Review of Little Dot MK-II Headphone Amp/Pre Amp Official replacement for the LDII++ 01/11/08 Review equipment listing: Creative Zen Xtra 30 Creative Zen Vision (First Version) Microsoft Zune 80 ASUS Notebook A8JS Zero 24/192 DAC/Head Amp/Pre-Amp Sennheiser HD-580 Sennheiser HD-650 Model ST-630 Laser Temperature Gun Pioneer SPEC Rack System Technics RS-1700 Reel to Reel Out of box experience: My new LD MKII shipped on Tuesday the 25th and received it on the following Monday! EMS shipping from China is extremely fast and reliable! The box was in great shape and I started un-boxing immediately. The MKII was cradled in full sized poly-foam surrounds that take up the entire inside of the box. The default tubes are also in this foam surround, each with its own hole for protection. The contents of the box were; the MKII, a 3.5 mini to RCA cord in retail package, a ¼ headphone adapter, three tiny blue jumpers, a power cord and the English user’s manual. Specifications: Input: Gold-Plated Unbalanced Phono (RCA) Jacks Output: 1/4" Gold-Plated Stereo Headphone out Driver Tubes: 6J6 Power Tubes: 6N6 Frequency Response: 20HZ - 50KHz (-1dB) THD+N: 0.1% (50mW into 300 ohms) Suitable Headphone Impedance: 32 - 600 ohms Pre-Amplifier Output Impedance: 10K ohms Power Output: 300mW into 300 ohms 200mW into 120 ohms 100mW into 32 ohms Average Power Usage: 28 watts Metric: 210mm (length) by 110mm (width) by 130mm (height) American: 8.26 inches (length) by 4.33 inches (width) by 4.18 inches (height) Weight: 2.5 kg or 5.5 lbs. Impressions on initial power up: The MKII has a new gloss black finish! The lettering and volume “notches” are done in silver, which looks much better than the photos seen earlier, which looked like white paint was used. Sporting a bright blue power LED and silver trimmed knob, the overall appearance of the MKII has improved nicely from the LDII++ headphone amp it replaces. The body of the MKII is the proven and tough double half design, which screws tight together with four screws on face plate and four screws on the back plate. The MKII is actually smaller than the LDII++. The length has been shaved by ½ inch, and the power transformer housing size has been shaved ½ inch in depth. Lined up next to each other, the MKII and the LDII++ are brothers for sure, but the MKII has a more refined and quality appearance. I removed the two lower screws on the face plate and rear plate, so I could access the bottom of the MKII. The new main board appears to be clean and efficient and this is where the similarities with the LDII++ end. The MKII has a newly designed SEPP (single-ended push-pull) circuitry, where the LDII++ used a cathode output circuitry. On the main board, are two gain DIP switches, one for each channel. There are two, two pin jumpers, one for each channel. They are for changing driver tube families. The MKII comes with unbranded (China 6J6) EF95 driver tubes and (China 6N6) 6H6N power tubes. After verifying the proper jumpers and setting the gain to 10, for my Senn HD-650s, I installed the tubes and hooked up the MKII to my new Zune80 MP4 player via its dock. With everything in place, I reached back and flipped the switch to power on. I was rewarded with the blue LED and power came up without incident. The protection circuits kept things muted until the tubes were ready and then softly activated each channel. The MKII really is an improvement in looks vs. the LDII++. The fit and finish are superior in almost every way imaginable. The sound tracks I’m using are WMA Lossless created using my Creative X-FI Music soundcard in my desktop PC from a digital source. I set the volume on my Zune80 to 20 (Highest setting), pushed play and turned the volume knob on the MKII to the 12:00 position. What I wasn’t prepared for was the blast of power that followed! I backed down the volume to 35% and just listened for a while. Even though the tubes are new, the sound was very dynamic! The bass goes down to normal levels, but lacks depth and subterranean punch. Mid lows thru mids are reasonably flat and sound nice. The highs are a little bit mixed, but this is most likely the new tubes. I need to give the unit some hours of play time, so I selected all tracks on repeat and left the MKII running for the next 48 hours. Impressions after 48 hour burn-in: At this point, the MKII has improved greatly. Far more dynamic and the highs now have more detail and extend much higher. The bass now reaches down for punch, but is still recessed. This is most likely the “no name” tubes weakness and not the MKII itself. I’m hearing a nice normal sound stage and there is no noise being amplified. I have decided that for the purposes of this impressionistic/replacement review, and to be fair to the MKII, I’m going to install the best tubes I have in both models, so the sonic differences between the old LDII++ and the new MKII can be appreciated with quality tube sets. I did not expect the default tubes to sound as good as they do, but they are not on the same level as the Russian power tubes and Mullard driver tubes in my LDII++. I now have the blue jumpers in place for EF92 compatibility, so I will spend however long it takes to determine which tube combinations sound best in the MKII, and which combination mirrors the sound of the LDII++ (if possible). Seven Continuous Days Later. Burn-in Complete: It has