DR-40 converting built-in mics to line-in

[Satascy]

Hi,
i love my DR-40. One thing would be very fine, if i could use the internal mics for line inputs. That means, switchable. Of course, an additional connector should be built in (warranty is no more a problem), therefore i think of a 3.5 stereo jack-connector with a change over switch. A 20-30 db attuanator in the front-end should do the propper leveling.
This is my idea and project. A circuit of the input section of the DR-40 would be very helpful. Does anybody have it in their stuff?
And i would gladly appreaciate any thoughts and comments.
Thanx alot.
Btw, electronics is not an unknown planet for me...

Satascy

 

[Art Anderson]

I'd be interested in what you come up with. I couldn't find any schematics of any handheld DR series but this video shows someone examining the inside of a DR-05, especially how the mic capsules are physically assembled and grounded Might help you with keeping track of what goes where on a tear down.

 

[GTBecker]

I've added two 1/8" jacks on my DR_44WL. When a plug is inserted, the corresponding X/Y mic is disconnected and external mic-level audio can be supplied. An external attenuator allows line level input.

The mod was difficult. Finding room for the jacks that could be made to fit - requiring modification of the internal steel frame - was a PITA, as was routing the necessary small wiring from the top of the audio board near the mics to the jacks. The jack grounding needed to be isolated from the steel frame, too, or an internal ground loop - an annoying low-level digital buzz - resulted.

Teac/Tascam engineering liked the idea and was impressed that it was possible to squeeze it in, but asked why I didn't simply buy a four-external-channel recorder (the answer was cost). I ultimately removed the mod after waiting for a replacement bottom plastic shell from Tascam support.

I suggest that you do not try this mod.

Tom

 

[Art Anderson]

Super effort there Tom. Thanks for sharing.

Sure, I'd like a hand held from Tascam with 4 external inputs too but there's that higher expense creeping in. I had to draw the line somewhere. I really do like keeping tracks separate until I'm back at my place to use a DAW, so a mixer feeding 4 tracks or more into the DR-40's 2 line ins would be a poor solution for me.

It's the same reason I chose to NOT buy another DLSR camera and got a fixed lens "bridge" camera instead. Just about all the menu features and no temptation to keep buying lenses to address every situation. My needs are not what they used to be anyway.

 

[GTBecker]

I still use the DR-44WL often and carry it almost as often as I had a camera around my neck when I, too, was seriously shooting. At my peak I carried a bag full of lenses, but I've found that I'm most interested in macrophotography these days instead of fisheyes or 500mm long shots, so the camera I carry now is an Olympus TG-860 - superb image, little, waterproof, WiFi, affordable).

While the DR-44WL is great for candid stereo, if I'm inclined to use external mics I usually want to use three or four channels, beyond the capability of the handheld. Instead, I built an ammo box with a Behringer UMC404HD $100 USB interface that feeds my Moto Z phone through USB Audio Recorder Pro, a great Android app that handles four channels easily. Between the DR-44WL and the Behringer box I have six channels (eight if I also use the X/Ys on the handheld as a safety), still easily in the field.

 

[CMichael]

Hi Tom,

that was a nice effort and a clean looking job. I'm considering doing a similar mod myself. I'd like to know why you removed it! If it worked as described why not keep it? Were there unforseen noise issues? Out of curiosity, did you measure the DC Mic voltage to the X/Y mics? Did you keep that DC source or wire the XLR DC to the 3.5mm jacks or disconnect and use external power? And did you happen to determine if the internal (X/Y) mic pres are protected from external 48V DC?

One last thing, do you (or anyone) happen to know if the 1/4" TRS inputs are wired in parallel with the XLRs? In other words, can the TRS inputs accept mic level or are they strictly line level? If not, had you considered that mod?

Thanks,
- Chris

 

[Art Anderson]

On the "one last thing" - those inputs are just combi jacks for convenience of accepting either 3 pin XLR or TRS 1/4 phone plugs. ie. the same circuit path internally. What they accept for a signal isn't affected by the connection, it's affected by the selection of the slide switch on the left side of the unit - Ext In switch > LINE • MIC • MIC + PHANTOM.

That switch choice applies to both jacks. You can't have the left input LINE and the right input MIC + PHANTOM, for example. Also, they are true balanced inputs. Some people have issues connecting sources that don't play nice with balanced inputs, e.g. the Audio Technica ATR3350 lavalier mic.

 

[CMichael]

Thanks, Art. It's a bit unclear from the manual. It sounds like the corresponding TRS and XLR signals of each combo jack are connected together. The switch must just change the input gain between Line and Mic levels. So Mic+Phantom should accept Mic levels and provide phantom on both TRS and XLR.

