Review: Accustic Arts Reference Tube Hybrid DAC II DA converter


Category: Digital

This will be my third go around reviewing a DAC from the German company Accustic Arts. In between having the MK-3, MK-4, and now their Reference Tube Hybrid as my digital front end, I have had the pleasure to auditioned many of the highest regarded DACS and CDPS in the last couple of years. Many of this digital pieces offered great performance, a few were sonic "turkeys" regardless of some steller reviews, but based on great performance without having to get a second morgage to purchase it, I keep coming back to Accustic Arts.

The MK-4 was a significant improvement over the MK-3 and I still believe it's one of the finer sounding DACS around today. That's way I was skeptical about how much better/different would Accustic Arts new "baby" would be compared with their older DAC.

As in all my reviews I do not get into specifications, you can go to Accustic Arts website to get the details, but always comment on build quality and physical appearance. Like its older siblings the Tube Hybrid is just beautifully built and really is "eye candy". The German engineering and craftmanship is very easy to admire. I know one important technical aspect that this is the first DAC in the world that does not use tubes in the analog section, but somewhere further upstream when bits are still bits before the analog conversion stage. What the tubes are doing and how they are used in the overall design circuitry I don't have the foggist notion, just that sonic bliss is taking place.

When I discovered that Accustic Arts new reference would use tubes I was somewhat concerned for the following reasons: 1) My past experience with tube based DACS, such as the Zanden and a very high level Audio Note, was that they offered a very wonderful midrange but they lacked macrodynamics and extension on both the top and bottom ends. 2) The transparency/clarity and very small details I love in the overall sonic perspective of my system were lost.

SONIC PERFORMANCE

I do not like to result to sonic cliches to describe the sonics of a piece I'm reviewing, but this DAC is a "killer"! I hope all of us can agree that once you get to a high level of excellence in audio gear, their are many great pieces and differences become more quantitive then qualitative. We also have to factor in personnal taste and system synergy in to the equation. Taking all of this into account let me try to explain way this is the best digital I have heard in my system to the present time.

1) The Tube Hybrid retains all of the transparence/clarity and microdetails of the MK-4.

2) I will not say that the Tube Hybrid's extension on the top and bottom are better then the MK-4, but the the overall slam and dynamics is slightly more "lively" and natural sounding. Remember, the MK-4 was no slouch in these sonic areas to begin with.

3) Now we get into the specifics of why the Tube Hybrid is a "killer" in qualitative terms.

A) Unlike adding a "warm/euphonic" aspect to the music this DAC adds what many would call a touch of "bloom/fullness" without destroying the overall linear cohesiveness of the sonic perspective. Another more concrete way of saying it would be that image density and the overall harmonic structure ( leading edge, body, and decay trails) is more natural or what alot of audiophiles would dscribe as "analog" sounding.

B) This DAC offers an overall more sense of liquidity and smoothness, but not at the expensive of slam/punch/dynamics or sounding "soft" to be pleasing to the listener.

C) I have a hunch that another reason why the Tube Hybrid sounds more "real" is that it is more tonally linear compared to the MK-4, and any other digital piece I have heard on Redbook, which makes it sound of one piece top to bottom.

D) The Tube Hybrid offers the most natural timbres I have ever gotten from a digital front end.

E) I don't believe that my system's overall soundstage dramatically improved with the Tube Hybrid, the MK-4 was a champ in this area, but the layering and the air around players also went to a qualitatively higher level.

When I wrote a review here on the GON on the Stealth Metacarbon IC's I struggled to use words to describe the sound of "nothing", meaning these cables just get out of the way of the music so the illusion of real music being played by real people just gets spills into your mind and gut. Well, this DAC hits my sonic ear's the same way, it just sounds more like real music then I have ever heard in my listening room before. The Tube Hybrid sonics can be broken down into specifics, as I have tried to do, but its the overall natural/easy/lifelike sonic illusion without the loss of details,prat,sparkle that makes this a very special piece indeed.

