One of the less obvious, for classically-trained engineers, phenomena discussed in perfectionist, uncompromising audio circles (most call it audiophilism) is the effect of power supply on the sound. Generally, no matter how well one knows the audio world know and irrespective of one’s professional background, it’s commonly recognized that power supply quality is an important factor affecting each product’s measurement results. It's just that the involvement of engineers usually ends at the level of integrated voltage controllers, slightly oversized transformers, and marginally better filtering capacitors. In static measurements such designs show very good ripple and stable desired voltage. The problem is that they also modify the sound. In the wrong direction, at that.
How can it be verified? One of the basic ways is the so-called “objective” measurement method. It can be used to determine the level of harmonic distortion, noise, ripple, etc. But it works best at the constant power consumption. One cannot use it to point out e.g. the effect of negative feedback on the sound in stabilizing circuits. And that effect turns out to be deadly. How to demonstrate it? The most objective method that shows changes we cannot yet measure or interpret is by examination – in this case by auditioning.

Tests with discrete circuits, both transistor- and tube-based, prove that integrated voltage controllers are not a good solution in high-end systems. Consequently, they have been replaced by the said solid state or vacuum tube discrete circuits, which brought really good results. But it can be done differently. What has recently become increasingly popular is battery-based power supply. Its popularity is associated with the boom of PC audio, including USB DACs, headphone amplifiers, USB-S/PDIF converters, etc.
While those tests have been carried out for years, it seems that so far lacked high quality rechargeable batteries and experience with their application. The battery is not a miracle answer to power supply ills, as it often generates completely different problems. Previously, the sound from battery-powered components used to be anemic, lacking dynamics and definition. Sure, it was pleasant and creamy but nothing more than that. I have heard many such components and never really taken to battery power.
That has changed within the last two – I believe – years, and my personal conversion began with my review of the Human Audio Libretto HD CD player, fully powered from an outboard battery. Then came Arcam RDAC’s power supply from Bakoon (see HERE) and finally the magnum opus Bakoon Products HPA-21, for now my reference headphone amplifier. Battery powered.

A short history of…
Ear Stream according to Michał Wyroba

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It has been just over a year since the last review of the Black Pearl-related product. It was the press premiere of the Pearl Ear Stream Sonic amplifier in “High Fidelity”, reviewed by the chief editor Wojciech Pacuła. I must admit that in spite of receiving the Best Product 2012 award it was not a perfect product, its design improved until the last minute yet proving structurally and sonically uneven. I accepted the award as an encouragement to continue working on the design. It was brought to my attention by fellow audiophiles and was clear from the review. Based on my own auditions and further wrestling with the design I came to the conclusion that something was not quite right. I make no effort to conceal my interest in being the best, not in the sense of received titles but finding it out on my own, as it were organoleptically. And if something is not perfect, to make it a candidate to be the best becomes reliant on blind luck and competition’s mistakes.

Some time ago I noticed that designing audio components shares a lot of similarities with cooking. One must choose only the best quality ingredients or components, then find out – mostly by trial and error – their ideal proportions and how to use each of them. In electronics it translates to their proper layout on the circuit board or in a point-to-point assembly. Although I did not plan this, changing the proportion of components selected for the Ear Stream headphone amplifiers took the next few months followed by a couple month’s work on the optimal amplifier topology and geometry. For example, the type of two resistors in the gain circuit has been changed to a specifically identified manufacturer and series, with more such systematizing activities. The nearer the desired result, the smaller the ratio of steps forward to steps back, not counting many side steps and getting nowhere.
I can say that I completed the composition stage a few weeks ago, including interior and exterior wiring and its arrangement, etc. Suffice it to say that the choice of umbilical cable connecting the amplifier to the external battery proved very important, with at least a few tested cables and their geometry, including silver plated copper wire in Teflon insulation, and silver and copper cables from various manufacturers. I ended up with a certain type of a hot air-twisted speaker cable with one silver plated copper conductor and the other one fully copper wire. I also tested various feet under the amplifier and the battery, but in the end the stock silicone supplied with the enclosures turned out to be optimal, at least within the intended budget. The customer can always replace them with preferred dedicated feet.


