Which enclosure to use?

[fidelio]

Hi all,

I'm sure this has been asked before, but I couldn't find it when I searched so here goes. How do you know which size enclosure to buy when you are building your own pedal? I've built a few from BYOC where the enclosure was supplied, so no problem there. But I just built the Small Clone using a PCB from Tonepad, and I am having some trouble. I tried the 1590B but it was way too small (boneheaded error on my part, should have checked the dimensions of the PCB first). So I went up a size, and ordered a pre-drilled 125B from pedal parts plus. The PCB's dimensions now fit, but I can't seem to fit it in there among the footswitch and jacks. If the footswitch hole had been drilled a little farther down, it would probably have been OK. Unfortunately, I don't have the tools or space to drill my own. Does anyone have any tried and true method for picking out the right enclosure for the job? I guess I could just use 1590BB for everything but that seems excessive.

[Cozybuilder]

The best thing is to drill your own enclosure-  a drill press is best, but if you are strapped for room and/or cash, invest in a hand drill, center punch, some tiny pilot drills, a step-drillbit, and a drill size guide to check the switch/jack/pot etc to make sure you drill the correct size hole.

I usually put a piece of masking tape over the spot to be drilled, measure carefully, mark with a pencil, re-measure and then check the drawing again, erase the mistake and measure correctly, then center punch and drill. Predrilled enclosures are something to avoid (unless it comes in a quality kit or they are oversized).

For a predrilled enclosure, to get the board to fit you might need to use different sized caps on the PCB (ie tantalum instead of aluminum electros), or mount them in a way such that they can be bent over slightly without interfering with the fixed components (switch, jack, pot etc) or shorting on other board components. So mount the fixed components in the box first, and test fit the PCB making note of where the likely interferences are and figure a way to resolve those before soldering.

[deadastronaut]

when i first started building i went straight to 1590bb size...

made building easier,..gives you bit of freedom where YOU want parts.. ..



regarding pcb dimensions, as a noob again, i remember printing and etching a board

then realised the chip pins were way off.......probably all done it.....but you only do it once

[Mark Hammer]

It does take a number of builds to acquire an intuition or sixth sense about layout.  Once you have that, you can find yourself able to stuff all manner of things into a 1590B or even 1590A.  But when starting out, I find Cozy's advice spot on.  Begin with a BB size or similar (I'll put in a vote for the two Small Bear Bare Box sizes), just to give yourself some space for a more forgiving layout.  As well, you'll likely want to use early builds as a test bed for trying out mods, and the extra panel space will let you do that.

[Granny Gremlin]

Most PCB sellers will tell you what size enclosure to use and provide drill templates; upsize accordingly (i.e. to a BB) depending on the mods you decide to implement (especially extra pots/switches).  My advice: any project saying to use a 1590B, get a 125B instead (same size but taller - gives you that much more wiggle room). I do that so that I can always have top mounted I/0 and power jacks (saves pedalboard space... with DIY this is a major concern for me ).

[Cozybuilder]

I agree, the 125B has a lot more room to work with than a 1590B, and it costs very little additional pedal board space (and mounting the I/O and power jacks on the rear really helps for a compact pedal board):



+1 on Small Bear's Bare boxes, great design 

[Gus]

The best thing is to drill your own enclosure-  a drill press is best, but if you are strapped for room and/or cash, invest in a hand drill, center punch, some tiny pilot drills, a step-drillbit, and a drill size guide to check the switch/jack/pot etc to make sure you drill the correct size hole.

I usually put a piece of masking tape over the spot to be drilled, measure carefully, mark with a pencil, re-measure and then check the drawing again, erase the mistake and measure correctly, then center punch and drill. Predrilled enclosures are something to avoid (unless it comes in a quality kit or they are oversized).

For a predrilled enclosure, to get the board to fit you might need to use different sized caps on the PCB (ie tantalum instead of aluminum electros), or mount them in a way such that they can be bent over slightly without interfering with the fixed components (switch, jack, pot etc) or shorting on other board components. So mount the fixed components in the box first, and test fit the PCB making note of where the likely interferences are and figure a way to resolve those before soldering.

Just to add I like to use a center drill after using a center punch.

