YULONG DA1: Flagship All-in-One with AK4499, 5W Class A BAL headphones and Pre-Amp
May 24, 2021 at 9:50 AM Post #16 of 48

dcguy73

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Is the output level (when using as a DAC) adjustable?
 
May 24, 2021 at 11:29 PM Post #17 of 48
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Is the output level (when using as a DAC) adjustable?

DA1 offers both line out and pre-amp output from its RCA and XLR connectors at back panel. When used as pure-DAC, it will set to line output and that is fixed level, volume control is disable. When you change to Pre-amp mode, the output will be variable level, you can adjust the volume.
 
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Jun 5, 2021 at 3:09 PM Post #19 of 48
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DA1 Home setup 01.jpg


DAC is the core competence of YULONG audio. Ever since the start-up of the company, YuLong has built more than a dozen of DACs with different chipset and covered a very wide price range. There is one objective that has been carried out persistently crossed all products: to implement the DAC with proper engineering under the available resource. In other word, the company doesn’t build DAC with selling points in mind, they just assume they can sell a lot of DAC if they do it right and their DAC sounds good.

For example, when we formulate the DA1 at the early stage, I suggested dual AK4499 instead of single AK4499. I came up with loads of reasons: all your competitors are doing that; indispensable market expectation; the cost of second DAC chipset is a worthwhile marketing expenses; natural new product (single AK4499 DAC) opportunity, … … YULONG firmly believed that a properly engineered AK4499 offers optimum audio performance over a bare-bone dual DAC design in compact All-in-One form factor, so despite there are lots of reasons to go for dual AK4499, YULONG decided to stick with single chipset design.

The AKM AK4499 DAC represents the highest standard of DAC technologies available today. Decodes up to PCM 32Bit/768kHz and DSD512, the AK4499 will stay current with the rapid pace of hi-res audio technologies. What makes the DAC chip so special is that, rated at THD+N of -124dB, it has the lowest harmonic distortion on the market. The DR and SNR at 137dB are also extraordinary when compare to any DA. These will definitely enhanced the resolution, clarity and density of the music playback.

DA1 with RODE.jpg


The AK4499 is AKM’s first current mode DAC chipset, it requires external IV circuit to convert the current output from DAC chipset to voltage output before subsequent analogue audio processing. What’s the point to have a current mode DAC rated at 137dB SNR if the IV circuit is not extremely low noise by design? YULONG takes this seriously and developed a 4-channel 1.7nV low noise 800mA high current IV conversion circuit and a fully discrete high current buffered output stage as optimized supporting circuit to the AK4499 DAC in DA1. Together with YULONG’s proprietary 4th generation JIC FPGA solution as pre-processing, and all there are powered by the 50W high power low noise power supply system as described previously, the complete DAC circuit is nothing short from spectacular. In fact, we have tested to confirm that if we use the same IV and power supply system to support dual AK4499 design, we can achieve better measurement on some parameters, but it won’t sound as good as the single AK4499 design in DA1.

YULONG DA1 Sales Guide - 04.jpg


Another important consideration in DAC hardware design is the choice of Crystal Oscillator (CXO). Just when the circuit design was finalized, the price and date announced, and the team was busied with material sourcing and production scheduling, we find out that a long awaited extremely low phase noise CXO (< 100dBc @ 10Hz) is finally available in large quantity. We have received sample of this CXO during R&D and was very excited, unfortunately the global shortage in electronic components had caused serious delay and we have decided to go ahead without another CXO that we are familiar with. Now that the new CXO become available at last minute, YuLong didn’t want to pass by any opportunity to improve the DA1, so despite the new CXO is 5 times more expensive than the current CXO, he still convinced that we should delay 1 months to wait for the delivery and fine tune the power supply design to accommodate the new CXO.

黑色-38db.jpg
 
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Jun 6, 2021 at 2:02 AM Post #22 of 48
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I thought AKM DAC chips are harder to acquire these days due to the recent factory fires?

We placed our order quite a while before AKM fire, we are grateful that AKM honour our order and ship us the AK4499 chips several weeks after the fire. That was a long and desperate wait, 12 months solid R&D will go down the drain if we didn't receive the chipset.
 