been a grueling full week swapping tube sets in and out of the MKII. I have some interesting news on behaviors discovered during this “tube rolling” festival. Prepare yourselves; this is very good news and a good bit startling: The first discovery was that it was hard to find a combination in the EF95 family that didn’t sound good! Some were better than others, but overall, the MKII ran this family with a robust sound signature that many will find pleasing. I imagine K701 owners would like the EF95 family of tubes. The second discovery was the increased dynamics of the MKII, no matter which tube family you use. It is very apparent both through headphones and through pre-amp use. Owners are going to be thrilled with this, no matter how they use the MKII. The third discovery was the impression that the MKII (using EF92 family) is like the LDII++ on steroids! Much more power is available both in overhead and in loudness. Lower bass notes do not strain or drain the MKII at all. Running up the volume does not seem to distort the MKII like the LDII++ did. This is most likely the circuitry changes showing through. The forth discovery was the refinement of the output signal with high quality tube sets. This has to be partially due to the amp circuitry changes. It seems like the MKII handles the upgraded tubes better and gets more out of them than the LDII++ did. Better soundstage, 3D positioning, dynamics and positive control of voices and instruments. At no time, did the MKII sound sloppy or out of control. Very nice indeed! The fifth discovery was less heat than the LDII++ even when driven hard with either tube family on-board. Here are the temperatures in Fahrenheit, after running for only 15 minutes: Area Tested______LDII++________MKII________DIFF Front Case________92___________82_________-10 Body_____________95___________82_________-13 Front Tubes_______140__________130________-10 Rear Tubes________255__________170________-85 Transformer_______125__________105________-20 I chose to do the temperature evaluation in this short time period, because the variables like room temperature, air flow and location would invalidate the findings of a long test. Catching both units while they were still heating up, gives us a better idea of what to expect normally. Without a doubt, the MKII is going to run cooler than the LDII++. The sixth discovery was when using less than excellent sources with the MKII. The MKII is more forgiving to less quality signals, in both families of tubes, but even more so with the EF95 family of tubes on-board. I had not expected this whatsoever. I went back and re-tested three more times to make sure I wasn’t hearing things. I even hooked up my old Creative Zen Nano, EQ flat and played a 320kbps MP3 track. It was real good! Much more so than my other tube amps! The seventh discovery was when using excellent sources with the MKII. With either tube family installed, the MKII proves its refinement when using a good clean source. It amplifies that clean signal extremely well, without losing anything and retaining all of the sources nuances and dynamics. Where Testing went from here: I got out my spare Mullard 6CQ6 (EF92) NOS driver tubes and a pair of Russian 6N6P “Soyuz” NOS power tubes. This set levels the playing field. My LDII++ has Russian 6C19pi NOS power tubes and Mullard M8161 (EF92) NOS driver tubes. All of these tubes have been previously “matured” and I can start listening immediately. This is as close as the MKII gets to sounding like the older LDII++. They sound so close to each other that only slight differences in sound signature exist between the two. Dynamics is another story though. The soundstage is improved on the MKII, both in width and depth. Instruments are more clearly defined and vocals are more realistic. Small nuances in the higher regions are clearer and easier to distinguish in the MKII. All of these improvements are enough to be noticeable to my sorry ears, so the majority will hear them as well. On a side thought, we are going from a truly wonderful sound already established with the LDII++ and its tube improvements, to the even higher level of dynamics and detail of the new MKII. To me, this represents “icing on the cake” and by no means belittles the LDII++. Impressions and testing after burn-in at 200 hours plus: This turned out to be the fun part. As it was with my LDII++ headphone amp/pre-amp, this MKII has matured into one outstanding headphone amp/pre-amp! That’s right! I have tested it as a pre-amp as well. Here is how I handled the testing. I hooked the MKII up to my Sonic Super T-amp and used my Zune80 as a source. This was a real pleasure! The pre-out carries the niceness of the tube combination through to the amp, making the final sound very nice. I swapped sources around for about 10 minutes of each, and the sound was fantastic. Again, I believe the improvements are due to the new circuit design of the MKII. I kept going back and substituting my Sennheiser HD-650s with my Sennheiser HD-580s, to see if I could find a weak spot in the listening enjoyment. What I discovered was that the HD-580s mirror imaged my findings on the HD-650s, but made the overall sound seem more “Rock” oriented. It was just different, not better or worse. The improved impact of the MKII was most noticeable on the HD-580s, but more pleasurable to the