Doge Electronics Doge7 Tube DAC

[Doge 7 front view]

An adventure in the World of Digital Audio

Product name: Doge 7 Tube DAC
Manufacturer: Doge Electronics - China
Cost: $1590. US. (Currency conversion)
(YMMV)

Reviewer: Roger McCuaig - TNT Canada
Reviewed: February, 2018

About Doge

People select components for their audio system based on many varying criteria. Some people are attracted to prestige names, exotic looking cases or the bragging rights that accompany 5 figure price tags. Doge is not for this crowd. Their business model is based on products that incorporate high quality in their design, component selection and construction methods, at the best possible price. One of the key elements to controlling their price is the factory-direct sales which eliminate distribution and retail mark-up. Of course, this strategy also eliminates the opportunity for a potential buyer to audition the product and speak to a live person in a retail store as well as the local customer service aspect. However, as time marches on there are less and less local retail shops, and in my case, auditioning a product often means a trek to Toronto or Montreal! Not sure that counts as local any more. This writer's experience dealing with audio shops has not always been good so dealing with a factory in China is not seen as an impediment. Not a great endorsment of the retail audio industry in Canada but after all this site is called "The Naked Truth".

The Adventure Begins

I am a vinyl guy. The vast majority of my audiophile time and efforts over the past 15 years has been focused on improving my vinyl playback system and adding to my vinyl collection. I have little knowledge and much less understanding of the vast and increasingly complex world of digital music. Well that didn't stop me from recently acquiring the Doge 7 DAC that plays almost every PCM and DSD format that exists. Being a long time, satisfied owner of a Doge 8 preamp certainly paved the way for me to purchase another Doge product. However, it turns out that when it comes to full feature digital audio playback equipment, I really didn't know what I really didn't know!

After a bit of a delay as DHL succeeded in sending my package to the wrong distribution centre, the box arrived. Doge spared no efforts in ensuring that it arrived in good condition. The unit was wrapped in a plastic bag, then triple cardboard boxes, plastic wrap over the boxes and a wooden framing crate over it all. It took me quite a while to get to the DAC! I was surprised to discover that there were no batteries provided for the remote. Doge explained that the applicable shipping regulations do not allow batteries. Fortunately, I had some on hand.

The Doge 7 shares the same style case and control buttons as my Doge 8 preamp only this time in a flat black. The front panel adds a cut-out for a digital display as well as a headphone jack. Inside, the 7 is again quite similar to the 8 with a clean layout and quality construction. Again, following the path of the Doge 8, this unit uses 12AX7 and 12AT7 tubes, the number of tubes varies depending on whether or not the balanced output (XLR) option is present. This has not been verified with the manufacturer but one is tempted to conclude that the analog part of this unit copies the circuit design of their excellent performing Doge 8 preamp. On the back panel one finds 6 inputs; USB, 2 x coax, 2 x optical and one AES. I have to admit that I didn't know what an AES port was until I received this unit and looked it up. For those readers who are in the same situation my reading explained that an AES port uses the same protocol as s-pdif but with an XLR type connector and a different voltage level. There are 2 unbalanced outputs and one balanced (my unit includes the XLR option). All of the back-plate hardware is of excellent quality.

When I placed the order for this DAC, I really thought that this was going to be a plug and play installation. For some modes of operation it was. For example, sending music to the DAC via s-pdif port, whether coax or optical, was simple and I was able to send music from the s-pdif outputs of my CD player and of my Squeezebox II (max. 48 kHz) player perfectly the first time and every time. I don't know if high sample rate PCM and/or DSD can be sent over this type of connection, I am not equipped to test this. Also, I have read that some Windows PC sound cards have s-pdif out ports. I don't have the appropriate sound card to do this either and intend to stick with USB from my PC.

Conversely, Sending music to the DAC via USB port from my Windows 10 PC was an adventure. In order to tell my story a bit of technical background information is necessary. As stated earlier, this is all new to me so please excuse my rather simplistic explanation. Most DAC chips cannot decode PCM sent via USB packets for sampling rates is greater than 96 kHz. To get around this Doge has installed a chip called an XMOS ahead of the ESS Sabre DAC chip. Doge explained that this is the only way around this constraint that is commercially available at this time. The XMOS chip converts the USB data stream back to s-pdif format which the DAC can then digest. Note that the ESS Sabre DAC is able to decode DSD format to s-pdif so the XMOS is only needed for certain PCM formats. In order for the XMOS chip to do it's job a driver must be installed in the PC. This is where the first problem started. Due to a change from the XMOS chip supplier I ended up with an out of date driver so of course the DAC wouldn't communicate with the PC. It took a couple of days and a lot of support from Doge to figure out what exactly the problem was and once the correct driver was installed the communication problem disappeared instantly. I understand that Doge is somewhat annoyed with their XMOS chip supplier over this. Also, Doge is looking at revising their test procedures to avoid this type of mishap in the future.

