Category Archives: Electronics

SB4000 Bus Compressor – Build – Day 3

Well, after an intermission of me being rather sick with an irritating cold/flu hybrid, talsit and I are BACK for some more SB4000 compressor building shenanigans….

This time we were went to a Sydney Hackerspace: for some drilling, dremeling, and general SB4000 case destruction….

Firstly we drilled out all of the mounting holes for the transformer, the power supply board and the main audio board.  These were carefully marked out using old fashioned centre-punch and pencil action, then, channeling the metal work skills of our high-school days, drilled out with a very nice drill press:

Despite a minor injury due to an exploding spring clamp ( note the band-aid ), talsit valiantly soldiered on to do some mighty-fine chisel shizzle:

From there we dremeled all of the drill holes for the separate parts of the rack case to remove the paint. This ensures that once screwed together, the case has a full electrical connection throughout, both for safety and for electrical isolation. The Faraday’s cage effect of enclosing all the sensitive audio electronics inside of a shielded and earthed case will help to keep the noise levels of the final product extremely low:

Join us next time for the final phase where we will solder all the case components to the power supply and main audio boards, and mount all the switches, connectors and potentiometers to the case….

SB4000 Bus Compressor – Build – Day 2

Hi there!

Today was the second day I have spent working on a build of this DIY kit:

I obtained a fully inclusive parts kit from this link: which may or may not be stocked when you read this, as their stock levels vary frequently.
I also obtained a PCB and front panel kit from here:

I’ll post some photos up from the start of the build yesterday, but I just wanted to share this experience with some words and images, so you can understand how much fun it was and how lucky I am to be in a position to be able to undertake something like this.

So let’s rewind again….  Huh?

OK, so, my name is Luke Emrose and I produce electronic music under the alias “evolutionary theory“.  I am a home producer based in Sydney, Australia, with a small studio and I am trying to slowly grow that studio.  I have a very detailed plan on precisely how to grow it, and what to grow it with.  My goal is, one day, to be writing electronic music soley using analog synthesizers and equipment I have build with my own hands and designs, running software that I’ve designed and programmed myself.  I am able to undertake such a giant goal for two mains reasons:  the first is that I spent much of my childhood keenly interested in electronics, building everything from some boring flashing lights, to, in high school, designing and building a fully functional 8 channel stereo audio mixing console ( Andrew, do you still have it? 😉 ), and the second is that my full time job is as a Core Software Engineer for a Visual Effects company specializing in Hollywood blockbusters.

Part of my current set of after-hours tasks is producing an entire album of material for vocalist and general legend Lee Safar.  To try and keep costs down, initially we’ll be mixing and mastering the first few album tracks at a professional studio facility, but in the background I am figuring out how to absorb as much of that work back here at my home studio as possible.  One piece of equipment that I knew I had to have is the Solid State Logic 4000 G-series Bus Compressor, which inspired the Gyraf DIY GSSL project:  The SB4000 kit that I’m discussing here was derived from the Gyraf GSSL and contains a number of extremely interesting improvements.  It took a long time for me to settle on this particular kit, but it was a combination of cost effectiveness, the quality of the kit, the copious amounts of positive feedback on the Prodigy-Pro forums about the kit, and a bunch of my own research that led me to the decision.

To build the kit I needed some help.  It’s been quite some years since I’ve laid eyes a soldering iron, let alone used one….  So, being lucky enough to go to work every day surrounded by some of the most intelligent and resourceful people I’ve ever met, meant that a close friend of mine, Talsit De Cod, could put up his hand and then his house for two days, to turn it into a batcave of circuit building ( his wife was very understanding about the mess we made, thanks for that 😉 xxx )….

So here we are, on day 2 of the build, each working away soldering at the main SB4000 audio board ( the first image is me, the second is Talsit ):

So here is the main audio board populated with resistors and diodes:

Here is a wide shot showing the mess we made of a table, the main audio board ( left ) plus the control board ( that houses the rotary dials and knobs that the user uses to interact with the compressor ), middle, and the power supply board ( which we built on day 1 ), right:

Here are a few more detailed shots of the power supply board ( which I am going to make some changes to by swapping some resistors for trimmers to more precisely control the supply rails to be +-15 and +-12V, currently it’s a little off at about 14.89V and -15.34V and similar for the 12V rails ).  I’m a sucker for accuracy ( as is Talsit…. ):

In this picture you can see the SB4000 Revision 4 PCB resistor hack ( the diagonal resistors to the left middle of the frame ).  If you decide to build this kit, please remember to read the build manual, which covers this in detail:

If you do not do this, the compressor in bypass mode will invert the phase of the signal.

Next we put in the ceramic capacitors ( the orange thingies 😉 ):

Then some polyester capacitors ( the blue ones ):

Soldering them all in place with great care:

After a LOT of soldering all of the polyester caps were in place, looking like a little city of awesome….

Next we put in the IC sockets ( the black bits ):

Now I know this next part might seem a little weird, but trust me, it IS necessary….

That’s right, we gave the board a wash with soapy water to clean off all of the flux we’d used during the first round of soldering ( flux is a compound that helps the solder stick to the components and board by both cleaning them quickly as a solvent and aiding in the thermal contact between the part and the PCB track and solder to bring them all together.  However, it’s very messy, highly corrosive and smells pretty horrid, so you godda get rid of it ):

Please note also that BEFORE washing with water, you need to use a flux remover solution; brushing the solder joints vigorously with a toothbrush ( to dissolve and start to remove the flux ), then use alcohol after that for a further clean, and brush again with a toothbrush or similar ( the alcohol dissolves all bad bits and cleans thoroughly ), and THEN wash in soapy water.

