Boulder 856

Boulder's 865 integrated amplifier is essentially an 810 preamp and an 860 power amp crammed into a single, large chassis. Like the 810, the 865 has four balanced line-level inputs; a sophisticated, microprocessor-controlled, optically activated volume control; and separate power supplies for the analog and microprocessor circuits.

Because the 865 is, literally, an 810 preamplifier, with controls and appearance identical to that model and built into the same chassis with an 860 power amplifier (with the slight exception of the 865's faceplate being 2" taller than the 810's), that means that the feature set of the 865's preamp section is the same as that described in FK's review of the 810 in December 2007. The 865's rear panel is slightly rejiggered from the 810 as well, as it now needs to accommodate speaker binding posts as well as inputs.

Like the 860, the 865 puts out 150Wpc "in [class-]A/B beyond approximately 10W," Jeff Nelson explained. In keeping with Nelson's philosophy of reducing noise as much as possible, each section of the 865 resides in its own compartment inside the amp's chassis, which is hewn from a solid billet of aluminum.

Like all Boulder products, the 865 is packed with high-quality parts?literally thousands of them. Nelson's inability to compromise leads him to hand-select gain-stage monolithic devices, use four-layer circuit boards, and deploy 16 bipolar output devices per channel. Boulder components are what they call "parts intensive."

Nelson is also a big believer in "correct and appropriate levels of feedback" for each gain stage. In fact, he said, other manufacturers' assertions that their designs are "zero-feedback" appall his inner engineer.

One feature of the 865 that's not common to all integrateds is its balanced Auxiliary Output, which can be used as a fixed output (for recording, for example) or as a variable output (controlling another music zone, perhaps).

Previous Next

Klik op de afbeelding voor een vergroting
Click picture for magnification

Solid-state, remote-controlled, class-A/B integrated amplifier.
Frequency response: 20Hz-20kHz, +0.0/-0.07dB, 0.015Hz-95kHz, +/-3dB.
Maximum continuous output power: 150Wpc into 8 or 4 ohms (21.9dBW, 18.9dBW), 300Wpc peak into 4 ohms (21.9dBW).
Maximum voltage gain: 46dB.
THD at maximum continuous power: 20Hz-2kHz, 0.0035%.
Signal/noise ratio: 108dB unweighted ref. 150W into 8 ohms, 20Hz-20kHz.
Maximum input level: 6.0V.
Input impedance: 100k ohms balanced, 40k ohms unbalanced.
Common-mode rejection (balanced): 60Hz, 90dB; 10kHz, 70dB. Crosstalk: -112dB or better.
Dimensions: 17" (435mm) W by 7.38" (190mm) H by 15.25" (390mm) D.
Weight: 52 lbs (23.6kg) net