Tascam DR-70D - what do you think?

[beachwood]

I'm wondering if they can be repaired? I bought mine recently from Amazon so I guess I could return it. Unfortunately I have already sold my DR40. They just don't make things like they used to.

 

[ggrantly]

Other than the cost factor, If you really want clean tracks recorded to cam that you intend to use, why not use a mixer instead of a recorder. For most cams with inputs, line-in off a mix-pre or 302 is pretty good. If all you need are reference tracks to synch in post, what does it matter?

Maybe I'm getting in on this late, but I don't understand the objective. You buy a recorder to improve the audio over recording to cam, and then want the recorder to feed the cam. I like to record to cam for basic dialogue recorded from stix, just because it's easier in post and the audio is usually good enough for that purpose. If you're on the hoof or want better audio, and have a recordist, all you really want or need is a reference track.

FWIW, Tascam has done well by me for customer service, but this isn't really something to get too excited about in a dirt cheap recorder.

Grant

 

[DPStewart]

I think it's a matter of options.
There are times when the recorder and recordist will be far from the camera, but there will also be times when using the DR70 essentially as a mixer would be the most convenient workflow with the fewest post steps. That is enough to warrant a little time spent on verifying these outputs I suppose.

Next quickest workflow would be recording to BOTH: using the DR70's recorded audio and simultaneously the same audio recorded into the camera, which will give you the best scratch tracks for quick alignment in post. Using the DR70's slate makes it even easier.

 

[OldCorpse]

My guess is that Tascam didn't put much thought to the design of the 3.5 mm OUT circuitry, expecting that most users were going to focus on the performance of the internal recorder.

Hmm. If that's to say that it's a design issue/defect, then all DR-70D's would have this. In that case my question becomes - how is the 3.5mm OUT on the DR-60D (or DR-60Dmkii), because if Tascam didn't put much thought into the design of the 70D, presumably the same is true of their 60D (and 60Dmkii)... there's no reason to suppose that they gave thought to the design of the 3.5 OUT on the 60D, but not on the 70D, right? In that case checking the 3.5mm on the 60D should be interesting, no? Anyone know how the 60D is in that respect?

 

[jaypass]

OK, my DR70 JUST showed up from UPS five minutes ago.

I also got word from Jared McKenna that a -25db attenuating cable may be the fix.

I have seen this be "it" before.

Yep, he sent me the same message!

I have found a solution to our dr 70d problem! But the moderators here still have yet to "approve" me, since I just signed up yesterday. anyway, the solution is to buy a -25db attenuator cable like from Sescom and simply use that to feed your camera from the line out, instead of a normal 1/8th stereo cable. I just tested it and the hiss is gone! you simply need to run your line out (from the monitor menu) hotter than you had before, of course, to make up for the -25 db. but for some reason, it gets rid of the hiss!! it's great.

I'm sure he'll join the conversation as soon as he gets approved, but for now I'll be looking into getting one of those cables.

 

[beachwood]

Call me old fashioned but I expect something I paid good money for to work as designed and advertised.

 

[DPStewart]

I got B&H sending me a -25db cable for my GH2's.
Here's why I think it will work:

The output of the DR70 is LINE. The inputs of the cameras are MIC.
That obviously means the LINE output of the DR70 is WAY hotter than it needs to be for feeding into a camera.
If you have a good strong signal in your DR70 and you're sending it out to the camera then you are sending WAY too hot a signal and the only way to prevent overloading the camera's MIC input is to lower the gain of the signal you are getting within the DR70 - that's the WRONG WAY to do it. All you do is bury your signal in the operating noise floor of that amp (the DR70's).
Most DSLR's do NOT have enough of a MIC INPUT gain range to deal with this level mismatch correctly.

But if TheDingo set up his test the way I'm going to do mine then I'll get the same results he did.

OK, so this is getting dragged out - but for everyone who's already got a DR70 or those looking to get one - let's get this UTTERLY resolved before we pass judgement on it.

I suppose I can post WAV files of everything too if folks want to stick their faces all the way up in the results.

 

[beachwood]

The DR70 output is switchable between line and mike outputs in the menu. So if I switch it to mike level out way does this not work. Having switch it to line level and spend $30 on an attenuator is not how it was designed to be used.

 

[DPStewart]

The DR70 output is switchable between line and mike outputs in the menu. So if I switch it to mike level out way does this not work. Having switch it to line level and spend $30 on an attenuator is not how it was designed to be used.

I heard from Jared again and he specified that he tried both internal settings; MIC and LINE and that didn't make a difference, but using the attenuating cable and raising the output gain DID fix it.
this makes complete sense if the output amp is laid out internally the way I suspect it is.

