product review: boulder 865 integrated amplifier · the boulder also lives up to its insinuated...

Product Review: Boulder 865 Integrated Amplifier | | |

Product Name: Boulder 865 Integrated Amplifier Product Type: Integrated Amplifier Price: $19,999 (AUS) Reviewed By: Edgar Kramer, Tested by: Steve Holding Magazine: Australian Hi-Fi: January February 2008 Distributor: Sensus Pty Ltd

Maybe it’s the water or that high mountain air and inspiring setting, but for some reason, the small town of Boulder, Colorado, seems to be home to a disproportionate number of creative and active high-end design companies. And when I say ‘high-end’, there are some pretty big hitters up in them thar’ mountains… PS Audio, Ayre Acoustics, Avalon Loudspeakers, and the company responsible for the subject of this review, the venerable Boulder Amplifiers.

The 865 is Boulder Amplifiers’ first-ever integrated amplifier and is based on the company’s lower-rung preamplifier and power amplifier, the 810 and 860 respectively. The term ‘lower-rung’ is of course a relative one in this case, because Boulder’s lower-rung pricepoint is equivalent, or beyond, that of a large majority of other companies’ statement products. Check out the 2000 series components to get an idea of the ‘ne plus ultra’ heights to which the company most often soars.

In typical Boulder fashion, the 865 is extremely well built and finished in the company’s trademark silver-grey anodised aluminium fascia. Also cosmetically in line with other 800 series products, the 865 features a protective metal mesh/grille over the extensive heatfins. Boulder Amplifiers is a firm believer in balanced

operation and is uncompromising when it comes to this topology, the 865 having a full-balanced, differential, three-stage input circuit ‘…resulting in ultra-low distortion and noise’ according to the company. So it follows that the 865 incorporates four balanced inputs and one auxiliary output—fixed or variable and switchable for a subwoofer, recording device or secondary amplifier—all configured within a centrally-oriented cluster. Not a single-ended connection in sight.

Those who want to connect an unbalanced source can easily do so, simply by using an appropriately-wired cable with an RCA (or other unbalanced) connector at the source end and a 3-pin XLR connector at the other. The negative input (Pin 3) should be wired to ground only at the RCA connector. This brings the negative input reference of the 865 to the unbalanced source ground, thus reducing ground loops. Yet another option is Boulder Amplifiers’ ABL2 input adapter.

Just below the signal connections are the IEC input and mains switch, fuse, a mini-jack cable remote input, master/slave switch for the Boulderlink connections, and 12v trigger in/out mini-jacks. Just to expand on Boulderlink, these RJ45 connections allow the microprocessors to communicate between components to allow such niceties as intercomponent sequential initiation and message display sharing. A single pair of high-quality and easy to hand-tighten speaker binding posts is provided for each channel. Boulder recommends against using banana plugs (the speaker terminals on the 865 don’t even accommodate them) and recommends the use of spade connectors. It turned out spades were nigh-on mandatory, because the binding posts don’t grip bare wire very well.

The front fascia is fashioned from a multifaceted piece of solid aluminium, with laser etched brand and model identification. A largish, dimmable, alpha-numeric display serves as the user-communications centre, and just below it is the small power LED that glows in a number of rainbow colours when the unit is in stand-by mode (this serves as notification of microprocessor stability to communicate that all is well). On a slightly raised surface is the beautifully-weighted and smooth optically coupled step-resistor volume control, originally developed for the top-of-the-line 2010 preamplifier. Below are two rows of chromed metal buttons for the individual inputs, display dimmer, stand-by on/off, balance and mute.

The microprocessor allows each individual input to be alpha-numerically named as well as programming the input’s individual gain/ level calibration, balance, start-up volume or Theatre Mode configuration for home theatre integration. Power output is rated at a healthy 150 watts continuous into 8Ω or 4Ω with a THD of 0.0035% from 20Hz to 2kHz and 0.018% at 20kHz. Frequency response is specified at 20Hz to 20kHz +0.00dB and –0.07dB. Input impedance is stated at 100kohm and voltage gain at 46dB. Volume control range is 100dB and is adjustable in 200 steps of 0.5dB via the unit’s main rotary control, as mentioned, or via ‘up’ and ‘down’ buttons on the remote control. The remote is an attractive ‘S’- shaped piece, carved from solid aluminium, that can control all the amplifier’s functions and seconds as a weapon against intruders.

The entire unit is impressive in every aspect of its build, finish and operation. All buttons are solid and function with a reassuring feel. The volume control is a pleasure to use and again, its operation inspires confidence in the engineering involved in the overall design. The same high standard continues on the inside. The surface mount technology (SMT) circuit board is picture-perfect in layout and design, and all circuit components are of the highest quality. A clever touch is the removable modular connection section that makes servicing, upgradeability and alternate configuration a simple affair.

