Peachtree Audio decco65 D/A integrated amplifier Page 2

It seemed to me that the decco65's tube buffer had slightly less sonic influence than the one in the iDecco: The newer amp took on less sonic warmth from its use, though the tube buffer did seem to add to its spaciousness and sense of scale. On the other hand, the solid-state buffer delivered tighter, cleaner bass, with less exaggeration of the decay components of notes—with no apparent penalties. Thus, all of the comments that follow are based on my use of the decco65 without its tube being activated.

Listening
My first impression of the Peachtree decco65, according to my listening notes: Someone with a good ear has voiced this amplifier. With line sources, this humble integrated sounded pleasantly up-front, with more color and texture than I expect from relatively inexpensive solid-state amplification—especially, it must be said, inexpensive class-D amplification. The decco65 had a distinctly tight, pacey bass register, while its treble range was believably crisp without being bright. Its sound lacked the "air" of more expensive electronics, but avoided sounding opaque or chalky with the sources I tried.

Spatially, the Peachtree's ability to convey scale was okay, though not up to the level one can hear with very good and very expensive tube amplification—but its sense of impact and touch was excellent for this price level. The percussion and horns throughout Lee Feldman's "River," as well as the attack components of the bass-clarinet notes in his "Trees Are People, Too," both from Album No.4: Trying to Put the Things Together that Never Been Together Before (CD, Bonafide UM-130-2), had great punch and tactile realism. So, too, did the autoharp and xylophone that lend such textural interest to the title song of PJ Harvey's Let England Shake (CD, Vagrant/Island VR651).

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Alongside this punchy, tactile, up-front amp, the decco65's DAC sounded clean, open, and commendably free from artificial texture and other digital nasties. Compared—quite reasonably, I think—with my AudioQuest DragonFly USB DAC ($249), the latest Peachtree DAC sounded both tighter and smoother: not artificially smooth, in the manner of those depressingly expensive digital components that often sound plasticky and fake to my ears, but naturally, organically smooth. By comparison, the DragonFly—which appeared to have a higher output than the Peachtree's internal converter, necessitating a bit of level-matching on the fly—was equally tactile, but characterized by slightly coarser textural contrasts, and with less-well-controlled bass.

A few examples: With "That Time Is Gone," a great up-tempo number with a "Mr. Soul" vibe from Falling Off the Sky, by the dB's (ripped from CD, Bar None BRN-CD-210), the decco65 DAC distinguished itself as both flatter and clearer. Subtle timbral and textural details, especially in the sounds of the electric organ, were easier to hear through the decco65's converter, which also tightened up the sound of the electric bass while maintaining fullness, depth, and impact. By comparison, bass-note decays were just a little bit sloppy through the DragonFly. And Hindemith's Escales Romantique, performed by Daniel Myssyk and Ensemble Instrumental (ripped from the Fidelio sampler Escales, no catalog number), sounded lovely: open, colorful, and sufficiently textured, the note attacks given their rightful, realistic prominence—but no more. And with Joanna Newsom's "Only Skin," from her 2006 album Ys (ripped from CD, Drag City DC303CD), the decco65's DAC allowed the squeak at the start of her vocal performance just enough prominence—not the excess lent it by the AudioQuest DAC—and gave her harp and various bass strings good weight without the DragonFly's slight excess of same.

There were, however, a couple of music files with which I favored the DragonFly's bigger bass and more distinctly drawn textures—eg, David Grier's performance of "Ookpik Waltz," from his Live at the Linda (ripped from CD, Dreadnought/Burnside 0701): There the decco65's DAC didn't give quite enough emphasis to note attacks, while the DragonFly provided more texture in the note sustains and decays, and allowed Grier's 1946 Martin D-28 a larger sense of scale.

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For its part, the decco65 did a fine job of playing the relatively few 192kHz music files on my iMac. A hi-rez file of "Marrakesh Express," from Crosby, Stills & Nash, delivered deeper, tighter bass and considerably more natural-sounding detail than an AIFF file ripped from the "Red Book" CD of the same recording (Atlantic/Rhino R2 73290). Steve Stills's fine electric bass playing sounded even finer than usual from the hi-rez/decco65 combination, driving the song in a more obvious and enjoyable manner than before. Vocal articulation was better, too, and the entire production sounded altogether more spacious—things that could also be said of the other 24/192 files at my disposal.

decco65 vs iDecco
I reviewed the Peachtree iDecco in December 2010 and ultimately purchased one, so a comparison seemed in order, especially of the two models used as integrated amplifiers. Using my Sony disc player and the AudioQuest DragonFly as line-level sources, the Peachtrees sounded less alike than I'd expected, notwithstanding their different power-amp topologies. The iDecco had more of a flair for atmosphere, nailing the hall sound of recordings so endowed—but, in the bargain, often pushing soloists farther toward the back. The decco65 was less spacey, with an up-front sound that helped cut through the murk of such recordings as Jeremy Backhouse and the Vasari Singers' performance of Herbert Howells's Requiem (CD, United 88033), and violinist Marianne Rônez and Affetti Musicali's two-disc set of Biber's Mystery Sonatas (Winter & Winter 910 029-2).