I always end all my reviews with the statement their is no "BEST" in high end audio, but many fine pieces along with the factors of personal taste and system synergy. The new Accustic Arts Tube Hybrid DAC II is among one of the finest DACS on the market today, and while it is not inexpensive it competes with DACS triple its price. This German company sure has some talented thinkers with great ears when it comes to digital gear. If your in the market I highly recommend you audition this DAC before you purchase another.

Associated gear
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teajay
hello.
being in the same boat(AA tube dac, mg 20 speakers)
my next purchase might be the Lamm ref pre or the cary slp05
or the supratek pre's.

i also keep thinking about the kallista transport , anyone tried this combo?if the transport makes so much difference, then kallista and aa reference drive 2(can be had for $8500 shipped)should be compared as well as mbl 1621 transport.
Thansk TJ for your quick reply. I'm curious to know why you jumped on the MBL transport before seeing if the AA reference transport is something you'd consider. Don't get me wrong the MBL is magnificent stuff, but knowing that the AA reference transport was going to come out... I thought you might have waited to compare before committing yourself...
Hi Mtkl567, here's the answers to your questions:

1) I use a Stealth Sextet BNC between the transport and DAC.

2) I use a Stealth Indra, single ended, between DAC and preamp.

3) I use a Townsend isolation platform under my transport, and have experiemented with different footers under the DAC and transport and have not discovered any great improvement regardless what product I have used.
Post OBO hotbird,

Differences between Accustic Arts Ref Drive2 and Drive Mk2

Drive Mk2 : CDM Pro 2 LF – drive module with cast metal frame and involved mechanical decoupling
Ref Drive2: CDM Pro 2 LF – drive module with heavy die cast metal frame and involved mechanical decoupling, embedded in a massive aluminium housing (subchassis-construction principle)

Drive Mk2 : Generously dimensioned magnetically shielded toroidal core transformer (75 VA)
Ref Drive2: Two generously dimensioned & magnetically shielded toroidal core transformer of premium quality (2 x 75VA)

Drive Mk 2: Optimum smoothing thanks to 45,000 µF power supply capacity
Ref Drive2: Very high power supply capacity (61,000 µF) for perfect power supply.

Drive Mk 2: Resonance minimising aluminium housing
Ref Drive2: Extremely stable, massive and resonance optimized housing, primarily made of 10mm aluminium plates, ultra stable and acoustically damped top load cover

Weight
Drive Mk 2: 15kg (35lbs)
Ref Drive2: 18kg (40libs)

Unique to Ref Drive2 only
1) Integrated, specially designed Accustic Artsâ„¢ line filter for perfect and extremely clean power supply (line filter switchable)
2) Polarity switch for correct phase of the mains voltage

Unique to Drive Mk2
Drawer with indirect blue lighting for Accustic Arts logo feature (lighting can be switched off)
Teajay, what digital interconnect(s) are you using between the Transport and DAC and from the DAC to your pre? Have you experimented at all with this and are you using any isolation under both?
Last week I replaced my AA Drive MK11 with a MBL 1521a transport. I was expecting a difference, but frankly was very surprized, happly so, with the significant improvement across the sonic landscape.

1 A larger soundstage with more air between the players.

2)A much greater ease/liquidity without lose of dynamics or slam.

3)Extension on the bottom end with more power and speed. I believe its the best bass I have ever had in my system.

4)Microdetails are more apparent but in a very natural way, I believe I'm hearing more because this transport has a much lower noise floor then the AA Drive MK11.

I would say the musical/enjoyment level using the MBL transport with the AA Reference Tube Hybrid DAC went up another 25% or 30% in my system. I still believe that the AA Tube Hybrid DAC is one of the best sounding digital pieces on the market today and when you factor in its cost compared to what it competes with sonicly, kinda of a bargain. I have no idea if the new AA reference transport will perform better/different then the MBL transport, but either way it shows two things; 1) Transports really can make a difference 2) How much more potential performance can be gotten out of this terrific DAC.
Understand, on the other hand I have a few very, very well recorded 16-bit 44.1Khz RBCDs that puts the majority of recordings, including most SACDs, out there to shame...

