Audio-GD R2R 7

Around a year ago Audio-gd announced the R2R 7, the first new discrete ladder DAC flagship from Audio-gd. With the previous flagships using the now discontinued PCM1704UK R2R DAC chip, the new flagship DAC from the Chinese company uses double-sided resistor ladder boards with switches, error correction provided by multiple on-board FPGAs.

Since the announcement much has changed. As well as changes to the inputs, two different firmware versions are available - the default "smooth" version, and the more lively "accurate" version, which increases the accuracy of the output of the digital processors.

In addition to that, the USB input was updated, first with isolation, and now with a dedicated power supply.

Alongside the features that can be turned on and off, the changes made reviewing the R2R 7 quite a challenge. As soon as you covered one thing, someone would suggest a tweak or change to settings or source and you'd be back again listening for subtle differences.

The main digital processor is still an Altera Cyclone IV, situated on the centre digital board, however even S/PDIF processing has been moved to programmed FPGAs. 11 processors in all reside in the R2R 7, making for some serious computing power.

How it adds up in terms of sound was another matter, and not a simple one at that.

The R2R 7 has 6 inputs, switchable from the front panel. The current options include 2x S/PDIF (with one optionally being AES/EBU), optical, 2x I2S (HDMI and RJ45) and USB. The USB now includes isolation and its own power supply. My original unit had neither, so since the maximum options for input are only available from I2S and USB, I stuck with USB via an iFi iUSB 3.0 for most of the review.

The dual I2S inputs recognise that no matter how much Kingwa improves on the quality of the inputs, many customers want to use a separate, high-quality transport of their own construction. I noticed significant performance differences between the inputs.

By default, the R2R 7 uses an 8x oversampling FIR, with no PLL or dithering used. However inside the DAC, via jumpers it is possible to turn on the PLL and dithering (recommended by myself and others) and set the oversampling to 4x, 2x, or even off altogether. In pure Non-Oversampling (NOS) mode, three types are available, with the 3rd version the highest quality, but the other two, less accurate versions available if required.

To add to the complexity, Kingwa contacted me to ask if I'd like to try firmware that sets the output of the DSP to be more accurate. It requires that a member of his staff remote-access your computer to run the firmware upgrade. I suggested that Kingwa implement some means of using a jumper to switch between modes as to change them, you have to switch off, connect, switch on and flash the DAC each time.

For the sake of simplicity, we’re calling the original software the “smooth” version, and the other, optional firmware the “accurate” version. This leaves the R2R 7 with an incredible combinations of options possible, compounded when you can get high-quality up-sampling software such as Audivana Plus in the mix.

The Focal Utopias had just arrived. I’d been waiting for them to more carefully compare the R2R 7 with Schiit Audio’s Yggdrasil. However, even using the best recordings I have, I can't tell definitively which DAC is which plugged into the inputs of the Studio Six with most music. This using either USB to both (and Roon) or Audio-gd’s now discontinued DI-U8 with S/PDIF and Audirvana. The latter set-up, not using the built-in USB receivers of the DACs, sounded a bit nicer to me.

Picking as much complex music with a detailed soundstage as possible, I managed to guess correctly which DAC was which, the Yggdrasil still sounding very marginally more spacious and the R2R 7 a very tiny bit more closed-in. We're talking barely perceptible differences though. This took effort I don't want to repeat though! It might show up better on a proper speaker rig.

With the R2R 7 having been left on now for some weeks, any changes in the sound had settled, so it was time for some more critical listening. This was almost a difficult task due as every time I started listening to music with it I became too engaged with track being played!

Typically Audio-gd's flagship DACs tended to be a bit on the warm side. Some people found the sound to be a bit imprecise, especially with the bass. It is particularly this problem which I didn't hear from the R2R 7. I was careful to compare the bass to that from the Yggdrasil, and I felt for the first time that the closed-form filter didn't provide the advantage that it had versus other DACs.