I know from internet forums that cable selection is total voodoo to many. However, I have to say that for an engineer it still falls within the confines of science. On the other hand, mechanical parts can also "play", which was actually already mentioned, and even… chemical components. It appears that the dielectric materials can be treated with various chemicals and it often has a significant influence on the sonic characteristic of a cable or component. Hence, we have the first argument for the "revision C" in the name. C for chemistry. We did not previously take it into account until the last months of this year. We, as in myself and my colleague, an active music lover and audiophile. His surname starts with "C ", so this is another reason to call the new version of Black Pearl this way and not another ;)
Our presumptions are simple – it is to sound natural, as close as possible to what we hear live or at music concerts, both in terms of scale and dynamics, as well as pure pleasure. Many of the improvements introduced to the Black Pearl have also influenced other Ear Stream products, namely the Sonic Pearl and Moonlight headphone amplifiers, as well as audio cables offered by our company. It should also be mentioned that the Black Pearl is not a new product. It is more than three years old, during which time it has steadily evolved teaching its designer humility and forcing him to gain music, audiophile and engineering experience. Progress achieved this way is a self-winding, slowly revolving mechanism that stimulates many reflections and often prompts to go back to what was already there, but now in a new and better light. It is a kind of circular motion along the spiral path which end is the target, and during which one can only see a current section. That makes the journey continue indefinitely.

The tiny unit once brought to me by Mr. Michał Wyroba, Ear Stream’s owner and designer, can be battery powered. It can be bought with a standard switching power supply or a more expensive linear stabilized power supply, but eventually you need to think about the battery. While the latter is most expensive of the three, it is the key to success.
The outboard power supply is much larger than the amplifier unit. To minimize the amplifier’s cost, its enclosure is a standard Hammond module, which is also used for the battery housing. There are no markings on the box that also add to the cost. Not that Mr. Wyroba is incapable of putting together a fat, fully loaded enclosure – just take a look at the Sonic Pearl amplifier reviewed by “High Fidelity” to get an idea. Such housing, however, costs a lot of money. It has a significant effect on the sound, but not everyone can afford it. And it is for those who are willing to sacrifice some quality for availability that the Black Pearl has been prepared. Not only can it be bought with various power supply options, but there is also a line output equipped version to operate as a minimalist preamplifier. This should be appreciated by the owners of active speakers and small computer audio systems. What follows is the list of various options and their pricing:

• Black Pearl headphone amplifier – 1699 PLN
• Black Pearl amplifier with line output – 1849 PLN
• 100~240V 50/60Hz switching power supply – 99 PLN (without power cord)
• 230V 50Hz linear stabilized power supply – 149 PLN
• Standalone battery – 799 PLN
• 100~240V 50/60Hz microprocessor charging unit – 399 PLN

Records auditioned during this review

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• Carole Creveling, Here Comes Carole Creveling”, Euterpean Productions/Sinatra Society of Japan XQAM-1021, CD (1956/2008).
• Daft Punk, Random Access Memories, Columbia Records/Sony Music Japan SICP-3817, CD (2013);
• Eva Cassidy, Songbird, Blix Street Records/JVC VICJ-010-0045, XRCD24 (1998/2010).
• Joe Pass, For Django, Pacific Jazz/EMI Music Japan TOCJ-90027, HQCD (1964/2006).
• John Coltrane, One Down, One Up, Impulse! 9862143, 2 x CD (2005).
• OMD, English Electric, 100%/Sony Music Japan SICP-3810, CD (2013);
• Project by Jarre for VIP room, Geometry of Love, Aero Prod 606932, CD (2003).
• The Modern Jazz Quartet, Pyramid, Atlantic Records/Warner Music Japan WPCR-25125, “Atlantic 60th”, CD (1960/2006).
• Warne Marsh Quartet, Music For Prancing, Mode/Muzak MZCS-1111, „Mode Paper Sleeve Collection vol.1”, CD (1957/2006).

