Mic preamp for dslrs from old camera adapters

 

With the advancement of technology, It’s quite common for perfectly functional equipment to become obsolete, and essentially worthless. As is the case with Standard Definition miniDV cameras. They may work, and the professional ones like the Panasonic AG-DVC30 still look the part, but they have been left behind in history.

Attached to the top of most DVC30’s is a unit with the model number AG Mya30g. Just what is the AG Mya30g? Well it is an audio pre-amplifier, allowing the operator to connect professional XLR microphones to the camera, and to allow control over those Mics. It can supply phantom power to two XLR microphones, and provides you with a range of settings for the audio.

Here you can see all the controls over the audio you get with the preamp, and they are all useable with this easy mod.

These features include:

Mic / Line switching – Line level is useful if you wish to feed the camera with a line level output from a mixer. Mic level is obviously for microphones. The original article I’ve used for reference says that this is the input gain of the interface.

Attenuation switch – Useful for cutting the level from a microphone that is outputting a high audio signal that is clipping at the input. This can happen when recording loud noises, or using very sensitive microphones.

+48v – This switch activates the Phantom Power to the unit. Many microphones require phantom power, and this allows you to activate this power.

CH Select – This switch decides the routing of the microphones. It can be a little confusing, but CH1-2 patches the audio from XLR input 2 through to both output 1 and 2. This is usually used to send the onboard shotgun mic to both channels of the camera. The CH2 option patches XLR input 1 to one output, and Input 2 to the other output. This is the option to use when you want to use 2 different microphones, for example, the shotgun mic, and a lapel microphone.

Output volume knobs – Embedded in one end are two little dials, that allow you to adjust the output level of the module.

Now, you can see there are a lot of features here that are missing from modern stills first DSLRs and Mirrorless cameras.

I had a thought when I came across some of these cameras, what if someone was to figure out how to utilise this old but still valid technology, to allow it to be used with modern cameras?

Well, as it turns out, I wasn’t the first person to have this idea. I came across the blog at monterdiy.net

http://www.monterdiy.net/adapter-panasonic-ag-mya30g-jako-mobilny-przedwzmacniacz/

It’s written in Polish, but thanks to the magic of Google, you can translate it well enough to get the idea of what is going on.

And He’s done a whole lot of investigation, and got a lot of very useful info, like the fact that the preamp module has it’s own inbuilt power regulator that can accept a voltage from 3.6 – 36vdc.

He has even posted the pinout of the connector that is wired to the terminal block is also shown.

Which makes it really easy to wire things up.

Here is my interpretation of the pinout for the connector.

 

You could wire everything to the existing cable, and not even open the box (that’s what I did to test if it would work), but if you want a neater solution, you could do as I did, and slice open the insulation to extract the wires, and connect power and audio to the now much slimmer cables.

Before I got too far into this, I cut the multi pin connector from the cable, and wired iti up to power and half a 3.5mm audio cable.

Choosing how to power the unit was one of my first things to decide on.

Thankfully, with such a wide range of voltage input, things are fairly easy. Pick a battery in the voltage range provided, and see how it goes.

In my initial prototyping, I chose to go with 4x AA rechargable batteries.

They give a nominal voltage of 4.8v, providing a decent amount of room for voltage drop as the batteries depleat.

Once I had wired everything up though, I decided to move to a Sony NP-F550 style battery mount. That allows me to use the same batteries that I have for my LED lights. For a battery mounting plate, I used the top off a cheap battery charger. It holds the batteries firmly enough (but not as sturdy as a more expensive locking unit), and you can buy the entire charger for around $5, versus $20+ for a proper battery mount.

The NP-F550 battery fits really well on the unit. You could get away with the even smaller batteries with ease I imagine

For the connection to the camera, I simply cut a 3.5mm audio cable in half, and used one half, wiring it up to the appropriate wires from the unit.

The biggest issue I have with this unit, is that it’s difficult to adjust the gain on the unit on the fly. The gain controls are so small and hidden away. I guess it means that they won’t be bumped, but it’s still a pain.

Once I had everything wired up and working, I needed a way to mount everything to a camera. I came up with a pretty neat, and basic solution.