I tried the non-oversampling mode that is available by placing one of the included jumpers inside the unit. However with CD-quality music the sound just became vague and ill-defined. I experimented with up-sampling via Audirvana in this mode. Trying the DSD up-sampling modes, the music sounded strange and unnatural, so I quickly gave up that idea.

I tried a few experiments with regular up-sampling to 352.8 or 384k, using the 2x/4x setting in Audirvana Plus. With settings that emulate a linear phase filter (more or less all the sliders to the right) I felt that the music was a bit more precise, noticeable on songs such as Hollow Talk (Choir of Young Believers) where the background sounds and subtle details of the instruments were more audible.

Once it became apparent that the PLL and dithering (necessary to deal with quantisation distortion) were off, putting them on seemed to clear up the sound a bit, so I left them on for the duration of my time with the DAC.

The "accurate" firmware, given that I can't quickly A/B between them, seems to increase the precision of each note, but with the loss of the "organic" enjoyment that an R2R DAC can provide. It would be very interesting to see measurements with the "accurate" firmware to see if the very low-level harmonic distortion is consequently lower.

The “accurate” firmware was more fussy with input quality. If I wanted a pleasant listen, a good transport was needed, either my Singxer F-1, though in the end the iFi iUSB 3.0 to the original USB input did very well. However the rewards, once the PLL and dithering were engaged were fantastic. With the slightly smooth, yet dynamic Soundaware P1 and Focal Utopias, listening was pure pleasure, reminding me much of the $100k Brise system I had auditioned at the Tokyo headphone festival.

Whereas with the "smooth" firmware, the Schiit Yggdrasil seemed somewhat dry in comparison, with the "accurate" firmware, the R2R 7 was the lively DAC and the Yggdrasil more laid-back, with possibly still a tiny bit more very-low-level detail.


Chord’s Hugo 2, fed via the iUSB or Schiit Wyrd still tops both, especially given an amp isn’t needed for most headphones, as it shows the soundstage of good 2-channel recordings with an uncannily good sense of depth and can extract the subtle warbles in the decay of guitar notes from Friday Night in San Francisco, and the subtle harmonic decay of piano notes from Horowitz in Moscow more so than the other DACs.

The new iFi Pro iDSD arrived after I shot the video and before I finished the written review, so before I sent the R2R 7 off I spent a bit of time comparing them. The R2R 7 was the sweeter DAC to listen with, the Pro iDSD, being almost, but not quite Chord-like in accuracy, revealing a very slight touch of what I call wood-like character of the Burr Brown DACs, even with the Gibbs Transient Optimised filter and Tube+ engaged.

What was ultimately apparent to me was that, set up carefully and switched on for a couple hours at least for best results, the R2R 7 can be an incredibly rewarding DAC to listen with. While it might sacrifice a tiny bit of detail compared to, say, the Hugo 2, instead it rewards with incredibly pleasurable listening.

On its last day here I connected it to the Audiovalve Solaris, which I have been using primarily with HiFiMan’s Susvaras, and the match made for wonderful day of listening.


Music Impressions

Set-up: Filtered USB input from Mac Mini; Master 9 via ACSS to Susvara, volume at 57-60; Accurate Firmware + NOS mode 3 or oversampling mode.

Restless Sinner - Black Rebel Motorcycle Club

The vocals and guitar jump out sharply from the centre of the audio image. It’s a very intense presentation, if the imaging is somewhat narrow. I feel that the sound is a bit distorted.

Oversampling mode:The soundstage widens and the overall precision increases. The presentation comes across as more “ruthless” than “intense”.

The Rifle’s Spiral - The Shins

Accurate mode pushes this right in your face. I don’t feel any benefit of NOS mode, which just seems to narrow the soundstage to no benefit.