[Mark Hammer]

I agree, the 125B has a lot more room to work with than a 1590B, and it costs very little additional pedal board space (and mounting the I/O and power jacks on the rear really helps for a compact pedal board):



+1 on Small Bear's Bare boxes, great design 

The overall footprint may not be that much bigger for the 125-C, but don't underestimate the importance of the extra  height.  It can often make the difference between sticking the jacks somewhere that ends up causing problems, or not, between finding out that the pots or toggles conflict with the height of tall electros on the board, and not.  As I noted earlier, eventually you'll get a sixth sense for these things, but until you do, it's nice to have a chassis that forgives all the things you didn't remember to plan for.

[LightSoundGeometry]

my MJM vibe pedal is really tall in height ..its sort of awkward and bulky ..oh boy does she sound sooo good though


I use the 1590BB all the time, the ones from small bear, blemished for 5 bucks. By the time you add the shipping, you really dont save too much but they are pretty nice for being blemished. I would go so far as to say, his blemished ones are on par with others sellers good ones...I have had good and bad with PPP, his wire is the best by far, no one can touch his hook up wire though.
http://smallbear-electronics.mybigcommerce.com/taiwanese-bb-size-powder-coat-seconds/

I do my own now mostly with spray paint. Trying to take the next step with waterslide and acrylic gloss of some sort; so far unsucessful. Not sure why..could be my printer or errors in my techniques . I suspect like anything else, and learned on here, the first step of being awesome at something(graphics) is sucking really bad at it (failing). Its working through it and overcoming what separates the wheat from the chaff. I will be good with graphics one day.

someone should bump the metal etching thread, the one with the battery and saltwater!

[LightSoundGeometry]

The best thing is to drill your own enclosure-  a drill press is best, but if you are strapped for room and/or cash, invest in a hand drill, center punch, some tiny pilot drills, a step-drillbit, and a drill size guide to check the switch/jack/pot etc to make sure you drill the correct size hole.

I usually put a piece of masking tape over the spot to be drilled, measure carefully, mark with a pencil, re-measure and then check the drawing again, erase the mistake and measure correctly, then center punch and drill. Predrilled enclosures are something to avoid (unless it comes in a quality kit or they are oversized).

For a predrilled enclosure, to get the board to fit you might need to use different sized caps on the PCB (ie tantalum instead of aluminum electros), or mount them in a way such that they can be bent over slightly without interfering with the fixed components (switch, jack, pot etc) or shorting on other board components. So mount the fixed components in the box first, and test fit the PCB making note of where the likely interferences are and figure a way to resolve those before soldering.

Cozy, so basically any electro cap can be substituted for a tant? any restrictions for the stuff I am messing with? I ask because boy do they save room.

[Granny Gremlin]

Cozy, so basically any electro cap can be substituted for a tant? any restrictions for the stuff I am messing with? I ask because boy do they save room.

What he's saying is the opposite - you can replace any electro with a tant if you have/can get or afford the right value.  You could maybe go the other way, but not necessarily - if a tant is specified in a build doc there is usually a reason; often that reason is due to typical electro tollerance of 20% is just not tight enough in a critical spot (but the value is too high to use film).

[fidelio]

I was going to ask that same question (well sort of - I was going to ask if a tantalum cap could replace alumimum under any circumstances). That's a really good idea, since the two things preventing the PCB from fitting in there are the height of the electrolytic caps and the in/out jacks. I tried flipping the PCB, so the component side was facing up towards the top of the pedal. I covered the inside of the back panel of the enclosure with electrical tape so it wouldn't short. It did fit that way. But something must have still been shorting, since the bypass worked but with the effect on, I got nothing. Finally gave up and ordered a 1590BB.

Thanks for all of the suggestions - a lot of good advice! I might try buying some electrical boxes at Lowe's on the cheap and getting a friend to drill them for me. I'll build him a Fuzz Face clone for his trouble.

[Cozybuilder]

The first pedal I built was a 3 transistor "Ultimate Fuzz", and it was housed in a metal junction box (with knockouts), 3 ½" x 3 ½" x 1 ½", and heavy bottom plate. That was about 1998, I still have it, but it never did sound all that good.

[Granny Gremlin]

That's a really good idea, since the two things preventing the PCB from fitting in there are the height of the electrolytic caps and the in/out jacks.

There's also "low profile" electros.  They are even shorter than tants (esp higher values - large tants can actually be pretty tall, but are easier to lay flat to the board because they're skinnier).

These:


vs these:


Usually a bit wider (might not fit on some tight PCB layouts, but when that happens I just mount it from the other side of the board; they are so short it doesn't get in the way even if it's right below a board mounted pot).  They do cost more than regular electros, but still cheaper than tants and more high value options.

