Please help with Audio Input Problem

[ELM]

Hello, thanks you for reading this - I hope someone with more experience can help me.

 

I am using the A7ii to record a regular weekly conference. The speakers at this conference talk into microphones which go to an amplifier which plays the sound through speakers. Basic set up. Also videos are always played on a TV monitor, this is also passed through the amplifier, finally music is played through the amplifier.

 

My job is to video the speaker and capture the sound. Simple. The amplifier has banana plug output, so I have this coming to the A7ii and into the red 3.5 audio jack via an adaptor.

 

First off the music played through the system sounds awful. Really bad. The first week I got round this by getting copies of the music and overlaying it in Adobe Premier, I got away with this but was dissatisfied as the audio fidelity sounded much better and drew attention to a certain buzz coming from the main feed.

 

After week two, the people I record for noted a general lack of audio quality (they are happy with the picture) and I have to agree.

 

I found a way to turn down the audio input in camera. It was set at 26 out of 30 and I reduced it to 20, 15, 10 etc but it just dulls the bad quality sound. I stuck some headphones into the green socket in the camera but this just confirmed that bad quality sound was being recorded.

 

So, any suggestions? Is it the amplifier, do I need some kind of post amp regulator, should it be edited later with a audio program?

 

I am a stills photo enthusiast who has been roped into a free gig because someone saw my shiny sony and asked if it record videos. Any suggestion are welcome. Thanks

[trorvik]

My guess is that you are sending "speaker level" signals into the camera which expect a much lower level signal (a microphone level input). Do not do this. It might even damage the sound input of the camera. And even if you turn the recording volume all the way down to 1 the camera input cant handle this signal so the sound will be terrible.

You should get your sound from another output of the amplifier which is suited to the camera input (if there are any). If not you will need a converter which can convert the signal to microphone level.

 

Check out this article for an explanation:

 

http://www.sweetwater.com/sweetcare/articles/whats-the-difference-between-mic-instrument-line-and-speaker-level-signals/

[ELM]

Thanks so much, I do think that is what I am doing, I hope I have not damaged he input of the A7

 

 

My guess is that you are sending "speaker level" signals into the camera...

[ELM]

Hello, I would like to clarify the issue: I have attached a photo of the back of the amplifier that is in use. I am using the 'Line Out' cable into the A7 camera.

 

Can I confirm that this is speaker level volume please?

 

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[trorvik]

That clarifies it. Good that you used this output and not from the speaker outlets at the bottom :-) 

 

This output most likely delivers "line level" signals. Unlike "speaker level" (that is amplified a lot more and at a higher voltage level) my guess is this most likely didnt hurt your cameras sound inputs. But the level of the signal is still too loud for the camera to deal with. The recording will sound awful so dont send line level signals to your camera. It needs a mic level signal. 

 

Line level signals can come in different versions. Typical consumer line level (CD-players etc) -10dBV or professional line level  +4 dBu  (mixers etc.). 

This can be either of the two.  If there is a switch that adjusts the line level output between +4 and -10 than choose -10. But anyway you need to turn the signal into a mic level signal for the camera. There are various ways to do this. The one I think is cheapest is to buy an attenuator cable (a cable that decreses the level of the signal) that goes from line level to mic level. You might need something like this:

 

http://www.ebay.com/itm/Kopul-ACDR-35-Line-to-Mic-Attenuator-Cable-/271355081870?hash=item3f2e05f48e:g:YZQAAOSw3ydVjKsv

 

I cant tell you 100% for sure if this cable will be exact right for your mixers output level. But my guess is that it will bring the level within something your camera can handle. Sound signals are not my biggest strength. I have some common knowledge, but mayby someone else that are better at this might help you find the exact cable for you.

[ELM]

That clarifies it. Good that you used this output and not from the speaker outlets at the bottom :-) 

 

 

 

 

Thank you very much Trovik, your first post and the link you provided pointed me in the right direction. I found out about these attenuator cables in a subsequent search but your new post is also very helpful in reassuring me that I have not blown my A7ii to pieces.

 

I did find suggestions of using kit like this but am not sure if it brings it down to mic level from line level. Bit expensive for what I am doing too so if the attenuator cable works I'll go with that.

 

Thanks again

[tapil523]

 Bit expensive for what I am doing too so if the attenuator cable works I'll go with that.

 

Your using a $3k+ camera but a kit that costs around 10% of what you paid for just the body of the camera alone is too expensive? Poor sound quality makes even 8k (it exists) pictures look amateur

 

Check out the ZOOM HN4 and ZOOM HN2 both can do what that kit can do at 1/3 the price. 

You can us the aux in on the hn2 and record directly to the card, mix it later in your editor. Im sure the sound cards of those mixers are better than the a7rii

 

OTHER THOUGHTS:

Long cheap aux cables make all kinds of noise and pull in static/radio interference im not sure how far away you are from the preout but you could try upping the quality of the cable your using and see how that works.

[trorvik]

From experience (I friend bought one) that particular Tascam recorder he mentioned actually needs an attenuator cable to deliver the best quality sound to at least the GH4. So my guess is the same goes for the a7-cameras as well.

 

The Zoom HN4 is great for the purpose. You can adjust the sound output level from that. But a simple attenuator cable will work (as long as its the right one that puts out the correct level for this camera). Good luck :-)

[Lincoln]

Yes, your problem is sending a line level signal to a camera which only takes mic level. What you need is a line->mic level adapters called pads. Generally come in XLR. The difference is line level (0dB) vs. mic level (-20dB). You signal is too hot to the camera and turning down the record volume on the camera will NOT do the trick.