Forever My Friend - Ray LaMontagne

I’m starting to suspect that accurate mode is too much of a good thing when listening to less than excellent recordings, as in Accurate/oversampling mode this album comes across in a way that is more mellow than the previous tracks. Ray’s voice, as well as instruments seem to site more in the background, giving a more relaxed presentation.

I thought that this was a good time to switch to a different input and so I moved to using my Raspberry Pi (DietPi) to iUSB 3.0 to Singxer F-1 set-up. I grouped the zones so I could compare them by switching inputs.

Going back through the previous tracks, the F-1 set-up sounds more mellow and less harsh. It’s very apparent switching inputs in the middle of a song. It doesn’t stop revealing the less than perfect nature of The Shins’ album, but seems to bring out a touch more of what is in the Ray LaMontagne album.

Every Heart - Acoustic Junction

With the volume up this high, a bit more than the level I usually listen at, this is still a bit too intense in accurate mode, possibly due to it being a lossy track via TIDAL.

As a comparison I played the tracks again through the Yggdrasil via a WaveIO board for input (in lieu of the fact that I don’t have a Gen 5 USB board yet).

The more mellow, yet precise impression the Yggdrasil gives was readily apparent. It makes the more intense/compressed tracks a bit more bearable.

If I feed the Combo 384 Amanero in the R2R 7 via the iUSB 3.0/DietPi set-up (Accurate FW in OS mode) the sound quality hit a fantastic sweet-spot of smoothness versus dynamics. It will be interesting to find out if the new isolated Amanero board has a similar effect to the iUSB 3.0.

Set-up: Combo 384 Amanero via iUSB 3.0/DietPi; Master 9 via ACSS to Susvara, volume at 57-60; Default Firmware.

For years we’ve mucked around with jumper and other settings and in the end, Kingwa’s defaults seem to be right every time. It’s much this way with the default set-up of the R2R 7, excepting that a better power supply and signal for the in-built USB helps. Again, this is without the newer isolated USB that is available.

The Shins, which could be harsh and too aggressive with the “accurate” firmware has a pleasant smoothness, and we aren’t treated to all that is wrong with the recording as before.

Revolutionary Kind - Gomez

The subtle harmonic richness which defines a typical resistor-ladder DAC makes this track deliciously pleasant to listen to without having to engage NOS mode.

Forever My Friend - Ray LaMontagne

This track can sound a bit dry on the Yggdrasil, but sounds rich and makes you want to move out of the R2R 7. I don’t know if it is firmware differences, but at what seemed like a bit too loud a volume (60 on the Master 9 via ACSS and with the Susvara) for me when using the accurate firmware now seems just about right with the default one.

Disclaimer


Before you read my impressions, please beware that every system is different. My experiences will also be different


My system is consisted of KG-T2 Electro static amplifier with all internal silver wires and external silver wires, XF2 Quad tubes and SQ E88CC from Phillips. Stax SR-009 headphones and the source is WM1Z with Docking cradles with internal Silver wiring, usb silver cables, UPOCC power cables for amplifier and Silver Power cables for R2R-7.


I am writing this impression to share with people who may be interested in buying the R2R7 and not sure what they may get. Before we go on to the sound impressions. I will have to impress first on customer services as the company is direct sale and out of China. This is very important


Customer service:


Kingwa as the owner and designer of the brand, he typically respond within 1 day and normally 2 days max. Otherwise, he may have just missed your email by junk folder or some short.


My unit was not understood by me at first, and thought that I may have problems with it. Kingwa was in full support to allow shipping back for replacement if problems found. Otherwise he could refund according to the policy. So, you have a peace of mind. Again, this is strictly my experiences as the first AudioGD owner of the product R2R7.


Technologies, and firmwares


If you are researching into the r2r7, you already well known what it is. There is no need to go circling around as I am not fully knowledgeable about it. The only thing I know for sure is that the R2R7 has plethora of different options to play around with DSP. It is also very very Raw! For all the DSP jumpers and setting, you can visit


Main site

What is so impressive is that it has so many FPGA chips (7X-FPGA) inside, and it is so Dope to think about. It recall my experience about 300 “this is madness!”. But no, “this is AudiogGD”! What prompt me to make purchase is 3x Linear/regulated power supplies, digital processing, analog channels Left and Right. You may find more interesting in the designs itself.


