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Gear / Technical Help => Ask The Tapers => Topic started by: sml42 on September 27, 2005, 09:08:00 AM
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Last week I was out taping, and at the end of the night during tear down I noticed that one of the mic connections was loose. I was stealthing dpa4060 > mps6030 > jb3. Listening back in the car (headphones) the opening act came out fine, but there was intermittent crackling on the recording of the main act. Okay, live and learn, mental note to self: check connections before each act. I figured I'd be able to patch the good channel over during the dropouts.
And then I transferred the recording, and found something weird... it looked like BOTH channels were partially dropping out. This was very strange and prompted more investigation in front of my hifi. The really strange thing, is, by loosening and wiggling one of the microdot connectors I was not able to reproduce the effect I recorded last week. I get one channel dropping out, as expected. However, I can reproduce a similar effect by loosening the line-in to my jb3... if I pull it out by about 1mm and wiggle it slightly I get the same effect: it sounds like both channels instantly lose a lot of low frequency content.
Here's a sample from my recording last week: http://www.landamore.com/badness.mp3
So, my questions:
1) Is this a known issue with the jb3 line-in? I know there have been reports of the plug not mating correctly, however I was under the impression the symptoms were of just losing one channel completely, and not a loss of low frequency in BOTH channels.
2) Is this recording salvageable, or do I just chalk it down to experience?
3) How to avoid this in the future? Looking at my jb3 now I'm running it in the supplied leather case, it looks like the case has moved slightly obscuring the line-in socket. Hmmm.. maybe I should chop off some of the leather to give better access to the line-in socket..
Comments and insights welcomed!
best regards,
stephen
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It is a known issue - most plugs do not seat correctly in the JB3. The loss of low frequency is a function of the partial insert (you're recording a mono signal made up of L+ and R+). Funny thing is this is an old technique sometimes used to derive a 'surround sound' channel as it is made up of only the difference in sound between left and right. In the old days we used to call it the 'Hafler circuit'.
Unfortunately your recording is shot. Here's how to test your setup and avoid the problem in the future http://ca.geocities.com/dkleined@rogers.com/audio/JB3input/JB3_input_jack.htm
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It is a known issue - most plugs do not seat correctly in the JB3. The loss of low frequency is a function of the partial insert (you're recording a mono signal made up of L+ and R+). Funny thing is this is an old technique sometimes used to derive a 'surround sound' channel as it is made up of only the difference in sound between left and right. In the old days we used to call it the 'Hafler circuit'.
Unfortunately your recording is shot. Here's how to test your setup and avoid the problem in the future http://ca.geocities.com/dkleined@rogers.com/audio/JB3input/JB3_input_jack.htm
The weird thing is, I've made over 100 recordings without hitting this problem. I guess I got lucky. Now that I know about it, I should be able to avoid this in the future...
The more I looked at it, I suspected the leather case. It has definately slipped/moved since I put the jb3 in the case... it wasn't lining up and when I pushed the plug home, it left an imprint in the leather. I've now enlarged the hole in the case... hopefully this + dremel the plastic will fix this problem for good.
+t for the feedback, thank you!
best regards,
stephen
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Stephen - the 'tap test' on that web page above will allow you to confirm if this is the problem or not. Good luck!