Which Chinese DAC to choose? We assemble a high-quality hi-end DAC from an inexpensive kit

Good afternoon:)

Today, audio DACs are not made only by the lazy. The entire Internet is littered with industrial, semi-industrial and completely handicraft products.

Since we are not lazy, we also want to do something of our own. And now, albeit slowly, but nevertheless, we are purposefully moving in this direction.

Among other tasks, we have to solve the issue of connecting the DAC to the computer. There are many options, but we are primarily interested in connecting via USB using specialized chips.

Of course, you can make your own “USB controller” using a microcontroller. Or assemble it on an FPGA. We are exploring these options. But they are much more complex and lengthy, and we really want to assemble something as quickly as possible :).

In our search for specialized microcircuits, we came across a description of the SA9027 chip. In essence, this is a simple ready-made USB audio controller. It takes care of all the work with USB. It communicates with a PC, receives an audio stream from it and transmits it via the I2S interface to the DAC... The chip supports receiving and processing an audio stream with a sampling frequency of up to 96 KHz and a bit depth of up to 32 bits. It should suit us.

To make a final decision, I decided to get acquainted with the microcircuit in person and spend several sleepless nights in its company : look at the modes, “feel” the signals, connect some kind of DAC to it...

They didn’t want to take the bare chip. I would have to immediately deal with the switching circuit, wire and manufacture the board, and solve other issues... But I don’t need this now. All I want is to see what the chip can do. Therefore, we decided to take a ready-made device.

In the vast expanses of our Motherland, nothing suitable was found, and we turned our gaze to the east. Aliexpress, as usual, did not disappoint and offered to buy inexpensively what we needed.

We ordered... The seller, customs and Russian post worked just brilliantly this time, and after 12 days the parcel was already with us.

Here's what we got:

Note: in my opinion, the inscription “USB HIFI AUDIO DAC” on the entire lid looks the same as a huge inscription “BOTTLE OF BEER” would look on a bottle of beer....

And here are its insides:

The device is assembled on two microcircuits. One of them is a USB audio controller, the second is a DAC. The ES9023P chip acts as a DAC. And the USB audio controller is exactly what we need - SA9027:

As I already wrote, we bought the DAC exclusively for experiments. In it we are only interested in the SA9027 chip. And yet, before gutting it and remodeling it, we decided to satisfy our curiosity and, at least very superficially, see what the purchased device can do.

Attention: All further measurement results are for informational purposes only. The measurements were carried out without proper preparation, in passing, using a PC and sound card. The sound card used is the first one available. The connecting wires are also random and pick up network interference (manifests itself in the form of peaks at power frequency harmonics). Since I am only interested in the level and spectrum of distortion, I reduced the noise level by averaging the measurements.

First of all, I took measurements for a sound card with a closed input:

After that, I connected the DAC and output a 1 KHz sine wave with an amplitude of 1.5 V through it.

Note: Peaks at frequencies that are multiples of 50 Hz are interference to the measuring wire. They have nothing to do with the DAC. But the harmonics of the 1 KHz signal are his creations.

The result is not bad. Especially when you consider the price of the device. Harmonic levels are low. But the tail is long. In general, the manufacturer of the DAC chip promised better results).

And now a few words about the dangers of ceramic capacitors

Not all of the distortion that is visible in the previous figure is created by the DAC chip. Some of them are generated in the passive components of the circuit. It is not my plan to bring this DAC to perfection. I want to gut him. But first, let's do a little experiment.

The audio output of the DAC is structured like this:

In principle, nothing unusual. Interchange by constant voltage and a filter that cuts off high-frequency components in the output signal. We will not discuss ratings and tuning frequencies. I was more interested in the type of capacitors C23 and C20. They were ceramic...

Ceramic capacitors love to generate distortion. Depending on the material, the effect may appear to a greater or lesser extent, but in my experience it is always there.

Made a couple of improvements:

The spectrum has become much cleaner. It is clearly visible that the level of harmonics has sharply decreased, starting from the third. It is quite logical to assume that their source was those same ceramic capacitors...

The well-known conclusion is that ceramics should not be used in audio circuits.

It seems that this has been known for a long time, but for some reason such constructions come across again and again. It is worth noting that in this way ceramics are used not only in inexpensive “Chinese” devices....

These are the results. Now there are a lot of experiments ahead with connecting your own DAC, screwing in an MK for control, etc... All this will come a little later.

