Short answer: the SPL Phonitor x. It ranks #15 of 43 DAC and headphone amp combos by measured performance, rated 4.6/5, at $3,200. The NAD C 658 ranks #39, rated 2.8/5, at $2,299, $901 cheaper, not enough of a saving to outweigh the sound-quality gap.
The SPL Phonitor x is the better-sounding pick. Audio Science Review measured a SINAD of 111 dB, clean for nearly all listening. Watch for: Its USB, coaxial and optical inputs require an optional DAC module, so digital playback costs extra.
What the NAD C 658 does well: It is a full streaming preamp with Ethernet, Wi-Fi, Bluetooth with aptX HD, two optical and two coaxial inputs, analog RCA inputs and an MM phono stage. The tradeoff: Audio Science Review measured only 90 dB SINAD, so sensitive in-ear monitors may reveal hiss or noise.
Buy the SPL Phonitor x. It is rated higher, and the $901 saving on the NAD C 658 is not enough to make up the difference.
Want more options? Browse the full Headphone Amps and DACs rankings.
Specifications Side By Side
| SPL Phonitor x | NAD C 658 | |
|---|---|---|
| Price | $3,200.00 | $2,299.00 |
| Ranked | #15 of 43 in DAC and Headphone Amp Combos | #39 of 43 in DAC and Headphone Amp Combos |
| Device Type | DAC and headphone amp | DAC and headphone amp |
| SINAD | 111 dB (measured by Audio Science Review) | 90 dB (measured by Audio Science Review) |
| Output Power (32 ohms) | 1,000 mW (manufacturer rated, single-ended 6.35 mm; balanced XLR rated 700 mW) | - |
| Headphone Outputs | 6.35 mm, 4-pin XLR balanced | Headphone jack |
| Balanced Output | Yes (4-pin XLR headphone, XLR line out) | Yes (XLR line out) |
| Inputs | XLR, RCA; USB-B, coaxial, optical with optional DAC768xs module | Ethernet, Wi-Fi, Bluetooth, 2 x optical, 2 x coaxial, 2 x line RCA, MM phono |
| Outputs | XLR, RCA | RCA preamp, XLR preamp, stereo subwoofer |
| DAC Chip | AK4490 (optional DAC768xs module) | ESS Sabre |
| Volume Control | Hardware knob (motorized Alps pot, IR remote learnable) | - |
| Dimensions | 10.9” x 3.9” x 11.8” (278 x 100 x 300 mm) | 17.1” x 3.9” x 15.9” (435 x 100 x 405 mm) |
| Weight | 9.7 lbs (4,400 g) | - |
| Bluetooth Codecs | - | SBC, aptX HD |
| Equalizer | - | Yes (Dirac Live room correction, bass and treble) |
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Prices on this page were last checked October 11, 2026 at 4:59 PM UTC. Product prices and availability are accurate as of that date/time and are subject to change; the price and availability shown on Amazon at the time of purchase will apply to the purchase of this product.
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The Two Amps and DACs In Full
SPL Phonitor x: $3,200.00 Amazon eBay
Pros: Audio Science Review measured a SINAD of 111 dB, clean for nearly all listening. It is rated for 1,000 mW into 32 ohms from the 6.35 mm jack and 700 mW from its 4-pin XLR balanced output, enough for most planar magnetic headphones. It adds XLR and RCA inputs and outputs, a motorized volume knob and a learnable IR remote.
Cons: Its USB, coaxial and optical inputs require an optional DAC module, so digital playback costs extra. It costs far more than the JDS Labs Element IV, which rates higher, measures cleaner and has more rated power.
Full SPL Phonitor x review and specifications →
| Balanced Output | Yes (4-pin XLR headphone, XLR line out) |
|---|---|
| DAC Chip | AK4490 (optional DAC768xs module) |
| Device Type | DAC and headphone amp |
| Dimensions | 10.9” x 3.9” x 11.8” (278 x 100 x 300 mm) |
| Headphone Outputs | 6.35 mm, 4-pin XLR balanced |
| Inputs | XLR, RCA; USB-B, coaxial, optical with optional DAC768xs module |
| Output Power (32 ohms) | 1,000 mW (manufacturer rated, single-ended 6.35 mm; balanced XLR rated 700 mW) |
| Outputs | XLR, RCA |
| SINAD | 111 dB (measured by Audio Science Review) |
| Volume Control | Hardware knob (motorized Alps pot, IR remote learnable) |
| Weight | 9.7 lbs (4,400 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
NAD C 658: $2,299.00 Upscale Audio eBay
Pros: It is a full streaming preamp with Ethernet, Wi-Fi, Bluetooth with aptX HD, two optical and two coaxial inputs, analog RCA inputs and an MM phono stage. Dirac Live room correction, stereo subwoofer outputs and XLR preamp outputs make it a flexible hub for a speaker system.
Cons: Audio Science Review measured only 90 dB SINAD, so sensitive in-ear monitors may reveal hiss or noise. NAD doesn’t publish a 32 ohm power figure for the headphone jack, and the SMSL M10 rates higher for far less.
Full NAD C 658 review and specifications →
| Balanced Output | Yes (XLR line out) |
|---|---|
| Bluetooth Codecs | SBC, aptX HD |
| DAC Chip | ESS Sabre |
| Device Type | DAC and headphone amp |
| Dimensions | 17.1” x 3.9” x 15.9” (435 x 100 x 405 mm) |
| Equalizer | Yes (Dirac Live room correction, bass and treble) |
| Headphone Outputs | Headphone jack |
| Inputs | Ethernet, Wi-Fi, Bluetooth, 2 x optical, 2 x coaxial, 2 x line RCA, MM phono |
| Outputs | RCA preamp, XLR preamp, stereo subwoofer |
| SINAD | 90 dB (measured by Audio Science Review) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons