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Price (when reviewed): 45 000 PLN

Contact: 255 S. Taylor Avenue
Louisville, CO 80027 | USA
tel.: (303) 449-8220



Provided for test by SOUNDCLUB


translation Marek Dyba
images Wojciech Pacuła

No 219

August 1, 2022

The American company BOULDER AMPLIFIERS is a manufacturer of high-end audio devices based in Louisville, Boulder County, Colorado. Since 1984, it has been specializing in the production of transistor amplifiers and preamplifiers, although the lineup also includes phono preamplifiers and D/A converters. One of the characteristic elements of the company's philosophy is the belief in the superiority of balanced over unbalanced designs and connections.

OULDER AMPLIFIERS IS ONE of the world's most important manufacturers of ultra-high-end electronics ” - this is how Steven Stone begins his article on this brand. On the one hand, it can be blamed on the fact that the brand is American, and the quote comes from an American monograph devoted to high-end electronics. However, it is an objective truth, and not a subjective view of an American audio journalist (more in the: Illustrated History of High-End Audio Volume Two: Electronics, ed. ROBERT HARLEY, Austin 2015).

The founder of the brand, JEFF NELSON, began his career in the late 1970s. with a company recording 8-track cassettes for radio stations. He then met Deane Jensen, the audio guru hired by recording studios to "fix problems" with equipment. Jensen has designed a discrete gain stage, the '990', which is a high-end alternative to integrated circuits. This module was adapted in many studios and later became the basis for Boulder amplifiers.

In the mid-1980s, the company's attention shifted from the professional market to the consumer (home) market. With time, it gained more and more followers, also in distant Asia. Its products have never been cheap, but over time they have become more and more sophisticated mechanically and electrically, and thus more and more expensive. In 1997, the 2050 Power Amplifier was introduced, which became an iconic Boulder device. As the first in its history, it featured new, unique heat sinks, 80 transistors per channel and offered a 1000 W output @ 8 Ω

The introduction by the end of the 2004 of the ‘800’ Series by the American company Boulder Amplifiers was a big event for us, audiophiles. This manufacturer got us used to the fact that its products are expensive or extremely expensive, and the new devices were much more affordable. They were still expensive - but not astronomically expensive anymore.

The '800' series was inaugurated with the first integrated amplifier in the history of this company, MODEL 865 |PL|. In 2020, i.e. six years later, '865' was replaced with a newer version, MODEL 866. Although it was nominally a development of an older design, it seems that new modules were used to build it, the issue of the visual design was also solved differently. Instead of a flat panel, we got a tilted front with longitudinal buttons and a touch screen. In keeping with Boulder's tradition, heatsinks with a unique shape were designed - they were fancifully curved cutters, not ordinary feathers.


LOOKING AT the '812' it's hard not to notice that this device was conceived as a miniature of the 866. This is indicated by both the similar front and the aforementioned heat sinks, very similar to those we saw earlier in the amplifier. Also the internal structure, as suggested by the manufacturer, was to some extent "borrowed" from the '866'. It is primarily about a discrete volume control system and a digital-to-analog converter. In turn, the headphone amplifier, an integral part of the '812', is the first device of this type in the company's history.

Which is what brings us to the issue related to determining the purpose of the tested device: what it actually is. The manufacturer describes it as a "DAC Preamplifier". This is partly true, both functionalities are present here. However, it is also a full-fledged headphone amplifier, with an analog input. But it seems more important to me that the '812' is equipped with an audio files transport module, which makes it simply a "file player with a preamplifier and headphone amplifier".

In press materials, Boulder emphasizes that all the circuits inside, as well as the chassis itself, were prepared by this company on its own. This is not entirely true. The SMPS - and there are two of these here - were bought from Delta, and the transport module is a Raspberry microcomputer. The other circuits, i.e. the DAC, preamplifier and headphone amplifier, as well as the chassis have been actually developed by the company.

⸜ FEATURES On the back of the 812 model there is an RJ45 port used by the device to communicate via home network and with the internet. '812' can also be connected to the network wirelessly, via Wi-Fi. Network communication is needed because the device has its own application that can be used to play files from NAS, the Internet or USB drives. It is available for iOS and Android, although it was not stable on my Samsung smartphone.

The files can also be played from local drives connected to one of the four USB ports on the rear panel, but they must have their own power supply. The files transport section works with NAS UPnP disks, it is also "compatible", as the manufacturer says, with the Roon system, as the so-called "Endpoint". The device also offers digital signal transmission wirelessly via AirPlay and via Bluetooth.