I think the sampling question is a relevant one, but it shouldn't be taken out of the context of the whole recording and reproduction chain, its IMHO a smaller part of the overall performance. Maybe in an all digital system its more important though, like what you mentioned above.

At least my CDSA DAC's ability to upsample to 5.6Mhz did not lead to a better musicality vs the AA Tube DAC II on the same music. Maybe I liked the tube coloring ... who knows

Just my 2 cents.
In the current issue of Sterophile (June 2008) there is a review of the Cabasse La Sphere speakers, which do a fair amount of digital processing. Analog signals are digitized at 48kHz which let to the Author's comment: "A lot of processing goes on within the Sphere system, and unless CD is your only source, 48kHz is a barely sufficient sampling rate. With the exception of vocal sibilants, this processing wasn't grossly audible per se, but it certainly affected the system's ability to sound real, as opposed to sounding really great."

I realize that the AA DAC is not digitizing analog sources, but it's not the first time that I heard the notion that 48kHz is barely sufficient, which leads me back to the original question.
OK, I see what you mean. Yeah, any company's choice to limit their product specifications to best match their own transport, or even in the case of the Accuphase DC801 which only works with their own DP800 transport. Can't blame them for following this strategy. Well, if you're looking for a 32-bit DAC then Esoteric's D-05 is about the same price...
Mtkh, I wasn't really comparing sound quality between sampling rates; all I was wondering is why does AA not actually support higher input sampling rates. There are some digital sources that output a non-adjustable sampling rate higher than 48kHz, which then would not work at all with the AA DAC. It just seems odd to me that AA has decided not to support those data sources at all, even if they felt 48kHz sounds better, especially considering how expensive the DAC costs.
Smeyers, my EMMlabs samples upto 5.6Mhz, both CD and SACD, however the same CDs and SACDs I compared sounded better through the AA Tube DAC II, more analog, better imaging, better defined and clearer sound stage, more depth. All I'm saying is that you've got listen to a product and see past the statistics and techno babble. Ofcourse, the same product can sound different in differing systems.
I'm still surprised that AA only accepts up to 48kHz. My Tact 2.2 XP can output up to 192kHz. I've noticed that some folks think they can hear a difference at the higher sampling rates; in any case I find it puzzling why AA has it limited as it seems to be de-rigeur among stand alone DACS these days.
FWIW: My previous Metronome T1A transport had both 48 and 96 kHz switch. I did not hear any difference...
I noticed that the AA Tube DAC accepts a maximum input sampling rate of only 48kHz; I was surprised to see this, particularly for a DAC at this level. Do you know why they limit it to this? A lot of digital sources today upsample to 96kHz and beyond, which would be incompatible with the AA DAC unless the sampling rate of the source is reduced. Do they feel that there is no sonic advantage of accepting a higher sampling rate?
Teajay, here a link to a pic of the open Drive 2. Its in German though.

http://www.areadvd.de/lm/AV_Hardware/messeberichthighend2008.shtml

Regards
Mattheus, unless AA did something radically different in the new transport there is no reason to leave a cd in it when you are not playing it. I never do, I just leave the puck/clamp off the spindle and close the top.

Do you have any idea if the new transport has a different puck/clamp compared to the MK11 drive as far as size or weight?
Teajay,

I will.

I also have a matched pair of Mullard cv4004 cryotubes which I used in the Metronome C1A DAC and who had a very big/positive impact on sound. But I will first enjoy the standard tubes (what brand are they?) before I start 'rolling' :-)

My brother in law came over and had a listen yesterday. His words to describe the sound of the AA are: 'it sounds just like a good turntable' ! Knowing he uses a VPI - Manley - Usher system, this means a lot.

