Good point. Very leaky or shorted caps would drag down the signal and probably the phantom power.
To have a truly balanced/differential signal that is NOT ground referenced (a true balanced/differential input should NOT have a problem at all with that) use a smartphone playing an MP3 file, while powered by its own battery and NOT connected to USB o any kind of charger to guarantee it´s truly floating.
Insert a phone plug at headphone out , wire plug ground leg ("sleeve") to XLR pin 3 , Tip (Hot) to XLR pin 2 and plug XLR into Mixer input,Channel 1 ... what happens?
Try it with/without Phantom .... any change?
Compare to mixer channel 2 , any difference?
Note: "in Theory" there "should" be an electrolytic cap, say 4.7uF x 50/63V in series with each of pins 2 and 3, with positi9ve towards XLR, to isolate Phantom voltage from phone out,
BUT since it´s truly floating, no DC voltage differential present, no ground reference.
Phone "ground" is actually "- Audio signal".
Personally for such tests I have a small DIY (what else? 😉 ) 9V battery powered oscillator, connected to pins 2 and 3, but a floating smartphone will do fine.
MP3 test tone: https://www.mediacollege.com/audio/tone/files/1kHz_44100Hz_16bit_30sec.mp3
Set player to "repeat 1" so you have a continuous tone, otherwise it lasts 30 seconds only.
A typical phones out from a smartphone provides about 100-200mV RMS
Yes, it looks like that would be C102 and C107 in the schematic posted, but is that for this mixer? Anyway, they would certainly be in there somewhere for DC blocking.
Could it be bad or dirty contacts on the 1/4" connector where the mic signal is routed thru? Plugging a signal into that might tell you something.
So, I do the same tests I did previously (1-2, 1-3 & 2-3) but with a mic attached? I'll do with the Samson CO2 first (working scenario) and same after with another.
Your getting loads of good suggestions from all angles ... Just take one at a time.
The shure site 1st test seemed fine for voltage.
So now do the 2nd test from the shure site for current?
Then J Fahey is telling you how to make a test lead up to connect a battery powered mobile phone headphone output socket to and XLR cable for you to be able to inject an audio signal:
1) Use a smartphone playing an MP3 file, while powered by its own battery and NOT connected to USB o any kind of charger.
2) Insert a headphone type jackplug plug in the headphone output socket
3) Then find an XLR cable and take the XLR plug off of one end
4) Wire the small headphone jackplug ground leg ("sleeve") to the XLR cable wire that connects to pin 3 ..... then wire the headphone jackplug Tip (Hot) to the XLR cable wire that connects to pin 2 (you now have a test cable that can "inject" signal.
5) Plug the XLR end of the test cable into Mixer input,Channel 1 ... what happens?
6) Try it with/without Phantom .... any change?
7) Compare to mixer channel 2 , any difference?
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USE THESE INSTRUCTIONS THEY ARE CLEARER ... I RAN OUT OF TIME TO EDIT THE PREVIOUS POST ... 🙂
The shure site 1st test seemed fine for voltage.
So now do the 2nd test from the shure site for current?
Then J Fahey is telling you how to make a test lead up to connect a battery powered mobile phone headphone output socket to an XLR cable for you to be able to inject an audio signal:
1) Use a smartphone playing an MP3 file, while powered by its own battery and NOT connected to USB or any kind of charger.
2) Insert a headphone type jackplug into the phone headphone output socket.
3) Then find an XLR cable and take an XLR plug off of one end ... or just open it so you can wire (or solder) to the contacts inside.
4) Wire (or solder) the small (mobile phone end) headphone jackplug ground leg ("sleeve") to the XLR cable wire that connects to pin 3 ..... then wire (or solder) the (mobile phone end) headphone jackplug Tip (Hot) to the XLR cable wire that connects to pin 2 ... (you now have a test cable that can "inject" audio signal).
5) Plug the XLR end of the test cable into Mixer input,Channel 1 and play the linked audio test track ... what happens?
6) Try it with/without Phantom .... any change?
7) Try it in mixer channel 2 , any difference?
Your getting loads of good suggestions from all angles ... Just take one at a time.
