KATO vs RAYS: which needs more amplifier?

The Moondrop KATO is 32Ω at 108.1 dB/mW; the Moondrop RAYS is 30Ω at 104.8 dB/mW. This page covers what they ask of an amplifier, not how they sound.

The RAYS needs 3.3 dB more than the KATO to reach the same loudness — 0.33 mW against 0.15 mW.

Side by side

The numbers that decide it

Specification	KATO	RAYS
Impedance	32 Ω	30 Ω
Sensitivity	108.1 dB/mW	104.8 dB/mW
Sensitivity (voltage)	123.0 dB/V	120.0 dB/V
Power for 100 dB	0.15 mW	0.33 mW
Voltage for 100 dB	70 mV	100 mV
Current for 100 dB	2.2 mA	3.3 mA
Highest source impedance that leaves them alone (one-eighth rule)	4.00 Ω	3.75 Ω
Sources that reach 100 dB out of 280	280	280

What separates them

Where the two part company

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.

3 sources stay below the audible-hiss threshold with the RAYS but cross it with the KATO (FiiO BTR11, FiiO K11 R2R, Rupert Neve RNHP).

280 of the 280 sources here reach 100 dB on both.

At the level you actually listen at

What each one needs from 80 to 105 dB

The RAYS is more demanding than 31% of the 567 non-electrostatic models in this database; the KATO than 21%.

dB SPL	KATO power	KATO voltage	RAYS power	RAYS voltage
80	1.5 µW	7 mV	3.3 µW	10 mV
85	4.9 µW	13 mV	0.01 mW	18 mV
90	0.02 mW	22 mV	0.03 mW	32 mV
95	0.05 mW	40 mV	0.10 mW	56 mV
100	0.15 mW	70 mV	0.33 mW	100 mV
105	0.49 mW	0.13 V	1.0 mW	0.18 V

What drives both

The cheapest source that satisfies both

Source	Price	Headroom, KATO	Headroom, RAYS	Output impedance	Noise
JadeAudio JA11	$20	22.9 dB	19.3 dB	0.5 Ω	1.7 µV
FiiO KA11	$29	31.1 dB	27.9 dB	0.7 Ω	1.7 µV
FiiO BTR13	$59	28.1 dB	24.8 dB	0.6 Ω	1.0 µV

Of the 280 sources here, 280 reach 100 dB on both. 66 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 66 is the JadeAudio JA11, at $20. It leaves 22.9 dB of headroom on the KATO and 19.3 dB on the RAYS, its output impedance is 0.5 Ω against a one-eighth limit of 4.00 Ω and 3.75 Ω, and its noise figure puts the hiss floor 12 dB and 15 dB below the 20 dB SPL this site treats as the point where a quiet room stops hiding it.

Try any other source.

Frequency response

What each sheet prints, and what it is worth

Model	As printed	Tolerance	Standard
KATO	10Hz-45kHz (IEC61094, Free Field)	not printed	IEC61094 (free field)
	20Hz-20kHz (IEC60318-4, -3dB)	-3 dB	IEC60318-4
RAYS	7Hz–39kHz	not printed	not printed
	20Hz–20kHz (IEC60318-4, -3dB)	-3 dB	IEC60318-4

Moondrop prints two ranges, “10Hz-45kHz (IEC61094, Free Field)” and “20Hz-20kHz (IEC60318-4, -3dB)”, for the KATO and two ranges, “7Hz–39kHz” and “20Hz–20kHz (IEC60318-4, -3dB)”, for the RAYS.

Both sheets print a tolerance, which is rare enough to be worth pointing at: only 58 of the 490 models with a printed range do. These two ranges can be set against each other, because each of them says how far down the response is allowed to be at the ends.

Not a measurement; maker by maker.

Both pages in full

Both have a page of their own. In full: Moondrop KATO and Moondrop RAYS. Every figure on this page comes from what Moondrop published, or is derived from it — what that maker publishes, counted.