The heart of the device is, still, the digital-to-analog converter and it gives it a meaning. It is based on the Analog Devices AD1955A chips, and the digital signal from all inputs is upsampled asynchronously to 24/192 form. The manufacturer says that the basic solutions were taken from the DAC used in the 866 model, and these - as it was written at its premiere in the press release - were inspired by the 2011 model. It is probably not about the design itself, but about the idea behind it. Boulder programs digital filters in-house and does not use the ones implemented in the chips.

The DAC section offers several digital inputs: two optical TOSLink inputs, one electric RCA and USB. The manufacturer does not specify any boundary parameters, that is, the maximum sampling rate, word length, or the type of files it supports. Let me remind you that for the 866 amplifier it was a PCM signal up to 384 kHz and 32 bits and DSD up to DSD128. The device played FLAC, WAV, Ogg, AC3, MP3, AIFF, Apple Lossless, as well as DSD (DSF) files.

The user can set the sensitivity of all inputs, including the digital inputs (!). This allows you to adjust the volume of each input so that there are no big differences in volume levels between them after switching from one to another; the adjustment can go as low as to -25 dB, in 0.5 dB steps. Just as much, but towards left and right, we can change the balance between the channels. The Boulder software also allows you to set the volume level after turning on the '812', as well as the maximum volume. All these adjustments are made via the Boulder Controller application.

From the front control panel one can select an active output - line or headphone, activate the "mute" mode and change the input. Headphone jacks are hidden under a magnetically held flap on the side. There are four of them: "large jack" ø 6.3 mm, mini-jack ø 3.75 mm, and two balanced one - Pentaconn ø 4.4 mm and 4-pin XLR. The last two are worth trying as the device is fully balanced, from input to output. The app allows you to choose between two headphone amp gain modes - low and high.


˻ HOW WE LISTENED BOULDER 812 was placed on the top shelf of the Finite Elemente Pagode Edition Mk II rack. On its power supply section I put the Verictum X Block passive EMI/RFI filter. The device was powered by the HARMONIX X-DC350M2R IMPROVED-VERSION cable.

BOULDER was conceived as the center of the audio system and I treated it as such. The files were sent to it via the SILENT ANGEL N16 LPS double LAN switch, with its two modules in series, powered by the TIGLON TPL-2000A cable and via the TIGLON TPL-2000L LAN cable; more about it HERE |PL|. In turn, the digital signal was sent to the RCA input from the transport section of the SACD AYON AUDIO CD-35 HF EDITION player. The sound of the Boulder was compared to both the Ayon player and the MYTEK BROOKLYN BRIDGE files player.

The analog signal from the '812' was sent via Acoustic Revive Triple-C balanced cables either to the Ayon Audio Spheris III preamplifier or directly to the Soulution 710 power amplifier. I assessed the headphone amplifier section using four headphone models:
• HiFiMAN HE-1000 v2 → REVIEW, HF № 151, November 1, 2016,
• Audeze LCD-3 → REVIEW |PL|, HF № 100, 16 August 2012,
• Sennheiser HD800,
• Lime Ears PNEUMA → REVIEW, HF № 209, September 16, 2021.

The first two models are planar-magnetic ones and the other two are dynamic designs, with the Lime Ears featuring an armature structure. In the case of the HiFiMANs and Sennheisers, I used a balanced 4-pin XLR connection.

˻ Recordings used for the test | a selection

⸜ LARS DANIELSSON & LESZEK MOŻDŻER, Pasodoble, ACT Music ACT 9458-2, CD (2007).
⸜ PAT METHENY, What’s It All About, Nonesuch Records/Warner Music Japan WPCR-14176, CD (2011).
⸜ STAN GETZ/JOAO GILBERTO, Getz/Gilberto, Verve/Lasting Impression Music LIM K2HD 036, K2HD Mastering, „24 Gold Direct-from-Master Edition UDM”, Master CD-R (1964/2009).
⸜ JEAN-MICHEL JARRE, Magnetic Fields, Dreyfus Disques/Epic EPC 488138 2, CD (1981/1997).
⸜ PAUL MCCARTNEY, Kisses on the Bottom, Universal Music/Universal Music LLC [Japan] UCCO-3038, SHM-CD (2012).

STEREOTYPES IN THE AUDIO WORLD are doing great and will do well in the near future. And I say this because one of the stereotypes I have encountered every now and then is the belief that the sound of Boulder amplifiers is clean, dynamic, but rather bright and not very rich. Indeed, while listening to the company's devices at various exhibitions and shows, one could form a similar opinion, which only strengthened this stereotype.

