Short answer: the Topping A90 Discrete. It ranks #4 of 19 headphone amplifiers by measured performance, rated 4.8/5, at $599. The Little Labs Monotor ranks #14, rated 3.6/5, at $580, $19 cheaper, a saving that is not big enough to make up the sound-quality gap.
The Topping A90 Discrete is the better-sounding pick. Audio Science Review measured a SINAD of 119 dB, so its noise and distortion are inaudible. The catch: It is a headphone amp only, so it needs a separate DAC.
What the Little Labs Monotor does well: Audio Science Review measured a SINAD of 109 dB, clean for nearly all listening. Watch for: Little Labs doesn’t publish a power figure into 32 ohms, and there are no balanced headphone outputs.
Buy the Topping A90 Discrete. It is rated higher, and the $19 saving on the Little Labs Monotor is not enough to make up the difference.
Still deciding? The full Headphone Amps and DACs rankings cover every ranked option.
Specifications Side By Side
| Topping A90 Discrete | Little Labs Monotor | |
|---|---|---|
| Price | $599.00 | $580.00 |
| Ranked | #4 of 19 in Headphone Amplifiers | #14 of 19 in Headphone Amplifiers |
| Device Type | Headphone amp | Headphone amp |
| SINAD | 119 dB (measured by Audio Science Review) | 109 dB (measured by Audio Science Review) |
| Output Power (32 ohms) | 6,700 mW (manufacturer rated, balanced) | - |
| Output Power (300 ohms) | 1,000 mW (manufacturer rated, balanced) | - |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced | 2 x 6.35 mm, 2 x 3.5 mm |
| Balanced Output | Yes (4.4 mm, 4-pin XLR) | No |
| Inputs | RCA, XLR | XLR/TRS combo, TRS, 3.5 mm aux |
| Outputs | RCA, XLR (preamp) | - |
| Volume Control | Hardware knob (relay R2R) and remote | Stepped attenuator knob |
| Dimensions | 8.7” x 1.8” x 6.3” (222 x 45 x 160 mm) | - |
Related Amp and DAC Comparisons
How Topping A90 Discrete compares with other leading options:
- Topping A30 Pro vs Topping A90 Discrete
- Topping A70 Pro vs Topping A90 Discrete
- Schiit Midgard vs Topping A90 Discrete
- SMSL VMV P2 vs Topping A90 Discrete
- Topping A90 Discrete vs Tom Christiansen Audio HPA-1
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
Topping A90 Discrete: $599.00 Amazon eBay
Pros: Audio Science Review measured a SINAD of 119 dB, so its noise and distortion are inaudible. A rated 6,700 mW into 32 ohms and 1,000 mW into 300 ohms from the balanced outputs is enough for nearly any headphone. It offers 6.35 mm, 4.4 mm and 4-pin XLR outputs, a relay volume control with remote, and RCA and XLR preamp outputs for powered speakers.
Cons: It is a headphone amp only, so it needs a separate DAC. The Topping A50 III rates the same and measures slightly cleaner at 121 dB for far less. The Topping A70 Pro rates the same with more rated power for less.
Full Topping A90 Discrete review and specifications →
| Balanced Output | Yes (4.4 mm, 4-pin XLR) |
|---|---|
| Device Type | Headphone amp |
| Dimensions | 8.7” x 1.8” x 6.3” (222 x 45 x 160 mm) |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced |
| Inputs | RCA, XLR |
| Output Power (300 ohms) | 1,000 mW (manufacturer rated, balanced) |
| Output Power (32 ohms) | 6,700 mW (manufacturer rated, balanced) |
| Outputs | RCA, XLR (preamp) |
| SINAD | 119 dB (measured by Audio Science Review) |
| Volume Control | Hardware knob (relay R2R) and remote |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Topping A90 Discrete vs Schiit Midgard
- Topping A90 Discrete vs Topping A70 Pro
- Topping A90 Discrete vs SMSL VMV P2
- Topping A90 Discrete vs Topping A30 Pro
- Topping A90 Discrete vs Tom Christiansen Audio HPA-1
- Topping A90 Discrete vs Violectric HPA V550 PRO
- Topping A90 Discrete vs Soncoz SGA1
- Topping A90 Discrete vs Rupert Neve Designs RNHP
- See all 9 comparisons
Little Labs Monotor: $580.00 Sweetwater eBay
Pros: Audio Science Review measured a SINAD of 109 dB, clean for nearly all listening. It has two 6.35 mm and two 3.5 mm headphone outputs, XLR/TRS combo, TRS and 3.5 mm inputs, and a stepped attenuator for precise volume matching.
Cons: Little Labs doesn’t publish a power figure into 32 ohms, and there are no balanced headphone outputs. The JDS Labs Atom Amp 2 rates higher, measured cleaner and is rated at 2,650 mW into 32 ohms for far less.
Full Little Labs Monotor review and specifications →
| Balanced Output | No |
|---|---|
| Device Type | Headphone amp |
| Headphone Outputs | 2 x 6.35 mm, 2 x 3.5 mm |
| Inputs | XLR/TRS combo, TRS, 3.5 mm aux |
| SINAD | 109 dB (measured by Audio Science Review) |
| Volume Control | Stepped attenuator knob |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Little Labs Monotor vs Benchmark HPA4
- Little Labs Monotor vs Rupert Neve Designs RNHP
- Little Labs Monotor vs Chord Alto
- Little Labs Monotor vs Soncoz SGA1
- Little Labs Monotor vs Fosi Audio SK01
- Little Labs Monotor vs HeadAmp Gilmore Lite Mk2
- Little Labs Monotor vs Tom Christiansen Audio HPA-1
- Little Labs Monotor vs Topping A70 Pro