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Digital-to-Analog Converter

Extended edition & limited edition

Manufacturer: Projekt NOSTROMO
Price (when reviewed):
• extended edition: 999 PLN
• limited edition: 1590 PLN

Contact: Marek Kowzan | ul. JANA MATEJKI 1G
66-600 Krosno Odrzańskie | POLSKA


Provided for test by: Projekt NOSTROMO


Written by: Wojciech Pacuła
Photo: Wojciech Pacuła
Translation: Marek Dyba

No 198

October 1, 2020


Alien was for me the first one ever to cause my jaw to drop. This movie hit all my soft spots: SF + horror + technique. I simply had to call my new project NOSTROMO (by Marek Kowzan).

he quality of a circuit used in an audio product is quite easy to verify - the longer it is on the market, the better its initial assumptions were. No wonder that in the lineups of renown, good, reliable companies, such as Pass Labs, McIntosh, Naim Audio, Linn and others, one finds still the same ideas that worked for them a dozen or sometimes several dozen years ago. Every now and then some modifications, iterations are introduced, but their core remains the same.

If we look at the Wolf converter from the Polish company Project Nostromo in this way, it turns out that its design must be really very good, because its first version was developed quite a long time ago, in 2011. When we tested it five years later, it was already at its 5th version. Mr. Marek Kowzan, the owner of the company and its designer said back then:

[Name originates from] Wolfson, the main D/A chip, the WM8741. The chip was made by the Wolfson Microelectronics (which was acquired by Cirrus Logic). I really like their products, most of my converters feature chips from this family. […]
When building this DAC, the main assumption was: to show the full potential of this chip, but in a simple way, without any fancy solutions build around it. But also without limiting the possibilities that we get from the manufacturer for its control. That is, control of oversampling and digital filters built into the WM8741.
More HERE, accessed on: 31.08.220

It's 2020 and this model is still in the Project Nostromo lineup. Slightly changed, but it is still the same layout and even has a similar name - only the number '2' has been added to it. Apart from the basic model there are also two other versions available: 'extended' and 'limited'. The price, compared to the original basic version of the Wolf, has changed very little, because it increased from PLN 780 to PLN 999 or to PLN 1,590. This is still not much, but also 50% more than for the base model. I asked Mr. Marek directly about the differences between them.

| A few simple words…

Owner, designer

⸤ MAREK KOWAN in Piekarnia Cichej Kobiety Club in Zielona Góra

THE MAIN IDEA that I’ve been following for several years is to build such devices that will allow both, a true passionate and an „ordinary” listener to pick up the emotions music contains. Live concerts are one of the reference points for me and I would like to use my equipment to bring the audience as close as possible to the atmosphere of a concert.

For several years I have been, one could say: a regular of most concerts in my favorite blues-jazz club Piekarnia Cichej Kobiety in Zielona Góra. I am also in contact with several music bands, sometimes learning about professional stage and recording equipment, and sometimes advising regarding some electronic solutions. Sometimes I also make custom special electronic devices.

In 2016, my DAC Wolf was tested by HF. It was OK, I was happy with it too, but I knew there was still some room for improvement. That is why I prepared a new version, the Wolf 2. Mainly, I wanted the maximum separation of analog channels on the DAC board itself - my goal was the most faithful rendering of the "space". Being at a concert, I can hear where the drums are, where the double bass or guitar are and I would like to hear the same in my home with my system.

One of the most frequently asked questions by customers concerns the tonality - for example, does my DAC "add weight to the bass", or "brighten the treble". I have a problem answering such questions. Because I do everything so that this does not happen, my main goal is that my product does not add or subtract anything to the music I listen to. Its main task is not to limit anything, to allow listener to hear everything that the artist communicates, without being a bottleneck.

To be able to get to this result I had to have a larger PCB area, and a larger PCB requires a different chassis, different control elements on the front panel etc. I changed the filter selection, in the current version there are only 4 selected by me as the most interesting ones, after conversations with many Wolf users of the first version.