Flicking the switch will activate the 865’s display to read ‘Waiting for amps’, your speakers will discernibly hum for a couple of seconds, then click loudly, and at that point the display will change to show the amplifier has automatically switched to the last chosen input. Now, you’re ready to go.

O Brother, where art thou?

The 865 amplifier’s sonic character is actually a tough one to pin-point and in a way that reviewers have bad dreams about. And I actually mean that as a compliment. I mean that the 865 is such a clean, such a neutral and honest transmitter of what is fed into it that to describe its sonic traits in such an inadequate medium as language seems harder than chain-gang labour. In other words, the 865 does what the ideal amplifier should do: transmit the information from the source to the speakers in an effortless manner without imparting its own signature or personality.

So, the listening impressions with the Boulder were an exercise in intellectually extracting descriptive information. For starters, well-produced guitar-heavy music as presented by Ani Di Franco in her live recording, Living in Clip, sounds clear and detailed without a trace of hardness or brightness. Ani’s violent strumming cuts through and provided the mated speakers are adept at dynamic contrast, the Boulder will pass the shading unscathed and without reduction.

Resolution is directly derived from the 865’s high level of accuracy. Ani’s vocals stand out in relief to the guitar, and in turn to the bass and drums. Each instrument is clearly discernable and separated from th e mix, and occupies a focused, solid point within the sound field. The precision with which the Boulder places images in the soundstage is laser-sharp but such exactitude comes at the marginal expense of lateral and stage depth. Images are spread a little shallower and narrower but with sharp relief in front of the speaker plane. The old stalwart recording, Harry Belafonte’s Live at Carnegie Hall is the perfect tool for illustrating this trait. When Harry wanders the stage, he’s uncannily present, his movements accurately traced within the sound field, it’s just that he’s in a slightly smaller stage. And when Harry lets fly his big, raspy chords, the 865 follows without faltering, meeting the dynamic challenge without raising a droplet of sweat.

The Boulder also lives up to its insinuated name with a big and powerful bass that can ‘shock and awe’. Red Hot Chilli Pepper’s Suck My Kiss rams home the message. Some amps have trouble resolving the closely-

miked kick drum and Flea’s simultaneous slappin’ and pluckin’ on his bass. Such amps tend to homogenise the two into a single bass thread. The Boulder is able to distinctly separate the two while maintaining their individual slam, brutality and detail.

Massed instruments such as violins in large orchestras, as in Sibelius’ Violin Concerto, are displayed with tremendous fidelity. The impression is one of many instruments playing together and in ‘concert’ with the rest of the musicians, not as the sonic equivalent of a single bulbous mass. However, when Vengorov hits his lone stride, the 865 cuts him centre-left, present within a life-size image and with his instrument reproduced with a fidelity of detail and timbre that is moving.

Conclusion

How does one suggest that a $20k integrated amp represents good value? Well, when you take into account the fanatical build quality, the comprehensive feature list, and the conveniences of an all-in-one package—as opposed to the cost of a separate preamp/amp combo and the interconnecting cables—then you start to realise the relative value offered here by the 865. Sonically the Boulder is a clean, crisp and tight performer that never strays into sterility. It delivers an image that is scarily real in terms of spatial accuracy and life-like presence and it controls your speakers with an iron fist in a silver/grey glove. If only all chain-gangs were this easy to work in…

Test Results

Readers interested in a full technical appraisal of the performance of the Boulder Amplifiers 965 Integrated Amplifier should continue on and read the LABORATORY REPORT published in the included PDF document. All readers should note that the results mentioned in the report. tabulated in performance charts and/or displayed using graphs and/or photographs should be construed as applying only to the specific sample tested.

Boulder 865 Integrated Amplifier Brand: Boulder Model: 865 Category: Integrated Amplifier RRP: $19,999 (AUS) Warranty: Five Years

Reprinted from Australian Hi-Fi magazine

TEST RESULTS

54 | Australian Hi-Fi

Test ResultsThe Boulder 865 was certainly not short of power, indeed it provides so much power into 4-ohm loads that I can’t for the life of me see why the company rates its 4-ohm output at just 150-watts. As you can see from the tabu-lated fi gures, Newport Test Labs measured the Boulder 865’s power output into 4-ohms at 1kHz as 361-watts (25.6dBw) single-channel driven and 310-watts (24.9dBw) with both channels driven. Even down at 20Hz, a fre-quency so low the power supply has to work overtime to deliver power continuously, the Boulder 865 was still capable of delivering 300-watts (24.7dBw) per channel, both chan-nels driven, into 4-ohms: exactly twice Boul-der’s specifi cation.