Japanese editions of CDs and SACDs are available from CD Japan

I am not sure whether it is the effect of gained experience, help from friends, or perhaps the benevolent criticism of some details once expressed in my review of the previous amplifier design (the latter probably to the least extent, but one can always hope), but I hear a distinct tonality change in the sound of Mr. Wyroba’s amplifier. Although, after some “digging” it turns out not to be a paradigm shift, but rather a modification of the previous one, yet substantial enough to change our perception.
As a matter of fact, the new amplifier is better tonally balanced, with a more refined accent placement of what is more and what is less important sonically. It is still evident, though, that one of the priorities was sound cleanliness. ‘Cleanliness’ is fairly general, but I’m sure that most “High Fidelity” readers know what I mean. It is reflected in the wealth of information, primarily in the treble. It is, however, the kind of wealth that does not irritate or make us tired. In the real world, all the sounds are “clean”. Even if sometimes they do not seem to be, the only problem is our organ of hearing. A recorded audio signal is completely different in that each recorded sound is distorted. The quality of listening, the sound quality depends on the level of that distortion. On top of all that is audio components’ induced distortion. Their basic role is such choice of own distortion (design compromises) to sound as close as possible to the live sound. And as practice shows that means that the measured frequency response will almost always be disadvantageous from the auditioning point of view; in other words, flat frequency response alone is no guarantee of success, and is usually a source of frustration resulting from too bright a sound, with over-accented treble or upper midrange.
With his Black Pearl, Mr. Wyroba did not wade into these waters at all. I do not know what the Earl Stream’s methodology of product development is, but I know from experience that this type of sound, this quality of sound that is, results from good engineering backed up by extensive auditions. Multi-stage auditions, using various headsets. Of course, this journey ends in compromise as there is no such thing as a “universal” headphone amplifier. It is tonality that’s almost always the problem – the differences between two sets of even similar headphones can be huge! However, good amplifiers, sounding best with a few selected headsets, will show their advantages with each headphone design.

Despite its compact design, ultra-minimalist layout and form “austerity”, the Black Pearl seems to be just such an amplifier. The sound that emanates from this modest box backed by a solid battery pack is really of the high quality. I will go even further to say that I like it better than what I heard from the much more expensive Sonic Pearl. I do not mean that the previously reviewed amplifier from Krakow manufacturer was worse, which is the paradox of the audio world – the better one is not necessarily the one we prefer. The thing is that the selection of all the elements in the Black Pearl appeal to me much more and that I preferred listening to it. At the end of the day, I would choose for my system the Black, not the Sonic Pearl. I am sure that since then Sonic Pearl has undergone a thorough transformation but I need to rely on my own experience rather than manufacturer’s claims.
I like the new amplifier from Ear Stream mostly because it so nicely combines sound clarity and its good saturation. The sound has a proper depth and foundation. There is no question of a “thin” sound, even with the HiFiMAN HE-6 magnetostatic headphones, somewhat “lighter” than dynamic headphone designs. Interestingly, the Black Pearl had no problem driving these cans, where many other powerful amplifier designs fell flat, sounding bright, squeaky and lacking dynamics.
Here the dynamics is excellent, really very good. It was particularly well heard with the magnetostatic headphones mentioned above and with the HE-400, but – perhaps even better – with the Sennheiser HD800. The latter sounded close to the listener, but not as much as the HiFiMANs with which certain “closeness” is normal. The Black Pearl paired with the Sennheisers shows the sound, for example mono recordings, that is close to us but not limited by the “walls”. It is indeed a palpable, dense and “thick” sound, so to speak. Lower midrange is in good proportion with the other sub-ranges, which is why the sound is almost always well-founded, consolidated. It is simply full or, in other words, natural.

Forza AudioWorks NOIR
Headphone cable

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I like the kind of sense of detail exhibited by products from Forza AudioWorks. I saw it earlier in products from Acuhorn, a Gdansk-based company. It results from working with natural materials, from seeing manufacturing as a value added activity and from a proper attention to detail – both individually and as a whole. This is evident in the products themselves, but also in their packaging and even in business card and website layout. The best word to describe it all is “organicity”. Mr. Mateusz “Muflon” Przychodzień, the head of Forza AudioWorks, obviously knows what he’s doing.

