A brief premise. I already know this small converter thanks to some posts and good reviews I have found on line. A couple of years ago I bought a second-hand one but I received it without the power supply and I noticed that, by shaking it, there was something moving inside. Obviously, the former owner had try some audiophile “experimentation”. Well, I opened it and saw that an op-amp had come off. I fixed it and plugged it to a wangled power supply. The first impression I had, was that the internal converter of my Trevi 3520 - in my garage system - was performing better. If you consider that it is a tough nut that employs the Crystal chip (same family of the 707’s), every hope of a sound improvement vanished immediately. However, I did not give up and changed the op-amp – a classic Burr Brown OPA2134 – with a National LM4562. I got a tangible improvement but it was not enough to push me to use the Trevi only as a transport. In the meantime, my brother was making some experiments with his Apple and streaming music. Thus, I lend it to him. Well, he got amazing performances and I gave it definitely to him with his great satisfaction.
End of the premise.
Now, after some time, I find myself reviewing a brand new exemplar distributed in Italy by Audio Azimuth/Playstereo, a real efficient and user-friendly organization. Maybe another story?
Let us see.
Well, what are we talking about? About the Super Pro 707 DAC USB, Digital/Analogue converter, small as a packet of cigarettes, provided of a wall-wart style power supply that outside is similar to those of the notebooks, but three times bigger than the DAC itself. This is why I call it little DAC, even if it deserves more respect… First, even if small, it has many connections: coaxial, optical, USB, a 3,5 mm mini jack headphone output and a mini jack stereo microphone input. Besides, the standard RCA analogue output plugs for the two stereo channels. The lucid finish is elegant and pleasing to the touch. Furthermore, there are three leds of different colour positioned where are the RCA sockets. One red is for the coaxial or high-res optical connection, which turns into a flashing blue for USB. Another one is green for the connection at normal resolution. In addition, to avoid any mistake, there is a power on LED with white light to illuminate the action area. The Super Pro company, with a good PCB (Printed Circuit Board) made in Philippines, has recently gained a certain reputation, among several Asiatic emergent hi-fi companies, thanks to this DAC, which has been sold with success all around the world. Strength points of this product are the reliability, the look and the good sound besides, last but not least, the low cost. The Chinese Pop Pulse takes care of the packing and the international commercialization.
Now let us cut straight to the significant part: the listening tests. I must say that this small DAC 707 needs a run-in of at least fifteen hours to grant an optimal performance.
And what a great state!
I cannot believe my ears!
The smallish performs great! I have tested three sources: CD player, netbook provided with Windows 7, Foobar and Asio4all, and a multimedia HD. With the CD player used as a transporter and through the digital coaxial connection, the sound was unexpectedly good, definitely better than with my old 707. But it is with the computer in USB configuration that I gave a start. Never heard this source performing so well in my home system, with any DAC I have tested before. Maybe it is just a question of ideal interface with the current settings of the netbooks but, actually, also with the multimedia HD with the optical output the performance is astounding.
Among the best things, there is some naturalness and an unusual soundstage also with 320 KB MP3 files, with WAV and FLAC, via USB from the netbook. This is the best result I have ever had with my system.
What is going on? What kind of implementation do they have made?
The most obvious thing is the power supply, a consistent switching Delta Electronics 12V 4A for computer use, provided with an IEC socket as input and a coaxial connector as output, plus a prisoner cable with ferrite core. But also the op-amp has its clout. Here we are talking about a very small irreplaceable LT1364 Linear Technology. Inside there are several differences if compared with the old and known 707. After all the review of the printed circuit has arrived at the 3.2se version. Well, evidently, at the Super Pro, people are keeping up with the times. Anyway, I am really impressed by the updated Super Pro 707 DAC USB.
Nevertheless, I have to stress the fact that the connection of the 707 causes a hum in the system that is perceptible only with low sound volumes, but present in any case. I think this hum comes from the power supply and appears on all the amp inputs. Therefore, it comes out from the network that receives something “dirty” from the connection of the cable-power supply-DAC system. I replace the power supply with a 5A stabilized linear one. Gotcha. With the new power supply there is no more hum. I test again the 707. Mm, after all I prefer this one even with the hum. The problem of the power supply is crucial. I have also asked the distributor for a new one. But the problem remains. I have also tried to insert the DAC in two different systems, both without earth by the way, but the slight hum persists. With another system with earth the problem is always present but less accentuated. However, as far as dynamics, rhythm, frequency extension and soundstage are concerned, this power supply is better than the other at my disposal. With not very low sounds level, I think is better using the original device but plug it off whether you intend to use another source.