E.G. Echo base with Reg electros on the front.... and a low profile electro (along with that tropical fish) on the rear:





In this case I did that not because I needed to lower the height on the front, but because the fish caps were large (wider than 5mm lead spacing and a bit fatter than typical box films) but I wanted to use them because I had so damn many lying about and this project needed a ton of that same value.  You can also see how some of those tants aren't that much shorter than the electros (though if I needed to there is room to lay that 2U2 tant on the bottom right flat by bending it over to the left).

[Cozybuilder]

I don't replace electros in the signal path with Tant, they don't sound so great, but for power filtering and bypass, they're fine. Caveat is they don't tolerate being wired in reverse polarity (no electro does), but the failure mode with a tant can be spectacular. If you use them, just make sure you get the polarity right. For small box builds, they allow you to do some really crazy stuff!

[amptramp]

Tantalum capacitors are made in a few varieties and their characteristics are different from normal aluminum electrolytics.  The most common type is the dry-slug tantalum.  The tantalum pentoxide dielectric has a dielectric constant of 27 as compared to aluminum oxide which is 9.1.  This is why a tantalum cap can be a third of the size of an aluminum cap.  Tantalum pentoxide tends to form in a film that is pinhole-free, so the leakage is quite low.  For some timing circuits, this is important.  So why isn't tantalum used more often?  It has a failure mode whereby the layer of tantalum pentoxide can revert to conductive tantalum dioxide around defect sites and if you are using it in a power supply bypass application, this conduction starts a fire that sweeps rapidly through the dielectric (in milliseconds) as it turns the pentoxide into dioxide.  Dry slug tantalum does work if the current is limited to the point where the energy supplied is insufficient to start a fire and the advantage of tantalum is that is works at high frequencies as well as low.  BTW tantalum is limited to 100 volt capability with most component ranges limited to 75 volts, so they are not useful at high voltages.

You may run into some military surplus wet-slug tantalum capacitors.  These are good as power supply bypasses, but they do not tolerate reverse voltage - any voltage reversal causes them to grow silver dendrites across the oxide and they short out instantly and irreversibly.  These are usually axial-leaded yellow devices with the positive end red.

Tantalum-cased tantalum foil capacitors are suitable for supply bypassing and are quite rare and expensive - the last time I used them was for an input filter for an inverter powering a satellite and keeping its batteries charged during its stay in the space shuttle.  Since tantalum has a density of 16.69 g/cc, you couldn't just throw a bunch in - you had to design the filter to use a minimum quantity.  The filter as built was within 1 db of the simulation everywhere and 0.5 db in most places so we were able to prove we got it right without adding any excess weight.

The more you know about components, the better you can design circuits.

[Granny Gremlin]

I don't replace electros in the signal path with Tant, they don't sound so great,

Neither do electros (maybe the fancy 'audio grade' ones I never am willing to pay more for, but somehow I doubt it).  That's why (in addition to the tollerance issue) that signal path 1uF electros in vintage circuits are often replaced with films in clone/copy projects.  You just don't have that option (at reasonable cost) with values higher than that. 

[LightSoundGeometry]

can anyone provide some working links for miniature or short electros? I seem to not be good with the google search bar ..only thing I really come up with is ppp has some 47uF radial short ones

ebay provided a few but were like 10 volts and i want 25+ if possible - tayda has some in one value only bu again are only 10 volts and I would like a minimum of 16-25v

[davent]

can anyone provide some working links for miniature or short electros? I seem to not be good with the google search bar ..only thing I really come up with is ppp has some 47uF radial short ones

ebay provided a few but were like 10 volts and i want 25+ if possible - tayda has some in one value only bu again are only 10 volts and I would like a minimum of 16-25v

Page 18 of this build guide has Mouser links to the common values of low profile electro caps. I have ones manufactured by Nichicon or Panasonic again available at Mouser. Pretty sure Mouser lets you sort a search by the cap dimension so pretty easy to pull out what's wanted.

http://www.madbeanpedals.com/downloads/BabyBoardGuide.pdf

dave

[bloxstompboxes]

can anyone provide some working links for miniature or short electros? I seem to not be good with the google search bar ..only thing I really come up with is ppp has some 47uF radial short ones

ebay provided a few but were like 10 volts and i want 25+ if possible - tayda has some in one value only bu again are only 10 volts and I would like a minimum of 16-25v

Steve at smallbear used to carry them. I suspect he still does. Can't check at the moment but I did get some from him a year and a half ago or so.