{"product_id":"accuphase-a-48s-class-a-stereo-power-amplifier","title":"Accuphase A-48S Class-A Stereo Power Amplifier","description":"\u003ch1\u003eAccuphase A-48S Class-A Stereo Power Amplifier at Vinyl Sound Buffalo, NY USA\u003c\/h1\u003e\n\n\u003cp\u003eThe Accuphase A-48S is a Class-A stereo power amplifier from Accuphase (Yokohama, Japan), available at Vinyl Sound in Buffalo, NY USA. The successor to the acclaimed A-48, the A-48S advances Accuphase's dedicated power amplifier lineup with a \u003cstrong\u003esix-fold parallel push-pull MOS-FET output stage operating in pure Class A\u003c\/strong\u003e, delivering 50 watts into 8 ohms, 100 watts into 4 ohms, 200 watts into 2 ohms, and 400 watts into 1 ohm with fully linear power doubling at each impedance step. Key advances over the A-48 include a \u003cstrong\u003esignal-to-noise ratio of 118dB\u003c\/strong\u003e — a 1dB improvement — a \u003cstrong\u003edamping factor of 1,000\u003c\/strong\u003e versus 800 on the A-48, larger 68,000μF filter capacitors, MCS+ circuitry, current feedback amplification topology, and balanced remote sensing, all in the same chassis dimensions as the previous model. The A-48S pairs directly with Accuphase preamplifiers including the C-2300 and C-3900 via balanced XLR for systems requiring a dedicated separates configuration at Vinyl Sound Buffalo, NY USA.\u003c\/p\u003e\n\n\u003ch2\u003eSix-Fold Parallel MOS-FET Class-A Output Stage and Instrumentation Amplifier Topology\u003c\/h2\u003e\n\u003cp\u003eThe A-48S output stage uses six pairs of power MOS-FETs per channel operating in pure Class A push-pull configuration, representing the same parallel count as the A-48 but delivering meaningfully improved specifications through optimized circuit design and the new MCS+ (Multiple Circuit Summing Plus) topology. Class-A operation eliminates the crossover distortion that occurs in Class AB amplifiers at the zero-crossing point between positive and negative output devices, maintaining continuous conduction current through all twelve output transistors per channel regardless of signal amplitude or instantaneous power demand. The six-fold parallel arrangement distributes bias current and signal current across twelve devices, reducing the per-device operating stress and improving the statistical consistency of the combined output characteristic. Linear power doubling across impedance steps — from 50W at 8 ohms through 400W at 1 ohm for music signals — confirms that the output stage presents an almost purely resistive impedance characteristic rather than the reactive impedance limitation that constrains many Class-A designs at low speaker impedances. The instrumentation amplifier power stage topology, borrowed from precision measurement equipment, configures the differential input, gain, and output stages as a fully isolated three-amplifier system for maximum common-mode rejection at the amplifier input and minimum distortion across the full output power range. Balanced remote sensing continuously monitors the output voltage directly at the speaker terminals rather than at the amplifier's internal output stage, correcting for the voltage drop across the binding post and output relay contacts in the feedback loop for improved voltage regulation at the speaker load.\u003c\/p\u003e\n\n\u003ch2\u003eMCS+ Circuitry, Current Feedback, and Power Supply\u003c\/h2\u003e\n\u003cp\u003eMCS+ (Multiple Circuit Summing Plus) is Accuphase's proprietary noise reduction topology that operates multiple parallel signal processing circuits simultaneously and averages their outputs to cancel uncorrelated noise and distortion between stages. Applied throughout the A-48S signal chain, MCS+ achieves the 118dB signal-to-noise ratio that places the A-48S among the quietest Class-A power amplifiers available, enabling the retrieval of low-level musical detail that higher-noise-floor amplifiers mask. Current feedback amplification topology maintains consistent bandwidth and slew rate at all output power levels, unlike voltage feedback designs whose bandwidth and transient response degrade as output current increases. The power supply section provides a massive high-efficiency toroidal transformer with 68,000μF total filter capacitance — an increase from the A-48's 60,000μF — delivering the sustained high-current reservoir that pure Class-A operation at 50 watts continuous demands through large orchestral passages and sustained bass transients. The damping factor of 1,000 reflects the combination of the instrumentation amplifier's high loop gain, current feedback topology, and balanced remote sensing, providing precise control over woofer cone motion for tight bass definition with demanding loudspeakers from Dynaudio, Spendor, Magico, Wilson Audio, and Klipsch available at Vinyl Sound Buffalo.\u003c\/p\u003e\n\n\u003ch2\u003eKey Features\u003c\/h2\u003e\n\u003cul\u003e\n  \u003cli\u003e\n\u003cstrong\u003eSix-Fold Parallel Push-Pull Class-A MOS-FETs:\u003c\/strong\u003e Twelve power MOS-FETs per channel in pure Class-A push-pull configuration eliminating crossover distortion, with linear power doubling at 50W\/8Ω, 100W\/4Ω, 200W\/2Ω, 400W\/1Ω.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e118dB Signal-to-Noise Ratio:\u003c\/strong\u003e 1dB improvement over the A-48 through MCS+ circuitry and optimized low-noise balanced input amplifier stage.