NAD D 3020 integrated amplifier Measurements

Sidebar 2: Measurements

The D 3020 was voted Stereophile's "Budget Component of 2014." Getting the review sample onto my test bench had been on my to-do list for way too long, but I was reminded of the unfinished task when I picked up the PS Audio Sprout for measurement from Herb Reichert, whose review of the latter appears elsewhere in this issue. I first checked the performance of the D 3020's digital inputs, looking at the signal from the headphone output jack with my Audio Precision SYS2722 system (see, and the January 2008 "As We See It").

The headphone output preserved absolute polarity for both analog and digital input signals, and the output impedance was on the high side, at 200 ohms at all audio frequencies. For analog input signals, the D 3020's headphone output offers a maximum gain of 28.6dB, but a digital signal with a level of –12dBFS clipped the headphone output with the volume control set to its maximum. At –14dBFS, the unclipped output level was 6.81V; so, except as noted, for the digital-input measurements I reduced the volume-control setting, to avoid clipping. The D 3020 locked to an S/PDIF datastream with sample rates up to 192kHz, even via TosLink, though the USB input was restricted to 96kHz and below. Apple's USB Prober utility identified the D 3020 as "NAD USB Audio" with the serial-number string "(C) 2011 Wavelength Audio, ltd." This implies that the D 3020 uses Gordon Rankin's "Streamlength" asynchronous USB protocol and USB Prober did indeed confirm that the USB input operated in the optimal isochronous asynchronous mode.

The reconstruction filter's impulse response (fig.1) was a conventional FIR type, with time-symmetrical ringing, while wideband spectral analysis of the analog output as the NAD decoded 44.1Hz data representing white noise at –4dBS (fig.2, magenta and red traces) indicated that the response rolled off quickly above half the sample rate (vertical green line). The sampling image at 25kHz of a full-scale tone at 19.1kHz (cyan, blue) was suppressed by more than 90dB. Note the rise in the ultrasonic noise floor in fig.2, suggesting that the D 3020's DAC stage uses some kind of sigma-delta upsampling. Fig.3 is a more conventional response measurement, taken with 44.1, 96, and 192kHz data. The overall shape of the response at ultrasonic frequencies is the same—a small, 0.4dB rise above the audioband—broken by a sharp rolloff just below 22 and 47kHz with the two lower rates.

Fig.1 NAD D 3020, headphone output, impulse response at 44.1kHz (4ms time window).

Fig.2 NAD D 3020, headphone output, wideband spectrum of white noise at –4dBFS (left channel red, right magenta) and 19.1kHz tone at 0dBFS (left blue, right cyan), with USB data sampled at 44.1kHz (20dB/vertical div.).

Fig.3 NAD D 3020, headphone output, frequency response at –12dBFS into 100k ohms with data sampled at: 44.1kHz (left channel green, right gray), 96kHz (left cyan, right magenta), 192kHz (left blue, right red) (1dB/vertical div.).

To assess the D 3020's digital resolution, I set the volume control to its maximum, an unrealistic situation that did allow me to examine by how many dB the noise floor dropped when I changed from 16-bit data representing a dithered 1kHz tone at –90dBFS to 24-bit data. Fig.4 shows that the noise floor dropped by almost 20dB, indicating ultimate resolution of better than 19 bits—superb performance, even without taking into account the D 3020's very affordable price. The NAD's reproduction of an undithered 16-bit, 1kHz sinewave at exactly –90.31dBFS (fig.5) was essentially perfect, with the three DC voltage levels described by the data easily visible. With undithered 24-bit data, the result was a superbly well-defined sinewave (fig.6).

Fig.4 NAD D 3020, headphone output, spectrum with noise and spuriae of dithered 1kHz tone at –90dBFS with: 16-bit data (left channel cyan, right magenta), 24-bit data (left blue, right red) (20dB/vertical div.).

Fig.5 NAD D 3020, headphone output, waveform of undithered 1kHz sinewave at –90.31dBFS, 16-bit data (left channel blue, right red).

Fig.6 NAD D 3020, headphone output, waveform of undithered 1kHz sinewave at –90.31dBFS, 24-bit data (left channel blue, right red).

Only when it came to jitter did I encounter some anomalous behavior via the D 3020's digital inputs. Fig.7 shows the spectrum of the headphone output with 24-bit J-Test data fed to the D 3020's USB input. No sidebands are visible around the 11.025kHz tone, and the noise floor is superbly clean. By contrast, fig.8 shows the spectrum of the analog output with the same data fed to the optical S/PDIF input. Some sidebands of unknown origin are visible, and the noise floor now has a peculiar sculpted appearance. This modulation of the noise floor was not apparent with the 19.1kHz tone in fig.2, which was taken with USB data. Repeating that test with S/PDIF data, I got a similar noise-floor modulation to that seen in fig.8.