Conclusions
I love analog, but I also enjoy living in the 21st century—and digital music is a part of that life: It demands to be accepted. To do otherwise is like saying, "I want to have a child, but I don't want to have a child who would ever want to dress in strange clothing or have his nose pierced." Reality is seldom as awful as some of us tend to expect.

In the case of the decidedly modern, decidedly easy Peachtree decco65, reality is quite pleasant: This is seriously good, seriously listenable digital sound, wedded to an amplifier that comes closer than most to being the electronic equivalent of a Mini Cooper: It's nearly impossible to use without smiling. Add to that a three-figure price, and you have not only an exceptional performer but an exceptional value. Peachtree Audio's decco65 is among the most recommendable affordable-perfectionist products I've had the pleasure of using.

COMPANY INFO
Peachtree Audio
2045 120th Avenue NE
Bellevue, WA 98005
(704) 391-9337
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COMMENTS
awehns's picture

Unless you are a human FFT analyzer, figures 4 and 5 can't be seen as spectra.

awehns's picture

Figure 3 isn't a waveform!

 

Love all these measurements though, so thanks.

John Atkinson's picture

Sorry about the mislabeled graphs. I am traveling today but I'll fix this later today.

Update: Okay, got to where I was going today (flying from Seattle to Ashland Oregon) and have fixed the caption problem.

John Atkinson

Editor, Stereophile

mattd's picture

Is the nova125 review available online? 

John Atkinson's picture

Quote:
Is the nova125 review available online?

Not yet, I m afraid.

John Atkinson

Editor, Stereophile

RoryB's picture

From the specifications of the amp section itself, it appears that the Decco65 is using the Texas Instruments TAS5613 150WPC class-D amplifier IC. This IC can deliver 65WPC into 8 ohms and 125W at 4 ohms with 1% THD, and claims both >90% efficiency and flat THD content across the entire audio bandwidth, with extended bandwidth to 80kHz. Pretty darn awesome for something the size of a postage stamp. The key to this, according to the TI data sheet for the IC, is their "PurePath HD" feedback scheme, which enables wide bandwidth and extremely low distortion (compared with other class-D ICs). A larger 300WPC amplifier IC is also available, the TAS5630. For those that are new to all this, an IC-based class-D amplifier builds everything but the input filtering caps and the output filter into the chip itself - which means the output devices are also onboard. A benefit to this is the extremely short signal paths on the amplifier IC's silicon die. By contrast, the popular ICEpower and Hypex UcD/nCore amplifiers use discrete components.

What this review says to me is that affordable class D amps (and particularly IC-based class-D amps) are finally "getting there" in terms of audio quality to where they can be used in a credible high-end audio product. I lost a channel in my class-AB amplifier recently and am using a Chinese stereo amp (Sinewave Genius200) based on the TAS5613 while the big iron is being repaired. Overall, my impressions mirror the author's - while not the last word in transparency, there is a wealth of detail being unveiled. Also, there are no sweeteners in the amp IC itself - tonally, it is on the neutral to cool side (like a class-AB amp based on bipolar FETs instead of MOSFETs). But the amp is remarkably free from the phasey 'hash' and elevated treble THD that I've heard from other class-D IC amps, mainly the low-cost Tripath variety or later ST Micro ICs (though the Tripaths were at least listenable), so imaging is much improved over what I've heard before from affordable class-D amps.

Still, the work is not done for engineers of class-D ICs, or those amp manufacturers that use them. Even the TI PurePath ICs are power-rated at THD levels  (1% THD and 10% THD) that would be considered unacceptable in a Class-AB amplifier at full power, so there is room for improvement. (The TAS5613 is rated for 0.03% THD at 1W - the foregoing statement is only meant to highlight that at full power, class-D amps still have distortion issues.) Also, this indicates that class-D amps should actually be de-rated slightly when comparing them to similarly rated class-AB units to put them on equal footing where THD is concerned. Still, I am glad to see these improved class-D ICs making their way into higher-end products as their performance rises to the necessary level.

There is still some room for designers to affect the sound of these amps, even though the 'guts' are hidden inside the IC. What amp designers can do is make careful choices in the selection of input filtering caps and also in the design of a properly-damped output filter that provides maximal bandwidth and uses components designed for high voltage and high current applications, such as metalized film capacitors, potted large-gauge inductors, and high power resistors of good quality. A well-designed output filter will be more than a simple second-order lowpass LC network - it will include a parallel leg containing a shunting capacitor in series with a damping resistor to prevent additional HF distortion from voltage spikes that overwhelm the amp IC's feedback network. The math for output filter design is very simple, so when amp manufacturers leave this stuff out, I wonder what they are thinking other than trying to shave off every penny of cost - not a mindset that will succeed in the high end.

Lastly, to stay competitive, I'd like to see ICEpower A/S and Hypex Electronics BV create their own IC designs incorporating their patented technologies, such as a second feedback loop that monitors the output of the output filter and attempts to exert greater control via the amp stage. The very short signal paths on an IC would be of clear benefit to these already class-leading technologies.

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