Expert review and test of the Pioneer A-70DA-K Integrated Amplifier by Australian Hi-Fi Magazine. Free pdf download included.

Pioneer’s merger with Onkyo two years ago (Pioneer sold its audio division to Onkyo in 2015 in exchange for a 14.95 per cent stake in the merged company) has resulted in the appearance of dozens of new Pioneer stereo hi-fi components, establishing the company’s strongest two-channel line-up in many years.

The A-70DA-K amplifier reviewed here is a fine example: it’s the top-of-the-line model in a range of five new two-channel amplifiers that kicks off with the A-10 ($599) and then steps up through the A-20 ($699), A-30K ($899), and A-50DA-K ($1,499) before culminating in the A-70DA-K. There’s even a pair of small two-way loudspeakers (Pioneer SBB22LR) designed by none other than Andrew Jones. According to Powermove, all five amplifiers use Class-D output stages.

It is important that you should not confuse the A-70DA-K reviewed here with the Pioneer A-70—they are completely different amplifiers. Why Pioneer would use similar model numbers for completely different—but related—products is baffling, because it confuses consumers, retailers… and even distributors.

The Equipment

The Onkyo merger certainly hasn’t changed the look of Pioneer’s amplifier range, all have the same ‘classic’ look, and it’s a look that’s barely changed since the 1970s, when Pioneer amplifiers were the biggest-selling and most popular in the world. What that means, however, is that there is no front-panel display of any type. Mostly one could argue whether an amplifier needs a front-panel display at all, but in the case of the A-70DA-K, the letter ‘D’ in the model name means that it has an onboard digital-to-analogue converter (with USB, coaxial and optical inputs), so a display would have been useful to show the quality level of the signal being processed (sampling frequency, bit-depth and so on. (Digital processing is accomplished using an ESS Sabre32 ES9016S DAC that supports up to 384 kHz LPCM and 11.2 MHz DSD.)

The ‘classic’ look extends to the Pioneer A-70DA-K still having ‘classic’ controls, this time evidenced by the rotary bass, treble and balance controls on the front panel, just to the left of the rotary volume control. Unless you have 20:20 vision you might have some difficulty working out what these controls are, because on my sample, which had a black finish, Pioneer used grey lettering to identify all the controls, and I found this lettering very difficult to read. It’s easier to read the lettering on the version with the silver finish but this model is not available in Australia… Powermove only brings in the black versions of Pioneer’s A-Series amplifiers.

Also ‘classic’ is the provision of a loudness control, used to deliver bass and treble boost when listening at low volume levels, which is supposed to deliver a sound that’s ‘more natural to the ear’ when listening at these low levels. Recent research has shown that the sound is not more natural as a result of this artificial boosting (see article HERE), but many people still like the sonic result of the loudness contour, so I can see why Pioneer has still included one. Indeed the company indicates this in its manual, which says nothing about ‘natural’ sound, but does say: ‘Boosts low and high frequencies to give added punch to playback even at a low volume level.’  It also says that the control: ‘should normally be left in the off position.’

Input selection is also by a rotary selector, and it has positions for Balanced, Phono, SACD/CD, Network, Line 1, Line 2, USB, Coaxial, Optical. As you rotate the selector through these positions, corresponding blue LEDs light up to indicate your selection. I was rather intrigued that our sample had the LEDs in two rows, with six LEDs on the top row and three LEDs in the bottom row. I was intrigued because I found this a rather ‘inelegant’ way of doing it. So I was not too surprised when I discovered that another Pioneer model, one that is only available overseas—the Pioneer A-70—has its LEDs in a single line, but there are only seven of them, with no room to add an extra two. So it would appear that rather than do a total re-design of the front panel for the A-70DA-K model, Pioneer has simply re-jigged it.

