Tascam DR-70D - what do you think?

I doubt if testing the mic inputs unterminated is a valid reading as I seem to recall that when we did acceptance tests on consoles etc that the noise has to be measured using a terminated source, i.e a low impedance load that replicates a mic being plugged into the input.

I wonder if all this talk of noisy inputs is more due to low budget mic's being used with low budget recorders or cameras with low budget mic amps. Also a lot of the time it is the low budget built in headphone amp that is to blame.

I have never had a problem with signal to noise ratio for general TV recording bearing in mind that the average dynamic range of a completed mix should be around 20db and sometimes far less than that.
 
GaryNattrass said:
I doubt if testing the mic inputs unterminated is a valid reading as I seem to recall that when we did acceptance tests on consoles etc that the noise has to be measured using a terminated source, i.e a low impedance load that replicates a mic being plugged into the input.
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This is one reason I use a SD mixer as the audio source for both the 1 kHz test-tone and the audio "silence". I've been testing like this for years and it always produces repeatable results. As soon as you plug in an audio mic you are most likely testing the noise-level from the mic and not the audio chain it's connected to.
 
What's odd with the DR-70 is that the signal from the 3.5mm OUT gets noisier as you lower the OUTPUT level, which is why a 25 dB Sescom cable will produce a better result. With most audio recorders I've worked with the signal gets less noisy when you reduce the amount of gain applied by the preamp.
 
yeah, i don't pretend to know, really, what's going on here. Again, all I know is the -25 attenutation cable solves my hiss issue. But yes, It would be awesome to know why exactly.
 
I guess I missed the switch to Line level when adding the attenuator.

So as ? (it's on the other page, but you know who you are ;~) ***(DPStewart - I looked back!) ) said there is a way that makes sense.

The line out is generally the "normal" out and boxes just stick an attenuator to go down to mic level. IF they do that before the output amp it would alter the S/N ratio. By using the cable and Line out you are keeping the Line out S/N ratio.

The way it could "fix" a grounding issue is that in some attenuating circuits you bleed a bit from hot to ground and don't just stick a resistor in series. IF the cable is doing that it might solve a grounding issue. You could also attenuate with a transformer which would isolate, but I would be VERY surprised if that were happening.

Given the tests I suspect that it is a poor gain staging choice by Tascam in doing the gain change before the out put amp as was brought up by DPStewart.
 
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I heard if you don't match or setup certain settings between GH4 and DR-70D, you will have sync issues in post. Can anyone confirm if the audio and video slip out of sync on long durations? Just trying to avoid doing a 1+ hour long record to test myself if someone else has already done it. Bit rate, MHz, Frame rate, etc. Crossing my fingers it just works.
 
One thing to mention as well I didn't see in the thread is you do not need the -25 db cable. Just change the Output gain from line to CAM.

Setting the output gain

  1. Press the MENU button to open the MENU screen.
  2. Turn the DATA dial to select MONITOR, and press the DATA dial.
    The MONITOR SETTING screen opens.
  3. Turn the DATA dial to select OUTPUT GAIN, and press
    the DATA dial.
  4. Turn the DATA dial to select the OUT or the LINE OUT
    jack, and press the DATA dial.


    1. LINE (default): Set the output gain for output to an external monitoring system (powered monitor speakers or amplifier and speakers)
      CAM: Set the output gain for output to a camera







 
dpavid said:
One thing to mention as well I didn't see in the thread is you do not need the -25 db cable. Just change the Output gain from line to CAM.
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But this produces recordings with the -55 dB noise-floor, where keeping it at LINE OUT and using a 25 dB Sescom cable will give you a noise-floor of -72 dB or better. ( the GH4 maxes out at -70 dB, but an external recorder can go lower. My Tascam DR-07 mk2 shows a noise floor of -72 dB when recording LINE OUT from the DR-70 )

I am wondering if this noise problem could be fixed with a firmware update ?
 
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dpavid said:
I heard if you don't match or setup certain settings between GH4 and DR-70D, you will have sync issues in post.
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Since neither the DR-70 or your GH4 are crystal locked, there is bound to be sync drift between the DR-70 internal recording and the GH4 recording over longer time periods. This is not that big a problem to sort out if you are already used to syncing camera footage with an external recorder.
 
As the Dingo mentioned there is no way to keep those two devices locked. How much actual drift you get is dependant on a lot of things and so hard to predict. But the new generation digital gear is generally pretty stable so if you are lucky you might get an hour with only a frame or two of drift.

This should only come up in a concert type situation since pretty much everywhere else your takes should be considerably shorter and this level of drift wont be a problem on takes under three minutes or so and only maybe a problem up to ten minutes.

I deally you would figure out in post if your sound was running fast or slow and do a one time time shift to correct it. But practically you can also just cut the sound every so often and resync. A drift under 1/4 of a frame or so won't be noticeable.
 
Ok, I ordered another Sescom cable to see if it really does sort things out as I want to be able to have two good audio recordings when I shoot.

Here's the cable that I ordered that attenuates the audio signal by -25 dB : Sescom LN2MIC-ZOOMH4N - Line to Microphone Attenuation Cable : $27

Here's the setup I used for testing...

