I somehow caught my eye on a DAC circuit based on PCM2704. And I really wanted to repeat it. I was captivated by its simplicity and good reviews. Then, when I began to gradually gain knowledge, it turned out that this chip was not the only one, and there were a dime a dozen sold amateur DACs. After reading some forums I found out. There is an opinion that the PCM2702E chip, although it has less functionality, but, according to reviews from writers, gives a more pleasant sound. So I decided to check these statements. Having rummaged around on the Internet, I found out that the PCM2702E is still considered a good DAC, although it has long crossed the age limit of 10 years. Moreover, there are many different circuits for implementing this converter with a filter and an amplifier, both on silicon and on tubes. Well, since lamps are now of greater interest to me, I opted for two schemes from Laconic Lab.
But first, about the implementation of the DAC module on PCM2702E.
3181
Exclusive PCM58 DAC with EF11, EF13 Telefunken “turtle” tubes in the master oscillator
The Telefunken turtle lamp is soldered directly into the PCM58 DAC board, its service life is 10-15 years
Selecting a Digital Filter
So, having chosen the final version of the digital-to-analog converter based on the Burr-Brown PCM58 DAC chip, I was faced with the full problem of integration into the digital filter circuit. I want to say that I don’t like digital-to-analog converters that use delta/sigma and similar algorithms for the unnatural effects that occur at their output. I tested a lot of digital filters and never came to a clear conclusion whether they are needed as part of a high-end DAC or not. Some fragments of music and entire compositions without a digital filter sound much more prominent, lively and richer than with it. And some without a digital filter are generally impossible to listen to, such a duality is incomprehensible... Here a lot depends on what the non-over-sampling DAC is working with, but the result is ambiguous in any case.
Even in my first digital-to-analog converters, I made toggle switches that allowed me to either connect a digital filter to the output of the DAC chip, or work directly. Five years of constant clicking have convinced me that audiophiles need to be given the opportunity to choose their own DAC operation: with or without a digital filter. In this regard, in the circuit of an experimental top-class digital-to-analog converter based on PCM58 Burr-Brown chips, I provided a connector with six modules that change within a few seconds. You can install either a shift register in the connector my development(see link), or a digital filter from the list below:
- CXD1144 in X4 mode;
- CXD1244;
- SM5842;
- SM5813 (DF1700);
- PMD100 in X8 mode.
Which is quite enough to select the sound character of a DAC to suit almost any taste. There is a separate article about comparing the sound and features of using different digital filter microcircuits. First of all, I can say that from the presented list, I like the digital filter chip CXD1144 the most, but this particular chip is very scarce, it is almost impossible to get it from suppliers and it will not be installed in a serial DAC based on PCM58 Burr-Brown.
Shift register
As for shift registers, just as with digital filters, I tried a lot of different options. On the Internet, information on shift registers is distributed by some incompetents or saboteurs who write about the “ten-story” schemes necessary for their implementation. In fact, in order to connect DACs with a resolution of 18, 20, 24 bit to a signal processor via the i2s bus and the Sony data transfer protocol, you need only 3 logical chips. In this case, there is no need to embed anything into the data bus. this leads to severe sound degradation.
I'm not talking about the fashion - installing complex PLIS format converters that simultaneously serve as a shift register. I tried this PLIS converter once as an experiment and became convinced that it was completely unsuitable for obtaining high-quality sound. The shift register is designed to delay the DAC load update signal by 2, 4, 8 bit clocks, respectively (for 18, 20 and 24 bit). The shift register itself must be assembled using high-quality vintage elements, tested for musicality and have a well-organized linear power supply. For the serial version of my DAC, I provided a shift register based on Signetix logic chips from the 80s, powered by a “parallel” voltage regulator on a vintage Telefunken transistor.
S/Pdif receiver
I'll tell you about the S/Pdif input receiver. The choice of the Yamaha YM3623 microcircuit was more spontaneous than based on any calculation. According to all Internet publications, this antediluvian microcircuit has huge jitter, which is unacceptable from the point of view of an engineering approach to the design of a high-end DAC. However, everything is not so simple here. It is this synchronous S/Pdif receiver with reclock that sounds much cooler than much newer and more sophisticated ones. Which raises a legitimate question: does the much worse sound of newer devices depend on the internal sophistication? Maybe that’s the point, that the input S/Pdif receiver of the Yamaha YM3623 inside is made in such a way that it couldn’t be simpler: minimum logic, minimum formats, current consumption less than 10 mA. Especially in comparison with the chip from Crystal cs8412 and the now fashionable DIR microcircuits.