Now hurdle number one was passed, on to the next one. If you are a Mac user you can skip this paragraph as it only pertains to setup with a Windows device. I decided to install Foobar 2000 as a music player on my PC. The reason for this choice is quite simple, it's the only free music player for Windows that I know of that will handle all of the music formats and sampling rates that the DAC can take. I quickly discovered that configuring Foobar to handle high sample rate PCM and DSD is something best left for programmers and kids who were born with a mouse in their hand. I gave up on that and switched to JRiver, basically because JRiver is the only other Windows compatible player that I know of that will do the job. With the guidance from Marc at Doge, the menu driven setup on JRiver went well and I was playing music via USB in all of the formats I had on my PC very quickly. Doge is in the process of preparing a support page with screen shots of the JRiver setting. In my case, it would have been trial and error to setup JRiver without the support from Doge as I didn't understand much of the settings. So, this new support page will be a necessity for the less tech savvy Doge 7 owners. For completeness I should add that I have been told that it is somewhat easier to set up music streaming over USB from an Apple PC. It seems that the Apple OS (whatever it's called) has some of the music player and necessary driver software built in. I don't have any details on this and don't ever intend to try it.

Now on to the third episode in the Doge 7 installation. It is with some embarrassment that this paragraph is being written as I am feeling rather stupid. Once the Doge 7 became fully functional I realized that there was significant hum in the system. The hum volume was quite unacceptable and annoying. Using an Android app called Audio Tool it was confirm that the hum was specifically at 60 Hz. So then started the hunt for a ground loop. This included a long series of plugging and unplugging components and installation of an isolation transformer in every imaginable location and combination of components, but the hum persisted. Eventually I was able to establish that the hum was located in the USB link between the PC and the DAC. So now I am thinking “Am I going to have to fork out $260. US plus duties and taxes for an Intona High Speed USB Isolator just to get my new DAC to play without hum?” Yes, I realize that there are other products available that cost less that will do the job however they don't work past 24/96 format! At around this point in time Doge informed me that there is a switch inside the DAC that can be set to noise reduction, this switch is not spoken of in the manual or on the web site? (see photo below) Nor do I know at this time how it works. Putting this switch into Noise Reduction position did reduce the hum but only slightly. Finally, in frustration I installed a ground lift adaptor on the power cord for the PC and the hum disappeared completely. Now I was thoroughly confused! How can this work when the isolation transformer didn't work? This haunted me until the next day when I dissected the wiring of the transformer and discovered that it didn't make sense for an isolation transformer. There weren't enough wires! I found the wiring diagram for this device on the internet and “Surprise” its an autotransformer, it doesn't provide any isolation at all. I had simply forgotten what I had purchased so many years earlier. I understand now after corresponding with some people who know a lot more about this subject than I do, that hum/noise over an audio link via USB is a common problem. Who knew! I guess you just have to know where to look to learn this kind of information. Once the ground lift was in place there was no detectable hum or noise originating in the DAC unit.

[Doge 7 Back view]
[Doge 7 Inside view] [Ground Noise Switch]

Playing the unit

From the emails exchanged with Doge I learned that the stock tubes are given very little burn-in time at the Shuguang factory. Doge does run them for 48 hours before shipping the unit however they recommend 150 hours of run time before these tubes come up to their best performance level. I well remember my experience with the Doge 8 where I removed the stock tubes after one day because they sounded very poor. So, the first step was to run the unit about 8 to 10 hours a day for over a week before attempting any serious listening.

The Doge 7 is somewhat unique in that it has two modes of operation. One mode of course being normal DAC Mode which sends a nominal 2.6 Vrms to the unbalanced output terminals. (5.2 V to the XLR terminals), the other being Pre-amp mode which allows the Sabre DAC chip to control the volume prior to sending it to the outputs. The maximum output in both modes is the same (25 Vrms unbalanced). Doge explains that this feature is provided so that the volume can be controlled from the remote for those who don't have a remote with their preamp. The function is built into the DAC chip so they decided to implement it. It is noteworthy that this is a digital domain volume control and therefore does not add any components to the analog signal path. The volume is displayed with a range of zero to 127. Doge informs me that this number is related to the gain in dB. The volume control knob is rather small however given that in most cases it will probably not be used this seems to be a reasonable choice. Also worth noting is that in my case, the output of the DAC is sufficiently high so that I can connect the DAC directly to my Canary CA330 amps and basically use the DAC as a line stage. It works fine. The output impedance of the Doge 7 DAC and the Doge 8 preamp are the same 600 ohms so my Canary amps are seeing the same type of source. Listening in both modes, the results are excellent so the rest of this report shall not consider operation modes. For the curious, the Preamp Mode was more transparent with more presence, logically because the signal completely bypasses a preamp stage and furthermore doesn't use a resistance type volume control.