A battery, if you do not get bother with recharging problems, could be a good solution. I have tried a 7A battery with lead gel: the sound was just less peremptory, mostly in the transients, even if clean and absolutely delicious and silent.
Anyhow, I decide to listen to the “original” configuration, maybe changing only the power cable with something more performing, like the old Pirelli Screenflex, now Prysmian, to stay on a medium price level. It is a very good listening experience with this polyvalent DAC 707 USB. Emerson Lake and Palmer are in my room inside a great scene… maybe too great, helped by the funny manipulations, overdubs and special effects.
Classical music, with a mix by Karajan, confirms a moving “presence effect” that contributes to please the sculptured, vigorous and intense performances of the German maestro conducting his faithful Berliners.
With the optical input coming from the multimedia HD is a real pleasure hearing the lossless files. Stan Getz and Bill Evans, supported by the great Elvin Jones on drums and alternatively by the bass players Richard Davis and Ron Carter, duet in sophisticated but catchy ways, with fast and involving rhythms, with a sharp separation of the instruments and a real correct tone, maybe just slightly limited in the low range. But it is with the netbook that I find, as I said before, the bigger surprise. A Violin Concert by Dvorak at 24 bit/96 khz makes me stand rooted to the spot for its majestic spatiality, the rise time in the attacks and the cleanness of the high range of the violin. This is the first time I hear the streaming music playing better than with any other source. And with a very small and concentrated DAC which cost is 129.00 euro!
The wonders of the technologic progress…
Now come the knotty points. Besides the hum, there is also a very poor user manual. Regarding the headphone socket, I have tested it, as usual, with the Sennheiser HD600: nothing special, just an adequate performance in comparison with the price of the device.
I suggest you not to save up on the quality of the cables. The object deserves something more than the provided cables, which are basic. Try to keep it stable maybe using some Blue Tack or Uhu Tac and similar stuff below the base. Watch out for the right direction of the plug.
In conclusion, although with the stressed problem mostly coming from the earth lack in the mains, the DAC 707 USB deserves an award, for its exemplar price/quality ratio, for its wide flexibility and for making possible good audiophile satisfactions without spending lots of money!
Just a piece of advice about the purchase: consider to buy a battery and charger if your mains is without earth.
Selection of listened music
Emerson, Lake and Palmer: The ultimate collection, double CD Sanctuary Records
Herbert Von Karajan: Dirige – Classica. Berliner Philarmoniker Orchestra. Double CD, Gruppo Editoriale L’Espresso
Stan Getz & Bill Evans: Stan Getz & Bill Evans, WAV file
Antonin Dvorak: Violin Concerto, E. Peinemann violin, Czech Philarmonic Orchestra, Dir. Peter Maag. Flac 24bit/96khz file
Official technical specifications:
D/A Receiver chip CS-8416, D/A converter chip, CS-4398 (24-192KHZ )
Dual LT1364C OPAMPS for analog output circuit
Optical digital input
Coaxial Digital Input
USB input (USB 1.0 and 2.0 compatible)
USB inputs runs direct I2S to D to A through CS 4398 chip resulting to better transparency and definition
CM-108 USB receiving chip
S/PDIF (RCA) Digital output active when USB is connected
S/PDIF (RCA) Digital input active when USB is *not* connected
Standard RCA analog output plugs
Output voltage ± 3.5V / 400mW
Audio output: 24bit/48khz (44.1Khz)
Dynamic range: 120dB
Signal to noise ratio: 107 dB
Equipped with: external power supply, USB cable, optical cable, RCA coaxial cable, cable for battery external supply.
Dimensions: 64x28x78 mm (WxHxD)
Official Italian dealer: to Audio Azimuth website
Online shop: to Play Stereo website
Official current price in Italy Italia: 129,00 EUR
Associated equipment: to Fabio "Puzzled" Barbato system
