Line-out on tascam dr-680 question

M

Marshall Harrington

Member
I'm going line-out from a Tascam DR-680 to a Blackmagic Cinema Camera. For the purpose of getting this going, I've simply connected one mic into channel 1 which is panned center. The pan output on the 680 is set to maximum on both the channel as well as the mix. The trim is adjusted to stay below clipping. The 680 levels look right and the sound coming out of the headphones from the 680 confirm the levels just as I'd expect.

I connected the DR-680 to the camera via the Laird 1/4" balanced to XLR pigtail, a similar custom made RCA to XLR pigtail, along with a 25' XLR to XLR section in between the two. All were made from the highest components and cables available and assembled by reputable custom cable manufacturers.

The camera is set to line level. Its audio input level adjustment and the headphone level are set to 100%. With all that the sound out of the headphones connected to the Blackmagic is faint. Incidentally I've got an Alphatronics EVF that monitors sound levels. Those meters are moving far less than the meters on the 680.

The outputs specs of the DR-680 are nominal -10 dBV at 200 ohms. Is that just not enough gain to get the job done or am I doing something wrong? I keep rading that I shold be +4 dBU.

I know some of you who either use the DR-680 regularly or have used them in the past have helped me in the past. Wondering what your take is on this. Should I just abandon line levels in the camera and switch to mic which seems very noisy even when I throttle the gain way back from the 680?
 
First, if your feeding a mic level input you will need to attenuate the 680's output.
Second, the DR-680's -10dB unbalanced RCA outputs are unaffected by the internal mixer. The internal mixer only affects the headphone monitor, track 7-8 stereo mix (if enabled) or the S/PDIF digital out. The easiest would be to take the headphone out and feed a mic level input via DI(s)or padded cable(s). Alternately, the RCAs could be fed to an external mixer or summing amp and feed the camera's audio a mono or stereo mix from that. If the external mixer is line level, the same attenuation issue applies.
BTW: If the RCAs are tied together w/o isolation, an impedance issue could be possible.. hence the low output.
I know very little about the Blackmagic camera, hopefully the audio interface is better than the REDs'.
 
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So, if we understand you correctly, you are coming out of the RCA output of the DR-680 into a "custom made" RCA to XLR-M pigtail.
Then you are using a 25-ft ordinary XLR F-M cable, and going into a XLR-F to 1.4-inch male pigtail, into the BMCC audio input.
Presumably your Alphatronics EVF is monitoring the SDI (or HDMI?) output from the BMCC.

How is your "custom made" RCA/XLR cable wired? Does it work OK elsewhere?
Same question for your XLR to 1/4-inch pigtail.
Assuming all your pigtails and cables have been checked OK?
Same result if you eliminate the XLR extension cable?

We don't really know what the audio level specs (mic or line level) are for the BMCC.
Blackmagic Design (like most video equipment makers) only regard audio as an afterthought.
Assuming the cables and pigtails are all wired properly, it seems quite possible that the BMCC
is expecting more signal for "line-level" input than the DR-680's -10dB output level.

It seems possible that you will need to use an attenuator adapter or cable and knock the
DR-680 output down to "mic level" to feed into the BMCC.
 
Richard Crowley said:
So, if we understand you correctly, you are coming out of the RCA output of the DR-680 into a "custom made" RCA to XLR-M pigtail.
Then you are using a 25-ft ordinary XLR F-M cable, and going into a XLR-F to 1.4-inch male pigtail, into the BMCC audio input.
Presumably your Alphatronics EVF is monitoring the SDI (or HDMI?) output from the BMCC.

How is your "custom made" RCA/XLR cable wired? It was patterned after the Laird only RCA to XLR.

Does it work OK elsewhere? Don't know, I just had them made and need to check them. There is sound and it's correctly panned and all, it's just much much quieter. The meters on the EVF move but much less when compared with the meter on the 680.

Same question for your XLR to 1/4-inch pigtail. It's this Laird cable: http://www.bhphotovideo.com/c/product/899693-REG/Laird_Telemedia_BMD_RASPS_XLF_03_2_5_K_Cinema.html

I had a companion cable made from
Assuming all your pigtails and cables have been checked OK?
Same result if you eliminate the XLR extension cable? I'll try this next.

We don't really know what the audio level specs (mic or line level) are for the BMCC.
Blackmagic Design (like most video equipment makers) only regard audio as an afterthought.
Assuming the cables and pigtails are all wired properly, it seems quite possible that the BMCC
is expecting more signal for "line-level" input than the DR-680's -10dB output level. I cannot rule out the cables and will track that line of thought down before heading another way.

It seems possible that you will need to use an attenuator adapter or cable and knock the
DR-680 output down to "mic level" to feed into the BMCC.
Click to expand...

That the BMCC requires quite a lot more gain for the line in looks to be the issue here and it may not be out of line. I spoke with Tascam who were very helpful and interested. Basically they said this unit is a top of the line consumer device that outputs to -10 db. Their entry pro device utilized balanced XLR outputs that output +4 db. That might be end of story.

The 680 makes a fine recording. I was hoping to be able to get a clean enough signal to the camera to skip syncing in all but the more complex shoots. The good news is I'm learning a ton thanks to all the help I get from the various forums and really appreciate that. Problems to be solved with many talented people pitching in.

Thanks.
 
OTOH, there is something to be said for just using the on-camera microphone just for recording sync. Unless you are shooting really long shots where you can't get reliable pickup. Not having to drag around an audio cable from the recorder to the camera can make it much easier for the crew.
 
That's what I have been doing. This was an attempt to get it right with the mix, have a reliable camera recorded track and also have the recorded audio track from the 680 as backup. I know it's a little complicated but once you get used to one thing you get into it's subtlety. In my experience there's no other way to do that then just use it a bunch. And when the situation arises where you need more you are already set to go. At least that's the idea.....
 
If the BMCC's line level mode is +4dB, a -10dB input would be low.. this is a normal occurrence. A matching box would help, but.. more gear. Other than that, it's easier to attenuate the -10dB or HP out down to mic level. I would think you would not want to use the inferior camera audio anyway, when the iso tracks are available and recorded in a far superior audio recording device.
FWIW, The 680's line-in mode does NOT send attenuated audio back though the preamps, which is common with most budget recorders and cameras
 
"FWIW, The 680's line-in mode does NOT send attenuated audio back though the preamps, which is common with most budget recorders and cameras"
So..whether XLR or TRS input at line, switching bypasses internal preamp? Based on schematic?
 
The 680's XLR - 1/4" TRS combo connector is wired in parallel, so either/or will be the same. Mic/Line level is selected via top panel switches. Tracks 1-4 have the combo connector; Tracks 5-6 are 1/4" only, but still mic/line switchable; Tracks 7-8 can be mix tracks or digital input. The preamps are OK, but not stellar, as one would expect at the price point.

-- Not to be confused with the Zoom H4N's XLR - !/4" TRS combo connectors which are wired differently. XLR=mic level only; 1/4 = line level only. (unbalanced consumer level)
 
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