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Review of the Audio-GD FUN - A modular Dac / Headphone amp / Preamp

Posted by Amine Slimani on January 24, 2010 at 6:41 AM

I - Preamble:

The Audio-GD FUN is the replacement of the Compass which has been extensivelydescribed here by Currawong on, so I won't go into the details. 


Like the Compass, it is a DAC / pre-amp / headphone amp in one enclosure. Butthe novelty here is that has a modular design that lets even the unskilled userto replace different modules to tailor the sound of the FUN accordingly.


The modules that can be replaced by the user are : the USB module, the Digitalreceiver module, the DAC, the Opamp, The Gain module, The output module. Well,almost everything seems to be replaceable except for the power supply!




Quick note on my current setup:


I have been listening and tweaking for months now to the dac19Mk3+C2C combowith my silver cabled Sennheiser. This set-up is both revealing and enjoyableto listen to it. So whenever, I mention a comparison to my reference system,keep in mind that the total cost of the components, cables and power filter are almost 10 times the price of the Audio-gd FUN.



My review method:


When reviewing or trying to assess a new component, I usually let it burn-infor quite some time (with minimal listening to it during that period), and thenI prefer to do long listening sessions to get a good feel of the new component.It is only at the end that I do some A/B tests with my reference set-up tocheck if my impressions are correct. 




II - Review of the A version (DIR9001 +AD1852 + ACSS + Diamond Buffer)



1 - Set-up & Musical selection


I did my review using a “best case scenario” in my system:


Foobar v1.0 –> Kernel Streaming –> m2tech Hiface –> Oyaide DB-510–> Audio-gd FUN –> Artisan Silver Dream Cable –> Sennheiser HD-650


Opamp used : LME49720 HA TO-99 (metal can version)


Power cord : Hifi Cables & Cie Powertrans Plus cord

Power filter : BADA LB-5600 (with Hifi Cables & Cie SimplePower Cord)

Vibration control : Herbie’s Audio Tenderfoot, Yamamoto footers, MaplePlatform, Sand Box

Usb cable : Wireworld Ultraviolet USB 



Some of the music used for this review:


MOZART Violin Concertos - Marianne Thorsen – 2L – 24/96

Sol Gabetta - Schostakowitsch Cellokonzert Nr. 2/Cello

Mahler - Symphony n 5 - Decca

Natalie Dessay - Italian Opera Arias - Emi Classics

Puccini - La Boheme - Decca

Glenn Gould – The Goldberg Variations 1981

Hans Zimmer - Gladiator Soundtrack

The Dave Brubeck Quartet - Take Five 

Soundrama - "The Pulse" (Test CD)

The World's Greatest Audiophile Vocal Recordings – Chesky – 24/96

Patrici Barber – Café Blue – HDTracks download

Diana Krall - Live in Paris

Norah Jones - Come Away With Me




2- DAC / Headphone amp combo


First, let me tell you a little anecdote: while reviewing the unit, and inorder to keep the conditions similar to what I am used to in my referenceset-up, I would usually swap the FUN with either the dac19mk3 or the C2C. Afterlistening for quite a while to the FUN sitting in place of the C2C, I thoughtthat the tonal balance was clear. Then I put it where the dac19mK3 usually sitsand the sound was darker (but still on the clear side). I was very puzzleduntil I remembered that the power cord of the C2C was plugged in the unfilteredsocket of my bada filter, while the dac19mK3 was plugged in the filtered socket(both units use the same power cords). 

So while reading my review, keep in mind that the audio-gd FUN but also itsinteraction with the rest of my playback chain.



Timbre and tonal balance:


The version A (ACSS) is tonally very well balanced from top to bottom. Itsmidrange is very clear and effortless. It is only when compared to thedac19mK3+C2C combo that it is apparent that the audio-gd FUN lacks timbrerefinement and the ultimate extension at the deep bass and extreme highs. However,I really like the neutral balance of the FUN because it is not trying toemphasize the mid-bass or mid-treble to fake the extension at the frequencyextremes. Many entry level product are plagued with mid bass bloat (to giveimpression of warmth) or mid treble sharpness (to give the impression of a highdefinition sound) and while it can be pleasing in the sort run, I personallyfind it annoying in the long run.


By the way, I first thought that it had a slight metallic timbre when Ilistened to it fresh out of the box, but it smoothed out with burn-in (I usedthe Isotek Burn-in CD for the burn-in period). 





The dynamics are good without compression but there is nothing exceptionalgoing on with the Sennheiser hd-650 which are notoriously known to be pickyabout amplification. 



Soundstage and imaging:


The soundstage/headstage was surprisingly good. It is not the widest I haveheard, but it has excellent depth. With the Silver cables Sennheiser, thesoundstage extends beyond the head.

