Reading the A5 specs though, it looks like it has a 14.9v output!?!? I must be reading that wrong. Anyone know if that’s correct? I must be misunderstanding something. That sounds unrealistic.
That is Peak-to-Peak Voltage aka 'effective' voltage (Vpp)! You are thinking of
Vrms which is "average" voltage or "actually seen" voltage in layman's terms.
Fiio A5 Vrms is 5.29V (
see below for more details).
No, the 1.8Vrms is a testing measurement only... after being leveled to 2Vrms for a High Performance Sine Wave @ 1kHz and 2.5Vrms analog input signal. This allows for consistency in testing across multiple devices but it is not always a "full" reflection of the device's capabilities nor the circuit's design considerations especially if "gain modes" are involved. Which in this case is indeed a factor to be considered as this 1.8VRms result was due to the ASR tester using FiiO A5's rather low "Low Gain" mode (which is intended for IEM/High-Sensitivity Headphone use).
I assure you that the A5 can easily output well over 1.8Vrms especially in High Gain mode... I should know I owned one

. Gosh, even my little Meizu HiFi DAC HeadAMP PRO dongle, when "
tricked", will output ~2Vrms with a thrust of 100mW @ 32Ω (13mW @ 300Ω).
I wish that both manufacturers and testers/reviewers would better (more clearly) explain these parameters as it often times can be unintentionally misleading and/or misunderstood (but since both
analog signal source input values and
headphone impedance/sensitivity ratings are all over the board I do admit it is extremely difficult for manufacturers to provide meaningful and consistent parameters that the consumer will experience in real-life).
FiiO A5 Parameters Provided by
@FiiO
Supplied Power: +/-11V
Peak Output Voltage: 14.96Vp-p (Vpp = Peak-to-Peak Voltage)
Max Output Current: 250mA
Output Power @ 32Ω: > 800 mW (> ~5.06Vrms / > ~158mA)
Output Power @ 300Ω: ≥ 150mW (≥ ~6.71Vrms / ≥ ~22mA)
Output Impedance: <0.3Ω
Now FiiO has traditionally always been
very conservative with their given parameters... meaning their products generally output greater numbers when "loaded" than shown on paper.
Here are the RMS values that we get via math:
14.96Vpp / 2 = 7.48Vp
7.48Vp * 0.707 = 5.29Vrms
250mA * 0.707 = 177mA rms
RMS Voltage: 5.29V (probably occurring @ ~30Ω in High Gain)
RMS Output Current: 177mA (probably occurring @ ~30Ω in High Gain)
And this is what we get in actual "real-life" performance (the following are measurements of my A5 in "High Gain" mode taken by a professional audio engineer back in 2017. In regards to the line signal input: apologies, I am unable to read my terrible hand writing nor can I recall the value but it definitely was not something bizarre or out of the ordinary):
Output Impedance = 0.26Ω
Output @ 16Ω = 2.89Vrms 522mW 181mA
Output @ 32Ω = 5.32Vrms 885mW 166mA
Output @ 150Ω = 5.87Vrms 230mW 39mA
Output @ 300Ω = 6.79Vrms 154mW 23mA
If I recall correctly when we tested at 600Ω impedance the output dropped drastically down to less than 1mW, if I am not mistaken, which is simply due to the amp's circuit voltage/current design limitations when driving headphones over 300Ω.
So you can see my FiiO A5 performed slightly better across the board than the given parameters provided by FiiO. All of my FiiO devices (E12A; A5; K3; BTR5) have been like this; performing better than advertised.