Best regards, Konstantin M

I invite you to visit, see all the newest and most interesting :) I will be glad to communicate) :

The main thing in our business is to take the right start! I don’t have to worry about building a product line from cheap consumer goods to the very high-end. Therefore, I can afford to immediately choose the digital-to-analog converter chip I like and build a design around it. So, the “mystical DAC” was taken as the basis "as they call it on the Internet. I will not make it from a small microcircuit big secret, but let's still keep the intrigue first.

Build a good DAC I’ve been planning for my beloved since the last century, but somehow I didn’t get around to it and more priority tasks took over. And here, to my delight, a customer appeared, on the one hand, able to appreciate good sound, on the other hand, willing to put up with a certain level of “homemade” in the finished device. Naturally, I will make every effort to ensure that my clients are satisfied with their choice. What my “pre-production” products lose in comparison with serial devices of popular brands is:

1. some of the editing is done with cobwebs on mole rats, and not on print, which has a positive effect on the sound quality, but, alas, will not be available in production samples;
2. I don't skimp on little things like surge protector or shunt tanks, which, by the way, has been caught by recognized authorities more than once;
3. My “brand” is not yet very widely known in narrow circles :)

Let's start, pay attention...

Where to begin? That's right, it's best to start with a ready-made device, even a simple one, but containing key components. In China for US $ 50 In general, a good set was purchased for self-assembly DAC. As I already said, the Chinese economic genius is not distinguished by any special technical talents, so everything in that set was at a minimum, exactly according to the datasheets. Except that the creators of the set built, as it seemed to them, very high quality: they stuck " KRENOK" with garlands. But the kits came with very appropriate R-core transformers.

On at this stage The task was not to somehow specifically control a digital receiver or DAC, so the hard-wired minimalist S/PDIF->I2S->DAC chain suited me quite well.

I didn't consciously try to find a DAC with a USB input. The reason is simple: the computer generates a lot of noise and there is no desire to let all this garbage into the audio device. Of course, there are methods, but I still haven’t come across a single DAC with proper isolation USB input(devices for 1K green and higher, as well as products of Russian audio “left-handers” do not count).

I consider it necessary to note that despite all my quibbles about the circuit design, etc., the quality of the printed circuit board is simply excellent!

Taking control of the situation into our own hands

In the documentation for the DAC, in one place it is written that the analog power leg must be bypassed with an electrolyte of 10 μF and ceramics of 0.1 μF. In the diagram, leg 18 is bypassed exactly like this.

A little further in the same document it is said that it is advisable to bypass the input on pin 17 with an electrolyte of 10 μF and ceramics of 0.1 μF. The developer acted in full compliance, a dutiful comrade, just great!

Another place in the documentation says that 17 leg Can run it straight to analog power. This is what we see in the diagram :)

The funny thing is, not only in the diagram, but also on printed circuit board everything is laid out like this: with two electrolytes and two 0.1 µF capacitors, with a short one right between the 17th and 18th legs of the chip (the path to the capacitors from the 17th leg goes under the chip body):

Everything came just this dirty from the factory. How I washed it is a different story :)

For those who are especially curious: the pitch of the legs of the microcircuit body is 0.65mm.

I once came across a gorgeous picture from my friend Vadich-Borisych on VKontakte: " resistance is futile". Here, it inspired me, it is as useless here as the duplicated shunt capacitors in the diagram above, I redrawn the “circuit” especially for you:

I needed to control what was happening on the 17th leg. I had to cut him alive. It’s good that they haven’t put a jumper under the chip yet - the prospect of unsoldering one leg of the SSOP case is somehow not encouraging.

Mediocrity goes overboard

What digital-to-analog converter is complete without operational amplifiers?

That's right, only high quality DAC. So I simply did not solder the modest filter on the NE5532. Maybe it was worth it to have something to listen to for comparison and make sure how unconvincingly deep loop-backed op-amps play... But I already have a CD player from a venerable manufacturer, which very diligently plays the very mediocre sound of op-amps, although hidden behind the sonorous name HDAM and soldered into small screens. And there are plenty of other similar “samples”.

Study, study, and... think!

Perhaps, without exception, on all DACs from manufacturers from the “heavenly Empire” I see the same locomotives from “KRENOK” (the photo on the right is not mine, caught on the Internet). By fanning out serial voltage stabilizers, the developers are obviously trying to achieve better power supply isolation and reduce the penetration of interference from the digital part to the analog part. Unfortunately, the masses lack what I call “current thinking” in circuit design. In fact, everything is simple and... a little sad.

