NAD C 658 BLUOS Streaming DAC Preamplifier
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NAD C 658 BLUOS Streaming DAC Preamplifier
NAD Made the Preamplifier Do the Streaming Too
The C 658 is a BluOS streamer, a DAC and a preamplifier in one Classic Series chassis. It was built for systems where the source is a network rather than a disc. A power amplifier is the only other box the front end needs.
Inputs cover a moving magnet phono stage, line-level analog, and a full set of digital connections. Outputs are balanced and single-ended, with an adjustable digital subwoofer crossover and bass management built in. Bluetooth works two ways, with aptX HD.
Dirac Live Comes in the Box, With the Microphone
NAD includes a Dirac Live Limited Bandwidth license and the calibration microphone. That corrects the room up to 500Hz, where most room trouble lives. If you want correction across the full range, Dirac sells a Full Frequency upgrade for the same unit.
BluOS runs the streaming side, covering multiroom playback and the major services, Qobuz Connect among them. The C 658 decodes MQA and handles files to 32-bit/192kHz. Dual MDC slots let NAD add capability later without a new chassis.
Where a Modular Preamplifier Pays You Back
MDC is NAD's modular card architecture. Two slots sit on the back panel, so the C 658 can take on functions it did not ship with. That is unusual at this price, and it is why a 2019 design is still current.
On the bench the line inputs measure distortion below 0.005 percent at 2V out. Signal-to-noise on those inputs beats 106dB, referenced to 500mV out. Response holds 20Hz to 20kHz within 0.3dB.
What the Phono Stage Measures, and What It Expects
The moving magnet phono input measures distortion below 0.01 percent at 2V out, with signal-to-noise better than 84dB. Channel separation across the preamplifier is better than 80dB at 1kHz and better than 70dB at 10kHz.
The chassis measures 17 1/8 by 3 15/16 by 16 inches and weighs 22.3 pounds. That is a full-width Classic Series case, so it stacks with the rest of the range rather than sitting awkwardly on a shelf of its own.
What Reviewers Are Saying
What Hi-Fi? gave the C 658 five stars on 28 April 2020, calling it "one of the most fully furnished, future-proofed and intuitive streamers" the magazine had come across at the time.
Al Griffin reviewed it for Sound & Vision on 5 February 2020. His verdict was that the C 658 "brings vinyl playback and Dirac Live room correction to the mix for a very complete package at an affordable price".
Griffin listed one drawback in the same review: an "Overly busy remote control". The BluOS app is the better daily control, and most owners set the handset aside after the first week.
Who Is This Preamplifier Best For?
- Your music lives on a network, not on discs — BluOS streaming, the DAC and the preamplifier share one chassis, so a separate streamer and its interconnect leave the system and one remote covers the lot.
- You want room correction without a specialist visit — the Dirac Live license and the calibration microphone are both in the box, so you can measure and correct the room the day it arrives at no extra cost.
- You are adding a subwoofer — an adjustable digital crossover and bass management are built in, so the subwoofer blends with your speakers without an outboard processor in the chain.
- You expect to keep this preamplifier a long time — two MDC slots let NAD add capability later, so a change in formats or connections need not mean replacing the whole front end.
- You play a moving coil cartridge — the built-in phono stage is moving magnet only. Add one of our phono preamplifiers with moving coil gain on a line input and the C 658 still handles switching, streaming and room correction for the rest of the system.
How Does It Connect to Your System?
A turntable with a moving magnet cartridge goes to the phono input. Line sources take the analog inputs, and digital sources fill the rest. Join the network over Ethernet or Wi-Fi and BluOS finds your services and shared folders.
Balanced or single-ended outputs run to your power amplifier. A subwoofer takes the dedicated output, with the crossover set in the menu. Run the supplied microphone once, save the Dirac profile, and the correction stays in place.
Pairs Well With
Building a system around the C 658? Start here:
- Power Amplifier: The one box the C 658 leaves for you to choose — browse Amplifiers.
- Turntable: The moving magnet stage is built in and ready — browse Turntables.
- Subwoofer: The crossover and bass management are already fitted — see our Subwoofers.
- Interconnects: Balanced or single-ended out to the power amp — see Interconnect Cables.
Frequently Asked Questions
Is the Dirac calibration microphone included?
Yes. The C 658 ships with a Dirac Live Limited Bandwidth license and the microphone, correcting the room up to 500Hz. Dirac sells a Full Frequency upgrade separately.
Which cartridges does the phono input accept?
Moving magnet. A moving coil cartridge needs an outboard stage or a step-up device feeding one of the line inputs.
What sample rates and formats does it handle?