As mentioned, the Doge 7 can play many music formats:

Although I am primarily interested and invested in vinyl records I have over the years collected a considerable amount of digital music, mostly Red Book format. (Compact Disk) Many of my CD's date from before my vinyl awakening, or things I bought at garage sales. All of my CD collection has been ripped to a hard drive on my PC, now residing in my newly installed music server PC. (my wife's old PC) My collection also includes a few albums in 24/96 and 24/192 PCM as well as some recently purchased DSD64 and DSD128 albums and some samples. Prior to acquisition of the Doge 7, my digital playback system consisted of an Arcam CD73 player playing via s-pdif into a Musical Fidelity X-DAC-V3 / X-PSU-V3 as well as a Squeezebox II also feeding s-pdif into the MF DAC. In the process of reviewing the Doge 7, I discovered that my Squeezebox II player limits the output to 48kHz! When I played a 24/96 music file from Logitech Media Server it displayed that it was a 24/96 file, if I looked on the Squeezebox II player it indicated 24/96, but after connecting this signal into the Doge 7 the display on the Doge read 48k! Who new! All these years... No wonder I had difficulty identifying difference between Red Book, 24/96 and 24/192! Thanks Doge for putting that information on the digital display.

During the listening time the following music formats were played:

The great majority of this time was devoted to playing from the JRiver player on my PC over the USB link.
The key component of the digital side of this DAC is of course the Canadian designed 32-bit ESS Sabre ES9018 DAC chip. ESS is a California based company however the R&D facility for their DAC products is in Kelowna, BC. Until the arrival of the ES9028PRO in 2016 (by the same company) the ES9018 was considered one of the top DAC chips available. Given the pedigree of this famous DAC chip one would expect great performance from the digital end of Doge 7. The analog end of the Doge 7 is basically a 100% tube line stage using 12AX7 and 12AT7 tubes. Given Doge's overwhelming success and the praises heaped on the Doge 8 preamp that uses the same tube combination one can certainly assume that a least some of the Doge 8 analog qualities migrated over to the Doge 7.

The better my system became over the past few years, the more playing a CD sounded like a step backwards. My digital playback components weren't keeping pace. Could the Doge 7 move the needle in the right direction? The Doge 7 delivers high-end performance in every way. It only took listening to one track to realize that there was a significant difference between the Doge 7 and my X-DAC-V3. The Doge is more refined, detailed, smooth and natural. The Doge 7 has an expansive, generous bass and mid-bass that at the same time is tight and controlled. This kind of bass performance was totally unexpected and genuinely surprised me. Now this is the second time that a Doge product has surprised me, the dynamic range of the Doge 8 preamp having given me a similar reaction a few years ago. The critical mid range where the heart of the music lives comes through as natural, balanced and detailed. The high end can expose a DAC's weaknesses but in this case there are no problems to declare. The top end was as natural as the rest with no sign of digital edginess. The overall result is detailed and dynamic yet smooth and natural.

The Chet Baker Test: I am an amateur trumpet player. Consequently I own a lot of trumpet music, classical, big band, jazz, I enjoy it all. One of my favorite trumpet players is Chet Baker, not because there is any great virtuosity in his playing but because of the feeling, the emotional charge he gives the music. One of the key ingredients that makes this work for him is his tone. His notes are always silky smooth. Any trumpet player can appreciate how difficult that is to accomplish. The Doge 7 consistently reproduced the full, round Chet Baker tone without any brittleness or harshness. Not an easy task for a digital component. The tone was still there and I enjoyed listening to “Chet” all the way through. When thinking about my listening time the same words keep coming back; full, expansive, airy, and natural, the voices and instruments never betraying their digital origins.

On several occasions I have listened to the Doge 7 for stretches of several hours without ever feeling digital fatigue or the dreaded digital headache. I am not saying that the Doge 7 can match the transparency and presence my Zyx Universe cartridge mounted in my Dynavector DV507MKII tonearm on my 80 pound fully rebuilt Lenco L75 which is connected to a Coincident Statement step up transformer and into the exceptional Doge 8 tube phono stage. I am saying that it's good enough so that I really enjoy playing from my digital music library all day long. My digital music playback system has finally taken a giant step towards catching up to my analog system. Really a significant, and possibly singular feat for something at this price point!

Conclusions

The Doge 7 Tube DAC is a new product. The unit that I received came from the first retail production batch. As with any product launch some of the things that I experienced should not be expected for future owners.