Look at some LM317 from the output side. You will probably find a 10 µF electrolyte and a few other small containers. Now let's estimate the time constant in this circuit: just look at the datasheet and make sure that the output resistance of the "crank" is very small, which is what the developers of the integrated stabilizer sought. To be honest, I’m too lazy to count now, but interference with frequencies from, say, 100 kHz and below the roll “sees” right at its output, that is, the control electrode and, as it was designed, transmits these pulsations “upstream on command,” diligently trying to maintain the voltage on its way out.

Current fluctuations reach the output of a higher voltage stabilizer. Following the same logic, fairly high-frequency current changes still flow almost unhindered throughout the entire chain of stabilizers. And they whistle and make noise to everyone around.

I see the only rational grain in the use of two linear stabilizers in a row is that small precision stabilizers usually do not tolerate high input voltages, and kits for self-assembly of DACs often fall into the hands of soldering riggers, who often do not even bother to look into documents for the components used, and the kits should still work...

The spread of sufficiently high-frequency interference can be easily prevented by adding... ordinary resistors to the circuit. Simple RC filters by entrance linear stabilizers will provide excellent decoupling of RF pulsations in both directions, sharply reducing the “distance” in the circuit where surge currents reach (including the “ground” wire!)

So the power supply has undergone major changes on the board. Alas, it was not without a couple of cut tracks and hanging installation.

Sometimes a small resistor is much more effective than a large capacitor:

We respect the heritage of our ancestors

Instead of a stupid bridge, we install super-fast diodes in the rectifier, which significantly reduces the current “shocks” when the diodes are turned off. This technique is quite popular and quite meaningful, so we will use it too:

By the way, it is precisely the lack of understanding of how to decouple linear stabilizers at HF ​​that leads meticulous developers to start installing a separate transformer for each block of the circuit. Another very popular one, but also costly solution problems of series stabilizers: use of combinations of current source - parallel stabilizer. IN in this case Everything is fine with the decoupling, but the power has to be dissipated with a considerable margin.

Let's not demand too much from the "whale"

A separate article is needed to describe a series of experiments with various stabilizers. Here I’ll just note that, to the credit of the developers from the Middle Kingdom, the LDO stabilizer they chose, lm1117, may best option from commercially produced and relatively affordable integrated stabilizers. All sorts of 78XU, LM317 and others like them simply rest due to the incongruously high output impedance (measured at 100 KHz). Alas, the precision LP2951 went into the same basket. The TL431 behaves a little better in a shunt stabilizer circuit, but it has its own story: TL431 can be very different, depending on who made them. 1117 wins by a landslide. Alas, it also turns out to be the noisiest stabilizer. It rumbles and squeaks, both with and without load.

I had to assemble the stabilizer myself, using discrete components. From just two modest transistors, following the HotFET ideology, we managed to “squeeze out” everything that in an integrated design requires dozens of transistors and still falls short. Of course, to ensure the work of the “sweet couple”, several more active components were required... but that’s again a completely different story.

Interesting result of macro photography: naked eye I didn’t notice that the board was not completely cleaned of flux.

Polymers rule the roost

The latest modification aimed at achieving the most accurate sound transmission was the “smoothing” of the power supply.

In critical places, the usual (albeit good ChemiCon) aluminum electrolytes from the kit were replaced with solid-state aluminum Sanyo OS-CON. Since I collected two identical sets in parallel, it was possible to arrange “A/B” testing. The difference is barely audible, but it is there! Without a signal with conventional electrolytes, at (very) high gain, there was a certain “noise space” in the headphones. Polymer electrolytes take us into the absolute.

Sanyo OS-CON - purple barrels without a notch on the lid.

If you don't want to think with your head, work with your hands

On almost all boards and DAC kits using digital receiver CS8416, the Chinese put a toggle switch so that the user can choose between optical and copper S/PDIF input (the photo on the right is a typical example caught on the Internet). So: there is no need for a switch there, the receiver chip can easily listen to two inputs without any outside help, be it a crude toggle switch or a smart microcontroller.

I’m sharing with you a trick I spotted on a demo board from Cristal Semiconductor themselves. It is enough to connect, for example, copper S/PDIF to RXN, and the output of the optical TOSLINK receiver to RXP0.

I hope there is no need to explain how this works? 😉

Even in the reference design, the companies screwed up and forgot the shunt capacitor in the TORX power supply :)

Economy or illiteracy?

