First build complete :0

[jplebre]

Hey all

Just finished my first build. I am pretty sure loads of things went wrong as it was first build, loads of experimentation, things read and misinterpreted, etc.
Right, the build is R.A. Penfold's soft distortion from it's really really small book. It sounded better breadboarded than in the PCB so I must have done something wrong :S

Things noted:
- Turning a schematic into a pcb layout is hard :S a lot of headscratching! Already have all the parts laid out to start doing a Dist+ but I'm not sure if I'll even attempt to do the perfboard layout myself :S
- I need more bits... some things are .5 bigger or smaller, and the unibit only goes in sizes of +2. Thanks all for your wonderful posts on drilling specially jacoby for his unibit+vegetable oil! it does work like a charm!
- I read in the book that the resistor network that bias the opamp input sets the input impedance. I tried to fiddle with it before I read some of the posts here. Am I correct to understand that the cap "resistance" (for the e-litic cap found on inputs) value is even more important? I raised the 2 resistors value (sounded better on breadboard actually, specially since I have a active guitar) and added a resistor before the input (yeah, I know... i was already slapped in the hand for trying it).
- Followed GausMarkov 1590B enclosure wiring (3dpt)! thank you for that awesome work!

Things wanted to ask:
- Had a really hard time getting everything into the box. How do you guys go about wiring everything? cause if you get your cables too short, it's impossible to have space to keep wiring, if you leave them too long, you can't fit everything in the box :S
- As above, some could clarify the input cap and how the impedance is set?
- Any other tip you could see for the next build?
- How to place the PCB in the box, without causing shorts with the actual enclosure itself (and looking a bit better than electrical tape :S

Ty in advance


It's from Penfold's Book. In UK people are alowed to copy and post for academic reasons if it goes against this forum I'll remove it (or moderators feel free to edit

[deadastronaut]

hi, that looks good for a first build, i like the idea of those ridges to hold the pcb..

yeah those penfolds books are great!. i have a few of them (in the uk).

some people build the pedal out of the box, then put it in it...

people do this using a wooden/cardboard template of how it will look, to hold all the parts together as if looking inside the box,
it just gives you a lot more room to solder when its not actually in there...and easier to test before boxing up, only to have to rip it all out if theres a problem

another thing is use double sided foam tape to stick your pcb/vero to the linside lid of the box...(if not ribbed)

or plastic 'standoffs'...but foam is smaller..

use heatshrink on your led wires, and any that my be prone to touching the case,jacks,etc....

checkout the GEO FAQ'S link at the top of this page.lots of info....

[jplebre]

Thanks deadastronaut!

Loved the tip about the heathshrink and might give double sided tape a go!
But do they sound anything remotely good or did I do something terribly wrong?

I'm going back a couple of steps and do the beginners boost. Just ran out of 22uF caps and waiting for a delivery.
Then I might try a dist+

Will have a look at that site you suggested.

I was looking for a post I saw a couple of days back where people were doing run downs of schematics telling what component does what. Any idea where that is as I can't find it?
Cheers

[Yibbon]

Perfboard / Stripboard can be a nightmare sometimes! Get into pcb etching sooner rather than later, much cleaner builds and still plenty of DIY fun involved! Neat soldering!

[jplebre]

Hi Ebon!

I did recently. Etched a couple of stuff out of tonepad and gauss markovs, and Steve Mavrone's Dist+.
It is actually pretty fun to go around like a mad scientist whilst you are etching!


Just need to learn Eagle.

[darron]

bloody hell that wiring is NEAT for a first build! I wish my builds looked this good by #10!! wire lengths are well measured.

[jplebre]

Thank you!

Just spent some time on your forum your stompboxes look great!!!
Gut shots please!!!

(and the stompbox you show on the website... now THAT's some wiring! I'm gutted that I bought tons of colours of that extra thick piece of junk gauge wire that makes everything so hard to squeeze in properly

I ordered with just the gauge thickness only to find out that UK has a slight different system.

Been a bit indecisive if I should twist the wires inside :S

[jplebre]

I think building studios the pace I have over the last year helped.
Tons of these:

[Greenmachine]

Excellent first build.  Twist the wires if you want, but I think they look amazing as-is.

[jplebre]

Thank you!

I do appreciate the incentive

[joegagan]

hahaha. i opened up the thread, took one look at the soldering on the omeg on the right, said to myself, this is a pro. i nailed ya, thanks for the confession. nice build, for sho

[CynicalMan]

- Had a really hard time getting everything into the box. How do you guys go about wiring everything? cause if you get your cables too short, it's impossible to have space to keep wiring, if you leave them too long, you can't fit everything in the box :S

I keep the box beside me, preferably drilled beforehand, and I use it to help estimate wire lengths. I don't actually solder with parts mounted in the box, and the estimation takes a little practice but I get fine results IMO.

- As above, some could clarify the input cap and how the impedance is set?

In that circuit, the input impedance is 50k, more or less. For an op amp input like that, you can usually act as if capacitors and power supplies have zero resistance and the op amp input has infinite resistance. Usually the input cap is selected so that all useful frequencies get through, so its impedance is low enough to ignore. For example, the reactance (AC part of impedance) of a 1uF capacitor is 159 ohms at 1kHz.

You can use this to calculate the actual input impedance:
Zin = 1/(2piCF)+1/(1/R1+1/R2+1/Zo)
Where C is the input capacitor, F is the frequency in question, R1 and R2 are the bias resistors, and Zo is the input impedance of the op amp. Really, all you need is Rb/2, assuming that the bias resistors are equal. Knowing that it's around 50k is enough.

- Any other tip you could see for the next build?

Looks great for a first build, way better than my first build (which was around my fourth attempted build  ). I'd suggest leaving less uninsulated wire between the insulation and whatever you're soldering to. This prevents flexing at the uninsulated part and reduces the chance that the wire will break. Also, it looks cleaner.

- How to place the PCB in the box, without causing shorts with the actual enclosure itself (and looking a bit better than electrical tape :S

I put my boards over the pots, component site up. Then, I put adhesive rubber feet on the back of the pots to prevent shorting. As long as my wires aren't too long and I don't leave any exposed wires on the top of the board, the board is more than stable enough. I disagree with Yibbon about stripboard; once you get some experience with it, it's way faster to use than a PCB. You don't have to etch or drill, and all you have to do instead is put on a few more jumpers and cut some traces. Way quicker.

[jplebre]

- As above, some could clarify the input cap and how the impedance is set?

In that circuit, the input impedance is 50k, more or less. For an op amp input like that, you can usually act as if capacitors and power supplies have zero resistance and the op amp input has infinite resistance. Usually the input cap is selected so that all useful frequencies get through, so its impedance is low enough to ignore. For example, the reactance (AC part of impedance) of a 1uF capacitor is 159 ohms at 1kHz.

You can use this to calculate the actual input impedance:
Zin = 1/(2piCF)+1/(1/R1+1/R2+1/Zo)
Where C is the input capacitor, F is the frequency in question, R1 and R2 are the bias resistors, and Zo is the input impedance of the op amp. Really, all you need is Rb/2, assuming that the bias resistors are equal. Knowing that it's around 50k is enough.
[/quote

brilliant, thanks! I need to actually use it a couple of times to fully grasp that, but makes more sense!