Short answer: the Topping A90 Discrete. It ranks #4 of 19 headphone amplifiers by measured performance, rated 4.8/5, at $599; the Tom Christiansen Audio HPA-1 ranks #10, rated 4.7/5, and costs $749, so there is little reason to consider the other one.
The case for the Topping A90 Discrete: Audio Science Review measured a SINAD of 119 dB, so its noise and distortion are inaudible. Watch for: It is a headphone amp only, so it needs a separate DAC.
The case for the Tom Christiansen Audio HPA-1: Audio Science Review measured a SINAD of 119 dB, so its noise and distortion are inaudible and the amp is effectively transparent. The catch: It costs several times more than the JDS Labs Atom Amp 2, which matches its rating with more than twice the rated power into 32 ohms.
Buy the Topping A90 Discrete. It is rated higher than the Tom Christiansen Audio HPA-1 and costs less, so it is the default pick unless a specific strength of the other one matters more to you.
Still deciding? The full Headphone Amps and DACs rankings cover every ranked option.
Specifications Side By Side
| Topping A90 Discrete | Tom Christiansen Audio HPA-1 | |
|---|---|---|
| Price | $599.00 | $749.00 |
| Ranked | #4 of 19 in Headphone Amplifiers | #10 of 19 in Headphone Amplifiers |
| Device Type | Headphone amp | Headphone amp |
| SINAD | 119 dB (measured by Audio Science Review) | 119 dB (measured by Audio Science Review) |
| Output Power (32 ohms) | 6,700 mW (manufacturer rated, balanced) | 1,200 mW (manufacturer rated) |
| Output Power (300 ohms) | 1,000 mW (manufacturer rated, balanced) | 250 mW (manufacturer rated) |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced | 6.35 mm |
| Balanced Output | Yes (4.4 mm, 4-pin XLR) | No |
| Inputs | RCA, XLR | RCA, XLR |
| Outputs | RCA, XLR (preamp) | - |
| Volume Control | Hardware knob (relay R2R) and remote | Hardware knob (ALPS RK27 potentiometer) |
| Dimensions | 8.7” x 1.8” x 6.3” (222 x 45 x 160 mm) | 5.5” x 2.2” x 8.3” (140 x 55 x 210 mm) |
| Weight | - | 1.9 lbs (850 g) |
Related Amp and DAC Comparisons
More worthwhile head-to-heads for Topping A90 Discrete:
- 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 Violectric HPA V550 PRO
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 Violectric HPA V550 PRO
- Topping A90 Discrete vs Soncoz SGA1
- Topping A90 Discrete vs Little Labs Monotor
- Topping A90 Discrete vs Rupert Neve Designs RNHP
- See all 9 comparisons
Tom Christiansen Audio HPA-1: $749.00 Tom Christiansen Audio eBay
Pros: Audio Science Review measured a SINAD of 119 dB, so its noise and distortion are inaudible and the amp is effectively transparent. A rated 1,200 mW into 32 ohms handles most planar magnetic headphones, with 250 mW into 300 ohms for high impedance dynamic models. It accepts both RCA and XLR inputs and uses a simple ALPS analog volume knob.
Cons: It costs several times more than the JDS Labs Atom Amp 2, which matches its rating with more than twice the rated power into 32 ohms. The only headphone output is a single 6.35 mm jack, so balanced headphone cables are not supported.
Full Tom Christiansen Audio HPA-1 review and specifications →
| Balanced Output | No |
|---|---|
| Device Type | Headphone amp |
| Dimensions | 5.5” x 2.2” x 8.3” (140 x 55 x 210 mm) |
| Headphone Outputs | 6.35 mm |
| Inputs | RCA, XLR |
| Output Power (300 ohms) | 250 mW (manufacturer rated) |
| Output Power (32 ohms) | 1,200 mW (manufacturer rated) |
| SINAD | 119 dB (measured by Audio Science Review) |
| Volume Control | Hardware knob (ALPS RK27 potentiometer) |
| Weight | 1.9 lbs (850 g) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons
- Tom Christiansen Audio HPA-1 vs Violectric HPA V550 PRO
- Tom Christiansen Audio HPA-1 vs Soncoz SGA1
- Tom Christiansen Audio HPA-1 vs SMSL VMV P2
- Tom Christiansen Audio HPA-1 vs Little Labs Monotor
- Tom Christiansen Audio HPA-1 vs Schiit Midgard
- Tom Christiansen Audio HPA-1 vs Rupert Neve Designs RNHP
- Tom Christiansen Audio HPA-1 vs Topping A70 Pro
- Tom Christiansen Audio HPA-1 vs Topping A30 Pro