Yet, you can find all the information about flashing different firmware that needs a USB Blaster. Which you could find here. If you are in the US, and is Amazon Prime member. You can search on with the keyword “FPGA USB Blaster” on any friendly site, if Taobao is a problem


Usb FPGA Blaster from Amazon prime

Then you will need to follow the guide


Firmware flash guide

This is a little bit annoying as you will have to register for an account with Intel, and fill out a form to download their software.


The most important step is to plug in the usb blaster and install it driver first. Let windows automatically find your driver in the folder that you installed the Quartus software. Do not navigate to specific driver folder as it won’t work.


Make sure to always turn off before connect/disconnect anything even JUMPERS


You can email Kingwa for the firmwares. I was told by (FredA) member on headfi that DSP firmwares will need Altera software and Digital boards will need Xillints software as it is running with Xillints. Though, I didn’t need Xillints, but I just want to include this in the impression.


Build quality


Well, to each of his own. I like the r2r7 for a solid, chunky, heavy built. Yet, simple, and elegant. It is so Raw physically that even switching/changing DSP, you will need to turn off, open top and insert jumpers. The logic is to be less invasive to the processing of the sound and it quality. Everything else that can conveniently help you out here will invade into the territory. The rest of how it is built, and why is it so well design, and what is the ground behind it, you can find it on the website


Sound quality: from my experiences below is a venture with USB sources. I briefly tried Coax/SPDIF and it would be the input I recommend out of the box.


I had periods going with this DAC, both negative and positive.



Positive period:



This happens when I realized that I was previously hearing “quantization errors” which was caused by the errors during the digital signals process and transmissions. I know my Wm1Z and it Cradle system is adequate, so it must be something else. Then different usb cables brought different impacts in the “hissing” quantity. It prompted me to look further, and to discovered that the Amanero Board with isolator have “Brass-Pins connections” for signals and every other signals lines. Could this be the reason that was tainting my usb source ? So I put myself onto it, and it did vastly improve (no more hissing). Going back and forth between different modes and setting now.


6Moons setting is now a bliss to listen to IPS0, IPS1, ATT0, ATT1. The signature reminds me of Old classic Aiwa players


The bass is big, Analog, and less control on some tracks, or it could be big, tight, speedy and full of controls on some other tracks. My lks004 bass fidelity was awesome (bass doesn’t sound mono tone anymore), and I used it for a reference points to find the flaws on the r2r7 out of the box as I only use USB inputs. But now, in comparison, the LKS-004 bass is very controlled, full of dynamic, but is lacking that “body”. The variations of tonal body variations. Yet, the fidelity is good, bass don’t feel boring as every beats has it own fidelity, but r2r7 is also telling me the level of tonal body control which lks004 does not. Especially that sub bass rumbling body and it rippling energy


Vocals is unbelievably beautiful, very emotional, vivid, strong, vibrato are at the very top fidelity. The same artist/singer in different tracks can have her skillful vibrato to be so expressive that I can tell the speed and her control skills behind it, and then the energy behind her voice on each “word” and “bridge”, it is totally top-tier high-end performances.


Treble spectrum is beyond showing the level of resolutions, extensions, and finer details. But it has been transcended into the next level with vivid energy, even a handshake hi-hat can be observed with different rhythim, speed, energy. Cymbals crashes also express the same feeling of accuracy, details, and full body. Yet, the “full body” I am trying to explain is far from what we would call “artificial”, and artificial in a sense is a boosted “warmth or brightness” on different frequency to mimic and try to achieve this “full body”. This “full body” is neither warmth nor bright, but it is “just right” and so I call it Organic. Especially the vividity and resolutions of wind chimes . The energy applied throughout the sound signature is Analog like “sound signatures”. Funnily enough, when I called out my lks004 for being a little warm before, that is really this specific feeling, certain instruments are being boosted in “warmth and body density” to mimic the Organic and vividity of what the R2R7 is doing at this very moment that I am annoying.