It's as you describe: the combination of 'hyper'detail, realism and full analog sound really is amazing. My brother in law stated it this way: it's as if the AA does not have a charcteristic sound, but you only hear the music as it is recorded.

I have a question: is it necessary to have a cd in the drive when it is not playing?
Mattheus, congrats on your new toys! If you look at what has been posted on this thread regarding tube rolling in the Tube Hybrid DAC, replacing the stock 12AX7's with NOS tubes the performance will even go to a higher level that you are enjoying as the pieces are burning in. So let us know what's happening regarding the new XLR cable from AA and other fun details. Enjoy.
Hello.

I received my AA Drive 1 mk2 SE and TubeDac2 today. These are my first impressions as I wrote them in my system's page on Audiogon:

"Accustic Arts combo is functioning. It really blows away my previous Metronome Technologie combo ! Even 'right out of the box' the AA gives a tremendous organic and 'analog' sound, without loosing detail or without loosing crispyness. Ofcourse the AA needs burning in, but right now all I can say is that it completely outperforms Metronome (which BTW after all is way overpriced). Compared to the AA combo, the Metronome sound is 'thin' and less involving, has less 'flesh around the bones'. I'm waiting for the AA digital XLR cable to arrive, which is especially made as ideal connection between the Drive 1 and TubeDac2. Will get back later on."
I have a picture and a technical description of the new AA reference transport Drive II. Send me a mail if you want it. It is indeed a top sliding mechanism, robust as they come. Retail price in Germany is EUR 7,000, that together with the Tube DAC II makes EUR 13,400 plus cables ... pricey combo!
I was hoping that 6moons post a picture of it on their review of their show (11pages) but they stopped short after posting 40% of their photos (they said they still had 60% left). The rest of the other websites, Enjoythemusic and soundstage add together do not even have as much photos as 6moons, such a shame.
Thank's Hotbird for posting the link to the AA room. Can't really tell, other than it doesn't look like a big ole Oracle transport ... :-)
Just manage to find a picture of an Accustic Arts setup at the Munich show. I wonder is that a new Reference transport at the top of the rack? It looks like the lid has changed to a clamping mechanism from a sliding one???

Accustic Arts with Monitor Audio(yucks)
Now that the High End show in Munich is already on, are there any photos or writeup on the new Accustic Art Reference Transport? Does it really look the same as Drive2? For a price that some say is above Tube DAC2, hopes it looks big and massive like an Oracle transport ;-)
Last information about the new AA reference transport Drive 2 is that pricing wise it will be slightly above the DAC II, at least in Europe. This thing better be worth it at about twice the Drive 1 price!!! I'm starting to wonder about the AA value proposition here... as most of the excellent sound comes from D/A conversion IMO
I can confirm the new transport (drive 2) will come out at the Munich High-End show end of April. No pricing known yet.

I ordered two Aktiv 6 power strips with some of their power cables. These will probably burn in within a week or so, not sure about the DAC II, most electronic components take 100+ hours of playtime at least. Use a burn-in disc, that would accellerate the process.
actually,
i heard that the new drive 1 transport (mk2) is just the same, with the upgraded cable as described above.

however the all new reference transport(drive 2) will come out in april with world premier at "High End 2008" in Munich

also can anyone tell me how long the dac 2 takes to get fully burned in, as mine is still harsh compared to the reimyo dac.
On the new transport I was told by the only German dealer that carries the whole AA line that the new transport really is only a special Cable Kit installation (from the US) that is easily installed on the current transport afterwards. No definite timing known just as yet.

Any of you have experience with the AA power strips and power cables? I was trying to compare to the PS Audio premier. I know not the same product, but on my amplification the AA strip was better than the premier.

Teajay, just like Moniker, it brought my whole RBCD playback to a higher level across the board. I preferred it much over SACD on my CDSA-SE player. Don't understand why there is so little discussion out there on this wonderful DAC.
Dev, Richard's Gon moniker is Hamburg. He went from a Levinson transport not a Accustic Arts to his CEC-TLOx in his system. When we talked regarding the differences it was across the board, soundstaging, dynamics, extension, liquidity, etc., and brought the overall sonics of his system to a higher level.