All other functions on the Pioneer A-70DA-K are provided via pushbuttons which, when activated, show they are active by having a blue LED light fitted to the button illuminate. These controls are for speaker selection (Speakers A or Speakers B, or both… or neither), phono cartridge selection (MC or MM), Power Amp Direct (for use in AV systems), Attenuator, Direct (bypasses the tone, balance and loudness controls), Loudness (On/Off), and Power (On/Off). The power control has an additional LED alongside it to indicate the status of the Pioneer’s automatic stand-by circuit.

Automatic standby (which by default is switched ‘On’ on the A-70DA-K) means that the circuitry monitors whether the Pioneer is playing a music signal, or if one of the front panel controls has been adjusted. If, after 30 minutes, it has not detected an audio signal or a control movement, the amplifier automatically switches itself to stand-by mode. This circuit is apparently required to be fitted to all amplifiers sold in Europe. You can manually disable it by pressing the APD (Automatic Power Down) button on the remote control or, if you’ve mislaid the remote, by simultaneously pressing and holding both the Power and Loudness buttons on the front panel for three seconds.

The remote control provided with the Pioneer duplicates all the front panel functions except for bass, treble and balance, and adds a ‘Mute’ function, the aforementioned APD function, and a button that allows you to adjust the brightness of all the LEDs fitted to the pushbuttons on the front panel. It also provides transport control buttons that will work with compatible Pioneer CD and SACD players as well as Pioneer Network players.

As you have probably guessed from the ‘Balanced’ designator on the input selector, the rear panel of the Pioneer has a set of balanced line level inputs (via XLR). All other inputs are unbalanced (via gold-plated RCA terminals). Although the A-70DA-K has both moving-magnet and moving-input circuits, they’re both accessed via the same pair of RCA terminals on the rear panel, so you can’t connect two turntables (or arms) simultaneously. There’s also a line-output, using RCA outputs (also gold-plated).

The Pioneer A-70DA measures 435×142×370mm (WHD) and weighs 17.2kg.

In Use and Listening Sessions

Just in case you were wondering about Pioneer’s reference to ‘Guaranteed Impedance 4–16Ω’ I can’t actually be certain of what it means, as I’ve never seen it before in a specification, but I assume that it means that Pioneer is saying the amplifier will perform according to specification with all speakers with a nominal impedance falling in the range between 4Ω and 16Ω.

I assume it’s saying this because the A-70DA-K has a Class-D output stage, and whereas the performance of amplifiers using Class-AB output stages is relatively constant irrespective of loudspeaker load (except for power output and distortion), the frequency response of some amplifiers using Class-D output stages can vary significantly depending on the impedance of the speakers connected. I am assuming that Pioneer is saying the output stage of the A-70 DA-K is load-invariant. However you should note that if you connect speakers to both the Speakers A and the Speakers B terminals and you plan on using both pairs simultaneously, both speakers MUST have a nominal impedance of 8Ω or more.

The Pioneer A-70DA-K was able to drive my reference speakers, which have a nominal impedance of slightly greater than 8Ω, and a below-average efficiency of 86dBSPL, to more-than-acceptable volume levels in my listening room, which is larger than the ‘standard’ main room in most Australian free-standing houses, which means that unless your own listening room is huge, you won’t need more power than the Pioneer is able to deliver, particularly if your speakers are more efficient than mine (which is highly likely!).

I was interested by the ‘Attenuator’ button, which Pioneer’s Owner’s Manual says you should: ‘Press when you wish to make fine adjustments to the sound volume when playing at very low sound volume levels.’ It appears that its sole function is to enable you to move the volume control further in order to get the same increase (or decrease) in volume you’d achieve from a smaller rotation without the circuit activated. The Attenuator also has the effect of limiting the maximum volume level, so that with the circuit on, and the volume control at maximum, the sound level in my room was only moderate. Although I could see how this decreased sensitivity might be useful if you had some medical issue that limited the use of your fingers, such as arthritis, I can’t see that the circuit is particularly useful if you aren’t so afflicted. Try it and see for yourself is all I can suggest. However, if you are playing music with the volume maxxed out and the attenuator on, make sure you turn the volume down before you switch the attenuator off, otherwise you could blast your speakers with high-volume sound, which could have the potential to damage them.