Here is a shot of the mounting plate with the 1/4 30 to hotshoe adapter attached.

I cut a square of aluminium I had kicking about, and taped a ¼ 20 hole in the middle of it. For long term use, I think the sheet is a little thin, and the thread might pull out, but for this initial testing, it works great. A small cheese plate from Ebay might work better, and allow more mounting options.

Into the aluminium base, I screwed a ¼ 20 to hotshoe adapter, allowing the whole unit to slot into the hot / cold shoe of you camera.

Everything is held together with hot glue for now. Hotglue sticks well enough for now, and allows me to change things if I desire later. Epoxy, or working out how to screw the components together would likely yield better, more permanent results, but I like to be able to tweak things in the future, so I’m a little hesitant to cover it in epoxy.

The preamp allows me to really turn down the internal preamps and avoid that Canon microphone hiss.

Testing with both my Canon EOS-M, and EOS-650d has yielded impressive results. I can turn the mic inputs in the cameras right down, and use the preamps in the Panasonic unit. This allows me to minimise the effect of the noisy preamps on the recordings.

So, now you can see, I have a great little microphone preamp that was destined for the scrap heap, but is now very useful again, with features often seen in products worth hundreds of dollars.

There are a few features that I may like to add to the unit in the future if I can figure out a way to do them without too much cost or effort.

A way to monitor the audio would be very helpful. As my cameras don’t have audio out, or permanent onscreen audio display, it can be hard to keep an eye on the audio levels you are recording. Splitting the mic output, and sending it to a headphone amp and/or VU meters would give some ability to monitor audio, even if it is only a rough idea.

Another thing that I may investigate is adding a port to the NPF battery sled, allowing me to run other items from the battery – specifically, my EOS-M, who’s batteries are small and run out quickly. This would be fairly easy to do.

Here we have the neat little unit, ready for use!

And that is about it as far as this build goes. I hope you have found this interesting, and if I have left out any details, let me know, or check out http://www.monterdiy.net/adapter-panasonic-ag-mya30g-jako-mobilny-przedwzmacniacz/ to get further details from the source.

 

 

Rode Videomic me – Featuring me, and a little bit of the mic

For my birthday, my wife bought me a Rode Videomic ME, and I made a short little video about it for YouTube, so here you go:

The Videomic Me is a directional microphone for smartphones, that plugs into the headset port on most smartphones.

The port has a mic input, for hands free headphones, like the ones that would have came with your phone. Conveniently, people worked out a while ago that you can plug other mics into the headset port, and get better audio from your smartphone.

Boya BY-V01 stereo on camera microphone

Today, I’m looking at the microphone is the BOYA BY-V01 Stereo X/Y Mini Condenser Microphone.

This cheap stereo microphone is available on eBay and other locations, for about $30 Australian. I bought it wanting something cheap and low profile to sit on my camera most of the time, so I can get better sounding audio when I’m shooting, and I don’t want the bulk and clutter of the Rode Videomic.

From the outside, it looks OK. It’s a nice size, doesn’t stick out too far, and seems reasonably built.

The mic in place on my Canon 650d

The mic in place on my Canon 650d

But fairly quickly, you’ll establish that while it does work, it does have some fairly hard to ignore issues. I was hoping, being an externally powered microphone, it would a reasonable level of gain on the output of the mic, but it appears that there isn’t a whole lot of additional amplification given to the recording level.

This isn’t ideal for most DSLR cameras with microphone inputs. They are often build with budget preamps if they are luck enough to have mic inputs at all. The high noise recordings aren’t the greatest. Usually, the best thing to do is to have a microphone that has a strong output, or run an external mixer or preamp so you can turn down the inputs on the camera.

But that’s not the big issue on this microphone.

The sound recorded to camera appears to be flipped from what you would expect, With the left channel coming from the right, and vice-versa. That is a fixable issue by either flipping the channels in post, or re wiring the mic, but the point is, you shouldn’t have to do either. Also, to make matters worse, even if you do fix it, the sound image is not properly centered. If a sound is coming directly to the front of the mic, it will appear to come from one side of the mic.

