Description: Vacuum-tube monoblock amplifier. Tube complement (each monoblock): eight 6550C, four 6922, two 5687. Rated output power: 20Hz-20kHz, <1% THD, 220W into 8, 4, and 2 ohms (23.4, 20.4, and 17.4dBW, respectively). Frequency response: 5Hz-75kHz, ±0.5dB at 1W; 15Hz-60kHz, ±0.5dB at 220W. Input sensitivity for full output power: 2.2V, balanced or single-ended inputs. Voltage gain: 25.6dB into 8 ohms, 22.6dB into 4 ohms, 19.6dB into 2 ohms. Input impedance: 100k ohms single-ended, 200k ohms balanced. Output impedance: 0.25 ohms at 1kHz. Damping factor:…
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Sidebar 2: BD's Associated Equipment
Analog source: VPI TNT IV turntable, JMW Memorial 12" tonearm, Grado Reference cartridge.
Digital sources: Wadia 830, Ultech UCD-100 CD players.
Preamplification: Sonic Frontiers Phono 1 phono preamplifier, Line 3 line stage; VAC CPA1 Mk.III preamplifier.
Power amplifiers: VTL Ichiban and Mark Levinson No.20.6 monoblocks; VAC Renaissance 70/70, Krell KSA-250.
Loudspeakers: Magnepan MG3.6/R, Thiel CS7.2.
Cables: JPS Superconductor 2, Kimber BiFocal XL, Nirvana S-L. AC cords: JPS Power, Analog, and Digital.
Accessories: MIT Z-Systems…
Sidebar 3: Measurements
A full set of measurements was made on the Sonic Frontiers Power 3 in its balanced mode, with selected measurements repeated in unbalanced (single-ended) mode. Unless noted otherwise, all measurements are for balanced configuration.
Following its one-hour warmup, the Power 3 was typically hot for a tube amplifier. Its input impedance measured a high 198k ohms (99.3k ohms unbalanced), its output impedance a maximum of 0.17 ohm at 20Hz and 1kHz, increasing to a maximum of 0.22 ohm at 20kHz. These are very low—and very good—values for a tube amplifier, and…
Kalman Rubinson wrote about the Power 3 in July 2000 (Vol.23 No.7):
I'm going to cheat a little here. My comments on the Sonic Frontiers Power 3 monoblock power amplifier are a Follow-Up to Brian Damkroger's review in the April 2000 issue...my feelings differ significantly from Brian's.
The Power 2 power amplifier sat in my listening room for more than a year. Over that time, and however much I resisted the prospect, I ended up choosing it—over every other amp and with almost every speaker—for enjoying music. Sure, the Bryston 7B-STs had more slam and punch, the Simaudio Moon W-…
Looking at all of the high-end headphones and headphone accessories available today, it's difficult to even remember how barren the head-fi landscape was in the early 1990s. Back then, headphones got no respect, except for exotic, expensive electrostatic models, yet most of the world listened to music through headphones all the time, mostly through crappy cans connected to portable players. (Well, maybe it wasn't that different a landscape.)
Tyll Hertsens started HeadRoom in 1992, marketing headphone amplifiers that included a proprietary Crossfeed circuit to a really tough…
Still. Although I fed the Desktop with digital signals at sampling rates of 48kHz and 96kHz—and heard it sound better for it—I had no way of knowing if it was locking on to input or downconverting it. But does it matter whether a tree falls in 44.1kHz or 96kHz, as long as I hear it as better? Perhaps not. The Desktop's lack of a front-panel display isn't a deal-breaker for me, but I do wish it had one.
Let's dance, little schoolgirl
The Grace m902 is a natural comparison for the pimped-out Desktop. They're within striking distance in price ($1700 vs $2095), they both allow analog…
Sidebar 1: Specifications
Description: Desktop headphone amplifier/line preamplifier with optional D/A module. Amplifier: Operating voltage: ±15VDC. Operating current: 50mA from each supply. Input impedance: approx. 70k ohm. Output impedance: approx. 0.5 ohm. Maximum output: 250mA. Maximum voltage gain: 19dB. DAC: Supported data formats: 16–24-bit/44.1, 48, 96kHz. Supported physical interfaces: TosLink, coaxial, USB.
Dimensions: 6.25" (160mm) W by 3.25" (83mm) H by 6.25" (160mm) D. Weight: 1.4 lbs (0.6kg).
Serial Number Of Unit Reviewed: None visible.
Prices: $2095 (total,…
Sidebar 2: Associated Equipment
Digital Sources: Apple PowerMac G5 computer; Ayre C5-xe, Musical Fidelity X-RayV3, Sony CDP-CX400 CD players.
Preamplifiers: Conrad-Johnson ACT2 & CT-5.
Power Amplifiers: McCormack DNA-500, Moscode 401HR.
Headphones: AKG-501, Etymotic ER-4S & ER-6, Grado RS-1, Sennheiser HD-580 & HD-600.
Loudspeakers: Dynaudio Focus 140, Thiel CS2.4.
Cables: Headphone: Stefan Audio Art Equinox, Sennheiser HD-600/Cardas. Interconnect: Shunyata Research Aries & Antares, Viola Labs Silver Balanced. Speaker: Shunyata Research Lyra. AC: Cardas…
Sidebar 3: Measurements
Looking first at the HeadRoom Desktop's performance in the analog domain, its input impedance was very high, at approximately 100k ohms across the audioband. It didn't invert signal polarity and the output impedance was a very low 1.6 ohms at all frequencies, from both the headphone jacks and the rear-panel RCA jacks. (This figure includes the series resistance of 6' of interconnect.) The maximum voltage gain at 1kHz depended on the setting of the front-panel gain switch. With this in the central, Low position, the Desktop attenuated the input signal by 8.1dB.…
Wes Phillips returned to the HeadRoom Desktop in November 2006 (Vol.29 No.11):
When I reviewed HeadRoom's maxed-out headphone amplifier and DAC in the April 2006 Stereophile, I commented that I'd be following up in a few months with some notes on the "plain" Desktop unit, sans the Max amplifier module ($499), Max DAC option ($399), and Alps volume control ($199). Indeed, I was "hard at work" listening to a basic Desktop with the Home amplifier module (a $199 upgrade from the Standard module that comes stock in the $599 Desktop).
Then HeadRoom's Tyll Hertsens called me to repossess…