All this mass of logic inside DIR and Crystal requires high-quality power supply and generates noise along the internal buses, which naturally creeps into the output of the microcircuit. After all, according to the logic of good sound, “the simpler the structure of the microcircuit, the more environmentally friendly, cleaner and more natural the environment inside it.”
These fabrications were confirmed in comparisons of the sound of a PCM58 DAC prototype with the ability to hot-plug S/Pdif receivers from different manufacturers and years of manufacture. As a result, I settled on the Yamaha YM3623, although it is criticized by all and sundry. Remember, the most expensive external digital-to-analog converters of the 80-90s, which were equipped with this particular microcircuit! The Yamaha YM3623 was also used in numerous professional audio processing equipment. For a high-end DAC, I chose this chip as a base one and supplemented it with an external receiver with hysteresis type AM26LS32 (in a ceramic housing) and an input S/Pdif transformer.
Tube Master Oscillator
Well, the main feature of my digital-to-analog converter is the built-in tube master oscillator based on Telefunken EF13 “turtles” and kenotron power supply based on an E311 lamp. The choice of these particular lamps for the serial DAC on the PMC58 is due to the fact that they are the ones that are easily taken out of the mass of vintage ones and are equipped with a metal case that acts as a screen. Their sound is more expressive than that of finger-type triodes, and their service life is so long that in the gentle modes of a DAC tube clock they can work for decades.
In my digital-to-analog converter on PCM58, I provided jumpers that allow you to select operating modes of the clock generator:
- Synchronous Recall. The clock is fed to the digital filter, to the resynchronization triggers and to the transport (in the transport, the signal may have to be divided by 2 or 3. For this option, I have a universal divider in my production program, described in the article about tube master oscillators);
- Asynchronous Recall. The digital filter receives the clock frequency from the S/Pdif stream, and the DAC itself is connected to the transport only with an S/Pdif cable. Thus, the master oscillator (clock) is involved only in the resynchronization node. The asynchronous relock option is slightly worse in sound than the synchronous one, but it allows you to connect the DAC to various CD players and transports, which is important for audiophiles who have not yet decided on a CD drive.
In both versions, the tube master oscillator operates constantly. All supply voltages are supplied to it from a high-quality external power source.
Power system
Great attention has been paid to the quality of the DAC's power supply. It does not contain any of the standard parametric (series with feedback) voltage stabilizers for such devices. This digital-to-analog converter has the best-sounding (IMHO) parallel shunt-type regulators. Most of them are assembled according to the simplest circuit on two high-quality and sound-tested parts: a vintage zener diode: Telefunken, Mullard, Motorola and vintage ballast resistors: NCF, Allen Bradley, Siemens.
Only two consumers are connected through a powerful parallel voltage regulator using a vintage Motorolla germanium PNP transistor. This is the PCM58 DAC power bus with a voltage of -12 V and a digital filter or shift register assembly. Some microcircuits consume a current of more than 50 mA, which a simple parametric stabilizer using a ballast resistor and a zener diode cannot produce.
I describe the differences in the sound of parallel and series voltage stabilizers in almost every article, and the parallel stabilizer always turns out to be better. Although it consumes significantly more current than series and, accordingly, requires a power transformer of greater power.
Electrolytic capacitors in the wiring of the DAC microcircuits are also very audible. In my DAC I have vintage 25 uF 35 V jars from Hydra, which outperform 90% of expensive electrolytes and sound simply excellent. In less critical places where minimum dimensions are required, niccons soldered from first generation CD players of a vertical design are installed. Unfortunately, I was unable to find modern electrolytes of similar dimensions with the same transparent sound. Therefore, I use proven vintage (naturally not dried out by time). In several places of the DAC there are ELNA Cerafine electrolytes and a lonely Black Gate of the NX series (thoughtlessly “plugging” Black Gate wherever possible harms the sound and wallet much more than their complete absence).