I suspect the source of this problem comes from the fact that this microphone is not actually an X/Y microphone like advertised. If you pull the mic apart (like I did), It is actually appears to be a mid/side microphone.

Being  a mid/side microphone isn’t an issue (apart from the misleading labelling), I am guessing the side capsule is not performing as an accurate figure 8 microphone, and it is biasing one side just a little bit.


Boya microphone array internals

Boya microphone internals

 

My verdict on this microphone is that its probably not worth the $30. I wouldn’t buy it again. If you have a camera with on board microphones (like most, if not all you’d consider mounting this to), You will likely get audio that is as good as, if not better than this microphone. Sure, there might be some purposes that see it being useful, like using it with the little deadcat in windy environments, that would probably yield slightly better results than the internal mic. The sound quality isn’t great, I’d say close to the on camera ones on the 650D, and it has issues with the stereo reproduction. I’d think twice about buying this mic. Save your money. for a little more you can get something a little better from a name brand like Rode, or Tascam. You’ll get much better results there.

SQN 4S Series 3a Field mixer, and Attenuation cables

My new field audio kit

My new field audio kit

Recently, I added a field mixer to my collection of audio gear. I’m looking at getting more into audio production for video, and figured a field mixer was a very handy place to start. When this mixer came up on eBay, it peaked my interest. It was packing quite a bit of extras for a pretty good price. I ummed and Arred, before giving in, and buying it. Along with the mixer the extras included the bag, a break away cable, a pair of Sony headphones that look like they are as old as the mixer, and a few XLR cables. Basically an instant field audio kit. WOOT!

 

Attenuation cables

As you might be able to see in the picture, I have teamed up the mixer with my Zoom H4n, and I’ve been working on the best way to link the two devices.

The easiest way is XLR out of the mixer, into XLR of the Zoom, but due to the Zoom’s limitation of not accepting line level inputs, this connection has to be a mic level one, and I end up having to turn up the Zoom’s preamps quite a bit to get the levels where they should be. This isn’t optimal, as it introduces a lot of noise back into the recording, which is precisely what I’m avoiding by going with a mixer / recorder combo.

Best results I’ve gotten so far is coming out of the mixer line level, and attenuating the levels down until they are at a level the Zoom H4n can handle. I’m still going into the Zoom as a mic signal, but by choosing an appropriate level attenuator,  I can set the Zoom’s input levels much lower than using the mic outputs of the mixer (with the -30db cables, I can set the Zoom’s inputs to 20, instead of the 70 or 80 it’s at coming out mic level)

I messed round trying to find something that worked, scouring the internet for attenuator circuits. There is quite a lot out there that want to teach you how to work out your own values for attenuators, but it was rather difficult to find a straight forward circuit that says “Use X and Y resistors for an attenuation of Z”. Eventually, I found this Proharmonic article, which was nice enough to give some clear figures for attenuators.

 

a -30dB pad schematic

This is my rendition of a U bridge attenuator. For other values, please check out their article, linked above.

 

 

 

Comparison

To get a sense of how it performs, here are a couple of samples:

I hope this has been helpful to people out there. I’m off to record myself talking about nothing for a while, until I can find something more interesting to record.

Cheers,
Matt.

Tascam iM2 stereo microphone review

OK, so the Tascam iM2 is hardly anything new, but I just got my hands on one, so I thought I’d write a quick review

I’m testing this on my 4th generation iPod as that is the newest iDevice I own. I will make it clear that this will NOT work on a iPhone 3gs, as I’ve tried it, and the phone doesn’t detect it.

The tascam iM2 is a stereo microphone, in a Near Coincident microphone pair configuration

It is a 16 bit recorder, not 24 bit like the rode iXY, but it is a fraction of the cost. This doesn’t make it useless. 16 bit is still perfectly usable, you just need to be a little more observant of your recording levels than you would if the same device was 24bit.

 

iPod attached to iM2

iPod attached to iM2

 

Connecting the Tascam iM2 is quite easy, just it into the dock connector, and away you go. The app I’m using is Rode’s Rode Rec app. There was a Tascam one, whoever it didn’t work reliably on my ipod. It would freak out, and require a force close of the app. On going to update the app to try to fix the Tascam app, the appstore notified me that it was no longer avaliable. Rode Rec seems like a better program anyway. It does have its good and bad points, but its the best app out there I could find for this use.