Power output into 8-ohm loads was both higher than specifi cation and also excellent, with the 865 delivering 185-watts (22.6dBw) per channel, both channels driven, irrespective of measurement frequency. That is, it would deliver this power level anywhere from 20Hz right up to 20kHz. Single-channel driven, the amplifi er’s power output increased usefully to 200-watts (23.0dBw) per channel and again, it proved that it could maintain this power level right across the audio spectrum, from 20Hz to 20kHz. Boulder doesn’t rate the 865 into 2-ohm loads at all, presumably because it has built in electronic protection that activates if the 865 is driven into very low impedances at very low frequencies, hence the ‘Pro’ notation in the tabulated results and the null result on the bar graph. However, you can gain an indi-cation of the 865’s capability under dynamic conditions with a music signal by looking at the results it delivered at higher frequen-cies, with the Boulder delivering 450-watts (26.5dBw) per channel with both channels driven and 544-watts (27.3dBw) per channel, single-channel driven.

Channel separation was also excellent, with Newport Test Labs measuring a best result of 116dB at 1kHz. Separation diminished very slightly at the extremes of the audio spectrum, but the results returned of 105dB (20Hz) and 100dB (20kHz) are still superb. Note also the complete lack of inter-channel phase differ-

ences, with the lab returning perfect 0.0° re-sults at 1kHz and 20kHz. The 0.01° error at 20Hz is actually small enough to be within measurement error. I don’t think I have seen any other amplifi er—integrated or power—re-turn such good fi gures. Channel balance was also extraordinarily good, at just 0.06dB.

The 865’s signal-to-noise ratios were ex-emplary: that result of 100dB weighted ref-erenced to rated output speaks for itself. Not too many integrated amplifi ers can return three-fi gure results. That the amplifi er did not quite meet specifi cation may have been that the amplifi er performs better at certain settings of the volume control than others, or that Boulder used a higher input level to ob-tain its specifi cation. (Newport Test Labs uses a standardised 500mV input for this test, which required the volume to be set at –32dB for the amplifi er to deliver rated output.) Since I’m mentioning input sensitivity, now would be a good time to point out that the 865 needs just 14.5mV at its input to deliver 1-watt at the output terminals, and will de-liver its rated output with just 175mV. These are good results.

Harmonic distortion was incredibly low, as you can see from the four graphs. Driven by a 1kHz test signal at an output level of 1-watt into an 8-ohm load, the 865’s output spec-trum was completely clean, save for a third-harmonic distortion component at a level of –102dB (0.0007%) and a fi fth harmonic at –106dB (0.0005%). Reducing the load imped-ance to 4-ohms added just one component to these two: a second harmonic at around 104dB. Overall THD+N at this output level was measured at 0.01%.

Increasing power to rated output (150-watts) saw the expected increase in distortion components, but although their number in-creased, the levels of all remained more than 100dB (0.001%) down in all cases, so they would have absolutely no bearing on the 865’s sound quality. Note on these graphs that the amplifi er’s noise fl oor is hovering just above –130dB right across the spectrum, so it’s obviously only the low-frequency com-ponents (visible as the narrow spikes at the

Boulder 865 Integrated Amplifi er

52-58Boulder HFJan08.indd 54 18/12/2007 3:16:29 PM

TEST RESULTS


extreme left of the graphs) that are contribut-ing to the overall unweighted noise fi gures. Overall THD+N at rated output was measured at 0.002%.

The Boulder 865’s frequency response was superb: particularly across the audio band and most particularly when driving a load that simulates that of a pair of loudspeakers. Graph 5a shows the 5Hz to 40kHz response into a standard non-inductive 8-ohm resistor, using an expanded vertical scale where the top of the graph is +1.0dB and the bottom –1.0dB. The trace starts just 0.15dB down at 5Hz and reaches reference (0dB) at 9Hz, then tracks across to 4kHz before starting to roll off slightly to be 0.2dB down at 20kHz and 0.9dB down at 40kHz. This means that normalised, the Boulder 865’s frequency response was measured as 20Hz to 20kHz ±0.1dB. Graph 5b adds a second trace showing the Boulder 865’s response into a simulated loudspeaker, this latter trace shown in red. Whereas most all other amplifi ers I have reported on for Aus-tralian HI-FI Magazine exhibit a severe droop across the midrange and often a peak at high-er frequencies, the 865’s response tracked the resistive trace within 0.05dB. This is excep-tional performance that means the amplifi er’s ‘sound’ will be the same irrespective of the speakers it’s driving. The low-frequency re-sponse of the Boulder extended far below the ability of Newport Test Labs’ ability to mea-

“This is exceptional performance that means the amplifi er’s ‘sound’ will be the same irrespective of the speakers it’s driving.”