For anyone who's ever used a guitar amp it should be pretty clear:
There are at least 2 gain stages to any amplifier circuit, the input to the amp and the output from the amp. (or even a third, as in the case of many guitar amps and processors that use overdrive) It sounds like the DR70 is lowering the input stage to achieve the MIC vs. LINE levels. This leaves the output stage and its noise floor untouched. It also explains why Jared got better results still when he raised the output volume level WHILE its overall mode was still set to LINE.
this is the basics of good gain staging.

I am still going to post all my results to confirm all this, but it's pretty safe to say that the $26 attenuating cable and a strong LINE level output from the DR70 is going to make the difference people are hoping to see from this thing.

 

[beachwood]

So after doing some additional research on line about this issue the attenuator method is the easiest way to get this working. So what would work best -25 or -35 attenuators.

 

[TheDingo]

I am still going to post all my results to confirm all this, but it's pretty safe to say that the $26 attenuating cable and a strong LINE level output from the DR70 is going to make the difference people are hoping to see from this thing.

Can you post a camera recording that has a 1 kHz test tone ( say 5-10 seconds ) at -12 dB followed by 20 seconds of "silence". By "silence" I mean your camera recording with NO mics plugged into the audio chain, so we are getting the lowest audio level recorded by the camera. ( if you plug in mics we will end up measuring the ambient room sound instead of the noise-floor of the audio chain )

I mention this because a -55 dB RMS noise-floor sounds pretty good to the casual listener, but doesn't cut it when you want to process your audio in post.

 

[DPStewart]

Can you post a camera recording that has a 1 kHz test tone ( say 5-10 seconds ) at -12 dB followed by 20 seconds of "silence". By "silence" I mean your camera recording with NO mics plugged into the audio chain, so we are getting the lowest audio level recorded by the camera. ( if you plug in mics we will end up measuring the ambient room sound instead of the noise-floor of the audio chain )

I mention this because a -55 dB RMS noise-floor sounds pretty good to the casual listener, but doesn't cut it when you want to process your audio in post.

Yeah man.
I'll probably generate at least a dozen files of everything in different states.

 

[jeredmckenna]

Ok. Here I am, finally

So, to SUM UP my thoughts on all this, (from my experience)

to *GET RID OF THE LINE OUT HISS FROM TASCAM DR 70D*

*credit goes to Jay Winland, a DP out of Seattle*

Using a -25 attenuation cable on the "line out" of the unit will eliminate the hiss. I'm using a sescom cable from Amazon.

DPStewart mentioned that it's because the amp that is driving the line out is simply set way to hot, period, and the unit seems to not have the ability to "turn down" the line out amp. BUT, the actual audio signal being recording INTO the unit is very clean. So the attenuation cable is our way of turning down that line out amp, so that the clean audio can pass through it nicely into our cameras. My assumption is that tascam meant to allow us to turn down that line out amp level, but it simply can't do it.

 

[beachwood]

I read this on Cheesycam forum
My understanding is the noise is a grounding problem. There was a YouTube reviewer who seems to have taken down the video in which he shared this revelation . The problem was fixed with a galvanic isolator in the line out to camera. Also by moving the recorder away some unknown distance, which of course defeats the purpose of the setup.
Found the isolation transformer at B&H for 65.00$ . it’s called the JK Audio Pureformer. Will test mine this weekend to see if it has same issue.
Perhaps Tascam will end up sending every owner a transformer as a recall fix or at least those who ask. Have a feeling we’ll be hearing a lot more about this.

 

[Noiz2]

Ok. Here I am, finally

So, to SUM UP my thoughts on all this, (from my experience)

to *GET RID OF THE LINE OUT HISS FROM TASCAM DR 70D*

*credit goes to Jay Winland, a DP out of Seattle*

Using a -25 attenuation cable on the "line out" of the unit will eliminate the hiss. I'm using a sescom cable from Amazon.

DPStewart mentioned that it's because the amp that is driving the line out is simply set way to hot, period, and the unit seems to not have the ability to "turn down" the line out amp. BUT, the actual audio signal being recording INTO the unit is very clean. So the attenuation cable is our way of turning down that line out amp, so that the clean audio can pass through it nicely into our cameras. My assumption is that tascam meant to allow us to turn down that line out amp level, but it simply can't do it.

Assuming this actually does work the explanation of why it works makes no sense at all. Though this cable may be fixing the grounding issue mentioned as the problem in the later post?

Just attenuating the signal will attenuate everything, so if it was very clean and hot it will be clean and lower. If it was noisy and hot it will be lower and still just as noisy (proportionately). So if this cable works there is some other reason it works, and that would be useful to know.

 

[OldCorpse]

Assuming this actually does work the explanation of why it works makes no sense at all. Though this cable may be fixing the grounding issue mentioned as the problem in the later post?

Just attenuating the signal will attenuate everything, so if it was very clean and hot it will be clean and lower. If it was noisy and hot it will be lower and still just as noisy (proportionately). So if this cable works there is some other reason it works, and that would be useful to know.

