Boulder 866 integrated amplifier Specifications

Sidebar 1: Specifications

Description: Stereo class-AB integrated amplifier with optional streaming DAC. Analog inputs: 3 pair XLR. Digital inputs: Ethernet, USB (4), AES (adaptable to S/ PDIF), TosLink, Wi-Fi. DAC accepts PCM up to 32/384, DSD up to DSD128. All files are upsampled and oversampled to a data rate of 192kHz, and data is moved asynchronously. Loudspeaker outputs: stereo pair 0.25" binding posts. Input voltage at max volume: 1.14V for maximum rated output at full rated power. Continuous maximum power output: 200Wpc into 8 ohms (23dBW), 400Wpc into 4 ohms (23dBW). Peak power into 2 ohms: 700Wpc (25.4dBW). THD: 0.01%. Equivalent input noise (EIN) at 20kHz: 2µV. Input impedance: 100k ohms, balanced. Maximum analog gain: 40.4dB. Frequency response: 20Hz–20kHz, –0.04dB; –3dB at 0.015Hz and 150kHz. Power consumption: 1000W.
Dimensions: 17" (440mm) W × 15.4" (390mm) D × 7.25" (190mm) H. Weight: 54lb (24.5kg). Shipping dimensions: 24" (610mm) W × 23"(590mm) D × 14" (360mm) H. Shipping weight: 64lb (29kg).
Finish: Silver anodized aluminum.
Serial number of unit reviewed: 12629. Made in the United States.
Price: $13,450 (analog only), $14,950 (with streaming DAC); upgrading from analog-only costs $2500. Approximate number of US dealers: 18. Warranty: 5 years.
Manufacturer: Boulder Amplifiers, Inc. 255 S. Taylor Ave., Louisville, CO 80027. Tel: (303) 495-2260 x116. Web:

Boulder Amplifiers, Inc.
255 S. Taylor Ave.
Louisville, CO 80027
(303) 495-2260 x116

georgehifi's picture

How nice it is to see extended frequency response and a pure untouched 10k square wave like this without the need of an Audio Precision auxiliary AUX-0025 passive low-pass filter to hide/mask the switching noise oscillations all over it. Like Class-D needs to make it look not even half as good as this, and with out the AP filter!! buzz saw comes to mind, but sadly that not shown anymore, as it's too visually bad for business.

Cheers George

RH's picture

- - - "I appreciate warm sound, but acoustic music does not sound overtly "warm" in the various halls I frequent. "

I'm not sure how exactly to interpret that part of the review. But from my perspective as someone obsessed with the differences between live and reproduced sound, one of the distinguishing characteristics to me of live acoustic sources is "warmth." The average sax, trumpet, trombone, even acoustic guitar, sounds so much bigger than on most audiophile playback systems I've heard. Most reproduction to me has a reductive, hardening effect on most acoustic sources. "Warmth" in terms of fullness of "body" and richness of harmonics is just what I hear in acoustic music vs reproduced, virtually wherever I am situated to the music, or in whatever hall I listen.

Of course, since essentially all reproduction is compromised in regards to reproducing true realism (especially if we are talking about symphonies!), it's a pick-your-compromise and we tend to zero in on the aspect of sound that strikes us as most consonant with reality. Some may zero in on the transient precision and dynamic presence of, say, some horn systems, others may find the more relaxed richness of another speaker gets at what they hear in real music. I tend toward (certain) tube amplification insofar as I hear a bit more of that roundness, body and relaxed warmth I pick up on when hearing live sources. YMMV of course...

brenro's picture

Save $6000 and buy a Krell K-300i.

Ortofan's picture

... Rotel Michi X3.

tonykaz's picture

Nice work, Mr.Jason!

The Boulder is probably a nice piece of gear but I'd still insist on a Round Volume knob, the bigger the better. I'd even like the power switch to be mounted behind the volume knob in an Old School way of things with the Volume knob acting as the OnOff control like an old Car Radio.

Does this Amp have a sloping Front Panel like the Pictures seem to show?

Anyway, nice work Jason,

Tony in Venice Florida

Anton's picture

It can compress to as little as four inches deep or expand to as much as 28 inches.

Front face angle is as you desire.

tonykaz's picture

Brilliant observation!

I wonder if they built it that way to save on the Dimensional Weight Shipping Formulations?

I have a bit of Vintage gear that mostly remains rather tiny but enlarges when the occasion arrises! I never show it to anyone, ( mostly out of embarrassment and because it ain't pretty ).

Tony in Venice Florida

Kal Rubinson's picture

It can compress to as little as four inches deep or expand to as much as 28 inches.

Does it move from Class A/B to pure Class A as it expands? :-)

Jason Victor Serinus's picture

a lot of us would be in a class above.

nomaslarge's picture

This does feel a little like one of those "damned with faint praise" reviews and the comparison to the k-300i is vague and leads one to believe that to the reviewer's ears it's really a tossup based on what you like (which obviously for most of us would lead to the conclusion of "I'll take the one that is $6k cheaper"). I know that JVS loved the k-300i and it was been very well reviewed elsewhere - I admit I've never heard it. But the K-300i is often compared to a unit I owned for a while - the Naim Uniti Nova. I thought the Nova was impressive and enjoyed it more than I thought I would given that when I got it I was coming from a pricey VAC tube rig. I briefly considered trying the K-300i while I had the Nova and spoke to a few people with experience of both units who felt that it would be a sideways move unless I really needed the extra power of the Krell. I then went to a Pass Int25 which to my ears was just in a different class than the Nova - I won't bore you with the details, I'll just leave it at the fact that for me this wasn't even a close comparison in terms of what these amps were capable of. And now recently I got a Boulder 866, which I find to be in an altogether different class than the Int25, by at least as significant a margin as I found the Pass to be superior to the Naim. The Boulder feels to me like it competes with some of the high-dollar separates that I've owned in the past. Because of the surprisingly high performance of the DAC, it almost seems like a bargain at its price. Of course, the commutative property doesn't always hold in audio... but for these reasons I am skeptical that the 866 and the K-300i are on a level playing field with only one's preferences and about $6k sticker price separating them.

Salva69's picture

Jason Victor Serinus could be a good music reviewer but as a gear reviewer, I feel sorry to say that he is the most boring I've ever read in the pages of Stereophile.

nomaslarge's picture

I find JVS to be an excellent writer but I don't get the sense the 866 inspired him very much which is... you know... the way it is sometimes with gear. Who knows why it is that some pieces excite us and others don't. The 866 has excited me quite a bit which is why I left my earlier comment.

tonykaz's picture

Music is a delightful life companion, sharing that experience is a nice gift to us all.

Thank you,

Tony in Venice Florida