There are no ceramic capacitors or CMD elements in the wiring of PCM58 chips. In those places where it is necessary to suppress interference, Siemens and Philips film capacitors are installed; their number, type and ratings in each device are selected by ear. There is not a single DAC with soldered parts “in the image and likeness” of the pilot sample. Each digital-to-analog converter is purely individual (almost) and is configured individually, and I don’t work by eye...
By the way, I noticed that increasing the value of electrolytic capacitors above a certain value, as a rule, makes the sound heavier. It’s probably not in vain that in the most musical and “soulful” vintage CD players, the electrolyte rating in the DAC chip circuit does not exceed 20-50 uF.
The power supply of the digital-to-analog converter contains full-wave (FWW) rectifiers using vintage 1N5060 diodes. These are the diodes that were installed in the first generation Philips CD players, which are still the standard of digital sound. An attempt to replace these diodes with modern Schottky devices, Ultrafasts, etc. leads to complete degradation and killing of sound... So, even in low-power rectifiers - only vintage and nothing else... The windings of power transformers are made of vintage wire with a midpoint. The DPPV circuit migrated to the DAC from tube amplifiers, and everyone knows that it plays better than a bridge one.
Trimming of microcircuitsPCM58
The signal to the PCM58 microcircuits is supplied from D flip-flops from Fairchild Semiconductor or 74LS74 Signetics, and the DAC update signal is replayed in them. In my opinion, updating the remaining data is harmful and pointless.
At the output of the digital-to-analog converter, I installed transformers with k.tr. 1/10 on vintage Telefunken permalloy. I once wound them for a preamplifier as MM/MC transformers. In a serial DAC, I will most likely install transformers with two coils based on permalloy from UTC industrial transformers, because by ear they appear air-transparent, and by instruments they are extremely broadband. The second pair of experimental post-dac transformers does not fit on the board, so in the photographs they stand next to it.
The need to use a ballast resistor in the positive power bus of a DAC on PCM58 chips prompted me to the solution that I used in a hybrid amplifier - to use a lamp filament as a ballast resistor. In that amplifier, I loaded a powerful field-effect transistor with a quiescent current of 3 amperes onto the filament of a GM-70 lamp. The device played very expressively and was as simple as a board, but in terms of heat generation and dimensions it was “monstrous” and unsuitable for series.
In the experimental DAC, this role was taken on by a finger lamp installed in the power supply. It uses only filament, and for a digital-to-analog converter its performance does not play any role, the main thing is that the filament is intact. The nature of the sound can be selected by plugging in a variety of lamps that match the filament voltage and current.
And one significant nuance: it was possible to carry out a very simple and effective adjustment of the linearity of the 4 most significant bits of the PCM58 chip. This unit contains German carbon tuning resistors from the 70s. Each channel is adjusted individually and only by ear. Trimmer resistors for military purposes are characterized by increased reliability.
— a multibit digital-to-analog converter made on four industrial 18-bit AD5871 DAC chips.
— a tube headphone amplifier with an impressive power of 8 W and the ability to replace the tubes with “solid-state” amplifier modules, which are purchased separately.
The devices are designed using a fully balanced amplification topology.
Appearance
All Schiit devices are made in the same style, and models from the upper price category are no exception. No sapphire crystals or diamonds in the handles, no unnecessary overpayments for gilding the case and screens. However, now the cases are full-size and look harmonious in any audiophile equipment rack.
The controls are still minimalist: a single button on the DAC that selects the desired input.
On the headphone amplifier, in addition to the volume control, there are switches for gain and selection of balanced or unbalanced input.
The rear panels of the devices are also laconic.
The Gungnir DAC has USB, optical and two coaxial inputs, one of which is BNC. It should be noted that BNC is a connector specifically designed to transmit high frequencies (as opposed to low frequency RCA). BNC is also optimal for high-quality digital signal transmission.
There are two pairs of unbalanced RCA outputs and balanced XLR outputs that operate simultaneously.
The Mjolnir 2 amplifier has balanced and unbalanced inputs on the rear panel, as well as outputs for connecting other equipment, such as a power amplifier for speaker systems.
The power switches on both devices are also located on the rear panel. And if in the case of a DAC that consumes a relatively small power of 20 watts, you can close your eyes to this and leave it constantly on, then in the case of a headphone amplifier that consumes 45 watts in idle mode and has a limited lamp life, this is quite inconvenient. At least in a rack you can’t easily turn off the power. This is exactly the case when you have to pay for the beauty and design of the front panels with convenience.