Lets’ talk About “wind instruments” I never dig deep into this specific instruments before. Yet, it has many different type, but the one type that is always so hard to “reproduce” accurately is Asian Bamboo Flutes. These type of flutes are so very hard to reproduce due to it sound signature which dwell in middle-mid into upper-high frequency, but with it body-energy dwelling into the similar frequency but is a lower step down. If not reproduced carefully, the sounds can become overly “saturated” or “under emphasized”. I can not find different “terminology” to put it in. In reality, Bamboo flutes when heard organically is very emotional, and very relaxing, kind of instrument that can “soothes the soul” off and away from it “stressful fatigue”. So, on my lks 004 and other DAC I have came accross, majority of them would be boosting the upper high frequency which became “bright” and then even boosted it energy body to become thicker, so it was no longer accurate anymore. The signature is now 2 steps above the body energy impression. Anyways, I don’t know how to try and explain it more clearly, but this had always been a reason that I never specifically aimed into this type of instruments.


So, R2R7, how does it do ? Very accurate rendering of this type of instrument, and is also the first time I can tell “flute bamboo is so Realistic!” It also has vivid Vibratos ! Yet, the oversaturated feeling will come when I use other OS modes, even in 2X-OS, it has piercing energy and also some glares. The glares and sizzling energy will just be increased in level according to 0x-OS, 2X-OS, 4x-OS, 8X-OS. The 6Moons setting is the 0X-OS with digital filtering Applied.


The soundstage is very deep, wide, opened and yet natural. It gets about the same width as lks004 but deeper and less saturated on the edges resolutions of a specific play, notes, hits. The other OS can sharpen these edges lines, but it doesn’t do it as well as LKS004 which is native OverSampling with the prowess of ESS9038Pro 2X. The soundstage can get pretty crazily Accurate in spartial dimensions in comparison to lks004 in recorded live performances albums


The layering are all very excellent, and the separation of each instruments together with each own fidelity, body, and presentations are top tier. There is not any single “fuzzy or veiled” moment, the observations on each instruments upon focusing myself to try and follow it is now complete. I am no longer confused as to where it comes from, when it started playing, and it body signature during the play can not be confused, and when it is ended.


The edges resolutions now has “absolutely 0 hints” of glare, or glassy, or sizzling, but is rather vivid, smooth, and clear. Again, I would use the term “hardened Maltose syrup” in textures.


Floor noises, is now “un-observable”


Reverberate, room echoes, acoustic reflections are all so very vivid, and accurate. It is the most accurate I have heard from digital equipments....well, never even observed it this way before. On orchestra tracks, I can clearly follow an instrument, and it reverberate from this acoustic reflections without being confused. Talk about “accuracy”


I tried another “input”, and it was SPDIF. Yet, the SPDIF is also very good coming from a Digital Player (Ibasso DX200), which can output DSD, and Kingwa confirmed that the R2R7 also do DSD from this input. I had so much problem with the USB modules, and the main reason was coming from this input that drove me crazy. However, the SPDIF is ountouched and untampered with, and it was nothing but short of “good and acceptable performances”, enough that even if I was to mainly use SPDIF, I wouldn’t want to tinker with it.


So a kindly reminder is that if you adore the sound of “silver materials”, you can request from Kingwa when you order ? Or if you adore “OCC materials” the DAC comes with it, specially on SPDIF, and I heavily recommend using this input, unless you have no choice, the other inputs seems “somewhat flawed” in my opinion. From what i have experienced so far, I do not like those Ribbon cables, and Brass pin modules, which put up a struggle with me.