Fig.7 NAD D 3020, headphone output, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit data from MacBook Pro via USB (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

Fig.8 NAD D 3020, headphone output, high-resolution jitter spectrum of analog output signal, 11.025kHz at –6dBFS, sampled at 44.1kHz with LSB toggled at 229Hz: 24-bit data from MacBook Pro via TosLink (left channel blue, right red). Center frequency of trace, 11.025kHz; frequency range, ±3.5kHz.

Whereas the original 3020 used a conventional output stage, based on a complementary pair of 2N2055/MJ2955 bipolar transistors, the D 3020, as its name implies, is a class-D design, and so produces ultrasonic noise that would overload the Audio Precision's input circuitry. I therefore performed most of the tests of the D 3020 as a power amplifier using, ahead of the analyzer, an Audio Precision AUX-0025 passive low-pass filter, which eliminates noise above 200kHz. (Without the filter and with no signal, there was 140mV of ultrasonic noise with a center frequency around 485kHz present at the NAD's speaker terminals.)

Assessed at the speaker outputs, the D 3020 offered a modest maximum gain for line-level sources of 33.8dNB and was non-inverting. The input impedance ranged from 14.3k ohms at 20Hz to 11k ohms at 20kHz; the output impedance was around 0.15 ohm at all audio frequencies, resulting in a modulation of the amplifier's frequency response of less than ±0.15dB with our standard simulated loudspeaker (fig.9, gray trace). The response was –0.5dB at 20kHz, above which it rolled off sharply. (The headphone output was flat to 200kHz.) Commendably, the response didn't change at different volume-control settings, and switching the Bass equalization into circuit gave a boost of just over 6dB, centered between 70 and 80Hz, with a sharp rolloff below that region (fig.10). The D 3020's reproduction of a 10kHz squarewave with the Audio Precision low-pass filter in circuit was well defined, with just the slightest hint of overshoot on the leading edges (fig.11).

Fig.9 NAD D 3020, volume control set to maximum, frequency response at 2.83V into: simulated loudspeaker load (gray), 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta), 2 ohms (green) (0.5dB/vertical div.).

Fig.10 NAD D 3020, volume control set to –20dB, frequency response at 2.83V into 8 ohms with Bass EQ activated (left channel blue, right red) and inactive (left green, right gray) (2dB/vertical div.).

Fig.11 NAD D 3020, small-signal, 1kHz squarewave into 8 ohms.

Channel separation was >80dB in both directions below 1kHz, while the unweighted, wideband signal/noise ratio, ref. 1W into 8 ohms and taken with the volume control set to its maximum, but the input shorted and with the AP filter in-circuit, was an excellent 80.2dB; this improved to 91.3dB when A-weighted. Fig.12 shows a spectral analysis of the low-frequency noisefloor.

Fig.12 NAD D 3020, spectrum of 1kHz sinewave, DC–1kHz, at 1W into 8 ohms (linear frequency scale, 0dB ref. 1W).

Figs. 13 and 14 show how the percentage of THD+noise in the NAD's output changed with output power into 8 and 4 ohms, respectively. The minimum distortion level was low, and the D 3020 clipped (defined as when the THD+N reaches 1%) at 58Wpc into 8 ohms (17.6dBW) and 68Wpc into 4 ohms (15.3dBW). These two graphs reveal that the actual distortion is buried beneath the noise floor at levels below a few watts. I therefore examined how the THD+N percentage changed with frequency at 9V, equivalent to 10Wpc into 8 ohms or 20Wpc into 4 ohms. The result (fig.15) revealed no change in the distortion at different frequencies, a commendable result.

Fig.13 NAD D 3020, distortion (%) vs 1kHz continuous output power into 8 ohms.

Fig.14 NAD D 3020, distortion (%) vs 1kHz continuous output power into 4 ohms.

Fig.15 NAD D 3020, THD+N (%) vs frequency at 9V into: 8 ohms (left channel blue, right red), 4 ohms (left cyan, right magenta).

The distortion at lower powers was primarily the third harmonic (fig.16), with the second harmonic becoming predominant at higher powers (fig.17), though lower-level, higher-order harmonics are also present. Intermodulation distortion was also low, even at a level a few dB below visible waveform clipping (fig.18).

Fig.16 NAD D 3020, 1kHz waveform at 10W into 4 ohms, 0.014% THD+N (top); distortion and noise waveform with fundamental notched out (bottom, not to scale).

Fig.17 NAD D 3020, spectrum of 50Hz sinewave, DC–1kHz, at 35W into 4 ohms (linear frequency scale).

