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Old October 20th, 2010, 02:17 PM   #1
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-25db, -35db or -45db

Hi,
I've been doing lots of research but the information coming back has been confusing. I'm trying to connect my Marantz PMD-661 line out to my 5D2 mic input.

I've seen multiple cable solutions to attenuate the line level output from a recorder like the Tascam or the H4n to the 5D2 but its difficult to know which solution to choose.

I've heard that -45db or -50db attenuates too much signal and I'm afraid that the -25db leaves the signal too hot.

Here's the output of the Marantz:

Outputs
LINE
Type: RCA stereo jack
Input Sensitivity: 2.0 V / 10 kohm

I am told that this pro level output. Here's the ouput of the Tascam and the H4n:

standard output level: -10dBV

I hear this consumer level output. I know that -25db works well for the Tascam and the H4n. I'm just not sure how much would be good for the Marantz, -35db or -45db. Any help would be appreciated.

Thanks
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Old October 20th, 2010, 02:31 PM   #2
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Pro line level is +4dBu. Consumer line level is -10dBv. Because the 'dBu' and 'dBv' are slightly different units and the scales have different absolute voltages that represents '0dB', the pro line is actualy about 12dB hotter than the consumer. If you've found a -25 pad works well with a consumer line out and your camera, a -35 pad would be about right for a pro line output.
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Old October 20th, 2010, 02:33 PM   #3
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If all else fails, a variable attenuator would let you pick what you need. I have had good results with this unit from Audio-Technica: Audio-Technica AT8202 In-Line Attenuator AT8202 - B&H Photo
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Old October 20th, 2010, 02:56 PM   #4
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I have that AT8202 as well and it's done me fine. Also there are attenuation cables. Guy used this one going into a Zoom recorder: DVcreators.net | Blog | DVcreators Line to Mic Cable

In this video:
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Old October 20th, 2010, 03:29 PM   #5
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@Steve House - I just wish we had specific specs to know how to convert the cables. -25db is what others have used for the H4N and etc. What is interesting is that the link Chad gave references a cable for the TASCAM that is -50db which seems way too strong for consumer level output

@Battle Vaugn - Thanks. Sound professionals also has a number of variable attenuation cable:

USB Microphone, Stereo Microphone, Preamplifier, Digital Recorder, Custom Cables and more at Rock Bottom Prices from The Sound Professionals - Great deals on Microphone, Preamplifier, Digital Recorder, Cable and more!

It looks like a standard resistor (reminds me of the potentiometer we used to put on lamp cords in shop class back in high school). I'm curious about the quality versus a dedicated cable.

@Chad - Thanks for the link. Dude, has a -50db cable which seems like way too much attenuation. I wonder though if its trying to deal with AGC
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Old October 20th, 2010, 03:37 PM   #6
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If all you need is -20db there is this cable: Core Sound Attenuator Cables

It all depends on your gear specs. For me I have 2 of those AT in-line attenuators, and use -20 for most things - like coming out of a mixing board at a concert. I'll come out of the XLR "Tape Out" on the board, with an RCA to XLR cable, then the attenuator, then an xlr cable going into an R-4 pro. Or if I have a mic in a loud room, and I'm not using a mixer, I'll put the attenuator between the mic and camera's mic input.
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Old October 20th, 2010, 03:46 PM   #7
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Thanks Chad. I think I need -25db minimum, but not sure if I would need -35db or -45db. The Marantz has a stronger output than the H4n or the Tascam. I just don't want to attenuate too much which is why I'm waffling between -35db and -45db.
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Old October 20th, 2010, 03:52 PM   #8
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Get both, and be prepared for any situation. Or just adjust your gain staging to accommodate for too much attenuation.
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Old October 20th, 2010, 04:05 PM   #9
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That's a good point. I am trying not to use the camera to increase the gain I but I think that might be a bit too picky. Being ready for any situation I think is a good suggestion.
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Old October 21st, 2010, 09:28 PM   #10
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As you all know this is very confusing. This is what I ended up with. -30db PAD cable. I think for all intents and purposes -25db might have been better, but I don't mind a bit more attenuation. I always have the option of increasing gain on the 5D2.

I found a local store that could make the cable. What was important to me was that they were willing to try different settings, so let's say the attenuation was too much or too little. They were willing to go back and re-solder new resistors until we got it right.

We started with a -45db pad. Actually -45.9db. The attenuation was way too much. My goal was to have the attenuation setup so that the metering on my Marantz matched that of the 5D2. Obviously on the 5D2 you can set it on manual so I set it on basically one click before 0 gain. The 5D2 is not known to have quiet amplifiers so I figured the hotter the signal the less amplification I would need. Once setup, I could monitor from my Marantz and know that the signal should be properly matched onto the 5D2

With a -45db PAD cable I would have had to increase gain significantly (I'd say about 30 to 40% gain) for the signal to match. The disadvantage is that I'm using the camera's amplifier, but the advantage of this is that let's say I screw up and the cable breaks or is not plugged in properly. The camera on manual would still be able to pick up enough usable signal to be used as a scratch track to match with the recording on the Marantz.

I decided to go with -35db though, as I wanted to reduce how much I depended on the 5d2 amplifier. The technician ended up giving me -30db based on his resistor configuration. The 5D2 is now much closer. To have the two match I now gain 12.5% approx. If I used a -25db, I'm sure I would probably not have to use any gain at all. It's really up to the individual what they're comfortable with. I didn't want to go -25 or -20 because if I had too little attenuation, I don't want to have too hot a signal.

In my research it seems -45db or -50db is good when you have AGC only cameras, but because on the 5D2 we can manually control, personally I think -25db to -35db should all be fine, it just depends on how much you want to depend on the 5D2 amplifier. I won't know until I'm on the field but for now I'm comfortable with -30db PAD.
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