Short answer: the Topping A90 Discrete. It ranks #4 of 19 headphone amplifiers by measured performance, rated 4.8/5, at $599; the Violectric HPA V550 PRO ranks #11, rated 4.6/5, and costs $3,599.99, so there is little reason to consider the other one.
Why pick the Topping A90 Discrete: Audio Science Review measured a SINAD of 119 dB, so its noise and distortion are inaudible. The tradeoff: It is a headphone amp only, so it needs a separate DAC.
Why pick the Violectric HPA V550 PRO: Violectric rates it at 4,700 mW into 32 ohms and 1,450 mW into 300 ohms, enough to drive nearly any headphone, and Audio Science Review measured a SINAD of 111 dB, clean for nearly all listening. The tradeoff: The Topping A50 III rates higher and measured cleaner in Audio Science Review’s tests for a small fraction of the price.
Buy the Topping A90 Discrete. It is rated higher than the Violectric HPA V550 PRO and costs less, so only choose the other one for a particular feature it does better.
Want more options? Browse the full Headphone Amps and DACs rankings.
Specifications Side By Side
| Topping A90 Discrete | Violectric HPA V550 PRO | |
|---|---|---|
| Price | $599.00 | $3,599.99 |
| Ranked | #4 of 19 in Headphone Amplifiers | #11 of 19 in Headphone Amplifiers |
| Device Type | Headphone amp | Headphone amp |
| SINAD | 119 dB (measured by Audio Science Review) | 111 dB (measured by Audio Science Review) |
| Output Power (32 ohms) | 6,700 mW (manufacturer rated, balanced) | 4,700 mW (manufacturer rated) |
| Output Power (300 ohms) | 1,000 mW (manufacturer rated, balanced) | 1,450 mW (manufacturer rated) |
| Headphone Outputs | 6.35 mm, 4.4 mm balanced, 4-pin XLR balanced | 6.35 mm, 4-pin XLR balanced, 4.4 mm balanced |
| Balanced Output | Yes (4.4 mm, 4-pin XLR) | Yes (4-pin XLR, 4.4 mm, XLR line out) |
| Inputs | RCA, XLR | 2 x RCA, XLR |
| Outputs | RCA, XLR (preamp) | RCA, XLR |
| Volume Control | Hardware knob (relay R2R) and remote | Hardware knob (256-step relay attenuator, remote) |
| Dimensions | 8.7” x 1.8” x 6.3” (222 x 45 x 160 mm) | 11.4” x 3.1” x 9.8” (290 x 80 x 248 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 Soncoz SGA1
- Topping A90 Discrete vs Little Labs Monotor
- Topping A90 Discrete vs Rupert Neve Designs RNHP
- See all 9 comparisons
Violectric HPA V550 PRO: $3,599.99 Amazon eBay
Pros: Violectric rates it at 4,700 mW into 32 ohms and 1,450 mW into 300 ohms, enough to drive nearly any headphone, and Audio Science Review measured a SINAD of 111 dB, clean for nearly all listening. It offers 6.35 mm, 4-pin XLR and 4.4 mm balanced headphone outputs, RCA and XLR inputs and outputs, and a 256-step relay volume control with a remote.
Cons: The Topping A50 III rates higher and measured cleaner in Audio Science Review’s tests for a small fraction of the price. It is an analog amp only, so you still need a separate DAC.
Full Violectric HPA V550 PRO review and specifications →
| Balanced Output | Yes (4-pin XLR, 4.4 mm, XLR line out) |
|---|---|
| Device Type | Headphone amp |
| Dimensions | 11.4” x 3.1” x 9.8” (290 x 80 x 248 mm) |
| Headphone Outputs | 6.35 mm, 4-pin XLR balanced, 4.4 mm balanced |
| Inputs | 2 x RCA, XLR |
| Output Power (300 ohms) | 1,450 mW (manufacturer rated) |
| Output Power (32 ohms) | 4,700 mW (manufacturer rated) |
| Outputs | RCA, XLR |
| SINAD | 111 dB (measured by Audio Science Review) |
| Volume Control | Hardware knob (256-step relay attenuator, remote) |
- Reviews, Comparisons and Sound Samples
- Head-to-Head Comparisons