Boulder Amplifiers 866 – Full Review

The Boulder 866 in all its glory.

Hi Guys,

Well, I’ve actually really been looking forward to writing this review. Today we are talking about a piece of gear that has made the biggest improvement to my listening experience in a long, long time. The Boulder 866 Integrated amplifier. It is the proverbial tour de force of integrated amps, at least in those that I have experienced. 

Boulder Amplifiers is a company that was originally based in Boulder Colorado, hence their name. However, nowadays they are based in their new manufacturing facilities in Louisville Colorado. Boulder has a long history dating back to the mid 1980’s, and got their start manufacturing equipment for studio use. They slowly expanded into audiophile equipment and haven’t looked back since. The name Boulder seems too have become synonymous with very high quality, and yes, expensive, audio equipment. They build everything in house from what I understand, and have 5 different current product lines. The 500 series, 800 series, 1000 series, 2000 series, and 3000 series. I would highly recommend going to their website ( to peruse their offerings, from a tiny phono stage, to absolutely massive mono blocks that require a dedicated power line (the 3050’s.) 

Safe, well packaged.

I have never heard any of the higher up lines (1000,2000,3000) from Boulder, but I assume their performance does indeed improve upon the 866. This in itself is a bit hard to fathom, given how massively impressed I have been with the 866. Yes, this will be a glowing review, perhaps my most glowing review of late, but I honestly think the 866 deserves such praise. 

When the 866 arrived from Louisville, I slowly and carefully unpacked it, and was honestly shocked at the build quality. To this date I have not experienced a piece of gear that felt so “right” and “well put together.” The only thing that comes close to this in my experience is the Abyss AB-1266 Phi TC, my favourite headphones. The boulder is relatively simple in its looks, but it feels rock solid, boulder like, if you will. Boulders are largely offered in only one colour, a light grey anodized aluminum finish. I do know that should you be willing to pay what I’m guessing is a large up charge, they can do their pieces in black, but it’s difficult for them to do. I was more than happy with the Boulders grey colour, and I usually prefer black gear! 


In terms of connections, the 866 comes in two models at two price points. The analog version, and the digital version, which comes with a built in DAC section. I have the digital version here, so it has 3 analog XLR inputs, a USB disk input section (no USB-B for computer use,) an AES input, and optical input, and lastly, an ethernet input. Both the analog XLR inputs and AES input can be used with an RCA to XLR adapter should your source only have RCA outputs. 

866 Digital Edition Rear

With the difference in price between the analog and digital versions being small (12,250USD vs 14.450USD) I would highly recommend purchasing the digital version. Usually I have found DACs built in to amplifiers to be of “convenience only” quality. They always seemed to cost more than they were worth, and never performed at the level of the amplifier they were situated inside of. Not so with the 866. Seriously, this has been the most impressive and surprising part of using the 866. The DAC matches up perfectly with the 866’s sound signature (which I will get too soon) and performs far above its price point. I do think you could perhaps achieve better DAC performance at serious price points, if you wanted a specific sound signature. However, if you just want a great DAC that synergies perfectly with the amp section of the 866, buy the digital version and be done with it. The DAC section is that good. 

The units front.

In terms of sonics of the DAC section, it is dead flat neutral, with epic extension at both ends. This goes for the amp section as well, which I will come to in the next section. I think a lot of people associate “neutral” sounding gear with cold, sterile, and lifeless sound. I certainly have in the past. Not so here. I honestly think the 866 DAC (and amp) sections are the most neutral I have ever heard. But truly neutral, they never wander into a cold, sterile, and lifeless nature. This DAC is not warm, but it isn’t cold either. It straddles that balance in a way I haven’t heard before, whilst bringing detail and technical performance that would usually cost multitudes more. There are other DACs out there that will be *more* detailed, and technically competent, but I honestly question if they are worth it with the 866. Perhaps they would be better situated to be paired with separates from Boulder, as the 866 is just such a convenient and well done all in one unit. It serves a need in the market, and does it better than any other all in one I have encountered. 

Boot up screen.

In terms of inputs, I largely used the AES input from a Digital to Digital convertor, from my Laptop. However, Boulder has recently released a firmware update which allows Airplay use. Given that I have an Apple Laptop, I gave this feature a try. It worked very well, sounded very similar to the AES input, but I did notice that If I had the settings on Apple Music “maxed out” the play back would stutter. If I reduced it to lossless, but 24bit/48khz it played flawlessly. I think this stuttering playback may be related to my houses wifi connection, which is far from great. I’m looking into a possible wifi upgrade for the house, so if that happens and I can try this again, I will write an addendum later to this review. The 866 is also fully Roon certified, and acts as an all in one streaming solution. However, as I do not use Roon or streaming in general, I would recommend trying reading some of the other 866 reviews out there, as they will be able to cover this subject with better lived experience, and offer a more accurate viewpoint. From the little I have read, and my experience with the other features of the 866, I would expect it to work very well in this regard. 

Listening with the Magico A3

Now, Boulder has built their name on their amplifiers, not their DACs. Thus, I wondered what the amp section of the 866 would sound like. With 200w per channel into 8ohms, doubling down to 400w into 4ohms, the Boulder is very similar to my previous amplifier, the Kinki EX-M1. I will compare those later in the review. Again the amp section carries on with the main characteristics of the DAC section. Absolute neutrality. Never cold, or clinical. Never warm or rounded off. What has surprised me most about the 866’s amp section is the control over the driver, regardless of the speaker or headphone you are using. The bass control in particular is the best I have ever heard. Such finesse and a vice like, lightning quick response. This is the best I have ever heard the bass response from my speakers or headphones. In terms of detail, it is effortlessly detailed, and extended at both ends. The soundstage is not super wide like some tube amps can do, but it is extremely realistic and portrays an accurate sonic picture. Soundstage depth, again, is very well done, but perhaps not as deep as some tube amps can manage. In terms of solid state designs, this is the best I have ever heard, and shudder to think what the higher up lines of boulder amps are capable of. I know they are better, but I find it hard to imagine what “better” sounds like. 