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Jun 11, 2021 at 3:08 PM Post #23 of 48
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MAS refer to “Mobile As Source”. The term probably sounds new to you, but I guess we all wanted this feature as some point. From technology perspective, there is nothing difficult to implement this feature, but we try this with our own system, we probably feel discouraged because it doesn’t sound good when compare to our computer or regular setup. We always thought digital bit stream is only a matter of 0 and 1, they should always sound exactly the same, but do they?

To use mobile devices such as phone or tablets as music source to high-end DAC, there are two problems we need to solve: compatibility and signal quality.

Compatibilities is a technical issues as well as a practical constraints, there is nothing much we can do if the mobile appliance vendors makes life difficult to audiophile users, this is not a mainstream user group that they really targeted at, and even when a mobile product promote themselves as "audiophile phone" or "audiophile tablet", that doesn't necessarily mean we are trying to achieve the same goal, so we can just do whatever we can, provide decent experience, and hopeful created a norm that will finally influence the mobile vendors.

Android mobile devices

Theoretically, any mobile device that supports OTG USB Audio can output digital audio bit stream for outboard DAC. Earlier products occasionally only implemented OTG USB Storage but neglected OTG USB Audio, it’s pretty safe to assume all USB OTG device will provide OTG USB Audio.

One of the advantage to use Android device as source to your high quality DAC is the standardization of USB-C as interface, so you only a USB-C to USB-B cable to connect the device to your DAC (e.g., HERE and HERE)
EmptyName_100 白.jpg


While the hardware side of Android solution is standardized and straightforward, the software part is … very mixed feeling. To start with you need a music playback application that support USB Audio output, please don’t assume all applications will do that and the bitstream are all the same, it’s far from that.

The biggest bottleneck is built-in SRC (Sample Rate Conversion) in Android system. In order to eliminate the pop noise generated when audio signal changes its sampling frequency, Android OS will resample everything to 44.1kHz, 48kHz, or 192kHz, depends on the system capability and vendor’s choice of technologies. This is definitely something not desirable to audiophile users. Among the music app that I have come across, I strongly recommend USB Audio Player Pro (UAPP), this is the only that I know of can bypass the SRC in Android system and integrate gateways to popular streaming service at the same time, details explanation are available HERE and HERE.


iOS Mobile Device

iOS device are high quality audio source, they are well build and don't have the diversified hardware implementation issues (some of the low cost Android device are functional but hardly enjoyable for high fidelity purpose). Unfortunately iOS is not really Hi-Res friendly until recently when they enabled Hi-Res streaming in Apple Music this month. We were excited and were looking forward to the service launch. Unfortunately, it is a bit of a mess after we tried various possibilities. Basically if you want to enjoy the Hi-Res streaming from Apple Music right now, iPad Pro is your best bet because you can connect the USB output from iPad Pro to DA1 directly. If you were using iPad or iPhone, you need a Camera Connection Kit or Camera adapter in order to go beyond 48kHz. There are third party lightning to USB cables or adapters that claim to serve the purpose but IMHO they are not reliable. iOS has very straight license policy and any unauthorized product or accessories can be out of the game after a firmware update.

If you want to find out more about using Apple Music for MAS, check out HERE and HERE.

DA1 with Apple Music 96.jpg


High Quality Digital Playback from Mobile Devices

Mobile devices are highly integrated solution with loads of electronic components that interference one another in a very compact environment, this is not a desire situation from audiophile perspective, so even we can get it work technically, the outcome might not be very pleasing. Some of the high quality DAC is very sensitive to the quality of digital signal upstream and they probably will have a hard time to deal with the high jitter, unclean digital signal from mobile devices.

Fortunately, YULONG is in a better position to work with MAS concept, our JIC (Jitter and Interface control) will clean up the signal and reduce the jitter to a very low level. There has been reviews reported that our JIC equipped DAC “sounds just as good with a standard Surface Pro or off-the-shelf Dell workstation as it does with excellent music servers and disc transports”. (cf. DA10 review by project86). The DA10 was our 1st generation JIC and DA1 is the 4th generation update, we have enhanced the compatibility and accuracy, which make it even better for MAS.

