The 64 Audio Aspire 1 is 11Ω at 104.0 dB/mW; the 64 Audio Solo is 16Ω at 100.0 dB/mW. This page covers what they ask of an amplifier, not how they sound.
The Solo needs 4.0 dB more than the Aspire 1 to reach the same loudness — 1.0 mW against 0.40 mW.
| Specification | Aspire 1 | Solo |
|---|---|---|
| Impedance | 11 Ω | 16 Ω |
| Sensitivity | 104.0 dB/mW | 100.0 dB/mW |
| Sensitivity (voltage) | 123.6 dB/V | 118.0 dB/V |
| Power for 100 dB | 0.40 mW | 1.0 mW |
| Voltage for 100 dB | 66 mV | 0.13 V |
| Current for 100 dB | 6.0 mA | 7.9 mA |
| Highest source impedance that leaves them alone (one-eighth rule) | 1.38 Ω | 2.00 Ω |
| Sources that reach 100 dB out of 280 | 280 | 280 |
Every source in the database that drives one of them drives the other. On power, the choice between these two changes nothing about what amplifier you need.
8 sources are low enough in output impedance for the Solo under the one-eighth rule but not for the Aspire 1 (FiiO KA13, Schiit Vali 2+, Astell&Kern HC3, 5 more).
4 sources stay below the audible-hiss threshold with the Solo but cross it with the Aspire 1 (FiiO BTR11, FiiO K11 R2R, Lake People G111 Mk II, 1 more).
280 of the 280 sources here reach 100 dB on both.
The Solo is more demanding than 40% of the 567 non-electrostatic models in this database; the Aspire 1 than 20%.
| dB SPL | Aspire 1 power | Aspire 1 voltage | Solo power | Solo voltage |
|---|---|---|---|---|
| 80 | 4.0 µW | 7 mV | 0.01 mW | 13 mV |
| 85 | 0.01 mW | 12 mV | 0.03 mW | 22 mV |
| 90 | 0.04 mW | 21 mV | 0.10 mW | 40 mV |
| 95 | 0.13 mW | 37 mV | 0.32 mW | 71 mV |
| 100 | 0.40 mW | 66 mV | 1.0 mW | 0.13 V |
| 105 | 1.3 mW | 0.12 V | 3.2 mW | 0.22 V |
| Source | Price | Headroom, Aspire 1 | Headroom, Solo | Output impedance | Noise |
|---|---|---|---|---|---|
| JadeAudio JA11 | $20 | 14.1 dB | 11.8 dB | 0.5 Ω | 1.7 µV |
| FiiO KA11 | $29 | 26.3 dB | 23.9 dB | 0.7 Ω | 1.7 µV |
| FiiO BTR13 | $59 | 23.2 dB | 20.8 dB | 0.6 Ω | 1.0 µV |
Of the 280 sources here, 280 reach 100 dB on both. 61 of them also publish an output impedance low enough for both under the one-eighth rule and a noise figure that stays below the audible-hiss threshold with both.
The cheapest of the 61 is the JadeAudio JA11, at $20. It leaves 14.1 dB of headroom on the Aspire 1 and 11.8 dB on the Solo, its output impedance is 0.5 Ω against a one-eighth limit of 1.38 Ω and 2.00 Ω, and its noise figure puts the hiss floor 12 dB and 17 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.
| Model | As printed | Tolerance | Standard |
|---|---|---|---|
| Aspire 1 | 20Hz - 18kHz | not printed | not printed |
| Solo | 20 Hz – 20 kHz | not printed | not printed |
64 Audio prints 20Hz - 18kHz for the Aspire 1 and 20 Hz – 20 kHz for the Solo.
Neither range has a tolerance printed beside it, so a wider range on one sheet is not deeper bass or more treble.
Not a measurement; maker by maker.
Both have a page of their own. In full: 64 Audio Aspire 1 and 64 Audio Solo. Every figure on this page comes from what 64 Audio published, or is derived from it — what that maker publishes, counted.