The shure site 1st test seemed fine for voltage.
So now do the 2nd test from the shure site for current?
Then J Fahey is telling you how to make a test lead up to connect a battery powered mobile phone headphone output socket to an XLR cable for you to be able to inject an audio signal:
1) Use a smartphone playing an MP3 file, while powered by its own battery and NOT connected to USB or any kind of charger.
2) Insert a headphone type jackplug into the phone headphone output socket.
3) Then find an XLR cable and take an XLR plug off of one end ... or just open it so you can wire (or solder) to the contacts inside.
4) Wire (or solder) the small (mobile phone end) headphone jackplug ground leg ("sleeve") to the XLR cable wire that connects to pin 3 ..... then wire (or solder) the (mobile phone end) headphone jackplug Tip (Hot) to the XLR cable wire that connects to pin 2 ... (you now have a test cable that can "inject" audio signal).
5) Plug the XLR end of the test cable into Mixer input,Channel 1 and play the linked audio test track ... what happens?
6) Try it with/without Phantom .... any change?
7) Try it in mixer channel 2 , any difference?
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Sorry everyone, been out for a long family weekend! Will read all the new post tomorrow! Thanks a lot!!!
Good afternoon everyone, sorry for the way too long delay! Last weeks have been crazy.
Ok, first of all, I can't say enough THANK YOU guys for your time on this. Much appreciated.
@check12 , I've followed the steps you proposed, and here what I have found so far. I've used the Yamaha mixer (which has the problem) and my Zoom F4 (which I use for field recording).
Voltage : Everything is fine on both pins (47v on Yamaha's both pins, 48v on Zoom's both pins)
Current : Everything seems fine on both pins (0.01 amp on Yamaha's both pins, 0.01 amp on Zoom's both pins). My multimeter doesn't go lower...
Now where it gets Interesting. I've connected my phone headphone port as indicated with a mic cable.
Ok, first of all, I can't say enough THANK YOU guys for your time on this. Much appreciated.
@check12 , I've followed the steps you proposed, and here what I have found so far. I've used the Yamaha mixer (which has the problem) and my Zoom F4 (which I use for field recording).
Voltage : Everything is fine on both pins (47v on Yamaha's both pins, 48v on Zoom's both pins)
Current : Everything seems fine on both pins (0.01 amp on Yamaha's both pins, 0.01 amp on Zoom's both pins). My multimeter doesn't go lower...
Now where it gets Interesting. I've connected my phone headphone port as indicated with a mic cable.
- On Channel 2 (working), I get audio signal on both pins 3 and 2
- On Channel 1 (buggy), I only get audio signal on pin 3...
- Using the Headset Microphone TRS input, I get audio signal using either tip or ring (left or right)
well i was taking a look at the the tech bulletin and the block diagram shows that input 1 is routed through the HeadSet input, a switching jack and bad contacts there would result in loss of signal,no?
i'd try some contact cleaner and work that HeadSet input to see if it restores the signal path for the XLR...
after reviewing the thread a bit i feel like a bonehead for just suggesting something already mentioned .....i would open it up, grab a magnifying glass and inspect all the solders on the input connectors to see if any look suspect.
i'd try some contact cleaner and work that HeadSet input to see if it restores the signal path for the XLR...
after reviewing the thread a bit i feel like a bonehead for just suggesting something already mentioned .....i would open it up, grab a magnifying glass and inspect all the solders on the input connectors to see if any look suspect.
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Thank you I'll give this a try and come back to you! Not easy on this one... not much room on that pcb!
Ok, finally it is working fine...
First, I want to thank everyone who tried to help with my poor explanations and lack of knowledge. I was amazed how a remote community could be so quick and open to help! You guys rock!
I did all the tests, inspected both PCB on both sides with magnifier, cleaned everything for a x time with PCB cleaner and brushes...
Still, it was not working.
BUT, today, I plugged a XLR dynamic mic into CH1. Sounds was still lower as usual. Then, with this mic plugged, I added another with a 3.5mm plug into the headset microphone jack input (which normally is supposed to disable the XLR CH1 input). Realized it did not. Both where sending signal.
