AIGO EROS Q / AIGO EROS K / IRULU Surfans F20 / AGPTek H3 / HIFI WALKER H2

[speakn2pabst]

That's the part I'm not sure of either. You would be looking for like a dBV or dBu value - I don't know if there is some capability of using a calibration or setting for your specific model of sound card or something like that.

I haven't had any luck coaxing this value out using software.  Is this something that can be measured with a multimeter?  I was thinking of getting one anyway.  If so, what specific capability should I try to include in the meter?

[dconrad]

I haven't had any luck coaxing this value out using software.  Is this something that can be measured with a multimeter?  I was thinking of getting one anyway.  If so, what specific capability should I try to include in the meter?

Yeah I think a multimeter will work - you would use the AC Volts function. I think you would want to use a test file of maybe like 100Hz too - wall voltage is about 60 Hz in most places so that low frequency range what most multimeters are optimized to read. I don't know if they advertise something like "extended AC frequency", but that might be good. I don't know if you're familiar with Vrms measurements but they'll need to be converted to dBV to be comparable to the numbers we already have.

Edit 2: Looks like it's been merged, so just grab the latest build and let me know if everything works as expected!

EDIT: I finally got around to putting together a patch to enable line out - if you want to download it, build it and try it out, it's here: https://gerrit.rockbox.org/r/c/rockbox/+/5087. I tried it out and it's working well on my player, but I would definitely like to hear if it works as intended on yours as well.

[speakn2pabst]

I tried the zip listed on the AIGO Eros Q wiki page within the Native Port area and yes, the Line Out is working on my device with this version.  Great!

I'm still trying to make heads and tails of my multimeter so still need time to report a reading.  I haven't used one before and the closest memory in the ballpark would be using an oscilloscope and signal generator back in a Physics class many moons ago.  But I'm trying to get refreshed and will keep at it.

P.S. - I installed Room EQ Wizard for my distro and this is able to generate test WAV files for different frequencies.  So I have my 100 Hz test file at least.

[speakn2pabst]

OK playing a 100 Hz sine test file I got a reading of -0.4 mV from the Line Out.

I think that converts to -8 dBV but I would suggest checking that.

[dconrad]

I tried the zip listed on the AIGO Eros Q wiki page within the Native Port area and yes, the Line Out is working on my device with this version.  Great!

I'm still trying to make heads and tails of my multimeter so still need time to report a reading.  I haven't used one before and the closest memory in the ballpark would be using an oscilloscope and signal generator back in a Physics class many moons ago.  But I'm trying to get refreshed and will keep at it.

P.S. - I installed Room EQ Wizard for my distro and this is able to generate test WAV files for different frequencies.  So I have my 100 Hz test file at least.

OK playing a 100 Hz sine test file I got a reading of -0.4 mV from the Line Out.

I think that converts to -8 dBV but I would suggest checking that.

Sounds good, I'll update wiki to reflect that we have line out on the new devices now. Thanks so much for testing!

Are you sure you're using the AC Voltage setting on the multimeter? I don't think they typically give a negative reading in that mode (and I don't think a negative rms voltage really makes sense). Also, just to be sure, the file you created is "full scale", or maximum volume? When I did the same thing for my device, I just used Audacity to create a full-scale tone and exported to WAV.

Edit: For reference, I think you'll probably get a voltage reading somewhere around 2 Vrms.

[speakn2pabst]

I did indeed get the negative value from using a DC setting.

I've tried again this time double checking I'm in AC mode with the multimeter and it gives me a 1.11 reading while contacting the left and right channel ends of an aux/headphone cable plugged to the Line Out with the audacity provided 100 Hz WAV playing.

I plugged this into a formula I found online (hopefully correct)

20 x log 10(1.11/1) = dBV = 22.2

Hoping this is the desired reading.   

[dconrad]

I've tried again this time double checking I'm in AC mode with the multimeter and it gives me a 1.11 reading while contacting the left and right channel ends of an aux/headphone cable plugged to the Line Out with the audacity provided 100 Hz WAV playing.

I plugged this into a formula I found online (hopefully correct)

20 x log 10(1.11/1) = dBV = 22.2

Hoping this is the desired reading.   

That makes much more sense, thanks! Though for 1.11 volts I'm getting 0.9 dBV (+2 for "0dB": 2.9 dBV). Significantly less than I was expecting, which is definitely interesting. One last question, what do you have the Volume Limit setting set to?

[speakn2pabst]

Sure, I don't believe I've ever adjusted the Maximum Volume Limit. I found it to be set at -2 db.

[dconrad]

That's quite the surprise result to be sure! I'll update the wiki. Thanks again for testing!