I was also interested by the operation of the loudness control, whose action is supposed to be dynamic, with Pioneer saying: ‘when sound volume is raised, the amount of change produced by the loudness control is reduced.’ When listening, I thought the amount of change remained the same, but perhaps the difference is subtle, or happens at higher levels than I was using when trialling the loudness control’s action. Either way, I’d suggest that if you want to adjust the bass and treble to your preference at a particular volume level, you should instead use the bass and treble controls rather than the loudness contour function… not least because you’ll get more precise control this way.

I found the sound quality of the Pioneer A-70DA-K to be outstandingly good. I started using the moving-coil phono input, and found the noise levels of the phono circuit far lower than the levels of noise from both the LPs I played and from the turntable itself, and the frequency response was linear and very extended, so the RIAA accuracy of the phono stage is obviously spot-on. When I replayed the same LPs, using the same turntable, but using a moving-magnet cartridge rather than a moving-coil, I noted the same low-noise, and extended bandwidth traits, plus I found I could not overload the input, even with my most dynamic LP (my Telarc recording of Tchaikovsky’s 1812 Overture), so Pioneer has done a good job here.

The sound quality of the Pioneer A-70DA-K was far superior when playing CDs and SACDs: I found the bass lines were tighter and more impactful, extending more deeply and more solidly into the very lowest frequencies with a much greater sense of ease and the cannon-fire on the CD version of Tchaikovsky’s 1812 was more realistic than what I’d heard from the LP version. The clarity of the Pioneer’s performance also made it easier for me to hear musical lines, such as on Aimee Mann’s album ‘The Last Remains of the Dodo’, where it suddenly became quite easy to hear the quiet guitar towards the conclusion of How Am I Different? Also, just listen to the bass drum on Polly Come Home, from ‘Raising Sand’ (Robert Plant and Alison Krauss) to hear exactly what I mean about the Pioneer’s high levels of performance.

Midrange sound was also a model of clarity and precision. Pink Floyd’s Breathe Air, from DSOTM, can sometimes sound confused, with all the different sounds being conglomerated into a mass that just sits in space. The A-70DA-K was able to separate the different sound effects and spread them realistically across the sound stage, so they could each assume their own distinct sonic signature. Another ear-opener was the sound of Carole King’s mezzo-soprano vocals on ‘The Living Room Tour’, which are reproduced beautifully, but also listen to how the Pioneer A-70DA-K can separate out—yet simultaneously merge—King’s voice with that of her daughters Louise (on Where You Lead I Will Follow) and Sherry (on You Make Me Feel Like A Natural Woman). For male vocal (plus piano!) try Elton John’s We All Fall in Love Sometimes/Curtains from Captain Fantastic and the Brown Dirt Cowboy. The richness of the sound is truly sumptuous.

I found the Pioneer A-70DA-K’s ability to deliver dynamics was super-impressive, easily demonstrated by most of the tracks on Junior Mance’s ‘Harlem Lullaby’… at least those on which he plays piano—I can’t imagine what inspired him to use a harpsichord as a jazz instrument! (This is not Mance’s best album, by a long shot, but it is one of the best-recorded.)

Conclusion

If you don’t need a moving-coil phono stage or a balanced input and you can do without the Attenuator function, you can save yourself around $500 by opting for Pioneer’s A-50DA-K, which is identical (except for not having these features!) but if you do need them, the additional cost is less than you’d have to pay to get these features by adding external components.