I came across his company by accident, while reviewing the components from iFi. FAW product lineup includes audio cables, especially headphone cables. And what cables they are! The Noir under review, in an attractive black finish, is made in-house using OCC 7N Cryo copper conductors. It costs surprisingly little – its 1.5 m version equipped with the top Furutech PF-704 plug and dedicated for HiFiMAN headphones (also available for other types of headphones) sells for mere 160 euro. It’s really very inexpensive in terms of audio equipment. Actually, taking into account the components used it is next to nothing. Its assembly and finish quality, attention to detail do not indicate that. Even if it cost 500 euro I doubt it would be made better.
The Noir is made of four separately insulated interwoven conductor runs. The place where the runs for the left and right headphone channels part is a CNC cut aluminum splitter with a laser engraved FAW logo. The whole looks extremely professional and reliable. We even get a plastic warranty card! The packaging is a very eco-friendly cardboard box filled with wood chips (similar to that used by Entreq) and a cotton cable pouch (as that for stands from Sieveking Sound – recommended). Everything has its place, size and color. The whole looks as if it came to us straight from the hands of a slightly “eco-crazy” Japanese or Scandinavian designer. Very tasty indeed.

The house shows the owner – so it goes, doesn’t it? An audio paraphrase of this saying would be something like that: it sounds the way it looks. At least one of its versions. The reason for such a choice is that it’s not the first time during my review I happen to come across a situation where product’s appearance as well as its name very aptly describe its sound. Maybe not fully, but at least conveying the first impression. Mr. Przychodzień’s cable is black and bears a name that evokes a “dark” mood, and its sound is also somewhat “dark”. Note the inverted commas – they are on purpose.
The Noir’s sound is perceived as darker at first, no matter if compared to a stock cable or the very expensive, fully loaded Entreq http://www.entreq.com Challenger 2013. There is no denying that the Forza slightly withdraws high frequencies, focusing our attention on the midrange. This is actually more the case of its better integration with other sub-ranges than actual withdrawal. No, this is not a paradox – you will immediately hear that the treble is quieter and darker. Yet after a short accommodation you will also hear that everything sounds more coherent, as if previously there was too much treble. It was especially well audible with the stock HiFiMAN cable that pretty quickly dropped out of the “game”. More conclusive findings could be formulated with the Entreq cable – one of the best, if not the best, headphone cable I know.
The Swedish cable was slightly more resolved and had a stronger, more selective and better defined treble. However, the Polish cable made a clearly better pair with the HE-300 and HE-400. The sound was more natural, deeper and more enjoyable. Pairing it with the HE -300 resulted in a major about-face. These are great headphones but suffering from a somewhat withdrawn midrange. With the Noir they finally sounded thoroughbred, with proper “groove”, so to speak. For the first time I heard them sound coherent and deep. The story was slightly different with the HE-6. The midrange, propped with something deeper and more powerful offered by the Polish cable, was more velvety. On the other hand, a part of its refined resolution was gone. The tonality was better at the cost of reduced resolution.
Regardless of our preferences, however, the Forza AudioWorks cables are outstanding in every way, including their performance, packaging and sound. Their price is ridiculously low. Even if they cost five times more I would say you need to sign up for them right away. If you already own expensive headphone cables, for example the Challenger 2013 (or Konstantin), you should necessarily give them a listen, nevertheless. It would be best to buy them and use interchangeably with the ones you already have. If you do not yet own such a good cable do yourself and your headphones a favor: treat yourself and them to the Noir. It’s a small gift, but it may prove one of the best improvements in your system for years.