Fig.18 NAD D 3020, HF intermodulation spectrum, DC–30kHz, 19+20kHz at 23W peak into 8 ohms (linear frequency scale).

I was impressed by the NAD D 3020's technical performance. It packs a usefully powerful amplifier into a tiny package, and offers digital performance that is close to the state of the art, though its USB input is to be preferred. In fact, the only problems I had with this little gem was that the touch switch on its top panel, for bringing the amplifier out of and into standby, didn't always respond. And the first time I tried disabling the Bass boost with the tiny rear-panel pushbutton, the D 3020 locked up and wouldn't respond to any commands, necessitating a hard reboot.

Stephen Mejias concluded his original review of the D 3020 by asking, "Will [the D 3020] be the component that introduces a new generation of music lovers to true high-fidelity sound?" I'd like to think that the answer to that question is "Yes!"—John Atkinson

NAD Electronics International
633 Granite Court
Pickering, Ontario L1W 3K1
(905) 831-6555

tonykaz's picture

Mr. Mejias,

You've pretty much surrounded every detail of 3020's impressive accomplishments.

I recall the LINN dealers using it to break people into a quality audio experience, driving their version of the LS3/5a ( KANN ) explaining the first importance being the Turntable.

I probably owned half dozen of these things over the years, brought as trade-ins ( to my Audio Salon: Esoteric Audio ) for Conrad-Johnson or perhaps Electrocompaniet or some other items.

I'd set them up in a little system and sell em within a week or so, people still love them today, as far as I can tell.

I don't recall there being anything great about these things, they did work well, sounded presentable, were entry level priced, didn't fail requiring service, they were probably the best value in Consumer Audio, they were and still are "reliable". Well, what more could you ask for?: Plenty!

The 3020 acted as a Gateway Drug into Hi-End, into VPI Turntables, Koetsu Phono Carts., MIT 750 Cabling Systems, Full-Range ( power hungry ) Dynamic Speakers with 10" woofers, Magnaplaner MG-3s, Pre-amps and Pre-amp upgrades, Amps and then Reference Amps, Seffield Labs Records ( r.i.p. Doug Sax ) and Reference Recording Records and then ( don't make me say it ) VTL Super Amps and Wilson speakers ( oh-my-gosh ).

A whole bunch of the above began with the lowly 3020!

When people chose the 3020 instead of a Pioneer Receiver they made a choice to pursue music as their Hobby.

These are the people that read Absolute Sound and HP, they chose Belt Drives over JVC direct drive turntables.

The 3020 was the place where the music road split into two different directions. Lots more folks chose the Pioneer road but plenty went the 3020 direction: the "High" road, I'm still on this road today, headphones for me and Schiit instead of 3020 or D-3020.

Nice to read this reporting, you bring back memories.

Tony in Michigan

ednazarko's picture

I had a 3020, purchased one of the first ones to show up at my local audio dealer. (Remember local audio dealers?) Seriously upgraded my college dorm room audio system. Thorens turntable, Tandberg reel to reel deck. I always felt like it had more power than its rating, drove several different speakers including a set of original Advents. Led to several progressively more costly and powerful upgrades, eventually to an NAD power amp and tuner/preamp setup driving a double-Advent tower. But i couldn't let the 3020 go, until it just seemed silly to keep it around unused, about 1998. Well after the Thorens and Tandberg units were abandoned. My audio system addiction continues, continuing at the same level of "really, is this what I SHOULD be doing with this money?" that underpinned my purchase of the 3020.

Reading this review has gotten me thinking about the new 3020 to drive a system in another part of the house where we currently rely on listening to system in an adjacent room. I'm thinking, nice efficient set of open baffle speakers that will love 30wpc, fed streaming audio from a Logitech Touch.

I do wonder at the new 3020D including a DAC and Bluetooth. There seems to be a tendency to design "all in one" kinds of systems. Could the audio stage have been made better with the $$ spent on including a DAC that's probably competent but not great? I've experienced this in a few products the last 10 years, where compromises in the quality of a function were made in the service of cramming in one of everything, and in a couple of cases those quality compromises ended up being unacceptable. I'd end up A/B comparing the Touch's rendering against that of the 3020D. The Touch (one of three I have, plus two Transporters) has won a couple of similar competitions with integrated amp/DAC combinations.

The essence of what made the original 3020 great was that it was stripped down. To a college student (acting major to boot, can there be any student less financially sound?) it seemed that they were being smart about what they did with the money they were taking from me. My one bit of hesitation on the 3020D is exactly that. Am I buying the best $500 integrated amp, or a compromise of amp and DAC? But I am probably not a good representation of "the market".

