mini plug weirdness

[Derek Reich]

This seem like such a simple thing. Maybe I'm missing something terribly obvious (wouldn't be the first time), but I cannot seem to get a standard mini stereo adapter plug or cable to work on my 7D. I was trying some various ways to defeat the auto gain on one channel as I've read here in the forums, (Canon, are you EVER going to fix this with a firmware update???) but for some reason when I plug in a stereo to 2 channel mono adapter, either I only get audio on the L channel, or it sounds like both channels are canceling each other out. A direct mono plug with mic works fine, as does a stereo plug with only one channel going into it. (doesn't matter which mono input I use... the signal always comes in on the L channel) The camera's mic is recording both channels just fine, as does my Rode shotgun. But if I try to split the two channels and run white noise or any other signal into a splitter, it's either just one signal or both are horribly bleeding into each other. Are the two audio channels not supposed to be discrete? I've tried the 'Lockit Buddy' to run timecode in from another camera (both for TC matching and to have the TC defeat the auto gain) but again, the TC bleeds into the other channel, rendering it useless even for reference as the bleed is so bad trying to use that audio with Plural Eyes won't sync. How the heck do you get two separate audio signals in? I've tried mixers, line level, mic level, you name it. Suggestions?

[Allan Black]

Haven't got a 7D. But it sounds like there could be a phase cancellation somewhere .. in the splitter? Did you make up any of the cables yourself?

Are you sure you're using the correct mini-plug? There's 2.5mm and 3.5mm types.

As brass corrodes, try cleaning the tips with tiny spots of Brasso. If all else fails, take the cam and all the cables to your local cam dealer.

Cheers.

[Bob Willis]

Sounds like you need the cable here:
http://www.sescom.com/Product.asp
to do what you are trying to accomplish. You will also need to download the tone file and run the audio on a player each time into the 7D.

I'm not sure if you are attempting to record audio just to the 7D or to a separate recorder and then sync with Plural Eyes to the 7D audio. If you are just trying to get a sync reference you should not need to use this tone canceling workflow.

[Derek Reich]

Thanks, Bob, Allan-
It is the correct size mini plug, and I tried several different ones all manufactured and not built by me. At first I thought that I might have had a bad connection to the camera, however when plugging in the Rode shotgun, it delivers clean audio on both channels.
One weird thing I noticed when plugging in my Sennheiser shotgun as a test mic, was that when using the splitter, I would get clean audio on EITHER input jack, but BOTH recorded audio only on the 'L' channel. If I plugged another mic into the open jack, then both channels were very dampened and there was a loud hiss on both channels. This happened no matter which of the several different mini adapters I used. It actually would have been simpler if it was a bad jack on my camera, at least then I'd know what to deal with! But since the Rode delivers audio on both channels clean, and the internal mic also delivers clean audio on both channels, I can (hopefully) rule out a malfunctioning jack or a channel out on the camera.
As far as the tone canceling workflow.... I could probably just use the Rode and use Pluraleyes to sync, but it sure would be nice to have the option of 'usable' audio from the camera like the 5D if possible.

[Derek Reich]

anyone else have any ideas on this?
I even tried Canon CPS (3X!) and never got a reply.

[Colin McDonald]

Originally Posted by Derek Reich

Thanks, Bob, Allan-
It is the correct size mini plug, and I tried several different ones all manufactured and not built by me. At first I thought that I might have had a bad connection to the camera, however when plugging in the Rode shotgun, it delivers clean audio on both channels.

So you are saying that it works fine with your Rode shotgun? It might help if we knew which one and what cable you are using eg is it a VM Pro (which has a built in cable with a stereo 3.5 jack)?

[Derek Reich]

Yes, it works fine with the Rode.... clean audio on both channels. It's the Videomic (the first version) with it's integrated mini stereo plug. When I use a stereo mini 'y' adapter, I can get clean audio with my Sennheiser on one channel only (and I tried this with 3 different 'y' adapters and two different mini plug splitters all of which I know work fine) and no matter which side of the 'y' or splitter I run the Sennheiser into, the audio only shows up on the L channel. If I plug in two mics into the splitter, the L channel is severely dampened and a loud hiss is present on both channels.

