Corbin

I just got my stereo installed and I went to use my new SMD DD-1 to detect distortion from my head unit but I’m having some issues. (yes I’ve read the manual) so I’m using a 1khz test track off of Apple Music since my head unit doesn’t have a CD player. I have no speaker wire hooked up to my amp just the RCA’s from the head unit . I get a voltage on my multi meter but when I use the SMD DD-1 I can turn the head unit volume all the way up and I get no signal detection light and no distortion light. I also tried messing with the gain control on the amp and still no signal or distortion light. Head unit is set to flat in EQ and all crossovers are set to full range. Tried a 40hz test tone as well and same results. Just a power light and no signal or distortion lights. Head unit puts out 5 volts pre amp voltage. Multi meter shows voltage to all the channels including sub. My last issue is I tried messing with different tones and whatnot for about 30 minutes and sometimes when I turn the SMD on the distortion light is on all the time even when I’m not touching anything with the probes. Then when I turn it off and get it to turn on without acting up it still doesn’t work when trying to detect signal or distortion. Anyone have any insight or advice?