Cayin A-300B integrated amplifier review
by Art Dudley, Stereophile
By now, even the shortest-sighted cynic has to admit that the single-ended-triode (SET) amplifier, which reappeared on the domestic audio scene over a decade ago, represents more than just a passing fad. And while no amp of such questionable relevance to the average loudspeaker will ever be considered the norm, so is it true that the SET's charms have earned it a permanent seat at the table. There will always be manufacturers who want to build SETs, just as there will always be people who want to perform Shakespeare or distill absinthe.
The genre has also had a lucky break: the SET revival was followed closely by the emergence of a new manufacturing power, one with both a flair for tube electronics and the geopolitical wherewithal to keep consumer prices low. That power, of course, is the People's Republic of China—from which I'm happy to see new single-ended products regularly emerge.
Consider the Cayin A-300B integrated amp, made by Spark (aka Zhuhai Spark) of Guangdon Province. Ten or more years ago, you might have been able to find a 300B integrated amp this well built, and you might have been able to find a 300B amp this affordable—but you certainly wouldn't have found both in the same package.
Description
The package in question is a lushly chromed chassis with a terraced aluminum alloy faceplate, sculpted housings for the mains and output transformers, and a thickly enameled protective cage that fits so beautifully, you'd think someone actually cares whether or not you like it. An alloy remote control is also a part of the scenery.
Inside the A-300B is a mix of circuit boards and point-to-point wiring, each doing the job it ought to be doing. Remote-control circuitry, a phalanx of relays for input selection, and other bits and pieces account for the circuit board, while the wiring is well represented—and remarkably well executed—throughout most of the audio and power-supply circuitry. The wiring is neat, the soldering is saintly, and the parts are nice enough, with a sprinkling of such names as Multicap, Nichicon, and Alps. Inside my review sample were no rough metal edges, no questionable solder joints, and not so much as a speck of dust.
The A-300B's power supply holds no surprises, although I am impressed that, forward of the AC transformer (a toroid), it's an entirely dual-mono design. I'm also struck by the size and quality of the electrolytic capacitors chosen to smooth the AC: They share a pi filter of the usual sort with a hefty, frame-style choke. Each channel has its own 5AR4 tube for B+ rectification, while lower voltages (for tube filaments and logic circuits—a lovely if odd juxtaposition) are uncurled with solid-state rectifier blocks.
The Cayin's amplification design is similarly straightforward: The high-level input signal is directed to a 100k ohm volume potentiometer, from whence it's capacitively coupled to the grid of a 6SL7 dual-triode cascade, for pure voltage gain. The final plate of that tube drives the grid of a 6SN7 dual triode, configured as a cathode follower for low impedance. The full waveform then goes to the grid of a 300B output triode—biased, of course, for pure class-A operation.
The output tubes are run in fixed-bias mode, and each channel has its own easily accessed bias trim pot (a decent-quality digital voltmeter is required). My review sample of the A-300B arrived perfectly well adjusted for the Chinese output tubes supplied, and has required little in the way of further attention. (The Cayin's packing materials are good enough that the amp can be shipped with every tube in place.) There's also a heater-balance pot for each output tube, so the user can adjust the outputs for minimal hum as the tubes age. Filament voltage for each directly heated 300B is rectified, and appears to be just a shade over 5V. On the anode side of the tube I found a rail voltage of about 388V DC—neither the highest nor the lowest one sees in contemporary 300B amps.
The Cayin's circuitry may be straightforward; its transformers are anything but. According to the importer, VAS Industries, Inc., the primary and secondary windings of the frame-style output trannies are coated and sealed in vacuum chambers prior to being potted in the more traditional sense. That's done in the interest of preventing vibrations and enhancing consistency, longevity, and noiselessness.
Indeed, the Cayin A-300B was among the quietest single-ended amps I've used, in every way. I couldn't hear a bit of mechanical sound from the vicinity of the amplifier itself, and only the faintest 60Hz hum through my very efficient Lowther PM2A drivers/Medallion horns. Used with the somewhat less sensitive (92dB, as measured by John Atkinson) but still very efficient Audio Note AN-E Lexus Signature speakers, the Cayin was virtually silent at idle.
The A-300B's user controls are minimal. There's a large volume control at the center of the front panel, and to its right a small button for toggling through the various input selections (including the selection for an outboard preamplifier). One more button allows the user to toggle between zero and minimal feedback; I preferred and relied exclusively on the former. The remote handset duplicates all of those controls and adds one more: a mute toggle. Sadly, the A-300B has neither a balance knob nor a mono switch.