It also has pinpoint imaging. Listening to large scale orchestras, you get agood feeling where the instruments are positioned in both depth and width, andthe resolution is good enough that you can still recognize the tonal signatureof similar instruments playing next to each other inside the soundstage





The transparency to the recording is actually very good. Version A (with ACSS)has the least coloration of any other combination I tried. It lets you hear agood differentiation from one recording to another. Other combinations can bemore pleasing on a particular recording but you get stuck with that colorationon every recording which may be more suitable for other set-ups and personaltastes, but it is not a match for my system and personal preferences.

In fact, the audio-gd FUN is very picky about the quality of the recordings(mastering and encoding). My recommendation is that it shouldn’t be use withmp3s of less than 320kbps, and it would be preferably used with lossless orhigh rez files.



3 - Dac/preamp section



When using the DAC out and using the C2C as an external amp, the soundstagegrew a little bigger, mostly in width. There was also better three-dimensionalpalpability to the sound. The C2C reached deeper in the bass and had a fullersound (higher tonal density).

Overall the sound (in comparison with the FUN alone) was more effortless, morerelaxed and perhaps slightly warmer sounding. However, in this configuration,the increase in performance is subtle and considering the cost of the pair ofinterconnects, headamp and extra power cord, it is not worth it by anystandards.


However, the big surprise came when I used the DAC with its line out. Thesoundstage was much bigger and three-dimensional. The sound was more refined. Thelevel of details increased a lot. This was counterintuitive and I wasn’texactly expecting improvement when I tried it. In fact, the reason I tried thevariable line out was to see how much transparency was lost with the use of theextra buffer stage and volume. However, it is the opposite: the FUN is a muchbetter DAC from the variable line out. 

I went back and looked at the internal of the FUN and those of the Compass, andit seems that the FUN is lacking a buffer section unlike the Compass. Besidesthe need of a fixed volume output, I see no reason why the dac out has beenoffered as an option.


Anyway, I am happy to have discovered that the FUN has an excellent preampsection. The other preamps I have on hand, the audio-gd st-3 and little dot mk3are more colored and are definitely not as transparent.



4 - Headphone amp section


To assess the quality of the headphone amp section, I used the dac19mk3 as anexternal dac (using the Artisan Cables "Ultimate Silver Dream"interconnects) into the line input of the FUN. 

The first thing that stroke me was the size of the soundstage, it was muchbigger in all directions (width, height and depth) compared to its internaldac. 

The second thing that attracted my attention was the level of details which wasmuch higher through the dac19mk3 + headamp section of the FUN. 

Finally, the sound was more analog like, more natural with less edginess. 


Overall, I found the headphone amp quite satisfying on its own even if itdidn’t drive the Sennheiser as the C2C headamp does.



5- “Tweaks”


The Audio-gd FUN responds very well to tweaks. However, given its sellingprice, I don’t think it is wise recommending to future buyers sticking highpriced power cords and digital cables to it. Anyway, one thing is for sure, itbehaves like a “high-end” component and its sound can clearly be improved withgood power filtration and interconnects.



6- Overall


The performance of the Version A (DIR9001 +AD1852 + ACSS + Diamond Buffer) isquite impressive for the price. Used a dac/headamp combo, the sound is quitegood. Used a DAC with a variable output or as a Headphone amplifier theperformance is excellent (given the price). 




III - Review of different modules



1- Digital receivers




The CS8416 is rather warm and fuzzy sounding and it is not very detailed. Also,when I compared it to the usb input there was little sonic improvement over it. 





The DIR9001 is definitely better sounding, the portrayed images are a lotclearer (less fuzziness) and it has more bass weight. Overall, there is a lotmore going on and the low level details (room ambiance, echoes and reverbs, …;)that were masked with the CS8416 reappeared with the DIR9001. 



Usb vs. spdif


I was very surprised by the quality of the usb input. Compared to the dac-100and dac-19mk3, there is a definite improvement in performance. Using theWireworld ultraviolet cable, the sound is not bad at all with the USB input butyou just get more of everything when switching to the spdif input.





Unless you own a huge library of recordings at 24/192, I would recommendsticking with the stock digital receiver 24/96. 

The difference was apparent in my current system using the m2tech hiface +Oyaide or the Sobek digital cables. It could very well be less or morenoticeable in other systems depending on the interaction of those components.



What I would like to see in future versions


I really would to see future digital input modules with low jitter (like theDIR9001) and 24/192 support (CS8416). 

Also, I wonder if there is a way to put an SRC board along with DIR. 



2- USB


For now there is only one choice, the PCM2706. For the future, it would beinteresting to have a 24/96 capable usb module, maybe something based on theTenor chip?