Files up to 32-bit/192kHz, with MQA decoding. BluOS covers the major streaming services, including Qobuz Connect.
Can it replace my preamplifier outright?
Yes. Balanced and single-ended outputs feed a power amplifier directly, and the C 658 handles source switching, volume and room correction.
What are the MDC slots for?
They are NAD's modular expansion cards. Two slots let the C 658 gain connections or capability later without replacing the unit.
How does Bluetooth work on it?
Two-way aptX HD. You can stream to the C 658 from a phone, or send audio out from it to Bluetooth headphones.
See It in Action
The Hans Beekhuyzen Channel covers the C 658's Dirac and MQA implementation:
2 Channel Listening lives with the C 658 as an all-in-one network DAC:
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Learn More
Want to learn more about streaming preamplifiers, Dirac Live room correction, or phono cartridges? Visit our Learning Center for guides, tips, and expert advice.
- BluOS Network Streaming
- ESS Sabre DAC with MQA decoding
- Simplified Streaming directly from Quboz app – Hi-Res playback up to 24-bit/192 kHz on BluOS Devices (with update)
- Dirac Live Room Correction
- Gigabit Ethernet
- Dual Band Wi-Fi a/c/n
- 2-way Bluetooth aptX HD
- 2 x MDC Slots for Future Expansion
- MM Phono Input
- 2 x Line Inputs
- 2 x Optical Inputs
- 2 x Coax Inputs
- Balanced Preamp Output
- Preamp Output
- Stereo Subwoofer Output
- High Current Headphone Out
- USB socket for adding optional wireless output module
- IR In with Learning Function
- Trigger Out/In
Line in/Pre-Out
- THD (20Hz - 20kHz): <0.005% at 2V out
- Signal-to-Noise Ratio: >106dB (IHF; A-weighted, ref. 500mV out, unity gain)
- Channel separation: >80dB (1kHz); >70dB (10kHz)
- Input Impedance (R and C): 22 kohms + 100pF
- Maximum input signal: >4.5Vrms (ref. 0.1% THD)
- Output impedance: Source Z + 240 Ohm
- Input sensitivity: 93mV (ref. 500mV out, Volume maximum)
- Frequency response: ±0.3dB (20Hz - 20kHz)
- Maximum voltage output, IHF load: >4.5V (ref. 0.1% THD)
- Tone Controls: Treble: ±7.0dB at 20kHz, Bass: ±7.0dB at 60Hz; Balance: -10dB
Phono Input/Pre -Out
- THD (20Hz - 20kHz): <0.01% at 2V out
- Signal-to-Noise Ratio: >84dB (200 Ohm source; A-weighted, ref. 500mV out); >76dB (MM cartridge source, IHF; A-weighted, ref. 500mV out)
- Input sensitivity: 1.44mV (ref. 500mV out, Volume maximum)
- Frequency response: ±0.3dB (20Hz - 20kHz)
- Maximum input signal at 1kHz: >80mVrms (ref. 0.1% THD)
Line In/Headphone Out
- THD (20Hz - 20kHz): <0.005% at 1V out
- Signal-to-Noise Ratio: >110dB (32 Ohms loads; A-WTD, ref. 2V out, unity gain)
- Frequency response: ±0.3dB (20Hz - 20kHz)
- Channel separation: >60dB at 1kHz
- Output impedance: 6 Ohms
DAC
- Supported audio file formats: MP3, AAC, WMA, OGG, WMA-L, ALAC, OPUS
- High resolution audio formats: MQA, DSD, FLAC, WAV, AIFF
- Native sampling rates: up to 32bit/192kHz
- Bit depths: 16 – 24
BluOS
- Supported operating systems: Plays music from network shares on the following desktop operating systems: Microsoft Windows XP, 2000, Vista, 7, 8 to current Windows Operating Systems and Mac OS X versions
- User interface mobile operating system: BluOS – Free Android and iOS App available online at Google Play and Apple App store Supported cloud services: Spotify, Amazon Music, TIDAL, Deezer, Qobuz, HDTracks, HighResAudio, Murfie, JUKE, Napster, Slacker Radio, KKBox, Bugs
- Free internet radio: TuneIn Radio, iHeartRadio, Calm Radio, Radio Paradise
- Bluetooth quality: Bluetooth aptX HD wireless built-in
- Bluetooth connectivity: Two-Way (Transmit and Receive)
- Network connectivity: Gigabit Ethernet RJ45, 802.11 b/g/n WiFi
Physical
- Dimensions (WHD): 17 1/8" x 3 15/16" x 16"
- Weight: 22.3 lbs.
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