DIY-Central.com - Go Create something! - PCB Design, Electronics

I just gutted the guts of a Yamaha PM1000 channel strip. I will try to rack them in a standard 19" rack case. I'll be adding a custom power supply, and the usual XLR/TRS input and output jacks, phase, phantom switch, filter cutoff low-pass, hi-pass, etc...

So far, I'm successful in my testing after ripping and soldering everything together and adding a few modifications (i.e. using simple DPDT switches instead of 3Pole selector switches).

The Yamaha PM1000 are usually called Japanese "Neves" because of a similar approach in design. Just like the Neves, this is all discrete transistor and uses an input transformer and output transformer.

The EQ section is especially sweet because there is not a single IC on this preamp. The EQ section uses inductors and capacitors... totally analog manipulation and shaping of your frequency. (circa 1974)

I've tested them on drums and vocals and they really make the sound FAT. The EQ section shapes your sound anywhere from slight barely noticeable to extreme gain/reduction. Bass frequencies are solid. Of course, being an analog EQ, it is not as precise in shaping the sound as IC chip Equalizers. But the curve is smoother I would think.

This is what a PM1000 mixer looks like (circa 1975). Note, I did not use my fully operational 16 channel vintage mixer for this project. I have a few (8) spare PM1000 modules I got from eBay. I also have 2 master strips.

On a previous post, I posted a schematic of a passive direct box using Jensen Transformers.

I have a ROLLS DB25 passive direct box in my studio so I decided to open it up to see it's "guts".

The ROLLS DB25 is an inexpensive direct box using all passive components. That's right, no need for a 9V battery or wall wart to use this thing. Plus, it's got a transformer inside that takes care of converting from an unbalanced Hi-Z connection (from a guitar) to a balanced Lo-Z connection for connection to your mixer or preamp via XLR jacks.

In addition, it has a -20dB and -40dB pad, and a ground lift switch for "stubborn hum" reduction.

I've seen the new Zoom H4 Handy Recorder. I think it's a neat little thing! And best of all, it's "cheap" at $299. Of course, "cheap" is a relative word, but compared to other gear out there, this seems to be one of the low priced new entry. It looks good too!

While reading the H4 specs, this caught my eye... "The H4 features 2 studio-quality electret condenser microphones configured in an X/Y pattern for true stereo recording."  The keyword here is "electret microphone." And the picture seems to confirm that it's really just an electret mic.

So I'm thinking, maybe I can DIY my own stereo mic.

I've used an electret microphone on a non-audio project. I made a sound-triggered flash sync for my Canon EOS30D camera. In this case, I just used the audio output from the mic to trigger an SCR, which then triggered the camera flash.

Can we used the same electret mic to create a good enough sounding stereo mic? I think we can.

So I begin adapting my sound-triggered flash sync and while doing some Googling around, I came across this product.
Stereo Super Ear Amplifier Kit

It's a kit made by Velleman and it uses 2 electret mics, and a headphone output jack. Hmmmm.... interesting. So I ordered a kit (hey, it's less than $10 so if it didn't work, it's not too much of a loss). You can use the link above to order your own kit.

The circuit is simple... the Left and Right channel is the same, so the operation of the circuit is identical. Basically, an electret condenser microphone is biased for operation using a single resistor and capacitor. The output of the microphone goes to a potentiometer which acts as the volume control. This is then amplified by the NE5532 opamp, which is then routed to a headphone jack. Since the whole circuit operates from a single supply voltage (4.5Volts), the opamp uses a virtual ground by the use of 2 resistors in it's input pin. This of course, means that each leg of the split power supply will be only Vcc/2, where Vcc=4.5Volts.

I built this kit in less than an hour... while watching TV. And construction isn't hard and it's very simple. So if you're ready to jump into this Electronics hobby and looking for your first audio project, why not try this stereo mic kit? It's only less than $10.

Here are some pics during construction... enjoy.



There are assembly instructions and schematics on the box. Very easy to follow.

It's that time of the year... here are some gift ideas for your home studio.

Furman PL8II Rackmount Power Conditioner with Lights
So you have thousands of dollars in gear and you're plugging it "naked" to your wall outlet or with a $5 Walmart power strip? I recommend you buy this power conditioner that will give you added protection to your gear. All your gear plugs to the back and you have a single switch to turn on all your gear. The lights are very handy too illuminating your rack gear so you can see what you're doing.



Korg MA-30 Metronome
Keeping time is important. And this little device from KORG packs a lot of sophisticated features at a small size. You can do rythms such as triplets and quadruplets with inner beats removed.

Want to have your own electronic drum set but can't afford a Roland set? This guy built his own drum kit using Radio Shack Piezo transducers, some jacks, and a few wires.  Of course, you'd still need the drum machine like a TD-7, but this will save you  hundreds by making your own drum pads.



And the finished drum set...



More information can be found here.

A few years ago, the common wisdom was to "record as hot as you can." By HOT, I don't mean temperature wise. The wisdom at that time was to record your signal (from your guitar, keyboard, mic, etc.) so that the on-screen digital VU meters on your ProTools, Logic, DP, or Sonar is just hitting 0 dB, but not going over. Everybody knows that as soon as the red light turns on, you'll get clipping and digital clipping sounds nasty... like a fingernail scratching on a blackboard. ... The above argument sounds LOGICAL. There was even talk "you must use all of the bits as much as possible, so 0dB must be 1111111111111111 and that's good since we used up all the bits, nothing got wasted."

But something got forgotten along the way by the people who advised you to record close to 0dB in your DAW (Digital Audio Workstation... just a fancy name for a fast computer optimized for audio recording).

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