Passport specifications
Gungnir Multibit
- Digital-to-analog conversion chip: Analog Devices AD5781BRUZ ×4 (two per channel, balanced circuit)
- Digital filter: proprietary closed-loop type with bit precision function, implemented on an Analog Devices SHARC DSP processor
- Analog Path: Fully discrete JFET buffer stages for balanced output and JFET summing stages for single-ended output, direct coupled
- Operating frequency range: 20 Hz - 20 kHz, ±0.1 dB; 1 Hz - 200 kHz, −1 dB
- Maximum output amplitude: 4.0 V RMS (balanced output), 2.0 V RMS (unbalanced output)
- Total Harmonic Distortion (THD):<0,005% (20 Гц — 20 кГц, при полной выходной мощности)
- Intermodulation Distortion (IMD):<0,004% (измерены по стандарту CCIR)
- Signal-to-noise ratio (S/N): >115 dB (relative to 2 V RMS)
- Inputs: coaxial S/PDIF (RCA and BNC), optical S/PDIF (Toslink), USB
- Supported formats: up to 24 bit/192
- Outputs: One pair of balanced XLR connectors and two pairs of unbalanced RCA connectors
- Output impedance: 75 ohms
- Clock recovery: Bit-accurate at all native sample rates via Adapticlock analysis and VCXO/VCO regeneration
- Power supply: two transformers (one for digital, one for analog) with 8 control stages, including separate power rails for critical sections of the digital and analog paths
- Upgradability: separate USB input and DAC/analog circuit boards, replaceable
- Power consumption: 20 W
- Dimensions: 406×223×60 mm
- Weight: 4 kg
Mjolnir 2
- Operating frequency range: 20 Hz - 20 kHz (−0.1 dB), 2 Hz - 400 kHz (−3 dB)
- Maximum power at load impedance:
- 32 Ohm: 8.0 W RMS/ch
- 50 Ohm: 5.0 W RMS/ch
- 300 Ohm: 850 mW RMS/channel
- 600 ohms: 425 mW RMS/channel
- Total Harmonic Distortion: Less than 0.005% (20Hz - 20kHz, 1V RMS)
- Intermodulation distortion: less than 0.006% (CCIF test, 1V RMS)
- Signal-to-noise ratio: over 104 dB (unweighted, relative to 1 V RMS, in low gain mode)
- Interference: Less than −75 dB (20 Hz − 20 kHz)
- Output impedance: 1.0 ohm (high gain), 0.3 ohm (low gain)
- Gain: ×8 (18 dB) or ×1 (0 dB), front panel switch
- Topology: Tube voltage amplifier or LISST solid state voltage amplifier, Crossfet push-pull parallel output stage, Non-inverting single voltage gain stage
- Power source: a special transformer for the output stage of Cyclotron 4, powered by filter capacitors with a capacity of more than 65,000 μF, plus a separate transformer with a voltage of 200 V and storage capacitors with a capacity of more than 4000 μF for the high-voltage discretely controlled input stage
- Inputs: a pair of balanced XLR jacks and unbalanced RCA jacks, switchable using a toggle switch on the front panel
- Outputs: 4-pin balanced XLR, 6.3mm minijack, pair of 3-pin XLR pre-outs, one pair of unbalanced RCA
- Power consumption: 45 W
- Dimensions: 406×223×60 mm
- Weight: 5.4 kg
- Approximate price: 76,500 rubles (only with 6BZ7 lamps) at the time of preparation of the review
Internal structure and measurements
The internal structure of the Gungnir Multibit DAC will cause a positive reaction in any engineer. A hardened audiophile may think that for such a price, gold parts and film capacitors were underused. But wait, Schiit engineers have prepared another surprise for you!
On the motherboard, according to the accepted Schiit concept, there are separate modules for a multi-bit DAC and a USB input. Note that this does not reduce the cost of the device, but allows for higher quality wiring and operation of individual components compared to if everything were mounted on one board.
Particularly touching are the personal thanks to the engineers written on the boards; this once again confirms that the device was designed by people for people, and not by obscure OEM manufacturers solely for making money. The DAC has many interesting solutions aimed at improving sound quality.