I think I've ruled out a malfunctioning or bad cable, or a problem with any of the various mics I've used. I also had used a 'Lockit Buddy' in the past to get both clean audio on one channel timecode on the other channel (with auto gain defeated by timecode recording on the other channel). The idea was great in theory, but I could never get clean audio. The timecode always bled into the other channel, and I just figured I was doing something wrong. Now I suspect there is an issue with the mini plug on the camera.... nothing else seems to make sense to me unless someone has an idea I'm missing? I'll probably send the camera in, but hoped to have a chat with CPS first. Much to my surprise, I cannot get a reply out of them whatsoever, which is surprising. I've not needed CPS before, and this is the first time I've attempted to make use of the program, with quite disappointing results.

[Colin McDonald]

Very strange.

How do you define

'y' adapters

and

mini plug splitters

- I mean what's the difference in their function as you understand it (or is one a single solid component and the other a short lead with a plug on one end and two sockets on the other)?

[Derek Reich]

The 'y' adapters are a stereo mini male to a pair of mini mono female cables. (called 'y' adapters because of their appearance) Each mono input goes to one of the stereo inputs on the stereo mini plug with a short cable lead.
This cable adapter is a single unit and manufactured this way. I tried several of these which have been tested as functionally working.

The other adapters are a single 'plug' type unit, again a male stereo plug on one end, and two mono female jacks on the other end. Each female mono jack is assigned to one of the two stereo inputs on the stereo male end. This is a small modular plug (no cables). Again, I used several of these which I confirmed with other equipment to be functioning normally.

What is really throwing me is that when using either of these types of adapters, and I only plug in ONE microphone into either mono input, the audio always shows up on the L channel from the camera. If everything was working normally, I would have expected that one input would direct the audio to the L channel, and the other input would direct audio to the R channel with a stereo jack. This would lead me to suspect that there is a problem with the jack on the camera (since I have already determined that the adapters are working as they are supposed to) except that when I plug in the Rode video mic which uses a stereo mini plug.... everything works perfect. Audio on both L and R channels.
I feel like either a complete idiot (wouldn't be the first time) and missing something very obvious, or there is some very strange issue going on with the camera that I can't identify. It does explain why the time code device I tried to use wasn't working properly either, but doesn't explain what is going on.

[Colin McDonald]

The 'y' adapters are a stereo mini male to a pair of mini mono female cables. (called 'y' adapters because of their appearance) Each mono input goes to one of the stereo inputs on the stereo mini plug with a short cable lead.
This cable adapter is a single unit and manufactured this way. I tried several of these which have been tested as functionally working.

The other adapters are a single 'plug' type unit, again a male stereo plug on one end, and two mono female jacks on the other end. Each female mono jack is assigned to one of the two stereo inputs on the stereo male end. This is a small modular plug (no cables). Again, I used several of these which I confirmed with other equipment to be functioning normally.

Righty ho. I wondered if that was the case. Here's my take on this (hope I am not missing anything obvious):

This setup is likely to cause problems because the minijack plugs on the mics are stereo and the sockets are mono, and the alignment of the connections cannot be guaranteed. Ideally you would need mono (TS) minijacks at the end of the mic cables (and you aren't going to do that surgery are you!) or alternatively you could use a special cable with stereo jack sockets wired like the diagram below.

A simple Y cable that takes a TRS jack plug to 2 x TRS sockets (supplied from many places for using two sets of headphones) may also do the trick but may be more prone to hum and interference as you will be connecting your mics directly together and may even cause cancellation if the mics are different makes/models.

[Derek Reich]

I thought of that, and made sure that the connections to each side of either the 'Y' cable adapter or the mini-splitter were mono jacks since the inputs of both the 'Y' adapter cable and the splitter are mono each to make up the two channel (stereo) signal.
Plus, it doesn't explain why when using only one input on either the 'Y' cable or the splitter, that the audio would only show up on the L channel in the camera (regardless of which input is used)
Am I making sense with this? It's really making me a little nuts....