Mis à jour le 26 February 2019.
This week, we decided to try the new Denon PMA-50 integrated amplifier. A 2×50 W amplifier which stands out for its design (very different from what the Japanese brand is used to) as well as for its digital architecture. On the menu: USB port, Bluetooth apt-X & NFC, optical and coaxial digital inputs, decoding of PCM stream up to 24 bits / 192 kHz, Denon AL32 technology and even 2.8 and 5.6 MHz DSD decoding. The Denon PMA-50 has no equal within its range.
Denon PMA-50: what type of use?
The PMA-50 was designed to play DSD, studio and CD quality audio files via its USB port or stored on a computer. This device will definitely be of great interest to people who like to listen to Deezer, Spotify, Quobuz, Youtube or any other online streaming service as well as MP3 or FLAC files stored on their computer. The optical and coaxial digital inputs allow you to use the Denon PMA-50 with an HDTV or a CD player, for example. The analog input can be used to connect a portable source and the Bluetooth controller lets you listen to music streamed wirelessly from a smartphone or tablet (a very convenient way to listen to a web radio or online streaming service).
Denon PMA-50: which type of speakers?
On paper, the Denon-PMA-50 is no overly powerful beast. If this amp delivers 2×50 W at 4 Ohms and 2×25 at 8 Ohms, these measurements are at 1 kHz and we can imagine that the amplifier would deliver 2×20 W at 8 Ohms with a wideband signal (ranging from bass to treble). At first glance, its power seems to be rather modest. Nevertheless, these numbers can be interepreted differently and we can observe that power doubles between 8 and 4 Ohms, which is a rare thing and a sign of an excellent power supply. We ran our tests using Klipsch Heresy III speakers, which are equipped with a 30 cm bass driver and never did the Denon PMA-50 show any sign of weakness or confusion (we will come back to this point). Clearly, this amp can work with both compact speakers and demanding floor-standing models.
Denon PMA-50: CSR, signal loop and Denon AL32
When the CSR brand is mentioned,we can’t help but think about the Bluetooth apt-X codec which the society designed. A lesser known fact is that the CSR also builds digital amplification modules and this is exactly what Denon used for the PMA-50. There is no DAC in the PMA-50, which is completely different from most amplifiers featuring digital inputs. The entering digital signal (16 bits / 44.1 kHz, for example) is not converted to audible sounds then amplified. The digital stream is converted to PWM signals, modulated in intensity by the CSR chip before being filtered by small components placed in the output stage.
The signal is preserved in its digital state from start to finish, which results in an incredibly precise sound.
But there’s even more: a signal loop is created in order to compare the amplified signal which is delivered to the terminal (unavoidably altered due to the electrical properties of the speakers) to the incoming signal. To do so, the amplified analog signal is digitized then compared to the incoming digital signal (via USB, S/PDIF, Bluetooth, etc.). If there are any differences, the incoming signal is adapted in order to make up for the differences with the output signal.
This amplifier also features the Denon AL32 technology, which conducts an upsampling of incoming PCM digital signals (16/44, 16/48, 24/96, etc.) into 32 bits and 192 kHz, in order to make the signal more accurate in high frequencies. This process can be deactivated by selecting the Direct Source mode in the Denon PMA-50’s menu. This process is not applicable to DSD signals or PCM signals coded in 192 kHz. Finally, all digital inputs are filtered in order to get rid of any possible noise (especially with the USB port) and a pair of synchronisation clocks ensure optimal stream transmission from any connected source.
Denon PMA-50: setup and handling
Installation is rather easy due to the compact size of this amplifier, which can be placed horizontally or vertically (all there is to do is to move the rubber feet from the bottom panel to the side panel). On the back panel are the digital and analog inputs, the active subwoofer output (filtered) and the banana plug compatible screw terminals. The front panel features a 6.3 mm headphone output, an endless potentiometer, an input selector, a Bluetooth activation switch and an on/off button. The Denon logo is not on the front panel but is displayed by the TFT screen. The screen rotates in accordance with the amplifier’s orientation and features three brightness levels (which can be selected via its remote control). Each selected source is represented by a logo and a line of text. The format of the audio stream is systematically indicated, whether it is PCM or DSD.
Denon PMA-50: what we liked
The enjoyable, large potentiometer as well as the nicely textured brushed aluminium finish. As regards its specific use: the progression of the sound level. Regardless of the input, it is possible to adjust the volume in an extremely precise way up to – 80 dB. A very convenient feature for late night listening. We also liked the ultra-swift source change, the tone correction and the gain selection for the headphone output, which allows you to power a set of hi-fi headphones such as the Sennheiser HD-800 with absolutely no difficulty. Finally, we also liked the fact that the type of incoming stream as well as its resolution were displayed.