That's what I was thinking - you are attenuating after all, so the noise floor will rise and fall accordingly. If grounding was the issue, then why would a -25dB att. cable work when an ordinary 3.5 one doesn't... it's still a piece of metal making contact. I guess I don't understand the schematics here.

 

[DPStewart]

Assuming this actually does work the explanation of why it works makes no sense at all. Though this cable may be fixing the grounding issue mentioned as the problem in the later post?

Just attenuating the signal will attenuate everything, so if it was very clean and hot it will be clean and lower. If it was noisy and hot it will be lower and still just as noisy (proportionately). So if this cable works there is some other reason it works, and that would be useful to know.

I makes sense "if" the LINE output amp circuit is doing what I suspect it "might" be doing.
Meaning: If the LINE down to MIC level attenuator function inside the DR70 is lowering the audio data volume feeding INTO the output amp but not the final output stage of the output amp circuit - then all it is doing is burying the good signal in that output amp's operating noise. I have seen MANY amp circuits over the years that were designed in such a way that this is a possibility within its functions. That's not always a bad thing - it just means you have to know your gain-staging and control your signal-to-noise ratio yourself. I actually consider this a PLUS in a circuit design....but it makes it much less "fool proof".

Now if the LINE output amp level when it switches from LINE to MIC level is done at THE FINAL possible output stage on the amp circuit, then we will get the exact same signal to noise ratio at both settings and the noise will be "basically" non-fixable.
*However: sending the loudest possible output signal (not distorted) from the DR70 to a camera is generally going to be the cleanest signal the DR70 will produce at all. Lowering THAT signal with an attenuation cable is a completely valid technique provided that cable is of good quality.


** This possible grounding issue also sounds entirely possible to me. Even likely. And an isolation transformer is the first place I would look to solve that.
Whether this particular attenuating cable I've requested from B&H will perform any degree of isolation stands to be seen. I have used line attenuators that also acted as isolators - usually find products like that in P.A. gear and some studio gear.


What I'll be testing:

1. S/N of internal recording with nothing connected to the inputs.
2. S/N of internal recording with a LINE level source connected to the inputs but not actually sending any signal - to check for grounding or impedance effects.
3. S/N of internal recording with a LINE level source connected to the inputs sending a recording of silence - to check for any possible differences - and YES I have seen that happen in the past...
4. Studio recording (Focusrite audio interface) of the output of the DR70's LINE LEVEL output of all 3 above.
5. Studio recording of the output of the DR70's MIC LEVEL output of all 3 above.
6. The above 3 tests recorded over to IN CAMERA on one of my GH2's - Those camera-recorded tracks will then be compared to the tracks recorded both Internally and those recorded through the Focusrite into ProTools.
7. I will probably duplicate test #6 on the GH2 at a couple of different GH2-audio-input-gain settings.

The one big issue this testing won't address is if there is a grounding or impedance issue that is being caused SPECIFICALLY by the GH4's. I don't actually know anyone locally who has one, so I hope the GH2's are a good surrogate.

 

[TheDingo]

Using a -25 attenuation cable on the "line out" of the unit will eliminate the hiss. I'm using a sescom cable from Amazon.

This is something I did not test ( LINE OUT from the DR-70 CAM OUT brought down to MIC level for the GH4 ), but I can check it out later today.

 

[DPStewart]

This is something I did not test ( LINE OUT from the DR-70 CAM OUT brought down to MIC level for the GH4 ), but I can check it out later today.

Hey Dingo,
See my post above yours for why switching the output level inside the DR70 "might" not address the problem.

I'll have some tangible results for folks to scope out soon enough...

 

[TheDingo]

I just finished testing things again using LINE OUT from the DR-70 and my Tascam DR-07 Mk2 is now consistantly showing a noise floor of -72 dB RMS.

I don't have any way of attenuating the 3.5mm LINE out from the DR-70 ( I have a 25 dB Sescom cable but I can't find it right now ), so I have to adjust the DR-70 MONITOR OUTPUT LEVEL down to -38 dB in order to not overload the GH4, and I think this is where the extra noise is being introduced to the signal being fed to the GH4. So there's a good chance a 25 dB Sescom cable might be the fix for this noise problem.

Here's my set-up...

- SD MixPre-D LINE OUT going into channel 1 of the DR-70

- DR-70 INPUT is set to INPUT GAIN: LINE, LIMITER: OFF, LOWCUT: OFF

- DR-70 MONITOR: MONITOR SEL ( doesn't matter how this is set ), OUTPUT LEVEL : -14 dB, OUTPUT GAIN: LINE

- DR-70 level meter shows -12 dB with the 1 kHz test-tone from the MixPre-D

- With my DR-07 Mk2 I am using the MIC input with the recording level set to 10, level meter shows -12 dB