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.

 

 

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.

Lecci Pocket Sized DJ mixer

While browsing the pages of thinkgeek I stumbled across this little guy:

the Lecci mixer opened on my desk

The little mixer open on my desk

Incase you hadn’t already guessed, it is a little DJ mixer that runs on 4x AAA battery’s. Branded with Lecci in embossed Letters on top of the lid.

Continue reading

Camcorder Microphone Adapter

This is my latest project. It is a converter box that converts the 3.5mm stereo microphone input on my camcorder, into some common interfaces, Such as XLR, RCA, and dual 3.5 mono plugs.

Specifically, the driving idea was driven by the XLR inputs, and I was contemplating making a simple cable with 2 XLRs, but I decided to go with the jiffy box and extra inputs for flexiblilty

 drawing of the converter

Continue reading

2 Way audio Mixer

So I have an amp, and it has several RCA inputs. My computer is into one input. then when i got myself an XBOX 360, i plugged it into an extra input. Everything worked fine, but then i found i wanted to have the TV on my second monitor of my computer (i have a tuner card in it) or wanted to listen to music at the same time.

My solution was to pull out my Behringer mixer, that has 4x XLR inputs and 4x stereo inputs, and set that up on my desk, and it worked like a charm. The only problems being, the mixer doesn’t have any kind of power switch for it, so it was running constantly, and it has an ultra bright blue LED power light on it, and even though i don’t use the desk so much, i imagine running constantly wouldn’t help its life span much either.

So, off to google it was, and it didn’t take long to come across a scematic for a very simple 2 channel stereo mixer from ePanorama.net. ePanorama is a pretty cool site, with a lot of useful scematics and info that has helped me out in the past.

Here is the scematic from the site.

it can be found at:
http://www.epanorama.net/circuits/linemixer.html

Schematics I used to make the mixer

Schematics I used to make the mixer


This is the unit about 3/4 complete. i didn’t get any early photos, but then again, there isn’t that much to it, Much less, and its jus a pile of parts

This is the mixer half complete

This is the mixer half complete

This is a close up of the 4x 10k resistors, one for each signal. they are fairly neat. the board is a bit bigger then needed, but its already fairly small, so i don’t mind.

A close up of the massive circuit board

A close up of the massive circuit board

And finally, the finished box. Since the photo was taken, i’ve added another couple of labels to the front marking it up as XBOX and COMPUTER. the back wasn’t as neat as i had planned unfortunatly, but its ok, as its on the back anyway.

The completed mixer

The completed mixer

And there you go, one very simple, 2 way stereo mixer. I was so proud when the moment of truth came, i plugged it it, and it worked. i was a little worried it would buzz and cause all kinds of problems, but thus far, no issues have presented themselves, this little bad boy is working like a charm.

Cheers,
Matt