The USB receiver is made on the familiar CM6631A controller, but has galvanic isolation, and done correctly: the master oscillators are located on the “clean”, galvanically isolated side. Yes, it is more expensive, yes, it is more difficult to implement, but this is the only way to get a good result. And then it's done. So you can safely connect the DAC via USB to your computer and not worry about interference and ground loops. Note that in our case, Windows 10 independently found and installed the required driver. It was not possible to install USB drivers from the official website.
The S/PDIF receiver is made on the old familiar, but no worse, CS8416 chip.
Also on the motherboard, in addition to transformers, rectifiers and primary stabilizers, there is a rather interesting phase-locked loop unit, with its own oscillators at frequencies of 22.579 and 24.576 MHz. This proprietary technology is called Adapticlock and serves to further suppress digital signal jitter.
On the multibit DAC board, in addition to the AD5871 itself, there is an Analog Devices ADSP-21478 digital processor, which is used for digital signal filtering. After it and before the AD5871, according to all the canons of building high-quality DACs, there is a reclock made on separate digital D-trigger chips.
The post-DAC filter-amplifier is a separate, audiophile topic. Surprise! It is implemented on JFET field-effect transistors using non-OOC circuitry. Yes, there are microcircuits there, but the signal does not pass through them, they are only needed to maintain zero at the DC output. This is a gift to those who believe that negative feedback in the audio path is evil. Yes, this affected the measurements, but not the sound.
Objective measurements were carried out when working from USB under Windows 10.
In this case, the measurements can be characterized simply: the manufacturer did not sneeze at them, the zero-emission concept and sound were put at the forefront. And the technical specifications with many zeros after the decimal point, posted on the official website, serve rather to avoid unnecessary excitement among people who listen not to sound, but to graphs. We do both.
The tube spectrum of distortion produces field exhaust, and, apparently, this was done intentionally.
To verify this, the measuring card was connected directly to the output of the DAC, before the JFET filter-amplifier.
In this case, we see very low distortion of the AD5781 DACs themselves with a typically multi-bit signal spectrum. Just for fun, I listened to this version. Let's just say: without a harmonizing filter the sound is not very good. Despite their low distortion, DACs subjectively sound very sharp.
We also ran the J-test test file, which allows us to show flaws in the construction of the digital part, recalculation or increased jitter of the digital signal. The result is perfect: no side interference beyond the main comb. This confirms the very high quality of design of the digital, “pre-audiophile” part of the device.
A few words about the multibit converters used. The AD5781 is one of the best multibit converters produced today, but they are also very expensive, about $40 apiece. There are also AD5791, 20-bit precision, they already cost $100 apiece and are used in the top Schiit Yggdrasil DAC.
Despite the costs, we support the manufacturer in using parts that are produced here and now, and not obscure old warehouse leftovers or even Chinese fakes. This guarantees the quality and repeatability of product characteristics.
The post-DAC filter and output are made using JFET transistors in a SOT-23-5 package marked XL, which could not be identified. Wima foil capacitors and Nichicon KW electrolytic capacitors are also used.
The filter circuitry is fully balanced, so the unbalanced output only receives half of the output signal, essentially only two DACs are working instead of four. This affects measurements and subjective sound quality, so we do not recommend using an unbalanced connection to the amplifier, although it is possible.
The Schiit Mjolnir 2 headphone amplifier is designed according to a similar balanced ideology. But here the emphasis is already placed on the output power and stability of the power source to drive the most complex load.
Powerful 30-watt transformers, a capacitor bank with a total capacity of 65,000 uF, IRF610 output transistors capable of dissipating 54 watts of power, connected using the proprietary Crossfet topology - all this allows the amplifier to operate even with an 8-ohm load connected to the balanced output.
The manufacturer uses transistors of the same structure in both amplification arms, which ensures their excellent identity and lower distortion.
The heart of the amplifier, which provides the main signal amplification, is an electron tube with JFET transistors at the input. The present microcircuits are used only to maintain zero at the DC output; the signal does not pass through them. The amplifier's circuitry is unique and does not resemble standard solutions.
The unbalanced output is implemented quite differently; a separate bipolar transistor amplifier is provided for it, although the main amplification is also provided by the lamp. The maximum power of the unbalanced output is limited to 2 watts. Balanced and unbalanced outputs operate simultaneously, but at the same time independently of each other.