Why did I make a limited version? It started with testing integrated circuits (op-amps), those ordinary eight-pin ICs, "sitting" in DAC, in the LPF filter. Theoretically, there are two identical chips there, one per channel. The manufacturer of such an op-amp declares the same, repeatable parameters in each chip with the same symbol. Unfortunately this is not the case, or at least not always.

I started to test individual ICs from the same series using a band analyzer and, as it turned out, there were huge differences between them, despite the same symbol. I thought then - would it be audible if I matched two identical op-amps with identical parameters and put them in one DAC?

It turned out that it was clearly audible, and that is why I went even further - I used ultra-low noise voltage stabilizers, polymer capacitors in the main power line, as well as great Nichicon capacitors from the KZ series.
Even the fuse is special, wire-based and the whole is soldered with a special soldering tin with an addition of silver. Someone will say: "these are audiophile frills". Maybe so, but I can hear a clear difference in favor of the limited edition. After selling a few units, it turned out that its reception was very positive, and there were also a few customers willing to convert the regular version into a limited one. MK


WOLF 2 is a D/A converter with four digital inputs and a pair of unbalanced analog outputs. There is no headphone amplifier, no Bluetooth, no streaming. What's more - there is also no USB input. The latter is mastered by the Project Nostromo owner via external USB → S/PDIF converters; many other companies offer similar devices. The advantage of this solution is better power supply and - usually - better signal clocking of such a system. The downside is the need to use another digital cable (RCA-RCA), as well as something more important - resignation from DSD signal decoding in the D/A converter.

Wolf 2 is a small, neat device in an aluminum chassis that is a standard for this price range. One can buy an aluminum profile in the form of a long pipe and then cut it to the desired length. It is an inexpensive, solid solution. On the front there are knobs that allow user to select input and one of the digital filters - there are four of these at user’s disposal. The basis of the device is the Wolfson Electronics WM8741 digital to analog converter chip and integrated circuits in the output.

Mr. Kowzan has already talked about it - there are three versions of the Wolf 2 available Basic, Extended and Limited. Visually, the extended version differs from the basic version with a high-gloss, 3 mm thick front panel, which in the basic version is only 1.5 mm thick with matte finish. The limited edition features brass knobs.

As it reads in the company materials, "the most important changes, however, are hidden inside. "High-quality resistors in the analog circuit are threaded through, the capacitors in LPF are dedicated to audio, and the operational amplifiers are placed in precise sockets, which "enables easy, possible future replacement with other chips according to your preferences". The limited edition features even higher quality capacitors in the signal’s path and paired integrated circuits.


HOW WE LISTENED TO IT | The DACs were tested in the "High Fidelity" reference system. The test was an A/B/A comparison with reference devices, with A and B known. Both Project Nostromo converters were placed on the top shelf of the Finite Elemente Master Reference Pagode Edition rack. They were powered directly from wall sockets, connected to a separate power line with a separate fuse.

The test was divided into three stages. In the first one, I listened to the 'extended version' of the converter with an smps power supply it comes with. Then I replaced it with the Nostromo V4 linear power supply. And finally I listened to the 'limited version' with the proprietary Nostromo V4 power supply; you have to pay a little extra for the power supply, but it’s only PLN 388.

Two devices served as the source of the digital signal (S/PDIF): the transport section of the Ayon Audio CD-35 HF Edition SACD player (CDs) and the Lumïn T1 (files). The signal was sent via the Acrolink Mexcel 7N-DA6100 digital cable. The signal to the preamplifier was sent via Belden NOS cables.

