Channel D Lino C 2.0 Phonostage

Transimpedance Your Phono Cartridge!

Equipment report
Categories:
Phonostages
Channel D Lino C 2.0 Phonostage

The Channel D Lino C 2.0 is a current-mode (transimpedance) phonostage for low-output, low-impedance moving-coil cartridges. The cartridge input is designed for a balanced (differential, non-ground-referenced) connection. The electronic circuitry is direct-coupled (no coupling capacitors), and said to have wide bandwidth, low distortion, and ultra-low noise. Powered by an internal high-current AGM lead/acid battery, the Lino C 2.0 sports an output stage with 20-ohms output impedance, capable of driving cables with much more ease than those output stages with higher output impedances. To put things outlined in this succinct introduction in perspective, this is a lot of phonostage for its asking price of $2699.

The Lino C 2.0’s current-mode input differs from standard voltage-mode phonostages in how the signal is delivered to and used by the phonostage. A typical voltage-mode phonostage amplifies the voltage output of the cartridge with less concern paid to the amount of current the cartridge delivers. With most (but not all) voltage-mode phonostages, there are usually provisions to add/adjust loading in the form of resistors that damp the ultrasonic peak of the combined cartridge/phono cable interface. Many music lovers use this loading feature as a way of adjusting the tonal balance. A properly designed current-mode phonostage can provide a near-zero-ohm input load, which the cartridge sees as a near-short-circuit. As such, the voltage output of the cartridge becomes less important than the cartridge’s internal impedance and the amount of current it is supplying to the phonostage. Because of this “transimpedance” mode of operation, there are no provisions for loading the cartridge, since it is already near a zero-ohm impedance. This feature of a current-mode phonostage eliminates the calculation of proper loading values relative to cartridge/phono cable impedance (or subjective estimates of same) that are necessary with voltage-mode phonostages. That can be a benefit. The other side of this coin is there is no subjective tuning of cartridge performance via resistive loading. The resulting sonics are purely a reflection of the cartridge’s design and, to a lesser degree, whatever character the transimpedance phonostage brings with it—which is, hopefully, very little.

The Channel D Lino C 2.0 is said to have low distortion and ultra-low noise. Although I don’t have the test equipment Channel D used to measure the Lino C 2.0’s performance, I can tell readers that the unit is exceptionally quiet when viewed in limited spectral plots or listened to subjectively. I believe part of the reason for such performance is related to the internal, high-current, Absorbent Glass Mat (AGM), sealed-lead/acid battery-charging and power-supply circuit, the careful layout of many surface-mount components, and the trace-impedance matching employed in the design of the electronics within the Lino C 2.0. With the use of surface-mount technology and proper layout of printed circuit boards, I can say (having a multi-decade engineering background in digital and analog circuits) that the design of the Lino C seems carefully considered and executed to limit the deleterious effects of noise and distortion. 

The Lino C 2.0 is made to receive a balanced cartridge input via balanced input wiring—note I didn’t say the user must have a balanced XLR connector. While balanced wiring (twisted pairs of identical conductors within a shielded cable) from the cartridge to the Lino C 2.0’s input is required, an XLR connector isn’t. A set of special ground-isolated RCA-to-XLR adaptors for RCA cable connection are optional ($49) and useable with the Lino C 2.0 (as long as the twisted pair of conductors are connected to the center pin, and the outer connector of an RCA cable, the shield/ground, is not connected to the outer lead of the RCA plug).

Briefly, any phono cable/tonearm combination where twisted-pair-conductor cables are employed and the two conductors are not connected to the turntable (or shield) ground can be used. An example of a tonearm/cable that can’t be used would be a standard Rega ’arm where the shield is connected to one of the outer shells of the RCA, which is also a signal connection. Working examples of correctly wired tonearms I used in-house are the Basis Vector IV, Basis SuperArm 9, Graham Phantom III with Graham-supplied tonearm cable, and the Klaudio 12" Tangential tonearm with custom RCA cables utilizing twisted pair cables and RCA connections with isolated shield-ground phono cable. Of course, the balanced, XLR-connected, twisted-pair cables on one of the Basis Vector IV tonearms worked directly into the Lino C 2.0’s XLR balanced inputs without the need for the RCA-to-XLR connector.

Additional adjustments available on the Lino C 2.0 comprise a set of dip switches underneath the unit that allows for the final gain-stage setting to be varied from 0dB to +6dB or +12dB of total gain to put its output in line with the downstream preamplifier and, if applicable, other source components. The Lino C 2.0 has two independently amplified sets of low-impedance outputs (XLR and RCA) on the rear of the unit. There are RIAA bypass selector switches underneath the jacks for the balanced outputs (the independently amplified single-ended outputs are always RIAA corrected) that allow the XLR outputs to be flat—creating a high-gain current-mode linear amplifier for the cartridge connection. This feature allows the use of an A/D converter connection to the Lino C 2.0 for direct sampling of the linear (non-RIAA corrected) XLR balanced output for recording and for later applying RIAA correction in software for playback, using programs like Channel D’s own Pure Vinyl (this feature was not tested during the evaluation). The bottom of the Lino C 2.0 also has a printed screened-on spectral plot showing the exact unit’s serial number and measured RIAA accuracy over a 20Hz to 20kHz frequency band.

The Lino C 2.0 is powered by its internal AGM battery during playback. The circuitry senses when a signal is present at the current-mode input of the phonostage. When this signal is detected, the electronics internally disconnect the charging circuit from the system, which provides isolation from the external charger (due to the design of the external charger, galvanic isolation is also achieved). If you want to go further, you can unplug the AC side of the external charging circuit to go completely “off the grid.” (Just be sure to reconnect the AC plug when you’re finished listening.) One additional feature is a 2.5mm barrel jack underneath the unit that provides a 5V signal indicating when the Lino C 2.0 has detected output from the cartridge and is in operating mode. This allows for an automatic “off the grid” mode of operation with the use of an accessory device (not a Channel D product) that can be triggered to disconnect the connection of the power supply from the AC mains line during music playback. With this automatic “off the grid” mode accessory, the Lino C 2.0 is automatically connected back to the AC mains approximately 10 minutes after music hasn’t been played, to allow the charging circuits to recharge the internal battery. (Note: The user can contact Channel D for this accessory information or find it in the Installation and Use Manual.)