We expect MAS will become an inevitable norm down the road but MAS is meaningful only when the DAC is equipped with JIC or similar enhancement solution to improve the quality of the digital audio signal before the DAC.


DA1 JIC.jpg
 
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Jun 20, 2021 at 4:26 PM Post #25 of 48

galacticsoap

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Eagerly awaiting some reviews on this unit.

It looks like it ticks all the boxes but until I can get a sense of how this sounds it's hard to put down the tick over $US5K required for this stack.

At the advertised price it's being pitched against the usual suspects as far as Chinese TOTL DAC's are concerned. Plenty of competition with exceptional pedigree.

- Is there one in Sydney, Australia I can hear?
- Does the manufacturer offer an obligation free trial?
- How does it compare to the DA-10 across all the usual comparative markers?
 
Jul 8, 2021 at 1:50 AM Post #26 of 48

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This combination unit looks exciting. What is the current delivery time to USA for orders placed today? I'm working on some changes to my DAC sources and hope that this setup is available soon to try in my system.
 
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Jul 8, 2021 at 3:24 AM Post #27 of 48
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This combination unit looks exciting. What is the current delivery time to USA for orders placed today? I'm working on some changes to my DAC sources and hope that this setup is available soon to try in my system.

You can buy from Shenzhen Audio, 110V already in stock, so the biggest delay will be logistic arrangement. Drop them a line if you are interested, you can PM me if you run into problem.
 
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Jul 8, 2021 at 4:23 AM Post #28 of 48
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Eagerly awaiting some reviews on this unit.

It looks like it ticks all the boxes but until I can get a sense of how this sounds it's hard to put down the tick over $US5K required for this stack.

At the advertised price it's being pitched against the usual suspects as far as Chinese TOTL DAC's are concerned. Plenty of competition with exceptional pedigree.

- Is there one in Sydney, Australia I can hear?
- Does the manufacturer offer an obligation free trial?
- How does it compare to the DA-10 across all the usual comparative markers?

We have send out an review unit to an US reviewer, not sure about the date of review. Normally it'll take at least 2 months before the review is available online. This reviewer has covered DA10 and Aquila II previously, so he is the right person to compare DA1 with DA10. We put the DA1 at a completely different league against DA10, but we are not in a position to rate our own products. We can try our best to explain the different technically, but we can't tell you the sonic improvement impartially.

Unless there is some accidental development, YULONG will showcase DA1 in CanJam SoCal, hopefully we'll hear some user impression from CanJam SoCal impressions.

We don't have any authorized dealer in Sydney, unfortunately.
 
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Jul 12, 2021 at 2:31 PM Post #29 of 48
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DA1 with HEDDphone.jpg

After we explored the digital audio circuit, let’s take a closer look at the analog amplification circuit. :beerchug:

Cost effectiveness is a significant concern to AIO (AIO) product. Quite often, an AIO product is implemented with cut corners in order to delivers all the features within budget. Engineering competence and experience is also any constraint in the early days because digital and analog circuit design was fairly independent from each other a decade ago. It is not surprised that we have seen some AIO with strong DAC and weak amplifier or vice versa.

I remember I had this interesting conversation with YuLong back in 2014, that’s the time when I bought the D200 DAC/Amp from him after a long audition of his complete product line.

D200 is a typical strong DAC weak headphone amplifier combination. The DAC was designed around ES9016 and it was a fine implementation, but the headphone amp was a relatively low powered single-ended design. YuLong literally described that the headphone amplifier as a “bundled feature” to the DAC in a private discussion. I asked him why not focus on the DAC and skipped the incompetence headphone amplifier completely? That should lower the BOM and he can sell his product at lower price. That was the natural thinking of a consumer. YuLong explained that if he removed the headphone output, the AIO will become a pure DAC and he can only marketed the product to more niche group. This will shorten the BOM list but will increase the total BOM cost because the smaller production volume will drive up the unit price of components. In addition, when he spread the overhead to each production unit, the price will continue to go north, because of a smaller production volume again.