The soft glow of a vacuum tube warms the soul of any music lover. Tubes produce a special sound in some way, emphasize voices, timbres of instruments, muffle and soften the sound, veil garbage in the recording... But what if you want to cheer yourself up and listen, for example, to several Death Metal albums? Schiit has taken care of such desires by offering a solid state tube replacement circuit - LISST. Essentially, this is a two-stage amplifier mounted in a housing. And there will definitely be no veil with him - checked!
Technically, the Mjolnir 2 amplifier gives a very good impression, and in terms of circuit design it is not inferior to the Gungnir DAC, but what about the measurements?
For testing, we used a professional balanced Lynx L22 card, and in most cases the measurement results were limited precisely by its quality, and not by the amplifier.
Regardless of the use of a 6BZ7 vacuum tube or LISST solid state circuit, the balanced amplifier performs excellently into a 300 ohm load. When the load is reduced to 32 Ohms, only the second harmonic increases, which will not affect the sound in any way.
An unbalanced amplifier is more demanding on the load, and with a power of more than 100 mW into a 32 ohm load, distortion grows catastrophically. At a 300-ohm load, nothing like this happens. Therefore, for maximum quality, we still recommend using a balanced output.
The output impedance of the balanced output is about 0.8 Ohm, it perfectly damps any headphones, prevents uncontrolled resonance phenomena, which ultimately provides natural and dynamic sound.
Listening
We won’t bore you with listing the musical material used for listening; it all depends on personal preferences. Note that we were not limited to any specific styles of music; we listened to the Gungnir Multibit DAC on different systems, and used different headphones with the Mjolnir 2 amplifier, from Oppo PM-2 to Audio-Technica M50x. A person who has “grown up” to this class of audio technology knows perfectly well what he wants to get in sound and what he will use to listen to his favorite music.
The Gungnir Multibit DAC can be described as a source that is ready to play almost any music with high quality. It cannot be called too harsh or, conversely, too delicate. But a multibit heart is undoubtedly more predisposed to dynamic and fast music such as rock and metal, and pop music performed by Gungnir will sound much more interesting. Of particular note is the way the voice is reproduced: it seems much more alive. And in general, the mid-frequency range is reproduced perfectly. Instruments are reproduced separately, there is no mess of sounds at all. In many old familiar compositions, many new sounds were heard that were previously masked in the general rhythm. The bass is elastic and punchy, but at the same time there is not a hint of buzz. In some systems there may not be enough bass, but where there is bass, it will be excellent. High frequencies have never been the strong point of multibit DACs; in this case, the manufacturer tried to make them as neat and comfortable as possible. Yes, there is some roughness, but it is by no means dirt! Quite the contrary, in high-quality headphones you can hear much more detail in the high-frequency range than when using modern “sleek”, boring DACs like the AK4490. The limiting factor here is the quality of recording and mastering of the phonogram itself. Correct sound reproduction of the high-frequency range is also facilitated by a very low level of jitter; when connected via the USB input, the DAC plays perfectly! This is how we recommend listening, but if you have a high-quality audiophile digital source, you won't be disappointed with the coaxial connection.
To summarize, Gungnir Multibit can be characterized as the most neutral and even, perhaps, slightly detached source. He does not dump the musical picture directly on you (and deal with it as you wish), but presents it, delicately and accurately revealing the intention of the composer or sound engineer, without hiding or embellishing the details. The listener is more in the role of an observer, contemplating the riot of sounds from the side. You won't find yourself in the center of the orchestra or on stage next to the musicians. But you will hear everything. This is how people listen to music. Dynamic, fast, open. This is why old multibitniks love it, and this same trait has been preserved in the new Schiit Gungnir Multibit.
We admit that, having received this DAC for testing and carrying out preliminary measurements, we were somewhat disappointed with the low measurement results, and there was no wow effect during the initial listening. However, the longer this DAC was in our possession, the more we liked it, revealing more and more secrets of old familiar compositions and without causing any irritation even after very long listening. The sound is very comfortable, but at the same time clear - a rare combination. That is why it is recommended, when purchasing equipment, to conduct a fairly long test, at least for several days, and only after that draw conclusions. Perhaps the option that “hooked” you in the store with its dynamic and bright sound will blow your mind in just three days at home. With Gungnir Multibit, everything turned out the other way around.