Sound Devices MixPre-D LINE OUT ---> Tascam DR-70 MIC INPUT 1 ---> TASCAM DR-70 3.5mm LINE OUT ---> Panasonic GH4 Mic input

The DR-70's MIC 1 gain was adjusted until the 1 kHz test tone from the SD MixPre-D was showing a level of -12 dB on the DR-70's display.

The DR-70's 3.5mm LINE OUT was set to -10 dB ( on the DR-70 press the MENU button, then scroll down to MONITOR and press the scroll button to enter the MONITOR SETTING menu, set MONITOR SEL to MIX, set OUTPUT LEVEL to -10 dB, set the OUTPUT GAIN to LINE )

Connect the Sescom cable from the DR-70 3.5mm OUTPUT to the GH-4 MIC input. ( the angled cable end goes into the DR-70 and the straight end goes into the GH4 )

Set your GH4 audio level to -12 dB, and make sure your limiter is OFF for testing. ( I would turn it back on when shooting to be safe )

So after all this set-up I am now getting a noise floor from the GH4 of -70 dB ( which is as good as the GH4 can do ) with the test tone recording right at -12 dB where it should be.

So yes, I can confirm that this Sescom cable solves the DR-70's noisy 3.5mm LINE OUT problem.

...And once again in case anybody missed it, the reason why the DR-70 OUTPUT GAIN is set to LINE instead of CAM ( which stands for CAMERA or MIC level out ) is that the noise-floor of the DR-70 3.5mm audio output rises to -55 dB when set to CAM OUTPUT GAIN. Hopefully this can be fixed down the road with a firmware fix, but for now this Sescom cable is definitely doing the trick.

And one last comment, I tried plugging the Sescom cable into my Tascam DR-07 Mk2 portable recorder and I was able to record a noise-floor of -78 dB RMS by raising the DR-70 OUTPUT GAIN to +12 dB and lowering the DR-07 Mk2 recording gain down to 10. ( with the DR-70 OUTPUT GAIN at -10 like I used for the GH4 I was able to record a noise-floor of -75 dB with the Tascam DR-07 Mk2 recorder with the DR-07 Mk2 recording gain set to 22 )
 
^-- AND THAT'S EXACTLY WHAT WE NEEDED TO KNOW.

Thanks a TON there Dingo.

I've only had my -25db attenuating cable here for 3 days and have not had time to run these same tests yet. But I will within the next 48-hours to compare results. To see if there is any variation from unit to unit.

So, it seems to be what I suspected - the design of the output amplifier. This is not a problem. We have to get a cable to run into the camera anyway, so why not have it be the -25db attenuating cable. It makes for a simple and reliable fix for what was really the only flaw in an otherwise excellent and affordable audio system.
 
It seems tascam has released firmware updates on June 26th. I don't see, in the notes, anything about the line out noise level (that we've fixed with this Sescom attentuation cable). BUT, I'm wondering if anyone has tried the new firmware and if it has had an effect on this problem? I'td be nice to not HAVE to use my Sescom cable all the time.
 
jeredmckenna said:
It seems tascam has released firmware updates on June 26th. I don't see, in the notes, anything about the line out noise level (that we've fixed with this Sescom attentuation cable). BUT, I'm wondering if anyone has tried the new firmware and if it has had an effect on this problem? I'td be nice to not HAVE to use my Sescom cable all the time.
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Well, you have to use SOME cable, right? Just think of it as a "personalized" cable. :Drogar-BigGrin(DBG)

My interest in the new firmware would be to see if they made monitoring of individual channels any easier.
 
I updated the firmware on my DR-70D to version 1.11 ( the latest ) then re-ran the same 3.5mm LINE / MIC output test, and NOTHING has changed. The noise-bug is still there, so you still need to use a 25 or 35 dB pad ( or Sescom cable ) to obtain a decent low noise-floor output from the DR-70D recorder.

I had high hopes that Tascam were listening and might have fixed this bug, but no such luck.
 
TheDingo said:
I updated the firmware on my DR-70D to version 1.11 ( the latest ) then re-ran the same 3.5mm LINE / MIC output test, and NOTHING has changed. The noise-bug is still there, so you still need to use a 25 or 35 dB pad ( or Sescom cable ) to obtain a decent low noise-floor output from the DR-70D recorder.

I had high hopes that Tascam were listening and might have fixed this bug, but no such luck.
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It's a hardware issue.
It's the way they designed the gain-staging into the outputs.
I wouldn't really consider it a bug as much as it is in inflexible way of designing the output amplifier.

We have to use a specific cable in between the two units anyway - a few extra bucks for the attenuating cable totally solves the problem and allows for a really fantastic quality and flexibility from what is, in truth, an extremely affordable audio device.
 
TheDingo said:
+1

It's a great bargoon for what it does.

I haven't tried powering it via USB bus power yet, as I was thinking of using a large phone/tablet external battery to see how it compares with the 4 AA pack.
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Yeah man.

I've bought a few of those just to use as backup phone and tablet chargers and they have been surprisingly good.
I should throw one of them on this thing and run it out to see how much record time I get out of a $17 battery.
I could just velcro it to the side of the recorder!
 
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