizes the Pascal U-PRO 2S module, with its integrated switching power supply, and an additional power bank, which is split into analog (eg, phono) and digital (for class-D) sections; Besser says this dramatically improves the sound quality.

Many birds, one stone
A potpourri of setup items can be accessed from the CS 2.3's front panel, and also from the AVM RC X App once you've got it up and running. These include Volume Limit (factory default to 70%; change to 100% in the Personal Setup menu for highest quality); Bluetooth device pairing; Balance; Tone Control (set to Linear to deactivate); Loudness; Digital Filter (choose Steep, or Smooth); Display; Input Gain (each input can be set independently); Skip Unused Inputs; Auto Power Down (can be defeated); Update Firmware; and a lot more.

As previously mentioned, the CS 2.3's back panel has connections for two antennas, one for Wi-Fi, one for Bluetooth; both antennas are, of course, in the box. A network connection is necessary to make use of the AVM RC X App and, of course, the CS 2.3's many streaming features. AVM recommends a wired connection for best performance: "All AVM devices with integrated AVM X-STREAM Engine prefer a wired network connection, which usually allows a higher bandwidth and is also less susceptible to interference," the operating manual says. Assuming there's a wire close by, a wired connection is also much easier to set up. If you require a wireless connection, the manual's setup instructions are thorough, although the included screenshots from the app are blurry and difficult to read. I got it to work, but not without some effort. In my apartment setting, the CS 2.3 is sitting about 4' from my modem/router, so I used a wired connection.

There are many fine, multifunctional integrated amps on the market. One thing that sets the CS 2.3 apart is its CD transport—a really good, slot-loading design made for AVM by TEAC, not a cheapo mass-market DVD transport. The Inspiration CS 2.3 respects my trinity of personal listening: LP, CD, Streaming. You can also, of course, play downloads stored on a NAS or a flash drive connected to the 2.3's USB port.

Another thing that sets the CS 2.3 apart from many other streaming integrateds is the built-in phono stage. "A lot of people call their units 'all-in-ones' but either the phono stage is missing or a CD drive," Besser said. "I call them 'almost-all-in-ones.' The CS 2.3 also includes HDMI, for people who want to include TVs as well."

The phono stage for the CS 2.3 is no afterthought. It works with both MM and MC cartridges; MM loading is, of course, 47k ohms. MC loading is set via a pair of "phono" (RCA) jacks that accepts plugs for loading an MC cartridge with 100, 200, or 1000 ohms. Other values are available on request. "Little DIP switches for phono stages are junk," Besser commented. "They are built of very cheap materials, and they age rapidly, affecting resistance. And with phono stages you are dealing with very small signals." The phono stage in the CS 2.3 remains analog throughout.

Some components with built-in DACs digitize phono inputs. Not the CS 2.3: It keeps the phono signal analog throughout. That's good: I want to hear an LP played as it was meant to be played, not some ersatz virtual simulation.

---

Footnote 1: Note, however, that the Pascal module in the CS 2.3 does show a small dependence on output impedance—enough, perhaps, that loudspeakers with sharply rising impedance in the treble should perhaps be avoided. See fig.1 in Measurements.—Jim Austin