Recording used during review | a selection

Compact Disc
⸤ Enya, Enya, BBC Entertainment BBC CD 605, CD (1987)
⸤ John Coltrane Quartet, Ballads, Impulse!/Universal Music LLC (Japan) UCCU-40001, Platinum SHM-CD (1962/2013)
⸤ Nirvana, In Utero, Geffen GED 24536, CD (1993)
⸤ Pat Metheny, What’s It All About, Nonesuch Records/Warner Music Japan WPCR-14176, CD (2011);

⸤ Dua Lipa, Levitating (feat. Madonna and Misssy Eliott), Warner Music/Tidal Master, FLAC MQA Studio 24/44,1, SP (2020)
⸤ Katie Melua, Airtime, BMG Rights Management (UK) Ltd/Tidal Master, FLAC MQA Studio 24/44,1, SP (2020)
⸤ Robert Plant, Charlie Patton Highway (Turn it Up Pt. 1), Warner Music/Tidal Master FLAC MQA 24/44,1, SP (2020)
⸤ Yello, Point, Universal Music/Tidal Master, FLAC MQA 24/48 (2020);

| Wolf 2 extended version

I MUST ADMIT that nothing has changed in the way I perceive what Mr. Kowzan is doing. For what he managed to achieve within such a modest budget and such an inconspicuous device he deserves great respect. It is still, in short, an excellent sound.

For example, the timbres are noteworthy. They are saturated, full and dense. Comparing its sound in short samples in the A/B/A comparison against the reference player, the differences between them were shown primarily in the sound resolution, depth of instruments' bodies and depth of the sound stage. But when it comes to timbre, the difference was not overwhelmingly large. I would even say that - considering the price difference - negligible.

And this is probably the most important thing in this device. It offers us a beautiful palette of colors without warming up the presentation, without "stiffening it" and without cooling it down. Everything seemed to be in place with it. And when Coltrane blew extremely low at the end of To Young To Go Steady from the Ballads on the brilliant Platinum SHM-CD release, I could only nod my head in appreciation.

Fantastic, really great were not only top jazz albums in the form of the mentioned Coltrane, or Pat Metheny's guitars from the What's It All About?, or electronics from Enya's debut, but also powerful tracks from Nirvana’s In Utero. The voice and guitar opening Rape Me sounded strong, deep, cool. The converter builds large phantom images, shows a large volume of recordings, so its presentation is exciting and energetic, without the need to emphasize the attack of the sound.

I would even say that the attack is smoothed and rounded no matter which digital filter we use. It is shown most strongly with the number 1 filter, but most naturally with the number 4. Besides, in each position of this switch we will pay attention primarily to the midrange. Low bass is a bit withdrawn and we will not get such a full and dense "weaving" in the bottom as with expensive digital players, this cannot be done.

But it will not "bother" us either. With the new recording by Dua Lipa, Levitating (feat. Madonna and Misssy Eliott), available on Tidal as MQA Studio 24/48 files, the sound was strong, dense and had a low center of gravity. The low bass was throbbing nicely, had a soft character and reflected quite well what - I assume - the producers of the track were looking for. Importantly, there was no hint of sharpness in this sound, which immediately evoked the sound of the ten times more expensive Lumïn T1, with which the DAC was compared in this part of the test.

This is a thing that happened also with Robert Plant's new track Charlie Patton Highway (Turn it Up Pt. 1) and with each new track played from files. Wolf 2 in the 'extended' version "embraced" it all and showed me that hi-res files are better than 16/44.1 ones, but also that a good CD still sounds better than even the best file.

| Wolf 2 extended version & power supply

Replacing the classic wall-mounted switching power supply with the Nostromo V4 linear power supply really changed the sound. This was a bigger change than replacing a digital cable with a better one, changing the interconnects and even the signal source. All these are important, they added to the high class of this sound, but these were like an "overlay" for the basic changes that occur just after replacing the power supply.

With a large power supply, the sound is much more resolving. And hence - richer. Previously, the tracks were a bit similar to each other, because they all sounded nice, warm and dense. Now the differences between the new recordings by Robert Plant, Katie Melua, Dua Lipa and Yello were clearer and more important.

The upper midrange has also been cleaned up. Before it was nice, pleasant, now it offered more information. The all-encompassing "enveloping" sound that I had heard with the "extended" Wolf 2 and the standard power supply disappeared a bit. However, the softness and richness of colors did not disappear. And thus - the pleasure of listening didn’t either. And it was even deepened, because now each recording had a more distinct character of its own. So - it was better differentiated.