It can be very useful to read the documentation of manufacturers, especially those that make the very microcircuits that audiophiles then swear by. I reveal the most secret secret: reference design board, evaluation board and similar “probes” from manufacturers usually contain examples literate the use of those same microcircuits. Moreover, it is not at all necessary to buy all these boards, and the price tags for such “samples” can be very different: 50, 400, and can exceed a thousand greenbacks. But, my dear developers, the documentation for all these boards is posted in open access! Okay, good to teach.

So, what the Chinese did not read, or what they saved on: modest shunt ceramic capacitors of 1000 pF in parallel to 10 μF and 0.1 μF. It would seem - why, because with such capacitors we bypass frequencies from tens of megahertz and higher. The audio range is considered to be up to 20 kHz, well, up to hundreds of kHz. But no one has canceled the digital part in the digital-to-analog converter. So it is precisely the interference at tens of megahertz that freely walks through inexpensive self-built DACs, causing all PLLs to tremble in fear and thereby creating ideal conditions for the occurrence of terrifying JITTER.

Another popular way to save on matches

The vast majority of manufacturers of both digital audio sources and digital-to-analog converters save 30...50 cents on each device. We, the users, pay for this. Read details.

What's high-end without lamps?

I am amused by the hordes of tube-DAC and tube-headphone-amplifier"s in the price range from one and a half hundred to hundreds of dollars that have flooded the market in Lately. Apparently people like the way a light bulb hisses and distorts at 15...24 volts anode. However, an analysis of all the problems of such DACs and pseudo-tube amplifiers for headphones is a topic for a separate article, but not just one.

(photo on the right is an example, I don’t have such a lamp-tac)

Rich topic. I just skimmed the surface here and didn’t touch on the analog part at all. And how interesting it can be to properly plant the “ground” or organize a simple and, at the same time, convenient control apparatus. And what are attenuators worth - you can choose them with different resistances, build them according to different topologies, and connect them in different parts of the path. Coordinating sources with load is a very, very interesting question, you know!... But for today it’s time for me to wrap up.

BOM, or Bill of Materials

Of course, the matter is not limited to fifty dollars. The ceramic capacitors from the kit were replaced with film. Schottky diodes, high-quality electrolytes, and a lot more had to be added, not to mention the housing. And, of course, my HotFET amplifier: only 2 (two) amplification stages from the DAC output to the headphones or amplifier output. Neither more nor less, but in the amplifier itself I counted 32 transistors in the stereo version. Yes, all transistors are JFETs and depletion MOSFETs. No way I can’t fit into the green fifty kopecks even in terms of components 🙂 Note that this is without any audiophile esotericism. Well, yes, I also have my own opinion on this matter. After all, there are people who believe that by installing the “right” components, any circuit can be made to sound. If you, dear reader, are from their ranks, teach me, I will listen, argue, listen and tell everyone about my experiences right on this site.

So where is the promised freebie???

Friends, this article is just thoughts, notes in the margins, it was written hot on the heels of remaking a Chinese DAC. I myself would never get involved in such an adventure again: although it turned out well, it was too expensive in terms of time and effort. And I don’t recommend it to anyone. When I dealt with that set, the poison simply oozed out, which was reflected in the article :) I apologize for the slightly arrogant style of presentation, and if I did not live up to your expectations and did not offer the distribution of almost free high-end DACs to the population 😉

If you were interested, please let me know. There is still a lot of material in the bins, but the strength, motivation to publish and formalize all this comes mainly from reviews and comments from my readers.

Three models at once. For different purposes.

In the world modern electronics It’s difficult to keep a “company secret”, only one thing is clear – built-in DAC(digital-to-analog converter) and sound chip in your Macbook, iPhone or other player cannot be replaced or upgraded. After all, m music is stored digitally format , and headphones and speakers reproduce analog signal. What to do? Add another high-quality intermediate link between the signal from the player and your headphones or acoustics!

The production facilities of famous Hi-Fi brands are located in China, so you shouldn’t be surprised at the “Eastern” origin of your own Chinese audio brands like Fiio, so S.M.S.L.- This Chinese manufacturers, whose products are nevertheless known throughout the world. Company name is an acronym for the full Shenzhen ShuangMuSanLin Electronics Co.

The company began its work in 2008, in the city of Shenzhen, and now their products can be found on the market in 30 countries, and in China itself there is a network of hundreds of branded stores. It's interesting that S.M.S.L. This is only one of the brands under which Shenzhen ShuangMuSanLin Electronics Co. products are manufactured, but the most famous and popular. In particular, under the SMSL brand they produce both full-fledged DACs and full-size receivers, as well as headphone amplifiers, the key requirements for which remain portability, ergonomics and high quality sound. And ahead of events, I will say that these guys surprised me.

