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

It's done... some pictures.  Using my custom PCB for the power supply, and an MCI output transformer on the outputs to convert it to balanced outs.

It works... sounds nice and clean!  The EQ lets you sculpt the sound nicely. No hum, no noise. It's great!

I designed a new PSU for people who'd like to rack those Yamaha PM1000 channel strips.

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.

So if you're racking a PM1000 strip you bought from eBay, this PSU will be perfect for you. Output is +44VDC and +48VDC for the Phantom Power.

I'm having prototypes built. If you're interested, email me.

Screenshot:

PCB Rev.2.00



The new PCB designs will be smaller and double-sided measuring 2.25" x 2.25" 

I don't have this mass-manufactured, so I'm selling it at a low price just to recover some of my costs.  $20 each.  Email me first  before ordering. Thanks.

This is a continuation of my Sony Racking Job. Click here for previous article.
http://diy-central.com/DIYRackingSonyMXPPreampsAndEQModules.aspx

Things are progressing nicely. Some photos.

Finally cut the hole for the EQ section... took about 2+ hours... it's a pain doing this. And I have to be careful not to make the square holes too big because the tolerances are very tight.

Some closeup photos of the Preamp and EQ module.

Things are busy at DIY Central... I also had PCBs manufactured for my PRE-1048 preamp (link coming soon). This time, I used a company based in Malaysia.  I got the PCBs today too, same day as my PSU PCBs.

Well, I'm a bit disappointed at the quality. Let's just say it's nowhere near the quality of the other PCBs I got manufactured here in the US. (See photo of article below this.)

There's also no silkscreen (but I knew that before I placed the order).... it's also more expensive than the US manufacturer if you divide the total price by the number of PCBs you get.

To their credit, they got the PCBs manufactured correctly. :)

This is a continuation from this article.
http://www.diy-central.com/DIYSplitPowerSupplyWith48VPhantomPower.aspx

Well, I received the PCBs today but it seems there was a manufacturing error. Everything is flipped/mirrored... Here's how the top layer looks like... the bottom layer is also flipped/mirrored.

BUMMER!

I sent this picture to the manufacturer along with what the Eagle board is supposed to look like. I emailed them... and within a couple of hours, I got a call from them on the phone apologizing for the mistake and they found out where in their process they had the mistake... they're going to remanufacture my boards and resend them to me at no charge!  Talk about great service!  The quality of the boards and it's workmanship do look very nice too, and their prices are great.

This is my first order from them, and even if they did screwed this up, I think I'll use them in the future. I like how they handled the problem very well and took steps to correct it.

I'll keep you guys updated about the progress.

Just some preliminary pictures... I'll post the writeup later.

This is a Valley People Trans-Amp Mic Pre. No, this is not a discrete opamp like the 990 or API2520. This is a complete mic preamp in a "box."

The Trans-Samp have 9 pins at the bottom. I used some Mill-Max pins to socket them to the breadboard.

I decided to rack the few remaining Sony MXP preamp and EQ modules I have. This particular mic pre module is using a discrete opamp enclosed in some green colored epoxy or something.

I've already racked a previous Sony mic pre and EQ, so I want this 2nd unit to match the layout of the first one I did. The only difference is this particular project, the mic pre does not have the Jensen transformers, and instead is using some discrete opamp, and will be in a black 1u case.

Here are some preliminary pictures.



The Mic Pre and EQ module I'll be racking.



Preparing the 1u front panel for drilling holes.

Having a drill press makes the job so much easier than using a hand drill. Safety first... don't forget to use goggles. Freak accidents happen, like a drill bit breaking and flying into your eye! (good thing I had the goggles!) So no matter show "quick" a job it is, don't forget your safety glasses or goggles.

I decided to design my own PCB for a general split power supply with +48VDC phantom power. The one I'm currently using while compact in size doesn't leave any room for a heatsink. So I moved all TO-220 voltage regulators to the side so I'll be able to attach a big heatsink and keep those VR cool to the touch.

Here's the schematic and prototype PCB design. I'm having these PCBs fabricated, as a test prototype.

Schematic diagram. From this schematic, I created the PCB design and exported Gerber files.

Then using a third-party Gerber Viewer, I opened up the created Gerber files to double check my layout. So far, everything looks good.

You can buy this kit from PAIA, including the cool-retro case, complete with electronic parts, power supply, knobs, manuals. They even throw in the wires.  You have the option of using a desktop case with wooden sides, or mount it on a 2u rack panel.

The price I think is also pretty reasonable considering that some of these things sell in the several hundreds.

