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Author Topic: hissy sound with mixpre-d going into dslr  (Read 5444 times)

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Offline lewisfilms

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hissy sound with mixpre-d going into dslr
« on: August 27, 2013, 02:27:33 AM »
I have a countryman b3 lav going into a SD Mixpre D mixer going into a Canon 7D  (using a sound devices xl3 TA3 > 3.5mm cable).

It sounds pretty good on the mixer, but when I play back the file on the dslr, it sounds hissy/noisy.  I have the gain structure set so that the 0dbu tone on the mixer is about -20dbfs or so on the 7D. 

What am I doing wrong?

Also, can you recommend a solid audio recorder to pair with the Mixpre D?  (as well as the best output for interfacing the two)

Thanks!

Offline pdxdanmusic

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Re: hissy sound with mixpre-d going into dslr
« Reply #1 on: August 27, 2013, 08:51:05 AM »
I am not sure what is causing the hissy sound but you can contact Sound Devices for help.
I just bought a MixPre-D to go with my Marantz PMD 661 which does have a s/pdif input. I ordered a AES to s/pdif cable from Digigal to interconnect the two.

Offline DigiGal

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Re: hissy sound with mixpre-d going into dslr
« Reply #2 on: August 27, 2013, 02:58:14 PM »
The MixPre-D's DSLR output is: TA3: unbalanced mic-level output (-36 dBu); pin-2 left, pin-3 right, pin-1 ground, 200 ohm output impedance

If your DSLR has a noisy mic-pre that would certainly explain the hiss.  Perhaps there is an impedance imbalance, not familiar with the Canon 7D.  If you could possibly use a different output at line level or digital to feed your DSLR it would most certainly be better. 
Mics: AKG CK91/CK94/CK98/SE300 D-330BT | DPA 4060 4061 4266 | Neumann TLM 103 | Senn ME66/K6/K6RD MKE2 MD421 MD431 | Shure VP88 SM7B SM63L SM58 Anniversary Cables: Gotham GAC-4/1 Quad w/Neutrik EMC | Gotham GAC-2pair w/AKG MK90/3 connectors | DigiGal AES>S/PDIF cable Preamp: SD MixPre-D Recorders: SD MixPre 6 | Marantz PMD 661 Edit: 2011 27" 3.4GHz Quad i7 iMac High Sierra | 2020 13" MBA Quad i7 Catalina | Wave Editor | xACT | Transmission | FCP X 

Offline Church-Audio

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Re: hissy sound with mixpre-d going into dslr
« Reply #3 on: August 27, 2013, 07:18:42 PM »
I have a countryman b3 lav going into a SD Mixpre D mixer going into a Canon 7D  (using a sound devices xl3 TA3 > 3.5mm cable).

It sounds pretty good on the mixer, but when I play back the file on the dslr, it sounds hissy/noisy.  I have the gain structure set so that the 0dbu tone on the mixer is about -20dbfs or so on the 7D. 

What am I doing wrong?

Also, can you recommend a solid audio recorder to pair with the Mixpre D?  (as well as the best output for interfacing the two)

Thanks!
The problem is that your D7 has AGC that can not be turned off unless they did a firmware update recently. You need a battery box to run your Countryman mic with out any preamping. Try that first or my ca-9200 preamp that has a built in attenuator that allows you to bring the audio down in level to a point where the AGC is not freaking out. Then deal with lower audio levels in post or get the mic closer to the source. This is not an idea camera for good audio YET. Until they release new firmware that allows the AGC to be switched off.

AGC= automatic gain control. It will always aim for a target level. What is happening is you are sending it a weak signal and its trying to preamp the living hell out of it. The problem is that you have a very sensitive MIC level input. This input will overload if you try and send it any more gain from the preamp.. Unless you can attenuate the output and then set the gain on the first stage of the preamp you have now. The other issue is how are you interfacing the B3 with the preamp via a phantom module? It could also be that you have an issue with the B3 or the module using to convert it from phantom to plug in power to drive the B3.
If you just want a good recorder to go from your countryman to your B3 I would recommend A sony D10 OR D50. Go into the Line input from your preamp. Or better yet simply use  a simple battery box or my 9200 preamp * shameless plug * into the line input on your Sony D10 OR D50 or if you dont want to buy my preamp lol going mic in on the sony.

Chris
« Last Edit: August 27, 2013, 07:23:40 PM by Church-Audio »
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Offline DigiGal

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Re: hissy sound with mixpre-d going into dslr
« Reply #4 on: August 27, 2013, 07:35:37 PM »
So the Canon DSLR has got AGC - argh! That's really unfortunate, hope they do come out with a software update that allows it to be turned off, otherwise not very professional of them assuming it's supposed to be a pro camera. Good Luck!
Mics: AKG CK91/CK94/CK98/SE300 D-330BT | DPA 4060 4061 4266 | Neumann TLM 103 | Senn ME66/K6/K6RD MKE2 MD421 MD431 | Shure VP88 SM7B SM63L SM58 Anniversary Cables: Gotham GAC-4/1 Quad w/Neutrik EMC | Gotham GAC-2pair w/AKG MK90/3 connectors | DigiGal AES>S/PDIF cable Preamp: SD MixPre-D Recorders: SD MixPre 6 | Marantz PMD 661 Edit: 2011 27" 3.4GHz Quad i7 iMac High Sierra | 2020 13" MBA Quad i7 Catalina | Wave Editor | xACT | Transmission | FCP X 