In front of me are two devices from SMSL, completely problem solving improving audio quality. And third - for complete music geeks and supporters of home theaters with good sound. Three Shenzhen horsemen of the apocalypse Hi-Fi – iDol, M-3 And A2. There is a fourth, fifth and others, but today only these guys stopped by. And they are all worth the money.

China has learned how to make good packaging. Not just good, but also interesting. Here, look at the first and smallest - iDol.

Inside is a small box almost made of birch bark, and in it is a metal case of a miniature headphone preamplifier - the Russian soul rejoices at this combination. Original!

Pocket iDol and versatile M-3

What do we have here? Isn't this the most portable DAC I've ever seen? SMSL iDol the size of the remote control on your wired headset and at the same time with serious stuffing.

• KGI+N: ≤0.003%
• Signal to noise ratio: 105 dB
• Headphone output power: 100 mW + 100 mW (32 ohms @ 0.1%)
• Outputs: headphones, optical
• DAC: PCM5122

The amplifier is so light that even compared to modern smartphones its weight in your pocket is indistinguishable. A complete DAC that connects to Android smartphones and any computer via USB. And the desktop version SMSL M-3 earned money with mobile devices(small life hack below).

iOS gadgets were deprived, despite the “i” in the name. The only cable included with the preamps is USB A and microUSB. Steve, how can this be? However, it was not possible to experiment with Lightning adapters. Let's leave room for hope in our hearts!

Working iDol And M-3 with Android 4.0 and higher, Windows, MacOS and Linux (about three people reading this article are now sighing happily).

Everything is perfect under MacOS, all DACs were tested with it.

Everything is picked up on the fly, no bugs, no crackling (as with some external USB audio cards) and no problems.

The only thing worth noting is that the volume level when connected is not regulated by the system, but only by buttons on the preamplifier.

Sound. Are you waiting for this? Briefly - it is better than the audio output of all versions of Nexus, the standard output Macbook Air, Pro and, of course, Windows laptops. What's better? It’s as if you took and unscrewed the Drive knob, brushed away the dust from your audio files from Apple Music or iTunes Match and warmed up your headphones thoroughly. Both 55 Ohm headphones and 250 Ohm headphones baby iDol swings to the fullest.

The volume is sufficient, the sound is denser, brighter and more driving. Favorite tracks sound just great on it:

Scene compared to the professional interface from Emu or Asus Xonair Essense One and iDol And M-3 a little narrower and more tightly gathered in the center.

The sound seems to be additionally colored, but it is not “warm tube”, but bright and catchy.

What is the main difference SMSL M-3. This preamp and DAC is positioned as a desktop version. But it is more than mobile in size (compared to a pair of iPhone preamps “on an elastic band”) and, as noted above, there is a life hack. Let's take it external battery from USB, connect it to DC In, and in Input 1 smartphone or tablet.

Besides M-3 does not “eat” the smartphone battery like iDol. Otherwise, the difference is in the number of inputs/outputs and a little in the filling and characteristics.

• Output Power Level: 1.9 Vrms
• KGI+N:<0,006%
• Signal to noise ratio: >107 dB
• Dynamic range: >112 dB
• Channel Separation: >105 dB
• Inputs: USB, coaxial, optical
• Outputs: analog 2 x RCA, headphones

Pet SMSL A2

The third preamplifier is no longer a DAC, but quite serious, albeit small base For home theater or an acoustic stereo system. The SMSL A2 is anything but portable and has a hefty power supply.

40 W per channel and a subwoofer output are enough for a beginning film fan and audiophile. I just don’t recommend bypassing the instructions; there are several nuances regarding the settings. Here you can switch between inputs using a button on the front panel of the device; there is a built-in equalizer that allows you to adjust low and high frequencies.

• Output power: 2 x 40 W @ 4 ohms
• Signal to noise ratio: >90 dB
• Crosstalk:< -90 дБ
• Frequency range: 20 - 20.000 Hz (± 3 dB)
• Speaker impedance: 3 - 16 Ohm
• KGI+N:<0,05 %
• Inputs: 2 x RCA; 3.5 mm

I liked the sound of this preamplifier better. Although full-size acoustics are still more serious than headphones. From classics to Thom Yorke's signature howls and a remastered version of the collection of the somehow remembered Billy Idol - everyone sounds good.