Questions about electronic components for guitar pedals

Thread Starter

Ephex

Joined Jul 4, 2021
19
Hi!

I'm planning on making my own guitar pedal (boost) and have some questions.

Is through-hole technology or SMD recommended? I see that most pedals are made with THT and not SMD, does anyone know why? One thought I had was that space isn't an issue in guitar pedals, generally speaking, since they all have such large cases relative to the electronics that go inside. But that can't be it, can it? I am personally fine with both, but maybe the community of making DIY pedals is also a bit "used" to mainly going THT?

Is the type of component important, or is only the values important when chosing? For an example: this circuit below has several capacitors, some being polarized while some are not (C29 not being and C27 being polarized for an example).

1626284333951.png

It's from this YouTube video by Wampler Pedals and in the short views you get of the breadboard I can see that he's mostly using film capacitors, with a couple of electrolytic. Now, does it matter what kind of capacitor you use for the circuits performance (this case being for a guitar pedal), or do you only have to make sure the capacitance and max voltage are correct? Does it matter if the capacitor will be used as, for an example, a coupling or decoupling capacitor?

Polarized vs non-polarized: is this just something that the "correct" capacitor happened to be, or is it very important in some situations that a capacitor is polarized? Take C27 and C30: they both have a pretty "large" capacitance, and will therefore probably be electrolytic and therefore probably be polarized. Is this why?

Thankful for all answers!
 

Martin_R

Joined Aug 28, 2019
103
Guitar effects pedals have been around for as many years as rock and roll. Surface mount components weren't available then, and so leaded components were used exclusively. As far as components go, many designs were about the 'sound', and so the component choice was to create a certain type of distortion. For example, germanium diodes produce a softer 'fuzz' than silicon diodes when used in Fuzz boxes. Capacitor types are probably unimportant, the values though may be moreso, if they are shaping the frequency. Electrolytics must be connected the correct way round and have the correct or higher
voltage rating.
 

MaxHeadRoom

Joined Jul 18, 2013
23,951
Is through-hole technology or SMD recommended? I see that most pedals are made with THT and not SMD, does anyone know why?
I suspect it could ease of construction if one-off or DIY for e.g..
Using Vero strip thru-hole board makes it fairly simple.
 
Last edited:

MrChips

Joined Oct 2, 2009
24,651
Thru hole or SMD - makes little difference in this case. It depends on what parts you have on hand already and how comfortable you are with soldering SMD components.

In some cases the type of construction of electronic components does matter. In this case I wouldn't worry about it until you gain enough knowledge and experience to form your own opinion, unless you believe in using oxygen free cabling.

For capacitors, it comes down to physical size and availability.
For 1μF and lower, use non-polarized. For higher, use electrolytic capacitors.

In the circuit schematic you have posted, C30 is definitely electrolytic.
C29 is non-polar.
C3 can be either. Use whatever you have handy.
 

dendad

Joined Feb 20, 2016
3,940
I would probably use Tantalum caps for the big ones instead of electrolytics.
And through hole parts are easier to use for a prototype on Vero board as @MaxHeadRoom mentions. But if you were to make many, SMD is a good option.
That said, it may be worth using through hole anyway as it may make repair easier, and that could be a thing if it dies while on tour.
 

Audioguru again

Joined Oct 21, 2019
3,872
That same circuit was discussed for about a month or two at the Electronics Point website forum in a few threads about it and it has a few errors.
The polarity of C3 is shown backwards.
There must be a resistor (I recommend 270 ohms) between the C3 and the tone control so that the output of the opamp does not have the 22nF of C29 directly to ground on its output causing the opamp to oscillate when the tone control is set to the extreme left.
Two capacitors have the wrong values.
 

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MrChips

Joined Oct 2, 2009
24,651
Common materials used for making electrolytic capacitors are aluminum and tantalum.
There is nothing wrong with using aluminum electrolytic capacitors in this application for values 10μF and greater.
 

Thread Starter

Ephex

Joined Jul 4, 2021
19
That same circuit was discussed for about a month or two at the Electronics Point website forum in a few threads about it and it has a few errors.
The polarity of C3 is shown backwards.
There must be a resistor (I recommend 270 ohms) between the C3 and the tone control so that the output of the opamp does not have the 22nF of C29 directly to ground on its output causing the opamp to oscillate when the tone control is set to the extreme left.
Two capacitors have the wrong values.
Oh, alright! That's really useful information.

One more question: I don't understand the pots' wirings.

1626296781405.png

Is it like I've written it out? Also, why is the gain wired into the pot from "two directions"?
 

Audioguru again

Joined Oct 21, 2019
3,872
The gain is 501 times when the gain variable resistor is 500k and the gain is only 1 when it is a short circuit.
I would mark its outer terminals as CCW (counter clockwise) on the left terminal and CW (clockwise) on the right terminal. The slider terminal is the middle terminal.
 
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