The kit includes a burned EPROM (containing the programming). The code is also available on their website.  And note, this is not just some analog synth that doesn't play with others... it has MIDI. It responds to note-on/off data, including pitch, velocy and gate. So you can hook it up and make it part of your MIDI studio.

Writeup from their website.

The FatMan has all of the features that give analog it's big bottom
and punch in a MIDI controlled package. The classic Voltage Controlled
normalization is brought up to date with a Velocity CV not available on
pre-MIDI synths. Pitch wheel modulation is supported and Pitch and
Velocity CVs and gate signal are provided on the front panel for
driving PAiA or other linear response synthesizer modules.

And all those knobs. They invite experimentation and invention in
ways that a single control with functions buried under layers of
obscure menus never can. Just a few hours with the FatMan will teach
you more about the nature of sound than you might ever learn otherwise.
It's as at home in the physics lab as on-stage.

 

Isn't this a thing of beauty? And for a few dollars, you can build your own analog synth, a'la Bob Moog! Link to Project

Write up from the website:

These are instructions from converting a Renuzit Air Freshner to a trumpet mute. Another guy extended the concept by installing a mic and small preamp inside the air freshner case and hooking up a headphone.  Pretty cool.

Now you can toot and make it smell fresh at the same time!

Link for the trumpet mute. Link for the trumpet mute with mic, preamp and headphones.

This is a repost of my SSL Build Thread. Thanks to Gyraf.dk for the schematic plans.

The compressor is a clone based from the SSL4044E desk (1985 era). The SSL mixbus is actually an integrated part of the desk's main quad fader and autofade system. Click here for schematics.

There's been some mods to the original schematics for use with THAT VCAs. This page contains adjustments to the resistor values.

I also did some mods on my unit. Mainly, adding transformers at the output. Originally, the unit uses opamps for balanced outs. I have some MCI 416 output trafos that I used for my SSL unit.

The PCB...

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.

We did an unbalanced to balanced converter using dual opamp chips, the NE5532 opamp previously. While the previous circuit works, it uses a lot of components.... which means, more chances that something could go wrong.

Picture of old unbalanced to balanced converter

New Design

This new unbalanced to balanced converter uses a single chip and only 2 capacitors. We're using the Burr-Brown DRV134/135 chip. I got some DRV135 which comes in an SOIC package. There is a DRV134 which comes in an 8-pin DIP package.

This is a schematic plan for building a passive, transformer-based DI Box (Direct Box) from Jensen-Transformers.com. View the original PDF here.

You plug your hi-Z (or high impedance) guitar to jack J1. From here, it goes to a pad on/off switch. You also have 2 pad choices... -10dB and -20dB depending on the position of switch S2.

S3 is a hi-cut filter switch. If S1a (i.e. the pad switch) is switched ON, and the hi-cut filter is ON, the high frequencies are shunted to ground via C3.

The signal going back to your guitar amp via jack J2 is unaffected by the pad and hi-cut switches.

Transformer T1 is a JT-DB-E transformer. This takes care of matching impedance between your guitar and the mic preamp of your mixer. It also converts the guitar signal from unbalanced to balanced connection.  The red-brwn wires of the transformer goes to pin 2 and 3 of the XLR which forms the HOT (+) and COLD (-) connections.

Ground is connected to Pin 1 of the XLR. A ground lift switch is provided, S5, which isolates the pin 1 ground of the mixer from the rest of the circuit.



If you don't want to build one, here are some passive DI boxes.

ART ZDirect Passive DI View more products from ART The Zdirect is a high-quality, totally passive interface that lets you connect instrument-, line-, or speaker-level signals to a mixer or other balanced input through a high-performance audio isolation transformer. The high impedance single-ended 1/4 in. input is converted by the transformer into an isolated balanced low impedance signal source. Read Reviews... List Price: $30 Click for Sale price   Shipping cost: $4.99

Radial JDI Duplex Stereo Passive DI Box View more products from Radial A stereo version of the Radial JDI. Ideal for recording, broadcast, and live sound where extreme dynamics such as those produced by digital sampling devices and keyboards are encountered. Completely passive, the JD4 employs two Jensen JT-DBE transformers for 100% isolation and low phase distortion. Read Reviews... List Price: $350 Click for Sale price   FREE SHIPPING!

Radial JDI MK3 Passive Direct Box View more products from Radial The Radial JDI is considered by many to be the world’s finest direct box. It is a passive DI that employs a Jensen isolation transformer for optimum audio performance offering outstanding linearity at all frequencies, combined with extraordinary level handling without introducing distortion. Read Reviews... List Price: $200 Click for Sale price   FREE SHIPPING!