But I also know that the loudspeakers that I have been using for years, which I am proud of and which invariably surprise my guests, usually sound poor at shows. Based on such experience, the Harbeth M40.1 (and their subsequent versions) could be not even taken under consideration by many, which would be a great mistake. I have the impression that Boulder devices are a similar case.

˻ DAC ˺

SOUND OF THE '812' AS A D/A CONVERTER, with the signal sent from the Ayon Audio CD-35 HF Edition player drive, with deactivated internal volume control, which was replaced by the Ayon Audio Spheris III preamplifier, was far different from how this device should sound in common opinion.

The comparison to the reference player showed that the '812' has an incredibly clean presentation - that's true - but also that it is saturated and not bright at all. I would even say that the Austrian player delivers stronger distributed band extremes, both from the top and bottom. The American DAC - because I started my listening sessions with this function - emphasized the midrange more, slightly reducing the low bass and withdrawing the upper treble.

And, let's admit, it did not have an easy task - I started with the album by LARS DANIELSSON and LESZEK MOŻDŻER entitled Pasodoble. There are only two instruments in the recording, a double bass and a piano, but both played with fire and in an unusual way. It is very easy to brighten up, harden the attack, etc., which Boulder did not take advantage of. And the stereotype even dictated it. It did something else instead. It clearly articulated the attack of the sound, but then immediately switched to a silky sustain. This resulted in an incredibly pleasant, but also fantastically clear and selective presentation.

It was clear that the resolution of the device is lower than that of the reference player, but I am writing the same sentence for sources that cost even 200,000 zlotys, so this is nothing that would diminish the Boulder’s class. And it did show something that Ayon has, but that 90% of other sources, not only digital, but also analog ones, do not have, namely the internal "harmony" of all sounds and the energy that flows from it.

Probably thanks to this feature the PAT METHENY listened to with Boulder, from the album entitled What’s It All About, was shown in an incredibly natural way. The musician plays it solo, on three different guitars. The beginning with The Sound of Silence was played on a 42-string instrument, thus covering a very wide band. The DAC showed it brilliantly. It brought the foreground slightly closer to me and saturated the attack with information; this device shortens the decay a bit, hence the "approximation". The guitar was shown in an incredibly dynamic way, very natural, with saturated sub-ranges.

It was clear, I had no doubts about it, that the designers perfectly control the phase coherence. Admittedly, the focus of the image was not as perfect as with the Ayon, but - let me repeat - this is a completely different price range and hardly any device can do that. It is not about pointing out a weakness. Because it is a perfectly focused sound, and this is where the stereotype actually works. Rather, the point is that '812' slightly brings the foreground closer, widens its panorama, extending the sound sources.

It delivers a tangible presentation, a close perspective and silkiness, but with excellent selectivity and saturation. This combination of features meant that the disc of STAN GETZ and JOÃO GILBERTO Getz/Gilberto, played by me from the version "24 Gold Direct-from-Master Edition UDM" (Master CD-R), immediately afterwards, had both "flow" and depth. The vocals of the Gilberto couple were presented close to me, had a large volume, but also a natural softness - something that could also be heard in Getz's saxophone.

Each time, with each new album, I understood better and better - at least I think so - the idea that Boulder engineers have about their sound. On the one hand, it is based on a rhythm that controls everything in such a way that a story can be built upon it. But the stories are led by colors and dynamics. That is why both the duo from the beginning of the test, Metheny's solo, the acoustic sound of the Getz/Gilberto disc, as well as the electronic, analog instruments, JEAN-MICHEL JARRE's album entitled Magnetic Fields were perfect in their melodiousness.

The album of the French musician had so many layers, so many shades, so many midtones that it will be difficult for people brought up on inferior sound sources, including analog ones, to recognize it. The Boulder sounds to some extent "analog", which again contradicts the stereotypes - both about the brand and the Compact Disc format. The sound is dense, it has a velvety depth, and it also has an internal compactness. This is one of the best digital-to-analog converters I have heard in my life, despite the fact that it is relatively - for high-end and this manufacturer - inexpensive.


SWITCHING FROM THE EXTERNAL PREAMPLIFIER to the preamplifier section implemented in the Boulder 812 resulted in a reduction in the resolution and depth of the sound stage. It was to be expected, it was normal. What surprised me, however, was related to the tonality - it became warmer and denser. The sound was now even closer to me, it was more palpable, even though it seemed more rounded at the same time.

