From the time digital music became a mainstream format (in the early 80s), millions of CDs were produced, covering every genre of music. Owners of Red Book compact discs (like owners of LPs) are still eager to play and listen to the music stored on their silver discs. Ayon Audio’s vacuum-tube-based CD-3sx plays those CDs, and many other modern digital music formats (PCM/DSD) as well.
The CD-3sx is a Class A vacuum-tube, top-loading CD player/DAC with added preamp capabilities for analog sources. It can serve as a CD player, a multi-input PCM/DSD-capable DAC, and an analog-input preamp. This much versatility allows the unit to take up residence in a broad range of systems.
The CD-3sx comes with a magnetic CD-clamp to hold the disc in place. Securing the smoked acrylic/aluminum transport cover on top of the CD transport engages a small pin/switch in the assembly that enables playback. In front of the transport, seven recessed, illuminated buttons (play/pause, stop, next track, previous track, volume-, volume+, input selection) allow you to control basic features. A display in the center of the front panel shows information for CD playback, active input, playback data rates, volume level, upsampling, and filter status. A hidden on/off toggle switch for power is located on the bottom panel towards the front of the unit centered between the Ayon logo and the left side of the display.
The rear panel of the CD-3sx houses all the interface connections (AC power, digital inputs, analog inputs, and analog outputs), in addition to four configuration selector switches. The CD-3sx has two RCA analog inputs available for connecting additional sources. Digital inputs are AES/EBU, coaxial, TosLink optical, I2S (RJ45), DSD on three BNC jacks (left data, right data, clock), and USB (rates up to PCM 24-bit/192kHz and DSD128). A single digital out (SPDIF RCA) connector is provided. In addition to the variable-level output jacks, a second pair of jacks provides a fixed-level output. The main analog outputs are provided for traditional connection to a preamp, integrated, or power amplifier in both RCA and XLR. The polarity selector switch allows the user to choose normal (0 degrees) or inverted (180 degrees) absolute polarity. The gain selection allows maximum output to be set at normal (RCA 2.5Vrms, XLR 5Vrms) or high (RCA 5Vrms, XLR 10Vrms). The analog-out mode allows the setting of normal (for connection to an integrated amplifier or preamplifier) and direct (for connection directly to a power amplifier). The remaining switch on the rear selects the output type—RCA, XLR, or both.
One of the main features of the CD-3sx is a custom-designed Class A triode output stage based on the 6H30 vacuum tube for both single-ended and balanced operation. Each channel’s output stage uses its own circuitry and is physically separated from the other. The unit features a soft-start power-up (and warm-up) function to help extend tube life. Ayon claims the output impedance of the balanced and unbalanced outputs are both approximately 300 ohms. The company uses premium high-quality parts (capacitors, resistors, tube sockets, RCA/XLR jacks, and circuit board material) to improve performance. The main power supply has separate R-core transformers to isolate the analog and digital sections. The 6H30 output section has vacuum-tube-based rectification and DC-regulated filament supplies. There are no fewer than ten separate voltage regulators that distribute power throughout the CD-3sx. Ayon says the vacuum tubes used in the unit are visually examined, burned-in, and analyzed at the factory for plate current, transconductance, heater-to-cathode leakage, internal gas, and microphonic behavior in the tube-testing process. Because different tube manufactures don’t make tubes exactly the same way, Ayon doesn’t encourage tube-rolling. It believes the CD-3sx has been optimized by its experts for the highly selected and matched tubes installed at the factory and that “they will provide many years of excellent audio performance.” The 6H30 in the CD-3sx is expected to provide 8000 hours of service, but Ayon recommends replacement of the tubes after 5000–6000 hours of operation. Ayon believes high-quality craftsmanship, hand assembly, short/direct circuit paths, zero negative feedback, and minimalist design principles, among other improvements, make this unit the best-sounding CD player the company has built.
The digital section features the popular (and respected) ESS Technology ES9018 SABRE32 32-bit, hyperstream architecture, two-channel-audio D/A converter. In the CD-3sx, the ES9018 is configured to process digital signals up to a limit of 24-bit/192kHz PCM and DSD128 (double DSD). There is also a selectable sample-rate converter for any PCM input that can be enabled via remote control to upsample CD/PCM input data to 24/192 before feeding the signal to the ES9018 DAC. The CD transport has a DSP function which, when activated by the remote control, will output the CD data to the coaxial (SPDIF RCA) output and look for the CD data on the coaxial (SPDIF RCA) input. This loopback function allows the user to incorporate a digital room-correction or signal-processing device into the CD path between the digital output and input.
The supplied RC-3C remote control has additional features besides the standard CD playback controls mentioned above. Some of the these functions are Dim (sets the front-panel display brightness), Input (input source selection), Mute, Volume, Vol Sel (fixed output or variable), L-Bal-R (balance adjustment), and 24/192 (enables 24-bit/192kHz upsampling). The Filter button allows selection of Filter1 (a slow roll-off filter that’s said to sound smoother) or Filter2 (a fast roll-off filter that’s said to sound more analytical).
The set-up adjustability of the CD-3sx enables the unit to be optimized for individual sound preferences. Consequently, I tested the player in most of the available configurations, including the balanced/unbalanced output connections, variable/fixed volume enabled, normal/direct amp, all digital inputs (except I2S), analog RCA inputs, 24/192 upsampling on/off, Filter1/Filter2, and DSP digital input-to-output loop-back. Every set-up configuration functioned as advertised with no issues or anomalies.
For the bulk of the evaluation, the CD-3sx was set to the fixed output mode (bypassing the analog volume control) in order to make use of a separate preamplifier. After initial comparisons, Filter1 was preferred, because of the perceived increase in soundstage depth. Gain was set to high for most listening, although the low setting had ample output. The polarity setting remained in the 0-degree position while the analog output was set to XLR, and 24/192 upsampling was turned off for most USB-sourced music listening, since I preferred to hear what each original sample rate was contributing to the sound.