Radial Pro DI Passive Direct Box View more products from Radial The Radial ProDIs are high-quality, full-range passive direct boxes equipped with custom-made audio transformers for exceptional signal handling without saturation and with extremely low phase distortion in the critical bass and mid regions. The result is exceptional clarity and definition at an attractive price point. Read Reviews... List Price: $100 Click for Sale price   Shipping cost: $4.99

Just an update of my build: Click here to read Part 2.

Soldered 90% of the parts, including the Lundahl transformers, JFETS and transistors. I'm awaiting some parts that were "out of stock" from my first order.

Also, I ordered some wire assemblies with male/female jacks. I'll use them for connections between the main board and xlr jacks, pots, switches, etc... that way, if I need to troubleshoot the board, I can just unhook them instead of desoldering the wire from the board.

TIP: Before you complete assembly of your project, have a suitable chassis ready for it. From my experience, if I built a project without finishing the chassis first, that project becomes half-finished, working but not in a case. Laziness I know...

Also, if everything is in a chassis, you can wire everything and not have to worry about your solder connections or wires becoming loose. Everything is already in place, plus it makes it easier to work on it.

You can get your rack chassis, from 1u, 2u, all the way to 4u and 8u at par-metal.com.  They've got good prices and have nice quality racks.

Oscilloscopes are indispensable tools for anyone designing, manufacturing or repairing electronic equipment. In today’s fast-paced world, engineers need the best tools available to solve their measurement challenges quickly and accurately. As the eyes of the engineer, oscilloscopes are the key to meeting today’s demanding measurement challenges.

Tektronix presents the XYZs of Oscilloscopes. Learn about the different types of oscilloscopes, systems and controls, measurement, and how to operate an oscilloscope including measurement techniques.

Looking to save some money? Create your own cables! By spending a few dollars on jacks, shielded cables, solder and soldering iron, you can save a ton of money in cables.

For more money saving tips for your home studio, like building your own Neve preamps, SSL compressors, Yamaha "old-school" type preamps, MIDI controllers, check out my other projects.

Back to building your own cable...It's easy. Here are some step by step photos. 

At the bottom of this article, is a wiring guide for XLR to XLR, XLR to TRS, XLR to TS, and whatever combination you can think of.

On this guide, I'm wiring up an XLR cable.  First, we disassemble the cable by unscrewing the lock screw. Pull out the rubber plug (black thingy) and then you'll be able to push out the 3-pin connection assembly.




Since an XLR cable is a balanced cabel, we need a 3-wire cable. Also, make sure it is shielded to provide RF interference protection. 




Now, let's take a look at the XLR jack itself.  It's got 3 pins. Pin 1, 3 and 3. 

The convention is Pin 1 is the GROUND.
Pin 2 is the HOT (+) wire.
and Pin 3 is the COLD (-) wire.

Note: The COLD wire (-) is not the same as the GROUND wire. Don't short these two wires together!

Here's a closeup of the 3-pin assembly and you can see it's labeled for us. Great!  For this, I'm going to make my RED wire my HOT (+) wire and the WHITE wire as my COLD (-) wire.  (If you're wiring a headphone, the RED wire is usually designed for the RIGHT channel, and the WHITE wire for the LEFT channel)



Strip off a few millimeters of insulator, coat it with solder and solder it to the XLR jack terminals.



When you're done soldering the 3 wires, crimp the jack around the cable. This will provide support to the cable... i.e. when you yank off the jack, your wires wouldn't disconnect from your solder points.



Here, you can see the metal teeth crimped around the cable's jacket. Use a long-nose pliers to crimp it close. But don't crimp it too much that you mess up the cable.

Do the same procedure for the other end of the cable. This time using a Female XLR jack.  And here's our finished XLR cable.



If you need to DIY a different kind of cable, say a TRS jack or RCA, use the table below as a guide. This guide has been provided by Rane in their Technical Library section. Visit Rane website.

Credits: Rane

Visi the RANE website for more information about grounding, shielding, ground loops, etc.

Just a continuation of the saga of building my 1176 clone compressor/limiter. Click here for Part 1

Parts arrived a few days ago, and other than the audio input and output transformers and chassis, I think I have enough parts to build (2) units. Here are some pics...

First, we have the output LL5402 Lundahl transformer and the LL1540 input transformer. Made in Sweden.  These things are small.

I got most of the capacitors and the power transformer at digikey.com. They have good prices for these components.




The rest of the parts like the pots, resistors, and ceramic/mylar parts came from Mouser.com. It's a big pile!







I'll clear up my work area and maybe this Christmas break, I'll be able to start construction.  Oh yeah, need to order some 2u case from Par-Metal.com.  I only have spare 1u cases in my workshop at the moment.

We're ready to build the 1176!

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.