And of course after a good wash, you need a good blow-dry, so:

There we go, all nice and clean, ready for mounting the parts that are not sealed ( and hence can’t be washed ):

Next the relays ( dark blue ), ribbon cable connector ( black ), and screw terminals ( green ) went in:

Then the trimmers went in ( blue ):

During this whole time, the control board was being finished off too:

There were a few things we needed to solve, like how to mount the bourns potentiometers properly.  You get given a daughter board to place them on, but after much fiddling I think we are going to leave the daughter boards off and just mount them straight to the control PCB ( which might create issues with mechanical strength, but we don’t have much choice, since the supplied mounting nuts for the Bourns pots were incorrect and didn’t fit properly ( I’ll post some more images to show this shortly ):

Finally we started to drill the holes to mount the different components that attach to the main case, starting with the toroidal power transformer:

And that’s where we got up to today.  Not long to go now hopefully.  I feel it appropriate to end with a messy desk, awaiting the last portion of work:

DIY Audio Projects – Designing….

I’ve been working on some DIY audio projects for some time now that are finally far enough down the line, that I wanted to share them.

One of the more interesting projects ( and difficult…. ) is restoring some old designs, like the Moog Minimoog Model D circuits, from scratch, using new and readily available parts, yet still keeping as close as possible to all of the aspects of the original designs that made it sound “good”.

Luckily I have a very clever and resourceful friend ( whom also happens to be a brilliant photographer: talsit ) who is currently doing a lot of this DIY type stuff, and hence, I have a lot of very good help.

The first piece of work I had to do was source the original circuit diagrams, which I found here: fantasyjackpalance

Next, I had to source the parts, or, at least, extremely appropriate equivalents, which I’ve managed to do with the following supplier ( whom are also incidentally Australian, which is quite useful since I live in Sydney 😉 ): element14

Then I used LTSpice to simulate these circuits, and make any necessary improvements to them including accounting for changing the component types, or fixing poor performance based on circuit measurements.  Here is a screenshot of the VCF ( voltage controlled filter ) design I’ve been recently adapting to build ( quite a few of you will notice the unmistakable topology of this circuit, and notice it’s a Low Pass 24dB transistor ladder filter from the Minimoog Model D ) along with a simulation that exercises a bunch of different resonance values:

From there a transpose this schematic into Eagle:

Then from there I piece together a board layout for the parts:

And the next step is to actually build these projects.

Stay tuned, more to come soon….

etheory DIY audio begins….

I just received some electronic audio parts from Small Bear Electronics in the US.

They are National Semiconductor NOS LM308AH Op Amps and I’m going to use them shortly to build some customized ProCo Rat inspired distortion pedals, with some help from this site:

and here:

and a very good friend of mine, whom does both photography:

and also is a member of Robots and Dinosaurs:

and is rather skilled in custom PCB fabrication using a CNC machine….

But in typical etheory style, nothing is going to be standard.  I’m custom designing a stereo circuit board and modifying the pedals so that they can interface correctly with line-level equipment.

Watch this space for updates….  But one thing is for sure.  You’ll definitely be hearing the awesomeness from these custom designs soon….

A Moog MF-101 24dB Low Pass Filter joins the studio

Hi there!

After quite some waiting ( around 3 months ), I finally took delivery of a limited edition Novamusik special Moogerfooger MF-101 24dB Low Pass Filter.  The “special” part, is that it’s in the black and white scheme of the rest of the studio ( the finish is called “Whitewash” – unlike the standard black and wood finish ) and also that it’s got a good portion of the original circuitry of the older Moog filters.

My reason for getting this Moog filter is to accompany the SEM Pro filter.  The harsher/harder/brighter 12dB Multi-Mode Filter of the SEM truly sounds amazing ( as you can hear in some of my earlier posts ), but the main issue with it is that it’s so full-on some times, that you just can’t get the right sound ( i.e. something a little bit rounder and warmer ).  That’s where the MF-101 fits in rather well.  I’ve already found it sounds excellent placed after the output of the SEM, with the SEM filter cutoff at its highest frequency.  From here, I’m able to apply a Moog warm 24dB tone to the gorgeous SEM oscillators.  The result has given me the best of both worlds, since the mix control on the MF-101 allows me to dial in either all SEM or all MF-101 filter sounds.  I’ve found some excellent middle ground setting the mix to 50%, which allows me to accentuate the bass region of a sound ( with a very low cutoff on the MF-101 ), whilst allowing that bright brassy top/middle end to come through from the SEM.

My next project will be to interface the SEM control voltages to the MF-101 and vice versa, since the SEM outputs are what I believe to be 18V control signals, whereas the MF-101 only accepts 5V control signals.  I’m going to investigate some voltage divider solutions just using resistors, as I believe I should be able to just build this directly into some adapter cables.  This should allow me to build 3.5mm SEM 18V to 6.5mm MF-101 5V cables that handle the voltage conversions internally ( by soldering resistors into the connector housings ).  I’ve started some dialogue with Tom Oberheim about this as he’s pretty good at getting back quickly to questions via e-mail.

I’ll post some sounds soon….

Here’s a few images of the little fella taken with a Canon 7D through a Canon 50mm 1.8 Lens:

All images copyright 2011 by Luke Emrose