I have gotten no information yet regarding when AA will release their new transport or what they will be doing regarding the mechanics of it compared to the MKII transport.

Hi Teajay your welcome, will be interesting to read your findings once you have tried the Dream speaker cables within your system.

Stealth Digital cables:

1)I will do a more detailed evaluation and post it, I have to say that I was a bit taken back and shocked at the same time when I removed one and installed the other and heard the differences, instantly you could hear the floor noise being substantially lower and everything just seemed to open up. Actually what happened was a couple of friends were over to hear the CAT's and I had one of the digital cables just sitting off to the side and was asked to install it so they could hear if there was a difference or not. You should get the XLR version (AES)digital connection to evaluate your self because there is most defiantly a difference, this could be easily heard in my system with my trans (Oracle) and dac (AA Tube Hybrid) combo.

Transports:

1)Your friend Richard what is his GON name?
2)What differences did you hear from your trans and his CEC, there is a substantial difference in cost.
3)Regarding the new AA trans. do you have any info. pertaining this unit that you care to share? Design differences, cost.

Tubes and fuses:

1)I will get the fuses.
2)The Long Plate tubes, I still have not been able to get a pair any thoughts where I can get some.
Hi, Dev thanks for the information you left me regarding the Stealth Dream speaker wires, I hope to getting a pair to audition at the end of this week.

Now on to your questions:

1) I use the Stealth Sextet with BNC connections. I have never heard the XLR version in my system. Please share which cable produced which result when you ran the experiment.

2) I have not heard the most current CEC TL-ox with this DAC. Richard a fellow GON member who also owns the Tube Hybrid uses the CEC TL-ox and is enthralled with the results. He also has NOS Amperex Long Plates and the upgrarded fuses in his DAC.

3)Yes, the fuses make enough of a difference to make a difference to put them in.
Mtkhl567 I agree with you the AA Tube Hybrid DAC is a marvelous piece and I suspect there isn't much being posted because anyone who happens to own one is just enjoying their library of music. As Teajay has mentioned changing the two tubes most defiantly improves a already supurb piece. Two areas I have also noticed differences are different transports and via digital connection.

Currently I have two Stealth Sextet digital cables, AES and BNC and there is most defiantly a difference. Using one the images are much more focused but at the same time gives up body and texture. Bass response on one lets you hear the most hidden inner detail notes while the other is more congested clouded over.

Teajay I believe you are using a Stealth Sextet digital cable also, what connection are you using? Have you directly compared using the same manufactures cable but different digital connection? You should because you will be in for a surprise as there most defiantly is a difference in my set-up any ways using the the Oracle as the transport. You mentioned in your post above that a friend had the CEC transport have you had a chance to hear it with your dac? That would be a real interesting piece and I would have interest in your thoughts.

Can you believe it I still have not got around to replacing the two fuses I'm just enjoying the piece so much and keep forgetting to do it, is there that much audio difference?
Mtkhl567, I use the AA transport MK11 in my system and think its a great match with the DAC. I haved tried two other very good transports and did not hear enough of a sound difference to make the change. Yes, Accustic Arts is coming out sometime this year with their new reference level transport to match the Tube Hybrid DAC, I'll be auditioning for sure when it does come out.
Thanks Teajay, I have no experience with expensive DACs, so I can only say what the AA machine did in my system. Which was pretty wonderful. It just was tonally so right, soundstage wise hugely improved. Listened to some more types of music last night, and just confirmed that it's not only with Jazz and Orchestral music, but also pop and rock, female voice.

I agree with you on the transport of the Emm, it's not a strength... did you know AA are coming out with a new transport this year? What do you think of their current transport?
Mtkhl567, in the context of your world class reference system, it's quite a compliment you are giving to the sonics of the AA Tube Hybrid DAC.