Anyway, good job NAD. Since 1978 I've loved you and periodically, when my addiction hits, blamed you...

fetuso's picture

I've had the D3020 for about a month now and I love it. Maybe I'm missing something, but the remote isn't the problem many have made it out to be. There are six buttons of consequence and I had their locations memorized in about 2 minutes. I don't think I've actually had to look down at the remote in weeks. It's ridiculously simple and it fits nicely in the hand.

Actually, the remote is a harbinger of the unit itself in that it is elegantly simple and couldn't be easier to live with. Like I said, I've had it for a month and I have yet to look at the owner's manual. I read the manual on line before I purchased it and haven't looked at it since. The touch buttons are easy to operate, but occasionally it does fail to respond as I expected and I need to press it again. No big deal. It's a quirk of the device that I find kind of charming. Anyway, I mostly use the remote.

Overall I'm very happy with the D3020 and I hope to enjoy it for years to come.

tonykaz's picture

Right there is all the review any normal person needs.

Thanks for pitching-in here.

Tony in Michigan

olc's picture

I'm also happy overall with my D3020 but there are some annoying things. Sound-wise it's good with all the speakers I've thrown at it, a wide variety of them with a $500 budget (this is for my bedroom). It has plenty of inputs, and I got to put away my aptX Bluetooth receiver. But some of the ergonomics are not up to what one would expect. The front penal is just an array of lights indicating volume and input selected, and not touchscreen. The on/off touch control is fussy, requiring 2 or 3 attempts to get it to do its thing. The volume control is cheesy and the volume increases much with even a small twist. The black-on-black remote can't be seen except in strong light, especially a problem in the bedroom (but NAD is now distributing the D3020 with a white-on-black remote and if you call and push for it they will send you one). The better solution is a Harmony remote because you can directly select inputs from it.

Ergonomically the D3020 is a mess, but the performance and features outweigh that. I'm keeping it.

wadeh911's picture

Several years ago I ditched my Yamaha receiver to move up into the separate component world of Classe Parasound get the point. When that happened I lost my source and amp for my patio speakers as I didn't have the room in my rack. So my wife and i have been using bluetooth wireless speakers paired with either my iPhone or iPad streaming Pandora. Yesterday in our backyard with Yuengling Lights, we found our beach. Even the music from our new Bose Bluetooth speaker was thumpin, and then I walked back into the family room where my B&W 803 Diamonds were playing Led Zeppelin. Something had to be done.

I remembered reading a couple of Stereophile reviews about some of the small 2 channel class D receivers like the Sprout and the D3020, that offered bluetooth. So I dug up the old issues on Zinio and did some more reading. The D3020 seemed perfect except it was missing an ethernet connection as I detest dropouts, plus I needed DLNA compatibility to use JRiver to stream my digital music to it as a Renderer. JA's excellent technical measurements of the D3020 gave me the confidence the D7050 would be at least equal.

But at $795 for the D7050 new, I tried my best to find it used on Audiogon and ebay with no luck. Finally found a Reconditioned unit with factory warranty for $595 and bought it. Can't wait for the D7050 to arrive so I can fire it us. Thank you Stereophile for your good equipment reviews. I get my Stereophile in the mail, but really like the Zinio electronic subscription for back copies or when I'm traveling.

Would love to see NAD D7050 get a full review as it really seems to fit a need with all digital inputs and all wired and wireless interfaces.

partain's picture

I've had my D7050 for a year now , it sounds awesome , but the remote will ruin your day.
My problem is that I cannot find out if there's a way to add MQA processing to this amp. Can you bypass the internal DAC ?
I listen to TIDAL , to me the MQA sounds good. I want to get the full decode.

shorewalker's picture

I'm impressed that Mejias and Saglio both experienced a version of the NAD 3020 with a variable loudness control. I had no idea such a thing existed. My 7020e receiver variant from 1988 doesn't have one. Actually, I can't find a photo of a 3020 that had one either. I always see just four knobs: bass, treble, balance, volume.

Are people somehow confusing it with the Yamaha CR-3020 that had such a control?

FWIW, the 7020e - basically a 3020e with a tuner - still sounds terrific to me at 30 years of age. It's been in use all that time and not a thing has gone wrong. It's also easy to operate one-handed, since all the controls are easy-press physical buttons or easy-turn knobs.

I have it paired with NAD 8020e speakers which were made by KEF, and plugged into my computer. After three decades, I'm adding a Dragonfly DAC. It seems possible that this lot can make their half-century. The return on investment has been extraordinary.

I hope the D 3020 can do as well, and I would love to buy one, but sadly NAD has provided me no excuse to do so.

vicsay's picture

Great review!

I'm interesting to buy a D3020 for a pair of KEF Q100, but I'm afraid about the 20w :( if is enough power, also I have reading that the C316BEE is a good option from NAD, but what about the sound quality between these two Amps. Can you help me? Many thanks!