But whichever amplifier you decide on, you can rest assured that you’re buying a very solid, very well-built, high-performance integrated amplifier (with on-board DAC) the appearance of which on the market bodes well for a return of the brand to its former glories. #

Manufacturer: Pioneer Electronics

Laboratory Test Results

Pioneer’s primary main power output specification says the A-70AD-K is rated at 90-watts per channel, but if you look at the fine print, you’ll find that this is only when the amplifier is driving 4Ω loads and with a fairly high level of distortion (0.5%). Pioneer does state an 8Ω figure (60-watts) but this was obtained under the same test conditions. Newport Test Labs’ rather more stringent testing regimen, which uses the Australian standard for power output, has the Pioneer A-70DA-K meeting its claimed power output only at midrange frequencies and above, into either 4Ω or 6Ω loads. At 20Hz, the amplifier delivered only 53-watts into 8Ω loads (both channels driven) and 80-watts into 4Ω loads (again BCD). Single-channel driven, the amplifier’s output exceeded its specification by a goodly margin, with a minimum of 98-watts (and a maximum of 111-watts) into 4Ω, and a minimum of 65-watts (and a maximum of 68-watts) into 8Ω. The amplifier was also tested into 2Ω loads (for which it’s not rated at all), under which condition the A-70DA-K delivered more than 100-watts, both channels driven, right across the audio spectrum. All these results are shown in the tabulated chart below.

Separation between the channels was excellent, producing near-100dB figures across the low and midrange frequencies, and dropping down to 87dB at 20kHz. Channel balance was also excellent, at 0.058dB at 1kHz.

Distortion at an output of one watt into either 8Ω or 4Ω loads was very low. Graph 1 shows distortion at one watt into an 8Ω load and you can see there’s just a single second harmonic distortion component at –93dB (0.00223%), a third harmonic at –103dB (0.0007%) and a fourth at –105dB (0.00056%). That’s all. On this same graph you can see that the overall noise floor is more than 110dB down, though the noise increases at very low frequencies, as evidenced by the noise being at around –90dB at the extreme left of the graph.

Distortion at one watt into 4Ω was very similar to the result at 8Ω, with the second harmonic essentially at the same level, the level of the third harmonic increasing to –100dB (0.001%) and the level of the fourth harmonic to –103dB (0.0007%). The level of the noise floor increases very slightly, but not so much it would be perceptible. The overall THD+N figure measured by Newport Test Labs was 0.024%, well below the level of audibility.

At rated output distortion increases considerably into both 8Ω and 4Ω loads, as you can see from Graph 3 (60-watts into 8Ω) and Graph 4 (90-watts into 4Ω), but this increase is normal for all amplifiers. Into 8Ω, the second harmonic distortion component is at –75dB (0.01778%), the third at –80dB (0.01%), the fourth at –105dB (0.00056%), and a fifth at –108dB (0.00039%). As you can see, other higher-order harmonic distortion components are visible, but they’re all more than 110dB down, so each contributes less than 0.00031%, and although they’re visible, they would certainly not be audible.

Intermodulation distortion was very low. Graph 5 shows CCIF-IMD and on it you can see the two test signals at 19kHz and 20kHz just right of graph centre. There are only four sidebands, the first two (at 18kHz and 21kHz) are 87dB (0.00446%) and 88dB (0.00398%) down respectively, and the second two (at 17kHz and 22kHz) are around 105dB (0.00056%) and 102dB (0.00079%) down. Importantly, the regenerated difference signal (at 1kHz) is also more than 100dB (0.001%) down, which is also an excellent outcome.

The frequency response (Graph 6) measured by Newport Test Labs showed the Pioneer A-70DA-K’s Class-D output stage interacting a little with the 8Ω test load, resulting in a rise in the frequency response starting at 3kHz and peaking at 38kHz, but at you can see from the dB scale at the left of the graph, the total rise is less than 2dB, so across for the region encompassed by the graph, the frequency response was 5Hz to 40kHz ±0.9dB. Across the audio band, it was 20Hz to 20kHz ±0.5dB. As you can see from the wideband figures, the Pioneer’s frequency response extended to below 1Hz and was only 1dB down at 55Hz and 3dB down at 61kHz. (Pioneer specs the A-70DA-K with a response of 5Hz to 50kHz ±3dB, so Newport Test Lab’s results show the amplifier exceeds this specification by a long way)

Graph 7, which shows the action of the loudness control, shows that the amount of boost and cut delivered is the same at the two different volume levels measured, there being a 10dB difference in level between them. The action of the bass and treble controls, as shown in Graph 8, is greater than offered by most such controls, and exceeds specification, approaching 15dB of boost, in particular. The high-frequency boost does not appear to be shelved, which would have been better engineering practise.