In short, adding a below-par feature will involve extra components, but likely widen the target audience, and lowered the final retail price. YULONG is fully aware of the shortcomings and determined to develop AIO without cutting corners. He had devoted a lot of effort to improve the analogue amplification design. For instance, the DA10 incorporates a fully discrete, JFET input, Class A headphone amplification and that was a relative high quality headphone amplifier for similar priced AIO.

The headphone amplification circuit is fully balanced by design as you can notice that the circuit is composed of four symmetric sections. The fully discrete pure Class-A implementation is the result of several months of fine tuning as YULONG aims at a powerful AIO that can drive difficult loads and remain very refine and musical. The output stage is composed of 12 high output audio grade power transistors. These BJTs (Bipolar Junction Transistors) are really powerful and sing like a nightingale, they deliver up to 5 watts per channel output (at 32ohm loading) with stellar dynamic range in DA1. However, they are extremely hot when operates in Class-A, we have tried numerous methods to cool them down and our final option is to mount them horizontally so that the power transistors can use the CNC machines aluminium chassis as heat sink to cool down itself effectively.

DA1 Class A amplification.JPG

DA1 Head Amp Specification.jpg



The headphone amplification of DA10 is also fully balanced fully discrete pure Class A implementation and is rated at 3 watts per channels respectably. So how do they differ from one another? The devil is in the details and can only be differentiated when you look beyond the specification table. While voltage is frequently quoted as the benchmark of driving capability of an amplifier, it's the current that moves/controls the diaphragm (or the magnetic arrays). While high current output is inevitably very important, the responsiveness, the ability to output current accurately for momentary needs, the transient current capability (hope I used the correct terms) is the key to different state-of-the-art amplifier from good amplifier. DA1 Main Unit (without Power Station) can deliver 15A transient current, and DA10 is rated at around 1A under the same measurement. Without any doubt, YULONG DA1 is a significant upgrade from DA10. This is particularly noticeable when we tried the more demanding headphones such as Susvara, HEDDphone and LCD4.

DA1 with Susvara.jpg


As All-in-One, the DA1 can also be used as preamp for your home audio system, and by that we mean a real preamp, not just a line out with volume control. Preamp is supposed to converts the Line level signal into an output signal strong enough to be noise-tolerant and strong enough for power amplifiers or active speakers. If we merely add a volume control to attenuate the line out signal, it can function like a preamp but it won’t sound like a preamp.

The Class A headphone amplification circuit in DA1 can be switched to become a high quality Class A preamplifier. Rated at 6V at single-ended and 12V at balanced, the output is strong enough to feed into a power amplifier directly without any sign of compression and dynamic loss. Likewise you can create a high quality Desk-Fi system with DA1 and active studio monitors. YULONG has worked with a Hong Kong based audiophile label Hugo Production closely in pass few years. The Chief Mastering Engineer of Hugo Production is a frequent guest of our product refinement panel. Hugo Production has teamed up with YULONG at multiple shows and CD launch events, and in several occasions they resolve to simple setup using DA1 and active studio monitors, The preamp function of DA1 is well-tested in these occasions.

DA1 vol control-.jpg


The Volume of DA1 is controlled through a high precision low noise 99 steps digitally controlled analog volume control. YULONG firmly believes a properly designed analogue volume is preferred in high-end audio implementation because that’s how we can preserve the dynamic range of the digital audio circuit.
The volume control mechanism is shared between Head-Amp and Preamp and can provide linear and accurate adjustment for different headphone loads of paired with variety of home audio or studio sound systems. One of the biggest advantages of this volume control design is to ensure channel balanced at low volume level. This has become a significant problem to modern headphone system because headphones with relatively high sensitivity have dominated the market. Channel imbalanced at low volume level is very irritating with these headphones, so its important to design a high quality and reliable volume control so that DA1 can cop with a larger variety of headphones (and active monitors).

DA1 preamp with monitor.jpg
 
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Jul 12, 2021 at 3:09 PM Post #30 of 48

project86

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DA1 in the house, currently in the "just messing around with it" stage. So far pairing with the excellent Stack Audio Link II plus their matching linear PSU. But I suspect the DA1, like DA10 and Aquilla II before it, will do just as well with more basic transports like laptops etc.

So far initial impression is that this thing is a beast, particularly with the matching Power Station driving headphones directly.
 

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