Price: 161 euro
forzaaudioworks.com

But let me now go back to the cleanliness I mentioned at the beginning. The amount of treble with the Bakoon Products HPA-21 amplifier was larger and it had a better resolution and “weight” differentiation. The Black Pearl is, however, in the same exact “corridor”, treating the music material in a similar manner. I’m not sure whether it is a common characteristic of battery-powered components, but I think there is something to it, knowing the Bakoon pretty well and based on my experience with a dozen of such products (like the Human Audio Libretto HD CD player mentioned above). It is best audible with the treble as it is usually the first to fall prey to distortion.
The amplifier from Krakow loses to the Bakoon in the treble department, but no other design I know does it better than the Korean unit, or even comes close to it. What’s important here is that the Pearl does it in a similar way. The cymbals had a proper “thickness” and were not short dings but something substantial and sizeable. The treble as such had the same character, shown on the Warne Marsh Quartet album, a historic recording where the audible tape hiss and distortion, problems with drop-outs, etc., were not brought to the foreground but rather stayed with the music, as a part of it and its “witness”. On the other hand, listening to a very good production, such as Anna Maria Jopek’s album Barefoot (an analog recording of the highest caliber!), we get a precise but also musical information about what instrument was played and how, and where it was located. Leszek Możdżer’s prepared piano in Bukowina sounded very close, but without attacking the listener.
The amplifier also did pretty well at the other frequency end. Although the lower midrange was slightly more favored than the low bass extension, these were minor modifications rather than significant changes. What’s important is good saturation and fast transients, confirming the cleanliness of sound. The trance beat on the Hole To Feed / Fragile Tension CD single by Depeche Mode, really fast and dynamic, preserved a dense club sound nature.

Conclusion

It is not the best amplifier I know. It cannot do certain things as well as the reference. Although it very nicely differentiates the recordings, it does so by showing tonal and dynamics changes, passing over the changes of sound depth and soundstage depth (of course, in the sense of “head stage”). The sound is not as resolved as that of the Leben CS300 XS [Custom Version], and even less of the Bakoon. However, it shows a degree of refinement that is hard to come by in the headphone world, regardless of cost and technology. It mostly concerns sound credibility and density, suggesting something more than a flat piece of paper that can have even the most precisely contoured shape, but will always remain a two-dimensional and therefore false object (provided we accept three-dimensional reality to be true). Black Pearl’s bass does not extend as deep as that of some other good headphone amplifiers in the 2000-3000 PLN price range. However, since it has good color and the overall tonal balance is based on the lower midrange, we do not perceive it as lacking but rather as a part of sonic character, which is additionally completely acceptable. What’s more important for me is that the sound is colorful and mature. Perhaps nothing else is needed. If we can accept its simple and rather “rough” than refined looking enclosure, it may stay with us permanently. Forever. And if there comes an improvement, Mr. Wyroba will definitely provide us with an upgrade. It’s a unique advantage of owning a product from a small manufacturer.

A battery-powered amplifier has the advantage of being able to operate anywhere, even placed far from the mains power. I tested the Black Pearl in different places. While the Acoustic Revive TB-38H anti-vibration platform gave the best results, it sounded really good even on a wooden table.
During the review the reference point was constituted by two reference amplifiers, the battery-powered solid-state Bakoon Product HPA-12 and the AC powered Leben CS300 XS [Custom Version] tube amplifier. I additionally auditioned the iFi Audio iCAN headphone amp. The testing had a character of an A/B comparison, with the A and B known and with 1 minute long music samples. For several days I also listened to whole albums, just for the pleasure of good sound. During the whole time the amplifier did not present any problems.

Reviewed a year ago, the Sonic Pearl cost almost 6,000 PLN. Its enclosure design was perfect and accounted for a large proportion of that money. It would be wrong, however, to treat the carefully though out, high-quality housing as a mere whim. Experience teaches us that it has a significant effect on the sound. Therefore, abandoning the heavy cast of the Sonic Pearl enclosure for the universal Hammond casing, even if made of the same material (aluminum), looks like a conscious decision to sacrifice some of the sound quality. The idea seemed to probably be lowering the price as much as possible. As a result the Black Pearl sells for 1699 PLN. However, one needs to buy the power supply separately. That opens up several possibilities, with the best option being a rechargeable battery for 799 PLN. It is housed in the same looking if slightly deeper enclosure as the amplifier. The battery pack consists of 18 NiMH cells connected in series, with a total capacity of 2600 mAh. Its working time is 40 hours before it needs recharging, which is a very good result. Low battery is indicated by a switched off LED. Two DC sockets on the back panel make it possible to charge the battery while listening. The socket labeled as AMP provides a shorter electric current path, but both sockets are functionally equivalent. The battery pack is connected to the amplifier via a DC umbilical cord made of OFC copper, with one wire silver plated. The conductor pairs are heat twisted. The set includes an automatic charger with 0.9A maximum charging current that is lowered in the final charging stage. This allows fully charging the battery within three hours. The status indicator is a multi-colored LED.