The sound of the Mjolnir 2 headphone amplifier also deserves the most flattering epithets; it is not for nothing that it is the most expensive in the manufacturer’s line.
The amp's sound is completely neutral and clear, and the bass control is amazing. Listening with headphones through this amplifier allowed us to discover new subtleties of bass parts: for example, it turned out that in some compositions the sound engineer deliberately introduced distortion into the bass, which was never noticed when listening on speakers. In general, the bass has ceased to simply set the rhythm; it has become an interesting object of observation. The amplifier controls any headphones so masterfully that it seems that you can connect external speakers to it and listen to music in peace.
The use of 6BZ7 vacuum tubes or LISST solid state modules is purely a matter of taste. In both cases the sound is very good. The tubes tint and soften the mids, but give some veil in the highs. Solid-state modules provide the cleanest high frequencies, a wide stage and a neutral sound; they are more preferable for modern electronic and rock music.
To understand the subjective difference, we tested the amplifier's balanced and unbalanced outputs using Oppo PM-2 headphones and replacement cables with corresponding connectors. The outputs have only minimal differences in coloration and sound quality, but balanced outputs generally produce higher-end sound, resulting in better bass control and cleaner sound at the same volume. If you do not go beyond a reasonable volume, then both outputs have excellent sound, the difference is purely tasteful. If you want to give in, remember that the balanced output in high gain mode has a maximum amplitude of 20 volts! Probably, I still needed to connect the speakers.
Among the features of the amplifier, it should be noted that due to good bass control, it does not “inflate the low frequencies,” so if the headphones have a rolloff in the low-frequency region, then the bass will end up being not enough.
Conclusions
And made for each other! You understand this when you turn them on together and just start listening to music. You can spend more than one hour contemplating music, only time forces you to stop listening. Isn't this the main criterion for the quality of technology? We think yes. Schiit engineers think the same way, creating products that are worthy of admiration both in technical terms and in terms of the transmitted sensations.
The Aune T1 is a tube USB DAC with a built-in solid-state headphone amplifier that has sold over 50,000 units. all over the world.
Main Features
1. External linear high-quality power supply, which implements additional filtering. This solution helps eliminate noise from the power source.
2. The DAC is implemented on an asynchronous USB controller SA9027 and a PCM1793 chip.
3. Aune T1 Mk2 USB DAC is an external sound card, DAC and high quality headphone amplifier in one package. Aune T1 can also be used with powered speakers as part of your home hi-fi system.
4. Aune T1 works under Windows 7, 8, Vista, XP, Mac OS operating systems. Can be connected to iPad. No additional driver installation required.
5. The headphone amplifier module is made separately and can be replaced later when the corresponding upgrade is released. The lamp must warm up completely before playback begins. When you turn on the device, the light bulb heats up for 30 seconds, after which a white indicator lights up under it, and only then the device begins to function. The Aune T1 Mk2 USB DAC also features switching amplification modes.
6. New modular design. Multiple boards within the device are powered independently, eliminating crosstalk. The DAC also features a safety shutdown that prevents damage to your headphones or speakers when the device is turned off.
7. Aune T1 Mk2 USB DAC is made of high-quality audio components: ALPS potentiometer (Japan), WIMA capacitors (Germany), ENLA electrolytic professional audio capacitor and so on.
8. The amplifier will pump headphones with a resistance of 30-600 Ohms. The amplification circuit is OP+BUF.
9. Aune T1 Tube USB DAC has one line input and one line output.
Video (promo, English)
Specifications
Tube: 6922EH Electro-Harmonix (Made in Russia)
Frequency response: 20 Hz - 20 kHz
SNR: >=120 dB
Output power: 1000 mW/32 Ohm, 400 mW/120 Ohm, 150 mW/300 Ohm (maximum 20 V)
Output Impedance: 100 ohms, 10 ohms (headphones)
USB interface:
Data up to 24 bit / 96 kHz
Operating systems: Windows XP/Vista/7/8, Mac OS
Power: AC 220/110 V
Size: 155*97*40 mm (L*W*H)
Contents: power supply, USB cable, adapter 6.35 - 3.5 mm
