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MA1 Mk.II.3
Atma-SphereAmplifiersPower AmplifiersDiscontinued
Estimated price (community-sourced)
$6,299
Around — community and catalog average, updates slowly
About the MA1 Mk.II.3
The MA-1 Mk.II.3 is a pair of Class-A, fully differential, output-transformerless monoblock power amplifiers. Its direct-coupled Circlotronic output stage uses no output transformer, and the design combines balanced circuitry with RCA single-ended and XLR balanced inputs. The Mk.II.3 version is described as having an enhanced driver circuit and regulated driver supply; it also features a standby switch and can operate in Class A or Class A/B. Each amplifier uses 14 6AS7G output tubes and five 6SN7 driver tubes.
Specifications
Type: OTL monoblock power amplifier; sold as a pair
Output power: approximately 140 W per channel into 8 Ω (manufacturer specifications for later MA-1 versions list 140 W into 8 Ω and 135 W into 4 Ω; exact Mk.II.3 figures may vary)
Circuit: fully differential, Class A or Class A/B; direct-coupled Circlotronic output stage; no output transformer
Inputs: RCA single-ended and XLR balanced
Tube complement: 14 × 6AS7G output tubes and 5 × 6SN7 driver tubes per channel
Power consumption: approximately 500 W per chassis
Dimensions: approximately 18 × 17 × 8.5 in (46 × 43 × 22 cm) per chassis
Weight: approximately 35 lb (16 kg) per chassis