Description: Class-A, stereo, dual-mono, push-pull, tubed power amplifier. Tube complement: (4) Tung-Sol KT150; (4) gold pin JJ ECC82/12AU7. Inputs: One pair XLR (balanced), one pair RCA (unbalanced). Outputs: two sets five-way speaker binding posts with 4, 8, and 16 ohm taps. Output impedance: 4 ohm tap, 4.0 ohms; 8 ohm tap, 7.6 ohms; 16 ohm tap, 12.3 ohms. Maximum power: 100Wpc into 8 ohms (20dBW) (high bias), 85Wpc (19.3dBW) (medium bias), and 60Wpc (17.8dBW) (low bias). Frequency response: 20Hz–30kHz, –3dB. Input impedance: 10k ohms balanced, 47k ohms single-…
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Sidebar 2: Associated Equipment
Analog sources: Thorens TD 124 turntable/Jelco 350 S tonearm/EMT TSD 15N MC cartridge; Acoustic Signature Maximus NEO turntable/Acoustic Signature TA-1000 NEO tonearm/Luxman LMC-5 cartridge.
Digital sources: HoloAudio May DAC; Sonore opticalRendu; Roon Nucleus+; Small Green Computer power supply; TRENDnet switch; Apple iPad mini.
Preamplifiers: Shindo Labs Allegro (2), Sugden LA-4 line; Tavish Audio Design Adagio phono preamplifier.
Power amplifiers: Shindo Haut Brion, Pass Labs XA-25.
Loudspeakers: DeVore Fidelity Orangutan O/96, Spendor…
Sidebar 3: Measurements
I performed the measurements of the Zesto Bia 200 Select with my Audio Precision SYS2722 system. Following the instructions in the comprehensive manual, I carefully installed the small-signal tubes and the KT150 output tubes, the latter supplied as standard. With three auto bias settings for the KT150s, three output transformer taps—labeled 4 ohms, 8 ohms, and 16 ohms—and both single-ended and balanced inputs, this is a complicated amplifier. I performed a complete set of tests with the KT150s, using the single-ended inputs, all three bias settings, and all…
Manufacturer's Comment
Thank you everyone at Stereophile for all their support. We are so pleased with Ken Micallef 's review and all his comments on the musical performance of our amp.
I would like to point out to your readers important conditions regarding John Atkinson's technical measurements on this amp. Tubes are the only active component in a tube amplifier, so all tube amplifier measurements are sensitive to the condition of the tubes. Tubes need to be tested separately before testing the unit. In this case, the amplifier was used to test the tubes, so the measurement…
I mentioned in my CanJam NYC intro that CanJams offer more than just networking and headphone auditions. (You can read part 2 here.) They are also good places, I noted, to access the house sound of virtually every good DAC and amplifier that will fit on a tabletop.
In my realm, there are two main types of audiophile sound systems: floorstanding and desk-sitting. Because, in contrast to floor systems, the user is positioned at arm's reach, desktop systems have 3D aesthetic that turns amplifiers and digital converters into artfully crafted tabletop architecture. The Woo…
You won't see many Apple products in these pages, and for good reason. As Stereophile Editor Jim Austin wrote to me recently in an email, "Apple may have the best acoustic-design facilities in the world, but its products are designed by engineers who don't seem to respect perfectionist sound—which is appropriate for a company that aims for the vast middle of the bell curve." Has that changed?
It took Apple years to get halfway serious about music reproduction. The $2 trillion giant didn't offer lossless files via its Apple Music streaming service until mid-2021. Its early wired earphones…
Sidebar 1: On Bluetooth
One reason I green-lighted Rogier van Bakel's review of the Apple AirPod Pro 2 is that, while Bluetooth audio has a somewhat dubious past, its future seems promising (footnote 1). Bluetooth is a protocol that enables wireless audio and much else. Operating within the Bluetooth standard, or riding on top of it, are codecs for coding audio including SBC (the basic, default Bluetooth audio codec), AAC (preferred by Apple and used by YouTube), LDAC (from Sony), and several varieties of aptX (standard, HD, Adaptive, Lossless, and so on).
Sony and Qualcomm have…
Sidebar 2: Specifications
Description: Bluetooth wireless earbuds with noise cancellation. Model number MQD83AM/A. Volume swipe controls, active noise cancellation, adaptive transparency, personalized spatial audio.
Dimensions: For each bud: 1.22" (30.9mm) H × 0.86" (21.8mm) W × 0.94" (24.0mm) D. Weight 0.19oz (5.3gm). Charging case: 1.78" (45.2mm) H × 2.39" (60.6mm) W × 0.85" (21.7mm) D. Weight 1.79oz (50.8gm).
Price: $249. Warranty: One year.
Manufacturer: Apple, One Apple Park Way, Cupertino, CA 95014. Tel: (800) 692-7753. Web: apple.com.
Sidebar 3: Associated Equipment
Headphones and IEMs: First-generation AirPods Pro, Moondrop Aria, AKG N400, Etymotic ER4SR, HiFiMAN HE1000se, Audeze LCD-4, Sennheiser HD 600, Bose QuietComfort 25.
Headphone amplifiers: McIntosh MHA100, RME ADI-2 DAC FS. Sources iPhone 14 Pro Max, iPad Pro, Apple TV, Lenovo Think-Centre running Roon ROCK (Roon-Optimized Core Kit), Auralic Vega DAC.—Rogier van Bakel
As Vilray Bolles marched down Manhattan's Second Avenue on a rainy afternoon late in 2014, participating in a demonstration against police brutality, he slipped on the wet pavement, fell hard on his right hand, and broke his pinky. For a guitarist, a broken finger can be a major, if not catastrophic, setback. But the gods were smiling on Bolles. He was, in fact, a lapsed guitarist, having all but abandoned hopes of a musical career, and the universe was giving him a nudge, not just back into music but into a collaboration with Rachael Price, one of contemporary pop's great vocalists, who,…