Without a direct comparison, however, what I started with, the perfect timbre, came to the fore. It was still the rhythm that built a platform for it, but now the dynamics and punch weren't that important anymore. The saturation and density of the presentation turned out to be more important. That is why the bass from Jarre's album, the double bass from the Getz and Gilberto album, as well as the vocal of PAUL McCARTNEY from the Kisses on the Bottom, produced by Tommy LiPuma, the man responsible for the success of Diana Krall, and recorded by Al Schmitt, all these sound sources were beautifully saturated and low.

As I said, the preamplifier in the '812' is not very selective, which contradicts the idea of "wire with the current", which assumes that simplifying the signal path results in higher resolution and less coloration. This is true, but in the lower price ranges. In high-end, a high-end preamplifier is, in my opinion, indispensable. Even if we take this into account, it turns out that the '812' used as a DAC with a preamplifier - as well as a files player with a preamplifier, I’ll get back to it in a moment - is at what it does perfect. Better than the vast majority of devices of this type from the up to PLN 100,000 range.

˻ AUDIO FILES PLAYER ˺ The BOULDER ANDROID APP is not convenient to use, so it is worth investing in Roon right away - life will be much easier then. And it is worth it, if the files are an additional source for you. Even then, however, you have to remember that the Raspberry microcomputer implemented in the '812' is a nice device, I know it from many audio products, but it will not replace a dedicated audio transport.

Whatever the case, the Boulder device with high resolution files sounds warm, dense, saturated. It is not an artifact warmth, it does not result from coloration, but from saturation with information. Resolution is OK, but not crazy good. The designers focused on a strong, dense, warm foreground. Therefore, the depth of the stage is limited. Surprisingly, this module does not sound "digital" in any way. I would even say that the designers wanted to hide this feature as deeply as possible under the layers of colors, harmonics, etc.

Interestingly, when listening to entire albums, and not analyzing individual tracks, the advantages of this type of presentation began to dominate and I did not have to look for one aspect or another. This is a similar effect to - let me repeat - what is achieved with a turntable. Most turntables are heavily colored, yet they are listened to with fascination and commitment.

˻ HEADPHONES ˺ The headphone amplifier in the '812' model is the first product of this type in the history of Boulder. It takes care of very low distortions, amounting to 0.0010% and 0.0053% for - respectively - 2 and 20 kHz (at 32 Ω), completely negligible at a difficult load of 600 Ω (0.0011% and 0.0043 %). However, the output is limited to 200 mW and 80 mW (32 and 600 Ω respectively).

In the real world, that is in listening sessions, the Boulder with headphones sounded in a very similar way to its analog outputs. I had no doubts that the designers tried to imitate what they achieved with the XLR line outputs, but also that the DAC and volume control, common to the preamplifier and headphone amplifier, are largely responsible for the sound of the device.

As it turned out, we get a big, warm and close sound with the Boulder. The band's extremes are less prominent with it than the midrange, and the whole is dynamically calmed down. Despite the low power, I had no problems with driving all the headphones I had at my disposal and only the very difficult HiFiMAN HE-6 showed the limits of its current efficiency. And the point is not that the headphones will play very loudly with it, but that in terms of a comfortable volume levels, I have never had an impression that something in this sound was distorted.

It is not a high-resolution amplifier and it can be clearly heard that the focus is on tonality in its case. And the colors are indeed very nice, because they are presented in a fluid, dense and full-bodied way. It is a large scale presentation delivered close to the listener. Interestingly, the whole time I was listening, I preferred the Boulder with dynamic headphones, Sennheiser HD800 and Lime Ears Pneuma stage monitors.

The point is that I got the best-balanced sound with them. It was a sound without a lot of details, you won’t get it with this amplifier, without some outstanding dynamics - it was not the case either, but it was perfectly arranged and simply pleasant. And that seems to me the key to this section of the Boulder - listening through headphones will be extremely relaxing and, as I say, enjoyable. I never got bored with it, but also never had the need to finish the listening session ahead of time, tired of the sound.


BOULDER 812 IS a functionally complex device. We get four components with it: audio files player, DAC, preamplifier and headphone amplifier. As in every product of this type, there are dominant sections among them and those that are "built around" them.

The heart of the '812' is the digital-to-analog converter - I don't have any doubts about it. It is an excellent device that can be used in very expensive systems that will be built around it. The volume control section works very well, and if you want to put together a minimalist system with power amps and loudspeakers, or with active loudspeakers - it will do a very good job. Although adding an external preamplifier will open the sound and improve resolution, you will have to pay a lot for it.

The files transport and headphone amp sections are extras here, but the latter is a really good and welcome addition. With dynamic headphones from the top shelf we get a tangible, warm sound with a short perspective. It will never be too bright or too annoying, but we will not fall asleep with it, because a lot is happening in this sound. In turn, the files are in this case something like a MM phono preamplifier, featured in many integrated amplifiers. This is a nice addition if we treat it as a „free” bonus.