(Edit: The FUN is now available with a Tenor 24/96 USB chip)

3- DAC chips




The AD1852 offers a good amount of details compared to the WM8740 and it offersa well defined soundstage (deep and large). It is also more dynamic than theWolfson DAC but it is a lot more forward and aggressive sounding. The leadingedges of the notes are overemphasized which makes it a little bit “digital”sounding. 





In comparison to the AD1852, the WM8740 has a flatter soundstage. It has richermids (with a bit of mid bass bloat ?). Overall, it is less detailed, lesstransparent to the recording. It has slowed transients with a perceived rolledoff highs which give it a more analog like sound (but still not as good as whatyou get with pcm1704 based DACs)





When using SoX upsampling (44.1 -> 88.2) it removed some of the digitis fromboth DA chips and especially the AD1852. When using 24/96 material, there is ofcourse no need to using upsampling.

By the way, my ears have become more sensitive to the digital edginess ofdela-sigma DA chips since the time I have been listening to the dac19mk3 whichis one of the most analog sounding dacs I have heard to date (along with theAudiomat Tempo DAC 2.5) which is using PCM1704uk chips.

Anyway, with both DACs (AD1852, WM8740), the sound is much more enjoyable thanthe emu 0404 usb (which uses AK4397) and the less detailed and older dac-100.





My favorite is the ad1852. It is very transparent which means that peopleshould not use it with low bitrate mp3 or poorly mastered recordings. For thatkind of files, the WM8740 is more suited as it would smooth over the leadingedges notes of those low quality files and make the listening more bearable.



What I would like to see in future versions


While the AD1852 was my favorite of the two, I can’t help but wonder if theWM8741 would do a better job than the WM8740. Ideally, I would like to seeAudio-gd offer upgrade modules with the PCM1704 but I don’t know if that iseven technically possible given the available space on the DAC board. OtherDACs that come to mind are the AD1955, CS4398, AK4397 and PCM1794.



4- Opamps


I haven’t spent much time comparing opamps for this review, and I settled onthe LM49720HA TO-99 (metal can version) because they are simply the best opampsI have heard to date. Some other opamps I had on hand were the Earth hdam,OPA627 (on adaptor), LM4562.



5- Gain Modules




Compared to the Neutral module, the soundstage is bigger and mostinterestingly, it is pushed further back. The imaging is more threedimensional.

The sound can be best described as smooth and relaxed. 

The smoothness is not due to a roll off in the highs but to the natural balanceof the sound and to the effortless portrayal of details and resolution. 

The sound is very fast and clear yet it remains natural. There is no emphasisor substraction of anything. This means that if the recording is warm, you willhear warmth, and if the recording is dry you will hear it unfiltered andunprocessed. 

Those looking for a neutral piece of equipment should probably get version A(ACSS) instead of Version B which uses regular voltage gain modules.





While the Neural module might be “more neutral” than the other voltage modules,it is definitely warmer sounding and colored in comparison with the ACSSmodule. 

It seems less extended on top and has more mid-bass content. It has richerharmonics, and is “tubey” sounding compared to the ACSS. 

It is not bad, and in fact it is very good on its own, but when it is comparedto the ACSS module, it lacks details and seems to do more effort to get there. 

It is however more forgiving. And I am sure better suited for people who liketubes but not too much coloration at the same time. This module avoids themidrange dryness that some solid state amps unfortunately have.




(This part will be updated later)




(This part will be updated later)





Personally, I like the ACSS module. Its effortless yet very detailed portrayalof the sound is very addictive. It is neutral and also the closest sounding tothe C2C headphone amp that I absolutely love and that uses the same currentgain technology.

I have to admit that I only have about 100 hours of burn-in (using the Isotekburn-in CD) on the Neutral module while I had about 100 hours (+whateverburn-in it got in the factory) on the ACSS module. However, I highly doubt anyamount of burn-in will get it the Neutral to the level of transparency of theACSS module which is probably why most of the higher end audio-gd products usethe ACSS technology.

I have yet to try the musical and dynamic module, and I will update my findingslater.


What I would like to see in future versions


I wish to see future ACSS modules with different flavors. It is nice to havethe Neutral/Musical/Dynamic modules, but I would like to see the same choicefor the ACSS modules.



6- Buffer modules


Diamond output module


The Diamond output module is linear (good balance between the mids, highs andlows) but rather clear sounding (less tonally dense than the FET module). 

You get to see deeper into the soundstage and it has more air and betterinstrument separation than the FET module.

Also, there seems to be more low level details and transients are faster. 

Finally, it seemed to me that it had higher upper harmonics content whenlistening to instruments such as violins for example.

However, if I had to be picky, I would say that it lacks the “fullness” of thesound that you get with the FET module or when using the C2C headphone amp forexample. 


FET module output module


The FET module is warmer and fuller sounding. It is tonally richer in the midsand overall more forgiving about the quality of the recording. The slowedtransients make it seem like the top end is a little bit rolled off. 