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eDamping Factor 1,000:\u003c\/strong\u003e Significant improvement over A-48's 800 through balanced remote sensing and optimized feedback topology for tighter bass control and speaker driver precision.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMCS+ (Multiple Circuit Summing Plus):\u003c\/strong\u003e Multiple parallel circuit processing paths with output averaging for statistical noise and distortion cancellation throughout the signal chain.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eInstrumentation Amplifier Topology:\u003c\/strong\u003e Three-amplifier precision measurement instrument configuration for maximum common-mode rejection and minimum distortion across the full power range.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eCurrent Feedback Amplification:\u003c\/strong\u003e Maintains consistent bandwidth and slew rate at all output power levels for uniform transient response from micro-signals to full output.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBalanced Remote Sensing:\u003c\/strong\u003e Output voltage monitored directly at speaker terminals in the feedback loop for improved regulation independent of binding post and relay contact resistance.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003e68,000μF Filter Capacitors:\u003c\/strong\u003e Increased capacitance over A-48's 60,000μF for greater sustained current reservoir and improved dynamic headroom under sustained high-power Class-A loads.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eLarge High-Efficiency Toroidal Transformer:\u003c\/strong\u003e Custom-wound toroidal transformer for high efficiency and low magnetic leakage in the Class-A power supply.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003ePower Meters from -50dB:\u003c\/strong\u003e High-sensitivity power meters with wide dynamic range for monitoring output power from low listening levels through full Class-A output.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eBi-Amp and Bridged Mono:\u003c\/strong\u003e Front-panel selectable stereo, dual mono, and bridged mono configurations for system flexibility.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eMOS-FET Protection Circuitry:\u003c\/strong\u003e Solid-state protection using MOS-FET switches for speaker short-circuit, DC offset, and abnormal temperature protection without relay artifacts.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eHigh-Carbon Cast Iron Insulator Feet:\u003c\/strong\u003e Superior vibration damping through cast iron chassis feet for reduced microphonic contamination of the amplifier circuit.\u003c\/li\u003e\n  \u003cli\u003e\n\u003cstrong\u003eAluminum Hairline Finish Top Plate:\u003c\/strong\u003e Machined aluminum top surface with hairline finish for heat dissipation and Accuphase's signature build quality.\u003c\/li\u003e\n\u003c\/ul\u003e\n\n\u003ch2\u003eTechnical Specifications\u003c\/h2\u003e\n\u003ctable\u003e\n  \u003ctbody\u003e\n    \u003ctr\u003e\n\u003ctd\u003eAmplifier Class\u003c\/td\u003e\n\u003ctd\u003ePure Class A\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eOutput Power (8Ω)\u003c\/td\u003e\n\u003ctd\u003e50W per channel\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eOutput Power (4Ω)\u003c\/td\u003e\n\u003ctd\u003e100W per channel\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eOutput Power (2Ω)\u003c\/td\u003e\n\u003ctd\u003e200W per channel\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eOutput Power (1Ω, music)\u003c\/td\u003e\n\u003ctd\u003e400W per channel\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eOutput Devices\u003c\/td\u003e\n\u003ctd\u003e6-fold parallel push-pull power MOS-FETs per channel\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eSignal-to-Noise Ratio\u003c\/td\u003e\n\u003ctd\u003e118dB\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eDamping Factor\u003c\/td\u003e\n\u003ctd\u003e1,000\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eTopology\u003c\/td\u003e\n\u003ctd\u003eInstrumentation amplifier, current feedback, balanced remote sensing\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eNoise Reduction\u003c\/td\u003e\n\u003ctd\u003eMCS+ (Multiple Circuit Summing Plus)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eFilter Capacitors\u003c\/td\u003e\n\u003ctd\u003e68,000μF total\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003ePower Transformer\u003c\/td\u003e\n\u003ctd\u003eLarge high-efficiency toroidal, custom-designed\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eBalanced Input\u003c\/td\u003e\n\u003ctd\u003eXLR\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eSpeaker Terminals\u003c\/td\u003e\n\u003ctd\u003eLarge direct-connected terminals (bi-amp capable)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eOperating Modes\u003c\/td\u003e\n\u003ctd\u003eStereo, Dual Mono, Bridged Mono (front-panel selectable)\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003ePower Meters\u003c\/td\u003e\n\u003ctd\u003eHigh-sensitivity from -50dB\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eProtection\u003c\/td\u003e\n\u003ctd\u003eMOS-FET switches, DC detection, temperature monitoring, short-circuit protection\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eChassis\u003c\/td\u003e\n\u003ctd\u003eHigh-carbon cast iron insulator feet, aluminum hairline finish top plate\u003c\/td\u003e\n\u003c\/tr\u003e\n    \u003ctr\u003e\n\u003ctd\u003eOrigin\u003c\/td\u003e\n\u003ctd\u003eJapan\u003c\/td\u003e\n\u003c\/tr\u003e\n  \u003c\/tbody\u003e\n\u003c\/table\u003e\n\n\u003ch2\u003eFrequently Asked Questions\u003c\/h2\u003e\n\n\u003ch3\u003eWhat is the Accuphase A-48S?