The large power supply also deepens the soundstage. Previously, it was well organized, it had nice layers, but it was quite shallow. With the power supply, everything receded a bit, and the back of the stage, i.e. reverbs, small sounds, etc., all these elements were placed much deeper than before. What remained, however, was a nice timbre, as well as a slight blurring of the lower bass and the general impression of "completeness" of the sound - in that order.

| Wolf 2 limited version & power supply

The transition from the 'extended' version to the 'limited' version brought changes only of a slightly smaller caliber than the change of the power supply. This time the basic elements remained unchanged, it was still a characteristic sound for this brand. The difference was more in the greater selectivity of the more expensive version and a slight brightening of the upper midrange. Low bass was better controlled and more focused. Although, on the other hand, it was not as dense as before.

The new version presents information about space in a much better way - both by focusing the sound and placing it in more clearly defined places. It was a sound with higher energy than before. This could be heard with both hi-res files and CDs. This is clearly better sound, but also - attention - not so easy to control.

This is because together with higher resolution, better dynamics and selectivity, the recording itself was heard better. For this reason, with the limited edition, I liked CDs much better than files. While the extended version sounded just nice and fun, regardless of the signal quality, the more expensive version differentiated them significantly and not the entire Tidal playlist could be listened to in comfort.

But it was precisely when I was listening to the limited version that the differences between different CD editions mattered, as well as the differences in the quality of the production and encoding of the file, and even the quality of power delivered by power grid. This is a blessing and a curse that every music lover has to deal with and each of us has to answer if this is what we want.

| Summary

The new versions of the Wolf converter that I had tested in the past are clearly better than the original. The extended version is perfectly pleasant to listen to and inexpensive, and for a symbolic amount of money spent on the Nostromo V4 power supply, we will significantly improve the sound quality. It's just a hit product. In turn, the limited version is not for everyone. The thing is that the system has to be well balanced and dark rather than bright to repeat everything I wrote about the extended version and add to it much the better selectivity and resolution.

Both versions offer great tonalities, a large sound stage and a smooth, fluid sound with a low center of gravity. The lowest bass is not precisely focused, but it should not bother anyone - unless the tested DACs will be listened to with loudspeakers like the Harbeth M40.1 and the Soulution 710 amplifier, like it was in my case. This is a negligible „weakness” in "normal" setups. Besides, what you get is simply a reliable engineering and it’s about offering people good sound at very reasonable price. That is why we award both devices the BIG RED Fingerprint.


Chassis | The new version of the Wolf DAC, now the Wolf 2, has a shape different from its predecessor. The new device is wider and lower, measuring 103 and 35 mm respectively. But again its casing is made of a ready-made profile, which is cut to the required length - here it’s 192 mm. The front in both tested versions is made of acrylic in black, and the rear is made of aluminum. The device rests on four, glued rubber feet.

Front and rear | On the front there are two knobs, a button and nine LEDs. The knobs allow user to choose a digital filter and an active input, and the switch turns the power on. The red LEDs placed on each side in vertical rows of four indicate the selected filter and input. On the other hand, the ninth, largest LED is a two color one and it informs about synchronization with the source (green) or no synchronization (red). However, we do not get information about the parameters of the input signal.

It is a small device, so the back panel is crowded and it is difficult to fit the plugs of digital and analog cables next to each other if they are larger than average in diameter. On both sides there are analog outputs - Mr. Kowzan said that it was about the best channel separation. Closer to the center, also symmetrical to the axis, there are two digital RCA inputs and two optical ones; in the center there is a 12 V DC power input. Digital RCA sockets seem to be of a better quality than analog ones.

Inside | The electrical circuit is located on a single printed circuit board that occupies the entire interior of the device. In the middle there is the power section, with nice capacitors and a voltage stabilizer screwed to the heat sink, in the front there is a digital section, and on the sides - an analog one.