 

[Art Anderson]

CMichael. You are correct on all counts.
This unit was not designed for casual use or as a do-it-all recorder for hobbyists with cameras and external mics with 1/8" plugs. Those come in far too many flavors of wiring to be certain they are compatible. Sticking with a balanced input is best, whether it's XLR or TRS. Unbalanced 1/4" TS would be second choice and those are fine too.

But it's not friendly to 1/8" stuff made for smartphones, iPhones, etc. that's dual mono, stereo, 4 contact TRRS, etc. The balanced input circuits of the DR-40 will mess those up because it will invert one connection against another, as balanced inputs are supposed to do, and you either get no signal recorded, or noise, or very weak levels.

 

[GTBecker]

I removed the mod because it didn't address particularly well what I really wanted - two additional mic-level, phantom-powered XLRs. The jacks provided two unbalanced ~3.5v electret inputs. After some experience with the mod I concluded the jacks really weren't particularly useful since they always required external adapters to do what I wanted

All of my mics are phantom-powered condensers so I built a four-channel recorder in an ammo box using a Behringer UMC404HD USB interface and a smartphone running USB Audio Recorder Pro, an excellent Android app by eXtream Software Development. Between those two I can do four channels at 192kHz/24bit if I want. Not quite as convenient as the DR-44WL (which remains excellent for candid stereo) but it works well for most of what I do.


The four black XLRs are the inputs, the four-pin XLR is for charging or power out (there's a 12v AGM battery below the interface), two 5-pin XLRs parallel inputs 1 and 2 and supply power to a pair of heated mics to prevent condensation when recording in cool humidity (common here in Florida) and headphone out. This works very well and I usually still use the DR-44WL to record a stereo safety.

 

[CMichael]

Wow, impressive, Tom! I'm in a similar situation with a variety of recording requirements in the field and the need for a very compact setup. That includes the need for anywhere from 2-4 small-to-medium condensers (or large) and 1-2 line inputs. My mod would differ from yours since I'd likely add two pairs of unbalanced 3.5mm mic inputs, one which would switch in place of the internal mics and the other in place of the balanced combo jacks. You said that Tascam send you a replacement panel? Did that include the circuit board and combo jacks or just the plastic? How much was that?

 

[GTBecker]

> ... I'd likely add two pairs of unbalanced 3.5mm mic inputs...

You'll have a hard time finding room for four jacks, Chris. I suggest that you first get the DR-44WL service manual from Tascam and spend some time disassembling and reassembling the recorder so that you become familiar with where you might mount the smallest suitable jacks you can find.

I bought just the bottom plastic cover to replace the one I drilled through. It cost $7.65 plus $6.00 shipping. I don't have any notes on the service manual cost but it was affordable, too. Try sending an email to parts@tascam.com asking for the manual. If that doesn't work you can surely find your way through the support menu on tascam.com.

 

[CMichael]

Hi Tom, I'd only add two 3.5mm jacks, not four. They'd look mechanically identical to yours but would accept an unbalanced stereo pair for the Int mic pre and a pair for Ext Line/Mic. I'm somewhat familiar with the PCB and mechanical arrangement from a teardown video:

Thanks for the tip on the service manual!

 

[Art Anderson]

Just a brief update. I fed "the hunger" and finally got the DR-70D I really would have liked to afford when I got the DR-40. Now I have both models, plus a Zoom H1 - just because it was in a bargain bin, unboxed and missing the battery cover: $20? Are you kidding me? DONE. I also got a 1 year warranty for a few bucks extra. It is handy as an interview recorder. I run a lavalier down the guest's shirt, put the H1 in one of their pockets after hitting RECORD and the LOCK button. It gets synced up to the camcorder after the fact which is my preferred editing mode anyway. It's very convenient, and I wish Tascam would have included USB through put like this dinky H1 has.

Feb 2020 the same retailer had their annual inventory blowout sale and just one location of the 8 locations within two hours's drive, had just 1 of the DR-70D. I was fifth in line at the door and got it for $99 Cdn. I felt like I found a unicorn. Nothing but the unit itself but it is absolutely mint. It comes with a 90 day warranty I can extend to 1 year for a few bucks.

These models are pretty long in the tooth now but the retailers still want 3x that price so I'm really happy. With the firmware updates, a lot of the initial complaints in the dozens of reviews of the DR-70D back around 2015 have been resolved.

My DR-40 is also behaving (it used to shut off suddenly with no warning and lose everything). Plus the firmware updates (none in the last few years) added those extra options on how to set up individual L & R channel levels, etc.