I have recently talked to someone who had recently listened to all the top rated digital front ends, Dcs, Esoteric, Metronome, Zanden and he still felt that the Accustic Arts Tube Hybrid was the best of the bunch. And to think all the other DACS retail for at least $15000.00 to $20000.00 more then the Tube Hybrid!

I also believe, please no disrespect on my part, that the Meitner transport is not one of the better sounding trnsports to mate with the Tube Hybrid DAC. A dear friend has the Meitner reference DAC and uses a CEC TL-0 for redbook because it sounds significantly better then the Meitner transport with his Meitner DAC. So, I believe you would get even a higher level of performance with a different transport. If you heard the DAC with the stock tubes you would be amazed at the sonics with the best NOS tubes that I discuss on this thread.
It's been a while since someone posted here. I tried the AA Hybrid Tube DAC this weekend, and I also was mightily impressed with it. I used my Emm as a transport and connected it with a digital Wireworld Gold Eclipse XLR. Had some functional issues, like it doesn't play SACD signals, only RB, and everytime I changed a CD the digital error lght came on and the unit started clicking loudly. Any experience like that? But the sonics were to die for, just like you described in your review. I haven't heard anything digital sound this analog, including the Accuphase P800/D801 combo I listened to yesterday at 3X retail. I know I raved abbout my Emm and thought it much better than any Accuphase, but this tops them all easily in my system. Intreresting reading about the tubes/fuse tuning too. Personally I'd rather have fuses not designed into the signal path, like my Darts, but the overal sound the the AA Tube DAC was very convincing.

Thanks Teajay for the interesting review.
My last post stated that after trying Telefunkens and Mullards I came to the conclusion that the Amperex Bugle Boys offered the best of all sonic worlds when used in the Accustic Arts Tube Hybrid DAC.

Well, I just tried Amperex Bugle Boy 50's Long Plates, instead of my Amperex Bugle Boy 60's Short Plates and have got a new reference in tubes for the following reasons:

1)Greater transparency/clarity with more microdetails.

2)More air around players with a greater sense of 3D images in the soundstage.

3)More powerful dynamics and punch in the bottom end.

Yet, these Long Plates still keep the liquidity/easyness and warmth of timbres of the Short Plates with the above stated sonic improvements. I always find it amazing when you can get this rare combination of ease and resolution at the same time, which leads to a higher level of musical enjoyment.
Just wanted to share that I just got through auditioning in the AA Tube Hybrid DAC the last of the great "three european sisters" tubes, the other two are the Telefunken smoothplates and the Amperex "Bugle Boys", the last "sister" being the Mullard longplate square getter 12AX7.

Well, the Mullards lived up to their sonic reputation, warm, lush, romantic, yet still offering clarity/transparency with a big open soundstage and air, but they are not as extented on the top and bottom compared with Amperex Bugle Boys and are to creamy for my sonic taste. Certain things like cymbals and brass instruments that should "sparkle" and have "aliveness" were just to soft in the context of my system. If someone is either enamored with the sound of type two DACS like the Zanden or SET setups they would love how the DAC sounds with the Mullards.

So, after sonicly dancing with these three famous NOS 12AX7's, I'm sticking with Amperex Bugle Boys that are just about sonicly in the middle of Telefunkens and Mullards and to my ear's make the Accustic Arts Tube Hybrid and my whole system sing closer to what real music sounds like to me.
Hi Teajay, well my unit was really just getting broken-in and I sold my Andra's but I was still really enjoying it. They are being replaced with a new pair of MBL 101E's which I'm awaiting to receive, should get them in about 2-3 weeks time. I did remove the Chinese tubes and put in the Brimar, very silky mid and highs voices to die for and scary real if you go to Andy's tube description describing the sound of these tubes is bang on. The experience was like wiping off a smear on glass that you are trying to see through, everything was just that much more focused. I really am enjoying this unit, one of the nicest pieces I have ever had.

I placed an order for the same tubes you have and waiting for their arrival to compare, thanks for the contact I placed my order with Andy.

