STAX DA-100M power AMP connection

Hi ,have just purchased a pair of these but cant find a owners manual for them, my question is there are 2 pre amp inputs on each 1,marked DC the other AC ( which has subsonic -10db @7hz) marked below the input. which one do I connect the pre amp to? thanks steve
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which one do I connect the pre amp to? thanks steve

Great Class-A amps BTW very sought after, should run very hot if biased correctly. (you know there a pair for sale for $9K!!

One input is DC coupled (dc) the other is capacitor (ac) coupled. the dc should sound the best because there’s no cap in the signal path.
But the ac will be the safest if your pre or source has a switch on thump and you turn them on after the DA-100 is already on.

But if you are anal and want the best sound you need to adhere to this turn on sequence when using the dc input.
turn on the source first
then the pre
and after say 10sec the DA=100’s

and when turning off
amps first wait 10sec
then the pre
then the source.

Stax DA-100 M, Class-A Monaural Power Amplifiers
Manufacturer: Stax LTD, Japan
Input: 1400 mV (1000 ohms)
Rated power: 100 watts into 8 ohms
THD (1 kHz): 0.008 at 8 ohms
Frequency response: 0 Hz to 500 kHz + 0/-3 dB
Outputs: Speakers: 1 x screw/clips/banana
Power supply: AC 100V, 117V, 220V, 240V
Protection circuits: Thermal: triple protection
Dimensions: 200 x 268 x 433 mm
Weight per piece: 15 kg
"Special features: Class-A power amplifiers with "Super-Shunt" power supply. The full power is in the A-operation reachable. By heat pipe fall ventilators away, the damping factor is greater than 500. High-end monos with advanced sound, stable for all speakers, including electrostatic.
Test in "Stereoplay" 10/1981: Absolute top-class (Reference!)
Selling Price in Germany (pair): 9000,- DM"
Note: Make sure the heat pipes are not leaking.

Cheers George