Source http://stereophile.com/integratedamps/207cayin/
by Art Dudley, Stereophile
By now, even the shortest-sighted cynic has to admit that the single-ended-triode (SET) amplifier, which reappeared on the domestic audio scene over a decade ago, represents more than just a passing fad. And while no amp of such questionable relevance to the average loudspeaker will ever be considered the norm, so is it true that the SET's charms have earned it a permanent seat at the table. There will always be manufacturers who want to build SETs, just as there will always be people who want to perform Shakespeare or distill absinthe.
The genre has also had a lucky break: the SET revival was followed closely by the emergence of a new manufacturing power, one with both a flair for tube electronics and the geopolitical wherewithal to keep consumer prices low. That power, of course, is the People's Republic of China—from which I'm happy to see new single-ended products regularly emerge.
Consider the Cayin A-300B integrated amp, made by Spark (aka Zhuhai Spark) of Guangdon Province. Ten or more years ago, you might have been able to find a 300B integrated amp this well built, and you might have been able to find a 300B amp this affordable—but you certainly wouldn't have found both in the same package.
Description
The package in question is a lushly chromed chassis with a terraced aluminum alloy faceplate, sculpted housings for the mains and output transformers, and a thickly enameled protective cage that fits so beautifully, you'd think someone actually cares whether or not you like it. An alloy remote control is also a part of the scenery.
Inside the A-300B is a mix of circuit boards and point-to-point wiring, each doing the job it ought to be doing. Remote-control circuitry, a phalanx of relays for input selection, and other bits and pieces account for the circuit board, while the wiring is well represented—and remarkably well executed—throughout most of the audio and power-supply circuitry. The wiring is neat, the soldering is saintly, and the parts are nice enough, with a sprinkling of such names as Multicap, Nichicon, and Alps. Inside my review sample were no rough metal edges, no questionable solder joints, and not so much as a speck of dust.
The A-300B's power supply holds no surprises, although I am impressed that, forward of the AC transformer (a toroid), it's an entirely dual-mono design. I'm also struck by the size and quality of the electrolytic capacitors chosen to smooth the AC: They share a pi filter of the usual sort with a hefty, frame-style choke. Each channel has its own 5AR4 tube for B+ rectification, while lower voltages (for tube filaments and logic circuits—a lovely if odd juxtaposition) are uncurled with solid-state rectifier blocks.
The Cayin's amplification design is similarly straightforward: The high-level input signal is directed to a 100k ohm volume potentiometer, from whence it's capacitively coupled to the grid of a 6SL7 dual-triode cascade, for pure voltage gain. The final plate of that tube drives the grid of a 6SN7 dual triode, configured as a cathode follower for low impedance. The full waveform then goes to the grid of a 300B output triode—biased, of course, for pure class-A operation.
The output tubes are run in fixed-bias mode, and each channel has its own easily accessed bias trim pot (a decent-quality digital voltmeter is required). My review sample of the A-300B arrived perfectly well adjusted for the Chinese output tubes supplied, and has required little in the way of further attention. (The Cayin's packing materials are good enough that the amp can be shipped with every tube in place.) There's also a heater-balance pot for each output tube, so the user can adjust the outputs for minimal hum as the tubes age. Filament voltage for each directly heated 300B is rectified, and appears to be just a shade over 5V. On the anode side of the tube I found a rail voltage of about 388V DC—neither the highest nor the lowest one sees in contemporary 300B amps.
The Cayin's circuitry may be straightforward; its transformers are anything but. According to the importer, VAS Industries, Inc., the primary and secondary windings of the frame-style output trannies are coated and sealed in vacuum chambers prior to being potted in the more traditional sense. That's done in the interest of preventing vibrations and enhancing consistency, longevity, and noiselessness.
Indeed, the Cayin A-300B was among the quietest single-ended amps I've used, in every way. I couldn't hear a bit of mechanical sound from the vicinity of the amplifier itself, and only the faintest 60Hz hum through my very efficient Lowther PM2A drivers/Medallion horns. Used with the somewhat less sensitive (92dB, as measured by John Atkinson) but still very efficient Audio Note AN-E Lexus Signature speakers, the Cayin was virtually silent at idle.
The A-300B's user controls are minimal. There's a large volume control at the center of the front panel, and to its right a small button for toggling through the various input selections (including the selection for an outboard preamplifier). One more button allows the user to toggle between zero and minimal feedback; I preferred and relied exclusively on the former. The remote handset duplicates all of those controls and adds one more: a mute toggle. Sadly, the A-300B has neither a balance knob nor a mono switch.
Source http://stereophile.com/integratedamps/207cayin/
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