I'm sure my system components, amp and pre might be changing down the road since I'm getting the 101's but I'm in no hurry and will be doing comparisons. I read some where you were at a friends and he has the MBL 6010D and you really enjoyed it.
Hi Dev, was just curious about how its going with your DAC regarding overall satisfaction and if you did put different tubes in and if so what were the sonic results?

A friend was very interested in comparing his new Meitner CDP compared to the AA Tube Hybrid DAC on redbook. Well, lets just say the AA was way better in my system on that day. The Meitner sounded both "dry" and did not throw any were close the soundstage/air around players like the AA.
Thanks Teajay for the info. regarding the fuses and I will share my personal thoughts but in the near future as I want to let the unit break-in along with putting in some different tubes.

You really are great at writing reviews and after reading yours I don't really know what to add.

I had a friend over last night who has a very good ear and system and has heard my system many times as I have his, he could not believe the difference and said he thought my system was great before but now is just lost for words.
Dev, here's the information regarding the fuses:

Fuse holder 1A gets a 1A fuse. Fuse holder 102 gets a 1.6A. The arrows on the fuses face toward front faceplate. I have never tried HiFi fuses compared to the Isoclean's, so I don't know how they compare, but I do know that the Isoclean fuses are terrific in their effect sonicly. I will be putting them in my MG-20's, Flora, and XA-100's in the near future.

I have a hunch that the Telefunkens that you mention will have the same sonic signature as the one's I have and the other tube, Brimar, I have no idea regarding their sonics. In the context of my system I love how the Amperex Blue Boys help the DAC just produce beautiful music.

Would you share what your hearing in your own way what the Tube Hybrid offers that is different compared to the MK4? I find it interesting how people use different language to describe what they hear, so it would be great to hear your version regarding the DAC. Finally, when you get your NOS tubes and put them in, I think you will be amazed at how the performance improves, which is pretty terrific with the stock tubes already.

Hi Teajay, here are two more tubes for consideration that were recommended to me; NOS Telefunken cira 1962 with rib plate and BRIMAR B.V.A. from England.

What is the correct size of Isoclean fuses?, what are your thoughts of HiFi Fuses I'm sure either would be better than the stock fuses. Have you also changed the fuses in your Pass amps?

I am still restraining myself from changing the tubes in the dac for right now even though I can't wait to do so, instead I'm just absorbing the musical upgrade over my MK4 dac which is a wonderful piece.
Hi Dev, congratulations on your new AA Tube Hybrid DAC! It really is a terrific piece and I'm glad it lived up to what you were expecting. The MK4 is still a great DAC, however the Tube Hybrid goes to another sonic level.

I have come to a decision regarding which set of tubes I like more in the DAC. After another listening session with my dear friend Bob, who I refer to as the "Golden-eared" one we both came to the same conclusion, the Telefunkens offer power/dynamics/microdetails and finally unbelievable 3-D imaging in a very large soundstage which we both admired, but, he and I felt less "attached" in an emotional way to the music compared to the Ameperex Bugle Boys. The Telefunkens are not overly bright or etched sounding, however I think the word I would use to describe my experience of them in this DAC would be somewhat relentless and tonally cool, but boy on some types of music the balls to the wall dynamics and 3-D precise imaging was quite seductive, however the Bugle Boys for me sound more like real music with more natural timbres and an easy quality that allows you to relax into the music. Both tubes sound great in the DAC but different, and it really again comes down to personnal taste and system synergy.
Well aren't you having fun, fuses and tube changing. Teajay I finally got my unit and all I can say is WOW! WOW!, your review says it all.

I don't think others really realize just how fantastic this unit is until they actually get one into their own system and they better be ready to pick-up their jaw from the floor.

I am looking forward to changing the tubes and fuses as you have but for now I'm just going to enjoy. I already picked up a match pair but will wait to install.