I used the 866 extensively with both my Magico A3 speakers, and my Hifiman Susvara and Abyss AB1266TC using an adapter, and it performed flawlessly with all three. All the characteristics of the DAC and amplifier I have mentioned came through on each, the main thing I noticed being the absolute control over the driver, and ease of reproduction of transients. It honestly just stunned me, how natural , and real it sounded. Time and time again, it managed to knock my socks off. 

The 866 works very well with hard to drive headphones, you just need an adapter!

With my Kinki EX-M1, my previous amplifier (no DAC section,) which I really enjoy to this day, the Boulder has really shown me what is possible beyond it. The Kinki is a great amp, I feel, especially at its MSRP price point. It has a large soundstage, is powerful, with good detail retrieval, but certainly can be a bit lean sounding. I also feel that whenever I listen to the Kinki (and I felt this way before hearing the 866) I can hear it imparting its signature on the music. It’s a very enjoyable amp, but you know you are listening to it. With the 866, there is none of that. Obviously, at the price difference between the two, you would hope the Boulder is better, but I do feel the chinks in the Kinki’s armour are somewhat more readily apparent now. I will however keep the Kinki as my secondary amp, as I still feel it offers super performance for the money, and does its job very well. 

As I mentioned previously, the build quality on the Boulder is class leading. It is the best built, most solid, and well put together piece of gear I have ever experienced. It’s relatively simple in its design, but just feels “right” when you move it into position. The 866, as with all Boulders, doesn’t accept banana plugs, so make sure you have spades, or adapters ready for when it arrives. I suppose you could use bare wire in a pinch as well, but banana plugs are a no go. One thing to note is the boulder does get warm, never hot. It will get very warm to the touch with a spirited, lengthly listening session.

Neat heat sinks, photo from Boulder’s website.

All in all, the Boulder 866 is the most complete, best sounding, best built, piece of source equipment I have ever used or experienced. If you are looking at top level integrated amplifiers, I would seriously recommend considering the 866. In my time with it, it has not put a foot wrong. If you prefer a warm and romantic sound, the Boulder is not for you, but apart from that, I honestly can’t see someone not liking the 866. Of course, if you are very well heeled, there is obviously more performance to be had from the higher up Boulder lines, but those come with additional considerations (space, weight,) and cost. If you want an all in one, that looks nice, sound amazing, and doesn’t cost 100 grand? I can’t honestly think of a better option than the Boulder 866. 

The Boulder 866 gets my highest recommendation, and if I gave out awards in reviews it would sweep all of them. I can’t speak highly enough about it, and look forward to using it for years to come. It really is, that good. 

7 Comments Add yours

  1. chase says:

    Very thorough and informative article regarding the Boulder 866. When scrolling down , I was happy to see the mention of the Magico A3 included in the test. So, for a newbie to high end audio like myself, I had one basic question : what else is needed to add if anything to the Boulder 866 for primarily streaming audio purposes. Essentially, is the Boulder 866 enough without the use of a power amp for instance?. It does seem hi fi sound has progressed in leaps and bounds if the amount of separate components is now whittled down to just one or maybe two in total to drive speakers like the Magico A3. Not to mention saving so much money in the process.


    1. paulhealy123 says:

      Yes, the 866 (with the DAC option) is an all in one. Streaming DAC/Integrated amp (meaning an amp with volume control.) Great match with the A3, in my opinion.


  2. Ralph says:

    I do not quite understand how you used headphones? Could you explain? Many thanks R


    1. paulhealy123 says:

      Hi Ralph, sorry for the slow reply, your comment got filtered out for some reason. I use a spades to female 4pin XLR adapter to use with headphones. Works incredibly well with harder to drive headphones. It’s pretty common for things like the Hifiman HE6, Hifiman Susvara, AKG K1000, Abyss 1266 etc….The boulder also works well with easier to drive headphones via this method whereas some other speaker amps may exhibit a bit noise due to their higher gain. For easier to drive headphones its entirely overkill however, and I’d only recommend it for that use if you happened to have own it for speakers or hard to drive headphones anyways.


      1. Ralph says:

        Thank you for kind response!

        So what you do is connect, on the right and the left, the two spades of speaker connects to 3pin XLRs and then the two 3Pin XLRs to one 4pin XLR entering the headphone? Or rather are you connecting the headphones like a subwoofer and you connect one spade from the left and one spade from the right to a 4pin XLR that then enters the headphone?

        In any case an intriguing way of using an amp as headphone amp (of course only if noise level is low as you seem to say is the case with Boulder 866). Indeed I have the amp mainly for speakers but I was always frustrated to have good amps and then not be able to use them for headphones (even if they have HP outputs these are normally bad).

        best Ralph


      2. paulhealy123 says:

        Hi Ralph,

        I use a cable similar to the one in the link below. It would have to be spades instead of bananas to work with the boulder (or bare wire of course.) I’m not sure what the pin out for soldering your own would be. You connect the spades as you would a pair of speaker cables (right positive and negative, left positive and negative) and then those cables go into a single 4pin XLR which is female. You then connect your headphones using a male 4pin XLR balanced. This won’t work with headphones which have single ended cables, would need the 4pin XLR balanced connector.


      3. Ralph says:

        Great. Thanks a lot Paul. best Ralph
        (I realize that you as well have Meze Empyrean!)


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