The input features Wolfson Microelectronics digital receiver, the WM8804. It is a PCM signal receiver in the S/PDIF format with low jitter - and it sets the input signal parameters at 24 bits and 192 kHz. On the other side of the power line there is a proper D/A converter chip, the WM8741 from the same company. It is a multi-bit sigma-delta 32 bit, 192kHz chip with advanced architecture. It offers digital volume control (not used here), several digital filters, and an interpolation filter; I know from experience that the latter is largely responsible for the smooth, warm sound of this system.

The DAC's output is balanced and has a voltage form; I/U conversion is done in the converter. This simplifies the circuit, lowers the costs, but also “closes” the manufacturer's ability to influence the sound in this way. As always - quid pro quo. The balanced output of each channel is summed up reducing noise - the circuit is unbalanced. The signal’s track features a single, eight-pin integrated circuit per channel, with a heat sink attached. We also find there through-hole, precise resistors and nice capacitors from Wima and Miflex.

Power supply | The standard power supply that we get with the Wolf 2 converters in each version is a small, switched-mode wall power supply. However, you can order a Nostromo V4 stabilized linear power supply for an additional fee.

The Nostromo V4 has a housing made of durable plastic, used in industrial installations. There is an illuminated power switch on the top panel, and on the back there is an IEC socket and a coaxial power socket with DC output voltage - the latter is very similar to the one used by the Lumïn in the T1 model.

The power supply itself is based on a small IE transformer from the Polish company Indel, behind which there is a large, integrated rectifier bridge, three capacitors and a voltage stabilizing circuit. On the primary side, there are several noise-canceling elements - a toroidal choke and a foil capacitor from the Polish company Miflex - I should probably say: a NOS type. Round ferrite is threaded on a short power cord, suppressing high-frequency noise.

It’s a very nice design using high quality elements.

Technical specifications (according to the manufacturer):

D/A chip: WOLFSON WM8741
Supported input signal (up to):
• coaxial (RCA): 24 bits, 192 kHz
• optical (Toslink): 24 bits, 96 kHz
Dynamics: 128 dB
Crosstalk: -130 dB
Output signal: 2.1 VRMS (@ 0 dB)
Dimensions (W x H x D): 103 x 35 x 192 mm
Weight: around 1 kg


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3) Super Audio CD Player: AYON AUDIO CD-35 HF Edition No. 01/50 |REVIEW|
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7) Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|


Analog interconnect SACD Player - Line preamplifier: SILTECH Triple Crown (1 m) |ABOUT|
Analog interconnect Line preamplifier - Power amplifier: ACOUSTIC REVIVE RCA-1.0 Absolute-FM (1 m) |REVIEW|
Speaker cable: SILTECH Triple Crown (2.5 m) |ABOUT|

AC Power

Power cable | Mains Power Distribution Block - SACD Player: SILTECH Triple Crown
Power (2 m) |ARTICLE|
Power cable | Mains Power Distribution Block - Line preamplifier - ACOUSTIC REVIVE
Power Reference Triple-C (2 m) |REVIEW|
Power cable | Mains Power Distribution Block - Power amplifier - ACROLINK Mexcel 7N-PC9500 |ARTICLE|
Power cable | Power Receptacle - Mains Power Distribution Block: ACROLINK Mexcel 7N-PC9500 (2 m) |ARTICLE|
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Power Supply Conditioner: Acoustic Revive RPC-1 |REVIEW|
Power Supply Conditioner: Acoustic Revive RAS-14 Triple-C |REVIEW|
Passive filter EMI/RFI: VERICTUM Block |REVIEW|


Speaker stands: ACOUSTIC REVIVE (custom)
Hi-Fi rack: FINITE ELEMENTE Pagode Edition |ABOUT|
Anti-vibration platforms: ACOUSTIC REVIVE RAF-48H |ARTICLE|

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Phono preamplifier: Phono cartridges: Tonearm (12"): Reed 3P |REVIEW|

Clamp: PATHE WINGS Titanium PW-Ti 770 | Limited Edition

Record mats:


Headphone amplifier: AYON AUDIO HA-3 |REVIEW|

Headphones: Headphone Cables: Forza AudioWorks NOIR HYBRID HPC