Offline lewisfilms

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Re: hissy sound with mixpre-d going into dslr
« Reply #5 on: August 27, 2013, 08:45:26 PM »
Actually the 7D had a firmware update a while ago and now allows for a manual REC Level setting.  That is how I set the 0dbu tone on the mixpre d to be -20dbfs on the camera.  Unless... even with the manual rec level set, AGC is still foiling my sound somehow??  Is that possible?

Offline Church-Audio

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Re: hissy sound with mixpre-d going into dslr
« Reply #6 on: August 27, 2013, 09:19:09 PM »
Actually the 7D had a firmware update a while ago and now allows for a manual REC Level setting.  That is how I set the 0dbu tone on the mixpre d to be -20dbfs on the camera.  Unless... even with the manual rec level set, AGC is still foiling my sound somehow??  Is that possible?
I think this is definitely a gain issue or a mic issue. I would really try to get a battery box that you can connect that mic directly to and plug right into the camera and see how your audio is.
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Offline DigiGal

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Re: hissy sound with mixpre-d going into dslr
« Reply #7 on: August 27, 2013, 09:43:34 PM »
Since this appears to be a Canon DSLR or mic problem not a MixPre-D problem, here are some alternatives... provided you want to keep using the MixPre-D instead of going to a battery box or a ca-9200 preamp as suggested by Church-Audio.

If it's AGC you might want to try a AGC Disable Y-Splitter Cable for Canon 7D & Canon T2i  http://www.markertek.com/Cables/Audio-Cables/DSLR-Audio-Cables/Sescom/DSLR-AGCY.xhtml

If you wanted to try attenuating a line level output from the MixPre-D to the 7D mic input here are some various attenuation cables to pick from http://audio-video-supply.markertek.com/search#w=attenuator%20cable

Have you got another mic that you could try to swap out with your current setup to check if it's a b3 mic problem?  If the mic has a poor S/N ratio it will be noisy.
« Last Edit: August 27, 2013, 10:10:30 PM by DigiGal »
Mics: AKG CK91/CK94/CK98/SE300 D-330BT | DPA 4060 4061 4266 | Neumann TLM 103 | Senn ME66/K6/K6RD MKE2 MD421 MD431 | Shure VP88 SM7B SM63L SM58 Anniversary Cables: Gotham GAC-4/1 Quad w/Neutrik EMC | Gotham GAC-2pair w/AKG MK90/3 connectors | DigiGal AES>S/PDIF cable Preamp: SD MixPre-D Recorders: SD MixPre 6 | Marantz PMD 661 Edit: 2011 27" 3.4GHz Quad i7 iMac High Sierra | 2020 13" MBA Quad i7 Catalina | Wave Editor | xACT | Transmission | FCP X 

Offline pdxdanmusic

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Re: hissy sound with mixpre-d going into dslr
« Reply #8 on: August 27, 2013, 09:51:33 PM »
It might also be connected to the problem he mentioned in this thread.
http://taperssection.com/index.php?topic=164048.msg2054249#msg2054249

Offline Jez

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Re: hissy sound with mixpre-d going into dslr
« Reply #9 on: August 28, 2013, 09:23:42 AM »
I have a Canon 7D, and have been dabbling in video with it recently. As said, the 7D now has had a firmware update which allows disabling AGC. I'm getting quite good sound with nature subjects (at least good enough for my amateur usage) just by running the mics directly into the camera. Yes, the audio sounds bad when played back on the camera, but all is fine when it's been transferred to my computer.

Offline Keithaid

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Re: hissy sound with mixpre-d going into dslr
« Reply #10 on: September 06, 2013, 02:06:15 AM »
I have found the best results for connecting the Mix Pre-D to a DSLR (in my case the D800) was to go from the "Tape Out" jack (not the "Stereo Unbalanced Mic Output" which has a much lower level signal) with a 1/8" male to 1/8" male cable to the Mic In on the camera, while lowering the Mic level on the camera down to "2" or even "1."  You get a hotter signal out of the Mix Pre-D which allows you to almost eliminate hiss (which only starts becoming audible when you raise camera Mic Level above "3" or so) and still capture a high fidelity signal.  Not sure if all this holds true with the 7D, but worth a try if you have ability to control input gain.
The "Tape Out" jack is found directly underneath the "Unbalanced Output" in the Mix Pre-D.  It has the added advantage of accommodating a common, inexpensive type of connector, whereas the "Unbalanced Output" requires a TA3 to 1/8" cable which is harder to find and not so inexpensive.

BTW, the Sound Devices manual for the Mix Pre-D may state that the "Stereo Unbalanced Mic Output" was designed to interface with DSLRs, but that may or may not always be the only--or the best--method.

 

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