TEST RESULTS

sure accurately, extending to 0.01Hz –1dB and even further with the –3dB limit. High-frequency performance was also excellent, with the frequency response tested as being 1dB down at 55kHz and 3dB down at 99kHz. This is obviously a very wideband amplifi er, one that is easily capable of extracting all that DVD-A and SACD can offer… and more.

This exceptionally fl at and extended fre-quency response is refl ected in the amplifi er’s superior performance with square waves, with the 100Hz square wave oscillogram showing absolutely no evidence of tilting or curving that would respectively be the tell-tale be-trayal signs of group delay and low-frequency limitations. Indeed the 100Hz waveform is so good it’s almost indistinguishable from the 1kHz waveform, which is perfect, looking like it came direct from a signal generator. The 10kHz waveform shows some slight round-ing, as you’d expect from the 1dB down-point at 55kHz. The discontinuities where the wave starts to rise and fall are most likely artefacts caused by diffi culties interfacing several grounded test devices with the fl oating speak-er output of the Boulder 865. When loaded down with a capacitor to simulate a typical electrostatic loudspeaker load, the Boulder ex-hibits a little more ringing than is usual, but it’s quickly damped, which also indicates that the design is unconditionally stable.

CCIF intermodulation distortion (also known as twin-tone IMD) was exception-ally low, as you can see in Graph 6. The two peaks to the right of the graph are the 19kHz and 20kHz test signals. You can see two small (unwanted) sidebands either side of them at 18kHz and 21kHz but both are more than 90dB (0.003%) down and therefore of no consequence. More importantly, there is ab-solutely no sign of a regenerated difference signal down at 1kHz, where the noise fl oor is sitting at just under –100dB.

One reason for the amplifi er’s stunning ability to drive complex loads was demon-strated when Newport Test Labs measured the Boulder 865’s output impedance, which came in at an extraordinarily low 0.004-ohms, in turn putting damping factor (at 1kHz) at 2,000! I don’t think I have ever seen an am-plifi er with a higher damping factor.

Boulder has also managed to keep its cir-cuitry very ‘green’ with the amplifi er draw-ing a miserly 1.4-watts on standby and just 76-watts at idle. Mains power consumption inevitably rises when the amplifi er is work-ing hard, maxxing out at 665-watts when the amplifi er is operating at its rated power into 8-ohm loads.

I can’t remember a time when I have been so impressed by an integrated amplifi er’s per-formance. Steve Holding

Boulder 865 Integrated Amplifi er - Power Output

Channel Load (Ω) 20Hz

(watts)

20Hz

(dBW)

1kHz

watts)

1kHz

(dBW)

20kHz

(watts)

20kHz

(dBW)

1 8Ω 200 23.0 200 23.0 200 23.0

2 8Ω 185 22.6 185 22.6 185 22.6

1 4Ω 333 25.2 361 25.6 351 25.4

2 4Ω 300 24.7 310 24.9 310 24.9

1 2Ω Protection N/A 544 27.3 544 27.3

2 2Ω Protection N/A 450 26.5 450 26.5

Note: Figures in the dBW column represent the output level, in decibels, referred to one watt output.

Boulder 865 Integrated Amplifi er - Test Results

Test Measured Result Units/Comment

Frequency Response @ 1 watt 0.01Hz–55kHz –1dB

Frequency Response @ 1 watt 0.005Hz–99kHz –3dB

Channel Separation 105dB/116dB/100dB (20Hz/1kHz/20kHz)

Channel Balance 0.06dB @ 1kHz

Interchannel Phase 0.01/0.00/0.00 deg (20Hz/1k/20k)

THD+N 0.01% / 0.002% 1 watt/rated o/p

S/N Ratio (unweighted/weighted) 77dB/83dB dB re 1 watt output

S/N Ratio (unweighted/weighted) 95dB/100dB dB re rated output

Input Sensitivity (Input 1) 14.5mV/175mV (1 watt/rated o/p)

Output Impedance 0.004Ω OC = 2.85V

Damping Factor 2000 @ 1kHz

Power Consumption 1.4 watts/76.1 watts Standby/On

Power Consumption 119 watts /665 watts 1-watt/Rated op

Mains Voltage Variation 239–254 volts Min–Max





product review: boulder 865 integrated amplifier · the boulder also lives up to its insinuated...

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