The amplifier is small and fairly light - rigid cables raise it easily. There are no markings or engravings on the casing in order not to raise its cost. The front panel sports a small volume knob, an amber LED that indicates power on, and a gold-plated headphone jack. On the back there is a pair of RCA input connectors, a power supply socket and a toggle switch. Most of the interior space is occupied by large electrolytic capacitors in the power supply. The main board is small and the circuit is simplified as much as possible, which is actually the most difficult part of the whole design process. Its heart is two surface mount integrated circuits soldered to adaptor boards, working with two tantalum capacitors. The assembly is mixed with some components soldered to the PCB and some soldered point-to-point. The signal from the RCA inputs runs via thin wires to the small potentiometer on the front panel and then to the gain circuit. A minimalist assembly work, quite clearly showing the result of many single improvements.

D/A converter/headphone amplifier
ASUS XONAR ESSENCE STU

I didn’t even manage to send my review of the three versions of Xonar Essence One DAC/headphone amplifier for the "Audio" magazine, and I already had at home the latest product - the smaller Xonar Essence STU. I received it for a listen, without a pressure to write a full-scale review, so it took a while before I found the time and place for it and I think it’s a great time to briefly present it by way of comparison to the Black Pearl reviewed above. The comparison will, of course, not be precise as the Asus is not only a headphone amplifier, but also a DAC and headphone preamp, but I hope some things can be explained.

Xonar Essence One is a small device, but has a great visual design based on the best examples of the 1970s designs. The front panel sports two volume knobs, separately for the line and headphone outputs, and two switches – an input selector and a power switch. The currently selected input is indicated by a micro-LED; a separate LED indicates “bit perfect”, that is, whether the USB signal has not been altered. Two micro-LEDs show the currently selected signal gain. There are three digital inputs – USB, Toslink and RCA. The asynchronous USB input accepts digital audio signal up to 24-bit and 192kHz, including 88.2 and 176.4kHz sampling rates. There is also an analog mini-jack input and of course analog outputs on solid-looking RCA connectors. Next to them is a gain switch. The unit is powered by an external 12V DC switching power supply. The circuit is built on a CMedia CM6631 receiver/USB converter, a Burr-Brown PCM1792 DAC chip and Texas Instruments LME49720 audio op-amps. The line output is handled by a L4562M audio op-amp and the headphone output on an OPA2132. The circuit is surface mount, except for nice-looking capacitors. Quality clock generators are also visible. Well done.


The unit sounds fast and transparent. Sound cleanliness is the characteristic that appeared while I auditioned the One Muse and came back here. Good recordings have proper depth and palpability, without merging the sounds into one mass. The resolution is surprisingly high for such an affordable device. It allows a pleasant listening to various recordings, without nervously looking for ‘audiophile’ albums. Everything I listened to with the STU sounded pleasant and satisfactory, even with the demanding HE-6 magnetostatic headphones from HiFiMAN! What we get with more expensive headphone amplifiers and DACs is greater sound palpability and density. The bass will also extend deeper. As it is, however, the STU gives a foretaste of sophisticated play with the sound, proving best with the USB input. I do not know how it is, but the sound from USB is usually worse than via the S/PDIF link from the CD transport. Here they were very close, which allowed listening to music directly from your computer (which I actually do writing these words). The treble is slightly lightened up, so I would choose headphones with a slightly lower tonal balance. There are plenty of them. Asus worked particularly well paired with the AKG K3003 earphones and the HiFiMAN HE-300 over-ear headphones. They added a slight body to the sound – the STU is not a high-end product after all and cannot do certain things like saturate the color. But it’s not its problem, but rather its price’s. It's just a very nice, versatile product from a computer company. It is obviously on a roll.

Price (in Poland): 1390 zł
www.asus.com
www.audiocenter.pl