Rode Rec picks the stereo mic up without a problem. The free app restricts you to 44khz which is perfectly usable, however, by updating to the pro version, it unlocks 48khz which is slightly better if your planning to use the recordings in video (The differences should be marginal, however thats technically the best way of doing things)

 

Snap and go

Snap and go

 

Back side of the microphone

Back side of the microphone

 

The main problem with using the iM2 on my iPod is that the headphone port on the iPod is on the same end as the dock connector, meaning there is no way to monitor my recordings. This is a bit of a bummer, but I guess it can be worked around, mostly by “guessing” its recording good audio. A dock connector extender might be useful here, however I don’t have one, so that isn’t tested.

So how does it sound?

I’ve uploaded a very quick comparison between the iM2 and the Zoom H4n to Soundcloud so you can listen for yourself. Its far from scientific, but it gives a clear indication of the performance of the mic.

 

What I found was that surprisingly, the Tascam has a lot less hiss than the inbuilt Zoom mics. Even when adjusting the mics to match closely in signal levels, there is a much more prominent hiss in the Zoom’s tracks.

The Zoom had a slightly better stereo image however, where the Tascam sounded slightly flatter.

 

So is it usable? I think it is. I think it should make a great recorder for impromptu recording sessions, and should be capable of great atmos tracks while tripping around. I’ll be certainly keeping this near by at all times. Which is, coincidently, an advantage of this. Its small enough that I can leave it tucked in my bag, with my ipod, and be ready to go at a moments notice. The biggest issue will be remembering to make sure the ipod’s battery is charged.

 

See the problem?

See the problem?

Stereo Recording with iSK CM-20s in ORTF

I’ve been playing around with Audio recording with my H4n, and a pair of iSK CM-20s I bought reciently from Swamp Industries

I thought the iSK microphones were interesting. There was a bit of talk online about iSK mics, but not much about the CM-20s. From what I read, the iSK microphones were pretty usable, for their price. For $65, I thought I would risk it, and have some fun. I don’t have the ears and experience do drop hundreds (or thousands) of dollars on name brand, quality mics, so these are a good price for me.

My plan for the microphones were to trial some stereo recording, teaming them up with my zoom H4n. So, I’ve been reading a bit around the interwebs on stereo recording techniques

You may say, the zoom already does stereo with its inbuild XY pair. My reading suggests that XY stereo recording doesn’t give the best stereo space in the recording, and I wanted to find out for myself.

After some reading, I decided I would start with a ORTF setup to play with. ORTF sees the microphones set 110 degrees away from each-other, with the capsules spaced 17cm apart.

ORTF mic placement, as shown on the Wikipedia page.

ORTF mic placement, as shown on the Wikipedia page.

In order to get things aligned, I’d need some way of mounting the two microphones. I had a couple of T bars kicking around, but they were too wide for an ORTF setup. One of them I got pretty close by using the center mounting hole, but then I didn’t really have anywhere good to mount it to a tripod or mic stand.

It wasn’t too hard to make a new bar thought, with a piece of aluminium bar cut to length, and some suitable holes drilled and tapped to take the 1/4 20 thread that I’m using

Unfortunately using 1/4 20 thread means I need to add several adapters to get the microphone mounts to screw on, but I was using what I had for the most part, and I had the adapters anyway.

The other issue I had was the fact that when setting the two microphones to the correct angle, and correct distance, the backs of each microphone needed to occupy the same space. To fix this solution, I had add a spacer to raise one of the microphones up about the height of one microphone, so it would then be able to pass over the top of the first microphone.

My iSK microphones, setup in ORTF, on my custom bar

My iSK microphones, setup in ORTF, on my custom bar.

One thing to note, is ensure the microphones are patched the right way around. patching them into a mixer, with the left mic panned right, and the right mic panned left will flip the sound image.

I don’t have any sample audio to post right now, But I’ll post it up here when I get a chance.