I have a strange problem with my Tascam DR-40. The device has a single 3.5mm jack for line-out and headphones. While headphones are working well I don’t get a signal when using the same jack to output line-out to my hifi stereo amplifier.
I tried several different cables to verify that it’s not just a broken connection. I also tried to use line-out from a MP3 player into the amp to ensure it’s not the amp.
Finally I used the same line-out to RCA connector and just connected the RCA end of the cable with my headphones 3.5mm jack using some crocodile clamps and got a perfect signal. So, the DR40 seams to be ok, the AMP seams to be ok and also the phones seams to be ok, but still the AMP isn’t recognized by the DR40 if connected to the AMPs line in via line-out.
It seams the DR40 has some circuit to decide whether the line-out/headphone jack is plugged in measuring resistance or something like that on the line. Is that possible? At least it seams it isn’t enough to just mechanically plug in a jack, since while connected to the AMP the DR40 doesn’t switch from the build in speakers to line-out, so it obviously doesn’t notice it is connected.
Update: I also tried another Hifi amplifier and several bluetooth like external boxes. While these simple boomboxes work, the other Hifi amplifier also doesn’t work, so I think it has to do something with impedance or so.