Noise levels were very low, but the low levels measured are in part because due to the necessity to remove high-level, high-frequency switching signals generated by the Class-D circuitry, Newport Test Labs had to insert an AES-17 low-pass filter into the test chain in order to make the measurement. This means that the lab is essentially measuring only the noise within the audio band. With this filter in-circuit, the lab measured the signal-to-noise ratio at 74dB (A-weighted) referenced to an output of one watt, and at 100dB (A-weighted) referenced to rated output. Given the increase in popularity in Class-D designs, it would be easy to make a case for using an AES-17 filter when testing Class-AB amplifiers as well in order to level the testing playing field, because otherwise Class-AB amplifiers (which are typically measured without a filter in place) are having their high-frequency noise (above 20kHz) included in the measurements, effectively putting them at a disadvantage.

The high-frequency switching noise can be seen on two of the square wave oscillograms taken by Newport Test Labs (the others having been measured with the AES-17 filter in the measurement chain). There are two views of the Pioneer A-70DA-K’s square wave response shown for a 1kHz test signal. The one that shows a clean-looking square wave (though there’s an overshoot on the leading edge that indicates a peak in the frequency response well above the audio band) was measured with the low-pass filter in place. The other image of the same 1kHz test signal shows what the ‘raw’ output from the Pioneer’s Class-D output stage looks like before filtering. It is important to note that the high-frequency signal shown, although visible on the oscillogram, would be completely inaudible to the human ear, even if it were able to be reproduced by a loudspeaker system, which it’s not, because loudspeakers cannot reproduce such high-frequency sounds.

The 100Hz wave (low-pass filtered for clarity), exhibits a very slight tilt showing that the Pioneer A-70DA-K’s performance does not extend to d.c., but there is no bending that would show phase shift. The overshoot on the leading edge is as mentioned regarding the 1kHz square wave. The 10kHz square wave’s shape is affected both by the high-frequency peak and by the low-pass filter, which prevents the higher-order harmonics from ‘squaring-off’ the wave, so you’re not really looking at the performance of the Pioneer, but the performance of the filter used by Newport Test Labs. Performance into a highly capacitative load is excellent, with only a small amount of quickly-damped ringing, so the A-70DA-K will be completely stable, even when driving highly reactive loudspeakers.

Power consumption was very low, as you’d expect of a Class-D design, and the amplifier easily meets the new Australian standard for stand-by power consumption, pulling only 0.34-watts in standby.

Overall, Newport Test Labs’s suite of tests and measurements proved that Pioneer’s A-70DA-K is a very well-designed, high-performance Class-D integrated amplifier. # Steve Holding

The Pioneer brand name came into existence in 1937, when Nozomu Matsumoto built a dynamic loudspeaker he dubbed the Pioneer A-8, for a company he owned in Osaka called Fukuin Shokai Denki Seisakusho. The speaker was very popular, so in 1938 Matsumoto relocated to Tokyo and started a factory that repaired radios and speakers, as well as building loudspeakers. In 1951 he developed one of Japan’s first hi-fi loudspeakers, the PE-8, and in 1961 changed the company’s name to Pioneer Electronics. The company became world-famous in the early 70s as the result of its complete line of hi-fi systems, including loudspeakers and for its car stereo components. Towards the end of the 70s, Pioneer championed the laserdisc format, which preceded the DVD format, developing home laserdisc players, industrial players and complete karaoke installations using laserdiscs as the program source. In the early 90s, Pioneer diversified its business dramatically, moving away from audio components and introducing car navigation systems, projection televisions, plasma displays, satellite receivers, and DVD recorders, during which time it developed its famous Kuro Plasma television, regarded by most experts as the best in the world at the time.