Dusting off the modular synth

Started thinking about synthesizers the other day this prompted me to dust off the old modular synth and get it working again. I was expecting more trouble but in the most if not everything seems to be working.

To get things working I needed to untangle and sort the massive amount of power cables and other wiring. In reality I disconnected almost everything and reconnected it all again. At this point I had the mixer setup and powered. From there I could run a test on each module. Lo and behold thing were functioning.

Here are a few images. Most of this would fit in the palm of your hand and run from your mobile phone these days.  That said in this case I can see the entire interface and there is a very real tactile experience.  Of course I’m not taking this with me.

Templates from Ponoko

I just got these templates from Ponoko.
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New work in progress

A nice opamp big muff PCB 
Mad bean Shark Fin. Based on the maestro filter sample and hold. I’m obsessed with this circuit, I’ve built several versions of it and own some boutique iterations.
Ooh look an ugly face, this is another effect that had become a minor obsession. I’ve built more than a few of these. 
Mad bean zero point mini.  

Okay so, here we take a look behind the scenes at the pile of unfinished work. This picture was taken inches the left of the previous images. 

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Tube Steak build

Tube Steak build was originally published on Super-Freq

More OSH Park PCBs

These are some more PCBs from OSH Park. There is an IC Big Muff, Tube Steak, and a Woolly Mammoth.

The Tube Steak I created from a schematic posted by Charlie Barth at Moosapotamus.net. Tube Steak Fuzz is a cross between the Tube Sound Fuzz, and Way Huge Fat Sandwich. Here’s a link to Charlie’s article read it for yourself: Tube Steak Fuzz.

The IC Big Muff also called the op-amp Big Muff was a version of the Big Muff that used two op-amps in place of the four transistors used in the classic Big Muff Design. Here is a link to more information in the op-amp Big Muff.

The Woolly Mammoth is a PCB design that I made as a clone of the ZVex Woolly Mammoth. I really like the sound of this one. Designed as a fuzz for bass, it sounds good with guitar also. The design is based on the Fuzz Face.

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Zeke Bass distortion

Completed clone of the Ezekiel 25:17 Bass Distortion by D*A*M. I built this with PCBs from OSH Park, see my previous post.

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Zeke Bass Distortion – OSH Park

This Zeke Bass Distortion is a clone of the D*A*M Ezekiel 25:17 Bass distortion. The PCB came from OSH Park. This worked out well. The board is pretty big so soldering parts is easy. The rotary switch and pots are all mounted on the board, which makes assembly easy, this is a good PCB.

There was no documentation on OSH Park for this, so I reverse engineered the board to match the parts in the schematic. Here is the schematic I used with part numbers that match the PCB.

zeke

Overall the board turned out pretty good. I used a socket for the dual op-amp. I threw a random 1458 in that was sitting in a pile of parts on my bench, and it fired up first test. This is supposed to use a JRC 4558. I think I have a couple of these squirrelled away, I’ll dig them out before I box things up. I might try some other op-amps also.

There are three sets of diodes. D2-4 are Ge, D5-6 are Si, and D7-8 are LED. I used some 1N34 for the Ge, and 1n914 for the Si, and random 3mm LEDs from the parts bin.

With 3P4T switch the circuit is only using one pole. I only soldered the pins used by that pole. This way if I made a mistake, it’s been known to happen, I had fewer pins to de-solder. With these switches there is a small ring with a tab under the nut. Be sure to set this for four positions.

To mount the pots, I would suggest making a box first, mounting everything in the box. This will position the pots at the correct height above the board compared to the switch. Then solder from the top of the board. I made some holes in a piece of cardboard, and mounted everything in that before soldering, since I didn’t have a box drilled yet.

I put everything on the test rig, and it fired up first! Good for me, and thanks to bmossma at OSH Park. It’s always inspiring when things work on the first attempt. The sound was pretty good, it didn’t sound like much with guitar, with bass, the effect started to make sense. I tested with my baritone guitar and it seemed to sound pretty good with that also. Definitely more of an overdrive, distortion, than a fuzz to my ears.


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Fuzz Factory – OSH Park

Just soldered the first of three Fuzz Factory PCBs from OSH Park. Fired up on the first try. The board didn’t come with documentation, I had reverse engineer the board against the schematic to verify part numbers. Here is the schematic I used:

fuzz-factory

I used some AC128 transistors for Q2 and 3. The random choices from the lot sounded alright. I built this first board with sockets for the transistors for testing. I can test transistors on this board, if they sound good I can solder them into the other boards.