\u003c\/h3\u003e\n\u003cp\u003eThe Accuphase A-48S is a pure Class-A stereo power amplifier from Accuphase of Japan, available at Vinyl Sound Buffalo. It delivers 50 watts per channel in Class A through six-fold parallel push-pull power MOS-FETs, with linear power doubling to 400 watts into 1 ohm for music signals, a 118dB signal-to-noise ratio, damping factor of 1,000, MCS+ noise reduction, instrumentation amplifier topology, current feedback, balanced remote sensing, and a 68,000μF power supply. It is the successor to the A-48 with improved noise performance and damping factor in the same chassis.\u003c\/p\u003e\n\n\u003ch3\u003eHow does the A-48S compare to the A-48 and the A-75?\u003c\/h3\u003e\n\u003cp\u003eThe Accuphase A-48S advances over the A-48 through a 1dB improvement in signal-to-noise ratio to 118dB, an increase in damping factor from 800 to 1,000 through balanced remote sensing, and a larger 68,000μF filter capacitor bank versus 60,000μF. The output power rating advances from 360W into 1 ohm on the A-48 to 400W into 1 ohm on the A-48S. The A-75 is Accuphase's higher-tier Class-A monoblock power amplifier delivering 75 watts per channel with a more elaborate chassis and higher output device count. For systems requiring stereo amplification in a single chassis at the A-series price tier, the A-48S represents Accuphase's most capable stereo Class-A power amplifier.\u003c\/p\u003e\n\n\u003ch3\u003eWhat is MCS+ and how does it improve the A-48S over the A-48?\u003c\/h3\u003e\n\u003cp\u003eMCS+ (Multiple Circuit Summing Plus) is Accuphase's proprietary noise reduction topology that operates multiple parallel signal processing paths simultaneously, then averages their outputs to cancel the uncorrelated noise contributions of each individual path. Because thermal noise and semiconductor noise are statistically independent between parallel circuit paths, averaging multiple paths reduces the combined noise floor below what any single path can achieve. Applied throughout the A-48S's signal chain, MCS+ contributes to the 118dB signal-to-noise ratio that is 1dB quieter than the A-48, enabling the retrieval of low-level musical details that the A-48's slightly higher noise floor masks.\u003c\/p\u003e\n\n\u003ch3\u003eWhat is balanced remote sensing and why does it improve the damping factor?\u003c\/h3\u003e\n\u003cp\u003eBalanced remote sensing is a feedback technique that monitors the output voltage directly at the amplifier's speaker terminals rather than at the internal output stage, and uses this measurement as the error signal for the amplifier's global feedback loop. Standard power amplifiers measure output voltage at the internal circuit node, which means the voltage drop across the speaker binding posts, protection relay contacts, and output wiring is outside the feedback loop and cannot be corrected. Balanced remote sensing places these resistive elements inside the loop, allowing the amplifier to correct for their voltage drop and present a lower effective output impedance at the speaker terminals. The resulting damping factor of 1,000 on the A-48S versus 800 on the A-48 reflects this improved ability to control loudspeaker back-EMF for tighter bass and more precise driver control.\u003c\/p\u003e\n\n\u003ch3\u003eCan the A-48S be used in bridged mono for a monoblock configuration?\u003c\/h3\u003e\n\u003cp\u003eYes, the Accuphase A-48S includes front-panel selectable stereo, dual mono, and bridged mono operation. In bridged mono mode, both channels are combined to drive a single loudspeaker with doubled output voltage swing for approximately four times the power into the same load impedance. For demanding loudspeakers in large listening rooms, a pair of A-48S amplifiers configured as monoblocks provides reference-level Class-A driving capability. Vinyl Sound Buffalo can advise on the cabling and preamplifier requirements for a dual A-48S monoblock configuration with Accuphase or third-party preamplifiers.\u003c\/p\u003e\n\n\u003ch3\u003eWhere can I buy the Accuphase A-48S in Buffalo, NY?\u003c\/h3\u003e\n\u003cp\u003eThe Accuphase A-48S Class-A Stereo Power Amplifier is available at Vinyl Sound USA Inc. in Buffalo, NY, your authorised Accuphase dealer serving Western New York and the United States. Vinyl Sound carries the complete Accuphase power amplifier lineup. Visit vinylsound.com or contact the Buffalo store for current availability and expert system matching guidance pairing the A-48S with Accuphase preamplifiers and compatible loudspeakers.\u003c\/p\u003e","brand":"Accuphase","offers":[{"title":"Default Title","offer_id":53510168346931,"sku":null,"price":14975.0,"currency_code":"USD","in_stock":true}],"thumbnail_url":"\/\/cdn.shopify.com\/s\/files\/1\/0873\/0293\/0739\/files\/AccuphaseA-48SClass-AStereoPowerAmplifier_1_c13cf8fa-11b4-46bc-a6eb-d7a69f941882.png?v=1781748717","url":"https:\/\/vinylsound.com\/products\/accuphase-a-48s-class-a-stereo-power-amplifier","provider":"Vinyl Sound USA","version":"1.0","type":"link"}