I exchanged my Supratek Sauv. line stage out of my system and put my ARC REF3 back in prior to putting in the Tube dac and defiantly preferred the REF3. but then I put the Tube dac in, I don't know if it's a synergy thing happening or what but I am just in awe with what I'm hearing.



Just wanted to share that I replaced the stock fuses in the Tube Hybrid DAC with Isoclean Power audio grade fuses. These fuses are quite a tweak, they significantly improved the overall sonic picture(transparency/dynamics/details/soundstaging)of the DAC.

I also finally put in my matched pair of NOS Telefunkens, instead of the NOS Amperex "Bugle Boy's". So far I find the Telefunkens seem to be more dynamic/transparent/detailed but are slightly less "sweet/warm" compared with the Amperexs. I like the way the DAC sounds with both sets of tubes, which are both quite better then the stock tubes from China, but have not decided which set of tubes I like more yet.
Teajay, Thanks for the info.

Regarding the Pass, I demoed not in my own place but at a dealers 2- X-350.5's with Swan speakers including Esoteric PO-3 combo and Hovland 200 pre. In the same system I heard the XA-100.5's and preferred them. I had the 100's in my system and compared to the X-600.5's and preferred obviously what I have but a fair competitor would be the XA-160.5's in which I will do.

It's looking good, my Dac is at customs so I should have it for the weekend.
Hi Dev, I'll really be surprized if you are not quite delighted with Tube Hybrid DAC in comparsion with the MK4. I agree that the MK4 is still a great piece, however the Tube Hybrid is just that more "musical/natural" sonicly without giving up dynamics or microdetails.

I am enjoying the sound of my system so much I have not replaced yet the Amperex tubes with the Telefunkens. I do not have an extensive tube background, however as I researched the sonics of different tubes and talked to very knowledgeable tube guys it be came very clear to me that I did not want overly "lush/romantic" sounding tubes like Mullards, but tubes that would offer dynamics, extension, details, with maybe a touch of sweetness or warmth, hence the Amperex and the Telefunkens are supposed to be even more dynamic but a little "cooler" then the Amperex.

As far as were to get great tubes and deal with great gentleman, I recommend: Brent Jessee Recording & Supply, Inc.(Brent) 847-496-4546 or Vintage Tube Services,(Andy) 616-454-3467.

I'm a great Nelson Pass fan so I'm glad your enjoying your 600.5's. It would be interesting if you audition XA160.5s if you would like there sonics better in your system. I loved my X350.5 but thought the XA-100's were a step up in my system and made the change.

I have heard both the Ref 3 and the top level Supratek in other systems, but not in a home audition. I really still believe it would be worth the hassle, the single-ended vs xlr, for you to audition the Flora, it's really an amazing sounding linestage and offers world class performance for alot less money then other highly regarded linestages. I did not purchase the Flora for economic reasons, but just based on its superlative sonics compared to so many other linestages I had listened to.
Hi Teajay, have you tried your latest new tubes as of yet and if so what do you find the difference being.

Just curious, was there a reason why you choice these tubes?

Can you forward over where you got them, getting matched pairs from a reliable source is always nice to have and I'll need to get some.

I missed out getting a unit because I was out of town but I'm suppose to get one by week end, no demo's units available.

I bought a pair of PASS X600.5's and I'm really enjoying them with my Andra's, I prefer them over my McIntosh 501's.

I'm going to be able to get a pair of the XA160.5's to demo but I'm going to wait for a bit until I have the new Tube dac in my system for a bit, hope I have made the right choice. The MK4 is a reference piece that I really enjoy in my system.

I also read your review regarding the Flora pre., have you ever had a ARC REF3 or Supratek Sauv. (Cortese line stage)in your system to compare? I'm currently running all cables in balanced so to even demo this unit properly will be a task. Few reason; SE section's are not even broken-in along with I will have to then get a RCA cable and really should be the same as I'm use to which is Stealth Indra(with Stealth connectors, their latest version), as you know not cheap actually more than the Flora and it also needs to be broken-in. Just curious if it really is worth all the effort.