I like this board, the layout has pads for 16mm or 9mm pots. The width fits the narrow dimension of a 1590B box, which gives you the option to arrange the box in landscape like the original, or in portrait, like most standard stomp boxes. The Stab and Volume pots are mounted off board. While this adds some wiring, it saves cost by making the board smaller, OSH Park charges by the square inch, it also provides flexibility in how the box can be arranged. Hats off to the designer. Hats off to mr vex also.
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Osh Park PCBs

IMG_1158.JPGI just received this order from OSH Park. I order four boards. You are required to buy three copies of each board you order. The cost is $5 per square inch for 2 layer boards (with 3 copies of your board included in that price). Which is not bad, if the boards are small it’s a deal. For example, the SHO was $3.20 for three boards! The Fuzz Factory boards, were $7.75 for three, still a good deal. The Haunting Mids boards were just under $5 each, and the Zeke Bass Distortion was about $8.50 each.

Of course getting boards for designs that people upload with little info can be chancey. There should be more options on the site to comment, and mark boards as verified. Looks like not all projects are shared. User decide to share a project. Hopefully people make an order and test it before sharing.

The quality of the boards is great. A couple things I noticed. There is no solder mask. The pads are gold plated, which is nice. I find the solder mask easier to solder with. Look at the first image. You can see the backside of each of the four boards. Notice the board in the upper right. The pads are fairly small. I think, this is the default pad size in Eagle PCB. It’s not easy to solder, It’s not super difficult either. The two on the left have a more generous pad size. This size makes for a better soldering experience.

I’ll post again when build these boards…

For reference here are some links to the boards I ordered here:

https://oshpark.com/shared_projects/JtR27cHU

https://oshpark.com/shared_projects/xaBILSTV

https://oshpark.com/shared_projects/KE0blXBg

https://oshpark.com/shared_projects/nsJTeQK0

 

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Resources to get started making stompboxes

Getting Started

Someone asked me about getting started building stompboxes, so I thought I’d put it all in a forum post, for your enjoyment and edification.

Become a member of both of these forums. Search, and read what’s posted there. Post your work, and your questions. Lot’s nice knowledgable people.

Probably the oldest stompbox forum around. Really friendly and helpful people. Lots of good info.

http://www.diystompboxes.com/smfforum/

Another great forum, this one has been around for a while.

http://freestompboxes.org/

This forum, ostensibly, caters to the subject Madbean PCB projects, but the people here talk about everything. Not much traffic as the other two forums.

http://www.madbeanpedals.com/forum/

Kits

Probably the best kits out there. This would be a good place to start.

www.byocelectronics.com

Parts

While you were able to get enough parts to make a couple stompbox projects at RadioShack in the past, these you can’t really get more than a cell phone’s there. Sadly there are no brick and mortar stores that cell stompbox parts. Then again you can

Mouser All purpose electronics supply.

SmallBear The original stompbox supply

Mammoth They have everything, good quality, order boxes in colors, and pre-drilled

Pedal Parts Good prices for boxes

Tayda Cheap, good range of parts.

Futurlec Good prices, slow shipping.

Bitches Love My Switches (Yes, that really the name) great prices, prompt shipping. Good for switches, knobs, and jacks.

PCB

After building a few kits try building from just the PCB. You’ll have to source your own parts.

http://www.madbeanpedals.com/projects/index.html

These are very well done PCBs. I have built the the delays.

http://1776effects.com/

http://www.guitarpcb.com/

Here are a few more sources for PCBs, I haven’t tried these

http://lectric-fx.com/

http://diyeffects.com/products.htm

After you make a few projects you might want to try making your own PCB.

http://dirtypcbs.com/

This site is something special. It allows people to upload their PCB designs, and open sources them to the greater community. The prices look good.

https://www.oshpark.com/

Experimenting and making your designs

Get yourself some parts and a breadboard. Build a test rig, and an audio probe, and you’re in business. Besides the forums above, these sites have some information and projects to try.

http://www.runoffgroove.com/articles.html

Download the Stomboxology Article: Going Discreet. This is a great primer on transistors.

http://www.moosapotamus.net/

Sort of the grand daddy of stompbox info

http://www.geofex.com/

 

OSH PARK

This is a really cool service that manufactures open source PCB designs. You can order any of the open source designs on the site. Most of the stuff is not stompbox oriented. It takes a little google-fu to search up stompbox projects. You can also upload your own designs.

You have to order 3 PCB minimum for each board you order. The orders seem to get ganged with other orders so it sounds like your order doesn’t get printed immediately. That said the prices seem very reasonable.

https://www.oshpark.com/

I just placed an order for a few PCBs. I’ll post again when the order comes in…

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Good Articles on CMOS Chips in Stompboxes

Here are some good articles on using CMOS chips in stompboxes.

http://www.parasitstudio.se/building-blog/cmos-workshop-part-1

http://www.parasitstudio.se/building-blog/cmos-workshop-part-2-square-wave-fuzz

http://www.parasitstudio.se/building-blog/cmos-workshop-part-3-octave-down

 

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