With the Sennheiser hd-650, it seemed to me that it had less drive capabilitythan the Diamond output module. However, I don’t know if it is really a driveissue or more of the way I perceived dynamics between the two modules.




The differences are rather subtle between the 2 modules. It doesn't alterdramatically the sound of the FUN unit but it allows to fine tune the sound ofthe system between the more linear and detailed Diamond and the warmer soundingFET module. 

I perceived more differences between the two DACs (AD1852, WM8740) but unlikethe added sharpness and edginess I heard when switching from the WM8740 to theAD1852, the Diamond module just seemed more linear without any emphasis on theleading edges of the notes one might expect from a clearer sounding design. 

While I preferred the Diamond module with my silver cabled Sennheiser hd-650when doing short listening sessions, I am not sure if I would settle on it onthe long run. HD-650 owners that are still using them with the stock cable (ora smooth cable like the Moon Audio Blue Dragon) will probably go for theDiamond Module. Those using brighter cans or cables, would probably favor theFET module.



IV- Conclusion


To sum up, I had a great time listening and trying to the Audio-gd FUN. It is arefreshing little unit that helped many things I have asking myself for a longtime: are DAC chips audible, what about voltage vs. current gain, FET vs. otherbuffer topologies…? 


It was also a reality check. I have spent so much time listening critically tomy reference system that my mind was only able to focus tracking weaknesses. Ihad to use different tweaks to get the perfect tonal balance. The FUN, on theother hand, is a lot more versatile and easier to set-up in order to hit theperfect balance. 


Finally, and as far as I could tell, the Audio-GD FUN offers excellentperformance for the money. It is a versatile and modular little unit. It alsohas an excellent preamp section and very good DAC and headphone amp sections. Infact, this little unit is so good that I wonder if Audio-gd could make some oftheir higher end units with the same modularity as the FUN.




Follow-up 01 February 10:


AD1852 DAC:

After 300 hours+ of burn-in, some of the harshness I first noticed with theAD1852 is now gone. It still not as “sophisticated” and rich sounding as thedac19mk3 but I am comparing a unit that can work as a DAC/preamp/headphone witha pure DAC that is almost twice its price. Overall, I would say that I am veryimpressed with the sound of the AD1852 module. 

One thing I failed to notice in my initial review it the jumpers in the AD1852module (Kingwa, who read the review, e-mailed me to tell me I could try thesecond position of the jumper). 

The result was subtle but audible. On the second jumper mode, I noticed thatthe sound became less processed, more airy and that the soundstage was pushed alittle bit deeper. It is not a huge difference but every owner of the FUNshould try both modes. Personally, I preferred the second position of thejumper but it is more of a matter of taste than superiority vs. inferiority inthe two jumper modes. 



The Musical Module:

In my opinion, the musical gain module is much more interesting than theNeutral gain module. As described by Audio-gd, it is warm sounding, with a richmid-bass and a rolled off upper register. It is probably what people expectfrom tubes before they listen to them; at least it was what I imagined tubeswould sound like before I bought the little dot MKIII. 

Overall, the sound is smooth and syrupy whatever music is played with no hintof aggressiveness. It is a little bit too much for my taste but some peoplecould be looking for that sound or it could be a good match with some brightsounding cans.

The sound signature of the Musical module is the same whether the FUN is usedas a headphone amp or as a DAC from the preamp output.


The DAC/preamp out mode and the ACSS gain module:

After trying the Musical Module for a while as a DAC/headphone amp, I wanted totry the FUN as DAC (from its preamp output) and use the C2C as a headphone amp.The outcome was very disappointing: the soundstage was bigger than the internalamp but the sound was more diffused and lacked impact and density. Given theadditional price of the C2C amp, silver wires, and the extra power cord, Ithink it is really not worth it to use the FUN with the voltage gain moduleswith an external amp.

However, it was a totally different story when I put back the ACSS gainmodules. The sound improvement was such that I found the FUN in the ACSS modealone outperformed the FUN+C2C or the FUN alone with the musical mode. 

Putting back the ACSS gain modules brought a new level of low level details,extension throughout the frequency extremes and refinement over the voltagegain modules. The sound was smooth not because it rolls the highs like themusical gain module but because it has less distortion.

Those improvements were noticeable with the FUN used as a headphone amp as wellas a DAC/preamp. In fact, when I paired the FUN with the C2C headphone amp Ithought for a moment that the sound was as good as I had with the dac19mk3. WhenI did some A/B comparisons it was apparent that the dac19mk3 still had the edgebut I was impressed about how good the FUN was sounding. If I didn’t have abetter DAC to compare it with, it would be hard to find weaknesses listening tothe FUN alone.



Categories: Amplification, Source

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