Denon PMA-50: listening configuration
We mostly used the Denon PMA-50 along with a pair of Klipsch Heresy III speakers. Our sources were an HDTV, a CD player and a computer on which we stored MP3, FLAC and DSD files (we also listened to Deezer). The speaker cables were pre-assembled Audioquest StarQuad Type 4, the USB cable was an Audioquest Carbon USB, the optical cable an Audioquest Vodka and the coaxial RCA cable was a Viard Audio S/PDIF Premium HD.
Denon PMA-50: listening impressions
We were thrilled! The Denon PMA-50 stands out by offering fantastic clarity with every sound level, a great sound stage density (even at low level) and a capacity to keep up without any compression or aggressivity as we turned the volume up. The sound never gets sloppy or stifled. This applies to all audio formats, from Deezer to our DSD files. Voices are smoothly extracted without putting too much emphasis on the mediums. For example, when listening to Massive Attack’s Karmacoma, the voices of the two singers are perfectly distinct. This is no easy task considering that the rhythm section as well as the bass are very important in this track, which makes for a difficult sound restitution. The PMA-50 is incredibly easy going and powers the Heresy III’s 30 cm driver with no effort. When listening to Depeche Mode’s Enjoy the Silence (live in Barcelona, FLAC 16/44), a complex track in which instrument placement is difficult, the Denon PMA-50 confirms this feeling of an effortless amplifier. The listening experience is always wholesome, regardless of the source.
Deezer: we listened to a little bit of everything on the free version of the online music streaming service, thus with a very compressed stream. So be it, except for a slight lack of dynamic and a limited response in the high frequencies, it’s quite easy to spend a few hours listening to music. Jazz, classical music, pop music, everything sounds good. The USB connection is obviously well under control.
FLAC 16/44 and 24/192: the change in quality is instantaneous, bass is more firm and high frequencies much clearer. The Qobuz version of Random Access Memories by Daft Punk is very punchy and refined, even at high level.
DSD 2,8: the sound aesthetic changes all of a sudden. Music sounds more peaceful (although dynamic and lively), the medium is slightly in the back but very well integrated.
Dolby Digital (to stereo PCM): films or concerts, although very compressed with digital TV, are delivered by the PMA-50 with an exemplary articulation. There is nothing this amp can’t do.
Using the USB input correctly
The Denon PMA-50 features a type B USB port (slave) in order to allow any computer (as well as some NAS) to use it as an external sound card. With a Mac, all there is to do is plug the amp and choose it as an audio peripheral device. The same goes for Windows, except that it is necessary to install a driver provided by Denon. Good to know: the Windows audio mixer can deliver 16 bits / 44.1 kHz stream to the Denon PMA-50, which is ideal for listening to Deezer, MP3 or CD quality files. Yet, be careful, any audio file with a superior resolution (24 bits / 96 kHz for example) will be undersampled to 16 bits / 44.1 kHz. This limitation is not due to the Denon PMA-50 but to the Windows audio mixer. In order to bypass this issue, it is possible to use an audio player software able to comunicate directly with the Denon driver without going through the Windows mixer, such as Foobar2000 or JRiver Media Center. As the resolution of the PCM and DSD stream transmitted to the Denon PMA-50 is displayed by the amp, it is simple to check that your computer is properly set up.
Real-time DSD conversion via USB: a real asset
As the Denon PMA-50 is able to handle DSD stream up to 5.6 MHz, we wanted to see if there were any benefits in transmitting our CD quality FLAC files transcoded in DSD. To do so, we used Foobar2000 and JRiver Media Center. The Foobar2000 plugin which allows this operation (foo_input_sacd-0.7.7) offers 4 DSD conversion filters, the one called DSM Type D (FP32) being, according to us, the best. The improvement is obvious, the sound message is undoubtedly smoother.
Denon PMA-50: conclusion
This small digital amplifier has quickly become a firm favourite of ours. It features all the necessary inputs to listen to both digital and analog music, in any existing format. Bluetooth reception (we only tested it with AAC files) is satisfactory and the pairing by contact with a smartphone (NFC technology) is very convenient. If you are looking for a new way to listen to music, with a transparent sound signature, this amp will absolutely grab your attention. Whether you use it with compact speakers featuring small drivers or generous floor-standing speakers, this amplifier is a real success.