Also, very important if Dithering and PLLEN help out somewhat, it means your source is tainted somehow. Otherwise, 6Moons is the most accurate and absolute best of what this DAC can do.


I don’t know if improve upon this signature and performance is possible, but I will just put it here “ probably going to be very very hard “, and last but not least, for this price. It is excellent buy if not the Best Buy I have ever made. Simply compare this device to A&K digital player SP1000, this DAC is a much much better buy. I also do think the 26 bits from this DAC is fully capable of 140+ DB Dynamic range. Just like Kingwa mentioned, with the usage of FPGA all around the device, it can easily be affected by Firmware/Software. So far, there has been 2 versions: Accurate and Smooth. Every unit is shipped with 8X-OS and Smooth firmware.


The most important thing was my journey with R2R-7, and my discovery of Brass Pins connections from Amanero and USB modules of whatever using the same types. I went ahead and replaced it on the LKS004, and it did improve the sound signature too. Basically the very fines details which was portrayed further away and deep in the background is now more vivid, especially when LKS004 can saturate it further, it seems to give a more definitive sound to these plays. But when compare side to side. The only thing I can say is that both does very well for what it was designed to do. I previously thought the R2R7 would be superior, but no, not really. When both has the source corrected. They carry different sound signatures. It is so different that it only take seconds to tell which one is the preferred one.


R2r7 has smooth edges, and less grainy, little more fuzzy on the fine/nuances plays in the background (not over saturated), deeper, maybe slightly wider in soundstage vs 004. The overall signature is more analogy as the fluidity of each tonal body is “more full” and more “fluid”. Even the vocal and organic instruments Vibratos are more “continuous” and portrayed with more fluidity. It could be mistaken for being “warmth”, but it isn’t warmth. One of the most observable example is the different Pedal Bass Drum. The r2r7 would portray different type with different fidelity and body, where 004 has a more mono-tone approach.


Lks004 has sharper edges, more grainy but nor harsh, clearer definition on nuances/fine plays in the background (saturated). It has a bit more shallow depth, a little less width in soundstage compare to R2R7. The overall signature is faster, sharper, more airy. But it a setback at the Organic feeling. Carefully observing between the 2, the R2R7 can be said to be more Organic to my observations. The tonal body is more dynamic, more energetic but is faster. Vocal and instruments Vibratos are not as continuously flowing back to back as the R2R7 but rather more separated due to it speed. Yes, the 004 May seem to be more neutral due to it speed over all, but actually is more warmth in my observation as the mid-tone of many specific instruments tent to be boosted to try and tame the speed and mimicking the Organic timbres from R2R7.


For all that said. Both are great for the buy, each of them carry a unique sound signature which is equally enjoyable. The lks-004 doesn’t require attentions or modifications out of the box at all. I listened to it for a whole year without noticing the “flaws” on the Brass Pins. I even used it to hunt down the flaws on R2R-7.

My personal opinion is that for the price, the LKS-004 May pose a better buy, and less for tinkering with. But if you can request Kingwa to custom made your R2R7, or you use I2S/SPDIF/Coax, and you love the more Organic but vivid and fluidity of sweet presentations and more soundstage, the R2R7 will pose to be an excellent buy. R2R7 May pose to be the Best Buy for the price because you can find every technologically advances in it designs, and if you can handle a soldering iron. Therefore, to me, the R2R-7 is the Best Buy that I have made so far. Also, to me, the R2R-7 winning Blue-moon award is a totally deserved title. In this day and ages where DAC developments are faster than me driving to work, the components, the build, design, performance will be the points to base purchase decision on. Yet, like all thing that depreciate when purchase and used, but for such price and all the above, the losses won’t be as great as those 10-20k DAC

Do you love sub-bass ? Soundstage, fluidity, organic tone ? Or do you love speedy, snappy, airy, sharper nuances details ? How about R2R vs Sigma Delta ? I guess your answer would lead you to R2R7 or the 004