HD-650s. The pre-amp section of the MKII is every bit as good as the headphone section. This will be a big plus for those who want to use the dual purpose of the MKII. Not to stop here, I decided to test the MKII with the cleanest digital signal I could generate here in my home office. Using my Creative X-Fi as a transport, I went optical out to my Zero DAC/Amp, then analog out to the MKII’s inputs. I found two albums I have recently ripped to lossless WMA and used Creative’s Media Source 5 as a player. This time, I wanted to let the music do all the talking, so I dimmed the lights, reclined back, dawned my HD-650s and let the music reveal itself too me. What a real pleasure. I’m hearing little nuances and flavors in the music I don’t usually hear unless I am using one of my other amps. After about 20 minutes, I opened my eyes, stood up, walked over and stood in front of my MKIVse, confused because it wasn’t on. For a few seconds, I had lost what and why I was listening to the music, and had mistaken which amp I was listening too! I had to stop at that point, due to the big grin on my face. What a wonderful little amp this is, to take me on a musical journey inside my head and have me so immersed, I think I’m listening to an amp that costs over twice the money! It now was time to test the MKII in not so great of circumstances. I dug out my old Creative Zen Extra 30gig MP3 player. I haven’t used this in quite some time, but had left it on its charger down in the living room, so it was ready to go. I dug out the lowest quality mini male to RCA cable I have and hooked the two together. I grabbed my HD-580s and plugged them into the MKII. I double checked the Zen Extra and disabled the EQ. The best MP3s on this poor old player were 320kps, so I created a playlist with a handful of them. I ran the volume up to about 85% on the Zen Xtra. It has no line out and will start to distort in the 90% range. I pressed play and took a long listen. Wow. How terrible it sounded! While mumbling something about “garbage in” to myself, I re-activated the custom EQ and set about fixing the deficiencies. Sure enough, when I had it set properly, the sound was more than acceptable. So much so, that I cranked up the MKII to listen to a few of the tracks that I don’t have ripped cleanly on my PC yet! It then dawned on me that anyone who has older players like this one, could compensate for their players shortcomings and actually enjoy the MKII until they could afford to get a better source! The last and final test for the MKII, was to make it act as the headphone amp for my Vintage Pioneer SPEC stack. I ran RCAs from tape 2 record out to the SPEC1 to the MKIIs input. I plugged in my HD-650s, fired up the Pioneer equipment and its Technics RS-1700 Reel to Reel and located a nice tape of older rock and spooled it up. Switching the SPEC1 pre-amp to allow dubbing, I switched on the MKII and set its volume to ¼ and pressed play on the RS-1700. The first album was one by Head East and the first track started. Now I am officially impressed big-time! I sat right down on the floor in front of the Reel to Reel and listened as the MKII added a beautiful “tube” signature to Head East’s somewhat raspy vocals. The dynamics of the music were perfect and the full spectrum sound was wonderful to my ears! It wasn’t 10 minutes gone by when I realized I “wanted” to finish out the album. No more testing, time to enjoy the excellent sound I was hearing. Lasting impressions: First, I would say that the MKII is a very worthwhile improvement over the LDII++. The gains in all aspects of a great tube amp are more than noticeable. Quality and craftsmanship have improved inside and out, while maintaining a constant price point that most people are going to be able to afford. Negatives: The MKII still has the same plastic type knob that the LDII++ had. They can wear out early. Plan on replacing it with a quality brass knob of your favorite color. Conclusion: Little-Dot has created another winner. The challenge they had to create a new entry level headphone amplifier/pre-amp, that must at a minimum, match the LDII++ and meet expectations of outperforming the previous model, is a very large and complex challenge. They have risen to the challenge and far exceeded my expectations for sure. Headphones off to Sword Yang, David Z.P. and the Little-Dot crew, for a new and excellent headphone amp/per-amp, the MKII. Dave McLaughlin LD MKII owner and Audiophile since 1977 Note: As time goes by, I’ll update the forum with my additional impressions of the MKII. *******First Add-On to the review******** Here are the jumper and dip switch settings from the owner's manual, for the MKII: The jumpers, one for each channel (L&R) are for tube families. No jumpers = EF95's, Jumpers on = EF92's. The default is no jumpers for the default tubes. Look in the package that contains the RCA cord, you'll find your little blue jumpers they removed inside there. The two dip switches are for changing gain. Each dip switch box represents a channel (L&R) Make sure you configure each channel the same as the other channel. A. Switch 1 off, Switch 2 off = Gain 10 (Highest Impedance) B. Switch 1 on, Switch 2 off = Gain 7 (Medium Impedance) C. Switch 1 off, Switch 2 on = Gain 5 (Low Impedance) D. Switch 1 on, Switch 2 on = Gain 3 (Lowest Impedance) Factory setting should be A.