Having said that, I have to admit that Boulder surprised me with this device. The '812' is small and it sounds like a full-size, expensive product. Its sound is far from the stereotypical perception of this brand's devices and I am beginning to suspect that not good enough systems which these absolutely fantastic devices are presented, are actually to be blamed. The tested device has everything a real high-end needs and what music needs. Hence, a well-deserved ˻ RED FINGERPRINT ˺.


THE 812 IS A SMALL DEVICE, but very solidly constructed. Its chassis is bolted from aluminum plates by means of aluminum beams. The front is thicker than the other panels and is slightly sloped. This makes the device look more pugnacious. Additional stiffening of the design is provided by fancifully made heat sinks. To be honest, they are there a bit for a show, because no active elements are cooled by them, but - as I say - it looks great.

˻ FRONT AND REAR There is a small aluminum knob on the front panel, which we use to change the volume. Next to it, there are four buttons which activate the standby and mute modes, and select which output is active - line or headphone. And there is also a button to select inputs with white LEDs next to it. These indicate the selected input, but also - for a moment - the volume level.

The back looks like from a full-size products from other companies. It has been divided into two sections, which reflects the internal design of the 812. At the top there is a digital section, with four inputs - RCA, two optical and USB, as well as an RJ45 port for connection to Ethernet and four USB sockets for external drives. Below there is an analog section, with two pairs of inputs and one pair of outputs; all feature XLR sockets. Next to it, there is also an AC power inlet integrated with a mechanical switch. The XLR sockets are of a high class, screwed-on, and the rest of them of a somewhat lower class, soldered to the board and not particularly sophisticated.

˻ INSIDE As you might expect, the circuits inside were divided between several PCBs. At the top there is a digital input board and a small one with the audio files transport screwed to it. The latter is the only system, apart from power supplies, not manufactured by Boulder. It is a Raspberry Pi 3 B + minicomputer licensed by the Swedish company Proant AB, a specialist offering ready-made solutions for playing files, Wi-Fi antennas, etc.

The PCB with other inputs features an impedance matching transformer placed behind the RCA input, as well as an upsampler circuit - the signal from all digital sources is upsampled and then sent to the D/A chip. It is a Burr-Brown SRC4392 chip, which outputs 24/192 signal, upsampled asynchronously. Let me add that the USB input features the XMOS DSP chip. Interestingly, the digital section also has a volume control, although it is analog and discrete (solid-state). The volume knob is coupled to an optical encoder, which controls the circuits that switch active elements.

Below there is the actual D/A Converter divided between two boards, one for each channel. There are Analog Devices AD1955A chips, a multi-bit sigma-delta 24/192 chips, which also accepts DSD signals. The conversion of the current signal to the voltage signal is handled by two Burr-Brown OPA132 circuits with a FET input, characterized by a rapid signal raise.

And only then does the signal reach the largest PCB. It shows integrated circuits working as input selectors, as well as a headphone amplifier with four pairs of complementary transistors per channel. These are JFETs.

The whole is powered by two Delta switching mode power supplies. They are connected by aluminum armatures, to limit vibrations. A separate transformer supplies power to the digital section, and a separate one to the analog section. On PCBs with circuits, there are extensive sections that additionally "clean" the voltage. Also at the IEC socket there is a Pi type filter that minimizes noise.

The device is solidly made, has a well-thought-out, proprietary topology and a great mechanical design. Only the plastic, nondescript feet make you think about additional expenses in the future. And maybe the RCA digital input should be more solid.


Reference system 2022

1) Loudspeakers: HARBETH M40.1 |REVIEW|
2) Line preamplifier: AYON AUDIO Spheris III Linestage |REVIEW|
3) Super Audio CD Player: AYON AUDIO CD-35 HF Edition No. 01/50 |REVIEW|
4) Stands (loudspeakers): ACOUSTIC REVIVE (custom) |ABOUT|
5) Power amplifier: SOULUTION 710
6) Loudspeaker filter: SPEC REAL-SOUND PROCESSOR RSP-AZ9EX (prototype) |REVIEW|
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|
Power Receptacle: Acoustic Revive RTP-4eu ULTIMATE |REVIEW|
Anti-vibration platform under Acoustic Revive RTP-4eu ULTIMATE: Asura QUALITY RECOVERY SYSTEM Level 1 |REVIEW|
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|

  • HARMONIX TU-666M "BeauTone" MILLION MAESTRO 20th Anniversary Edition |REVIEW|


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