Listening
I've heard VAC amplification at many audio shows and a few dealer events over the last several years. But with few exceptions—one being at the Florida Audio Expo in early 2020, where I heard this very amplifier driving Acora SRB…
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Hayes noted a design advantage an integrated amplifier has over separates: an intimate common ground reference for the amplifier, preamplifier, and phono stage. When done correctly, this can give an integrated amp "that relatively nonelectronic, open, organic sound," he said. I experienced no tube troubles during my time with the Sigma 170i iQ.
Sidebar 1: Specifications
Description: Stereo integrated amplifier. Tube complement: 5 12AU7A; 1 12AX7A, 4 Gold Lion KT88s; 2 12AX7A for phono stage option. Line inputs: 4 RCA (optional XLR/ balanced input on Input 4; optional MM/MC phono on Input 1), Cinema Bypass. Outputs: Speaker connections 2–4, 4–8, 8–16 ohm taps; preamp out. Power output: 85Wpc into 4, 8, or 16 ohms (16.3, 19.3, 22.3dBW). Power bandwidth: 13Hz–70kHz. Phono option: Gain 37dB MM, 57dB MC. Frequency response: RIAA ±0.2dB. Residual noise 3mV at output (S/N ratio approx. 69dB). Overload: 117mV at 1kHz, 8V RMS output;…
Sidebar 2: Associated Equipment
Analog source: Clearaudio Performance DC Wood turntable with Tracer tonearm and Talisman v2 MC cartridge.
Digital sources: MBL N31 CD player/DAC; Mytek Brooklyn Bridge streamer/DAC/preamplifier.
Preamplification: Mytek Brooklyn Bridge streamer/DAC/ preamplifier.
Loudspeakers: Acora Acoustics SRB, MBL 126.
Cables: Ansuz Acoustics D2, AudioQuest NRG, and Morrow Audio (some interconnects).
Accessories: AudioQuest Niagara 1000 Low-Z Power Noise-Dissipation System with NRG 10 power cord, and Vodka Ethernet cable, Critical Mass Systems Maxxum…
Sidebar 3: Measurements
The VAC Sigma 170i iQ uses two pairs of Gold Lion KT88 tubes for its output stages and eight small-signal tubes. The tubes are identified with a number, this between the pins of the small-signal tubes. The tube locations are clearly indicated in the manual and the top panel has each tube socket marked with the appropriate tube number. I carefully followed the numbering when installing the tubes before connecting the amplifier first to my Audio Precision SYS2722 (see the January 2008 "As We See It"), then to the magazine's higher-performance APx555 analyzer in…
Time for some towers. In recent months, a succession of standmount speakers has passed through my listening room: GoldenEar BRXes, Bowers & Wilkins 705 Signatures, Marten Oscar Duos, original KEF LS50s, and the new LS50 Metas. All these loudspeakers sounded excellent, though different from one another. I felt that a floorstanding loudspeaker would make for an interesting change.
Italian company Sonus Faber is primarily known for its high-performance, relatively high-priced designs, like the $130,000/pair Aida that Michael Fremer reviewed in October 2018 or the $15,900/pair Guarneri…
The Lumina IIIs reproduced the 1/3-octave warble tones on Editor's Choice with good power down to the 80Hz band. While the 63Hz and 50Hz tones were quieter, the 40Hz and 32Hz tones had reasonable weight, the latter aided by the lowest-frequency mode in my room. The 25Hz and 20Hz warble tones were inaudible at my usual listening level. The half-step–spaced tonebursts on Editor's Choice spoke cleanly down to 100Hz but were lighter in weight in the bottom two octaves. When I listened to the speakers' back and side panels with a stethoscope while these tones played, I could hear some fairly…
Sidebar 1: Specifications
Description: Three-way, reflex-loaded, floorstanding loudspeaker. Drive-units: 1.14" (29mm) "DAD" (Damped Apex Dome) tweeter, 5" (150mm) pulp-cone midrange unit, two 5" (150mm) pulp-cone woofers. Crossover frequencies: 350Hz, 3.5kHz. Frequency range: 40Hz–24kHz. Nominal impedance: 4 ohms. Sensitivity: 89dB/2.83/m. Power handling: 50–250W.
Dimensions: 38.9" (989mm) H × 9" (228mm) W × 10.9" (278mm) D. Weight: 35.1lb (15.9kg) each.
Finish: Matte walnut or wengè baffle with maple inlays. Piano black is also available. Leather-wrapped top, sides, and back.…
Sidebar 2: Associated Equipment
Analog Source: Linn Sondek LP12 turntable with Lingo power supply, Linn Ekos tonearm, Linn Arkiv B cartridge, Channel D Seta L phono preamplifier.
Digital Sources: Grimm MU1 and Roon Nucleus+ file servers; Ayre Acoustics C-5xeMP universal player; PS Audio PerfectWave DirectStream D/A processor and MBL N31 CD player/DAC, Ayre Acoustics QA-9 A/D converter.
Preamplifiers: MBL N11, Pass Labs XP-32.
Power amplifiers: Parasound Halo JC 1+ monoblocks.
Loudspeakers: KEF LS50.
Cables: Digital: AudioQuest Vodka (Ethernet), AudioQuest Coffee (USB…
Sidebar 3: Measurements
I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Sonus Faber Lumina III's frequency response in the farfield and an Earthworks QTC-40 mike to measure the nearfield and in-room responses. I measured the speaker's impedance with MLSSA, checking the results with Dayton Audio's DATS v2 system.
Sonus Faber specifies the Lumina III's sensitivity as a high 89dB/2.83V/m. My estimate was even higher, at 91dB(B)/2.83V/m. The Lumina III's impedance is specified as 4 ohms. The impedance magnitude (fig.1, solid trace) remains between 4…
I'm waiting for a bypass.
My heart did not attack me. My arteries aren't clogged. I'm awaiting an electrical bypass to save my audio system's life.
As I reported last month, my audio system started choking on the house juice immediately upon power up after an emergency power generator was installed in my house. The system isn't running on generator power, but the generator's installation required installing some other hardware in the AC signal path: a switch that automatically transfers the house's power system to the generator when the power goes out. It's that new hardware that…