Manufacturers produce CD players and DACs that have performance specs that are way better than pretty much all analog devices, but that isn't enough, it has to sound real. The bottom line is that the Doge 7 has very successfully married a high-end DAC chip with their superb tube line stage pedigree to produce a package that makes one easily forget its digital roots and enjoy the music. Fundamentally, isn't that the most important attribute that one can ask for in a digital music playback system?

A comment on s-pdif: coax vs optical

I remember reading a couple of different authors saying that when given the choice between using a coax cable or an optical cable for an s-pdif link its better to go with the coax because conversion to optical s-pdif creates some jitter whereas coax requires no conversion therefore no jitter is added. I decided to test this. My CD player has both coax and optical outputs and the D7 has 2 each of coax and optical inputs. So, both digital outputs of the CD player were connected to the DAC and a variety of CD's played while switching DAC inputs with the remote. I was unable to detect any difference whatsoever. There are several possible conclusions:

A comment on Red Book vs Hi Def PCM vs DSD

Over the past few months I have done a lot of reading on the question and the never-ending debate about whether there is an audible difference between a normal CD recording (Red Book) vs. high sample rate PCM files vs. DSD format. I have found some very excellent, well written, technically supported articles by highly educated people (for example a Harvard professor) explaining that there is no audible difference. I have also found the same defending the other side of the argument. I have to say that the arguments used on the pro-difference side seemed often to a bit harder to follow. So, what does my listening experience on the new Doge 7 reveal?

I don't feel that at this time I have had enough listening time to draw any confident conclusions regarding the differences, if any, between the various formats. I think that it will take a lot more careful listening and head to head comparisons to be able to formulate an opinion. As of today, I can't say that I have detected a consistent difference between a PCM 24/96, 24/192 or DSD64 file. I only own one DSD128 file so I won't comment on that format. In some cases, not all, I believe that the high sample rate PCM files and the DSD files have a slightly improved fullness or airiness to the overall sound of the recording when compared to the same recording in Red Book format. If you are the proud owner of a Doge 7 you will need to decide if you will spend the extra money for the high-resolution formats?

About Tube rolling

Doge gives the buyer the choice of adding a balanced (XLR) output to the unit. The RCA/XLR output unit has six 12AX7 tubes and two 12AT7 tubes whereas the RCA only unit has four 12AX7 tubes and two 12AT7 tubes. The only reason that this is mentioned here is that if one decides to try tube rolling and only the RCA output is used then only 6 tubes in the RCA/XLR model need to be changed instead of 8. These are the six on the right side when facing the front plate of the unit. It is worth noting that the stock tubes provided by Doge sounded significantly better than the ones received in my Doge 8 unit 6 years ago and this makes tube rolling an option rather than a necessity.

Music List

Here is a partial list of the music played with some comments.

Specifications

Complete specs are available on the Doge web page listed above

Music File Formats: All existing formats
Bit Rates:

Tube Complement:


Bandwidth: 20 - 20kHz
S/N Ratio: 103 dB
6 Inputs: USB, OPT 1&2, Coax 1&2, AES.
2 Unbalanced Outputs, (Optional 1 balanced Out)
Max Output voltage 2.6V rms
Output Impedence: less than or equal to 600 ohms
Headphone Jack
Volume control
Variable and Fixed Outpu
Power Consumption 35 W.
Dimensions : 44 W x 36 D x 11 H (cm)
Net Weight : 15 kg.

My System

Speakers: Coincident Total Victory I; upgraded to Total Victory II by Isreal Blume (the creator), and also upgraded with extended feet and modified by me for bi-amping.(recent change)
Amplifiers: Canary CA330 monoblocks; with NOS rectifier and driver tubes and Genalex Gold Lion PX300B power triodes.
Preamplifiers: Doge 8; with 4 NOS 1960s Seimens 12AT7s and 4 pre-war NOS EI 12AX7s. Note: This unit has since been replaced with a Doge 8 Clarity.
Digital sources: Arcam CD72 CD player. (used as a transport only) Logitech Squeezebox Music streamer + external Powerwave HA-5 linear power supply. Both of the above devices are connected to a Musical Fidelity X-DAC V3 with matching X-PSU V3 power supply
Analog Sources: Main analog source: Lenco L75 #1: Fully rebuilt; 75 pound plinth, Dynavector DV507 MKII tonearm, Zyx Universe cartridge, Coincident Statement MC step up transformer
Second analog source: Lenco L75 #2: partly rebuilt, original Lenco tonearm, Denon DL160 cartridge, Project phono box SE II.
Interconnects: All interconnnects are DIY cables designed and built by the author with the exception of the MC step up output which is a Tara Labs RSC Vector 1 and the Dynavector phono cable that came with the tonearm.

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© Copyright 2018 Roger McCuaig - roger@tnt-audio.com - www.tnt-audio.com