I know many of you told me to play with the headset mic jack (inserting plugs, cleaning, blowing...). So, once more, I played with it like I did thousands of times... and POP, the XLR CH1 poped back into gear and now sounds perfect, just as through CH2 XLR!
Now I'm scared to touch the freaking headset jack, even though I used it in the past for some lavalier. Guest I'll use my field recording adaptors if ever I need to do do again (XLR + Phantom -> 3.5 bias).
I know @Enzo mentioned early on "I just looked the model up on my dealer support portal, No schematic. Just a service bulletin about canging brands of mini-jacks." Did you mean "changing brands"? If so I wonder if I could just replace that mini-jack for fun 😉 Please let me know Enzo if you have more information from the support portal.
Once again, thanks everyone, been quite an adventure... even though I could have just buy another interface a while ago. It's my curiosity and somehow care for the environment LOL!
Take good care,
David from Quebec, Canada
First, I want to thank everyone who tried to help with my poor explanations and lack of knowledge. I was amazed how a remote community could be so quick and open to help! You guys rock!
I did all the tests, inspected both PCB on both sides with magnifier, cleaned everything for a x time with PCB cleaner and brushes...
Still, it was not working.
BUT, today, I plugged a XLR dynamic mic into CH1. Sounds was still lower as usual. Then, with this mic plugged, I added another with a 3.5mm plug into the headset microphone jack input (which normally is supposed to disable the XLR CH1 input). Realized it did not. Both where sending signal.
I know many of you told me to play with the headset mic jack (inserting plugs, cleaning, blowing...). So, once more, I played with it like I did thousands of times... and POP, the XLR CH1 poped back into gear and now sounds perfect, just as through CH2 XLR!
Now I'm scared to touch the freaking headset jack, even though I used it in the past for some lavalier. Guest I'll use my field recording adaptors if ever I need to do do again (XLR + Phantom -> 3.5 bias).
I know @Enzo mentioned early on "I just looked the model up on my dealer support portal, No schematic. Just a service bulletin about canging brands of mini-jacks." Did you mean "changing brands"? If so I wonder if I could just replace that mini-jack for fun 😉 Please let me know Enzo if you have more information from the support portal.
Once again, thanks everyone, been quite an adventure... even though I could have just buy another interface a while ago. It's my curiosity and somehow care for the environment LOL!
Take good care,
David from Quebec, Canada
Over it sounds like one leg of the balanced input is dead.
As mentioned it could be a simple issue of the normally contacts in the mini mic input jack.
Do the mentioned phantom power check at the input jack, check between pin 1 and 2 and between pin 1 and 3.
That said you mentioned that a dynamic mic show the level issue as well, phantom power is not an issue there.
Try a another audio source to use as a test source and with a break out adapter cable or just a couple bare ends
of wire, ground/ shield plugged into pin 1 and the + audio plugged into pin 2 see if you get and audio and then try pin 3, if you get audio on only one pin or the other that is the issue, maybe the mini mic input jack contacts, possibly
a bad solder connection where the XLR connects to board or a micro mini surface mount component.
You could make up a break out cable for like a phone headphone jack and use just the shield and either the left or right audio.
MAKE SURE THE PHANTOM POWER IS TURNED OFF FOR THAT TEST.
As mentioned it could be a simple issue of the normally contacts in the mini mic input jack.
Do the mentioned phantom power check at the input jack, check between pin 1 and 2 and between pin 1 and 3.
That said you mentioned that a dynamic mic show the level issue as well, phantom power is not an issue there.
Try a another audio source to use as a test source and with a break out adapter cable or just a couple bare ends
of wire, ground/ shield plugged into pin 1 and the + audio plugged into pin 2 see if you get and audio and then try pin 3, if you get audio on only one pin or the other that is the issue, maybe the mini mic input jack contacts, possibly
a bad solder connection where the XLR connects to board or a micro mini surface mount component.
You could make up a break out cable for like a phone headphone jack and use just the shield and either the left or right audio.
MAKE SURE THE PHANTOM POWER IS TURNED OFF FOR THAT TEST.