How things sound when they go wrong.

[PMowdes]

Hi all

I was wondering if there is any sort of resource where I could actually listen to common faults with pedals, so that I am better able to fix them.

I've built a fair few different pedals now and there are a few that are working but i'm sure aren't right.  
For instance I have a Rub-a-Dub Reverb Deluxe  that picks up noise over time which resets when I sweep the mix pot.

And I have a Harmonic perculator that sounds kinda thin and tinny, and the only way I can describe it is that it sounds like my guitar did when I wired the pickups wrong (out of phase maybe??)

I don't feel that I am experienced enough to explain what these sounds are like and I think that it is holding me back.

Thanks in advance, and thanks for creating such a welcoming and inclusive community.

[Neil mcNasty]

I'm not sure about your Rub-A-Dub, but it might sound like a bad electrolytic cap...

My experience with the Harmonic Peculator is just like you describe it: Thin, Hard, Tinny and hardly no low end at all. As I understand it, that is part of the design...
But there are several version of the circuit; one version has a 10nf input cap and others have 50nf (47nf in todays standards).
If yours has a 10nf as a input cap, you could replace it with a 47nf in order to let more bass/low end pass trough.
The Output cap also varies between the versions as well; one having a 100nf, and others got 1uf.
This will affect how much low end is coming out the other end...

Hope this helps you to modify it to your liking!

[PMowdes]

Neil mcNasty wrote

I'm not sure about your Rub-A-Dub, but it might sound like a bad electrolytic cap...

My experience with the Harmonic Peculator is just like you describe it: Thin, Hard, Tinny and hardly no low end at all. As I understand it, that is part of the design...
But there are several version of the circuit; one version has a 10nf input cap and others have 50nf (47nf in todays standards).
If yours has a 10nf as a input cap, you could replace it with a 47nf in order to let more bass/low end pass trough.
The Output cap also varies between the versions as well; one having a 100nf, and others got 1uf.
This will affect how much low end is coming out the other end...

Hope this helps you to modify it to your liking!

Thanks Neil,

I'll give those a looking at.

I was kinda hoping for some reference material really.  Maybe this sort of thing comes with experience.

 I just find it hard to understand what it is supposed to sound like when you've not really heard it before, like if you make a recipe from a cook book and there's no picture or you've never tasted it before, how are you supposed to know what it looks and tastes like.

[Neil mcNasty]

As far as I know there is no such thing as a reference guide for this.
Actually, I guess it would be almost impossible to make such a guide unless you designed every circuit + has stumbled upon every problem possible multiple times.
Sure, there are some people who can immediately hear that a transistor is mis-biased, and some other issues, but as you say: That comes when you have built up a large amount of experience.
As an example: I suspect that the guy who runs D*A*M can diagnose a germanium based fuzz circuit very well, since that is what he does.

But there are quite a large amount of PDF books and guides in the Library Section of this forum.
Have you had a look at those?
There you will find a lot of links that you can check out in order to understand more about what is going on inside a pedal,

The way I (and probably many others) approach it:
Learn how to recognise what affects what in the circuit, starting out by reading schematics and figuring out: what section is the audio path, which section is dealing with power and biasing, and then start experimenting with how to tweak it to your liking.
This way you will start to break it down into sections, enabling you to go a step further and understand how the different components affect that specific block of the circuit.
IOW: Work your way trough it systematically step by step, starting out with the simpler stuff and working your way up to more complicated stuff as you progress.

Almost every pedal ever made has a demo on YouTube.
But be aware that a demo never sounds like it will do on your setup, with your playing style.
So the demos only give you a general idea about how it will sound, and what style of pedal it is.

In my world, I try not to focus on how it is "supposed to sound", but rather "do I like how it sounds?".
And if I do not like the sound after I have built something... I tweak it until I am happy with it.
Or throw it away/recycle the parts, if it's too far away from what I like or need.

[Beaker]

"And I have a Harmonic perculator that sounds kinda thin and tinny, and the only way I can describe it is that it sounds like my guitar did when I wired the pickups wrong (out of phase maybe??)"

Yep, thin, hard, tinny - and insanely loud! That's exactly what they're supposed to sound like. Don't forget that this is the Steve Albini pedal.

[induction]

Neil's advice is good.

It is sometimes possible for an experienced builder to diagnose faults by ear, but that comes from experience, and remembering what was wrong with the circuit the previous times you heard that particular sound. It's much, much harder to diagnose circuit problems based on someone else's description of the sound because there's no standardized vocabulary for sounds. (Is it a hum or a rumble? Are the mids haunting or elastic?) For example, misbiased transistors often have a recognizable sound, but it usually depends on which direction it's misbiased towards, and you'll never learn the sound from someone describing it to you. You have to hear it for yourself.

To make it worse, it's possible for some types of errors to have many possible sonic results, and likewise for the same sound to be caused by many different faults. For these reasons, an index of descriptions of sounds correlated to their causes would be difficult to create, and likely to cause more harm than good. There's a small range of ways that a given circuit can be built correctly, but the ways to mess it up are nearly limitless.

In any case, your ear is a good tool for letting you know that something is wrong. But if you want to know exactly what the problem is and how to fix it, voltage measurements, audio probes, and a familiarity with basic circuit blocks are the path to enlightenment.

[PMowdes]

Beaker wrote

"And I have a Harmonic perculator that sounds kinda thin and tinny, and the only way I can describe it is that it sounds like my guitar did when I wired the pickups wrong (out of phase maybe??)"

Yep, thin, hard, tinny - and insanely loud! That's exactly what they're supposed to sound like. Don't forget that this is the Steve Albini pedal.

Yeah man, i been listening to Songs about Fucking a lot recently.  And the new Dinosaur Jr album.

[Frank_NH]

Just a quick point on this topic.  One of the things that attracted me to the DIY pedals hobby is the prospect of making an existing design **better**.  With DIY, we can do this provided we have a good understanding of a circuit's operation and how different components affect the sound.  I've done my fair share of tweaking (e.g. modifying some capacitor values in the Marshall Shredmaster circuit), and it's very satisfying when the result is something that is better (for your guitar, amp and setup) than the original.

[PMowdes]

Frank_NH wrote

Just a quick point on this topic.  One of the things that attracted me to the DIY pedals hobby is the prospect of making an existing design **better**.  With DIY, we can do this provided we have a good understanding of a circuit's operation and how different components affect the sound.  I've done my fair share of tweaking (e.g. modifying some capacitor values in the Marshall Shredmaster circuit), and it's very satisfying when the result is something that is better (for your guitar, amp and setup) than the original.

Fair point Frank, I'm afraid I'm still at the trying to figure out the schematic and how it relates to the layout phase, so that I can figure out where to prod my audio probe.

I found the big muff page really useful in explaining how the circuit works and the various different stages.  If this forum had something like that for a bunch of more common effects it'd be a major help, but I understand that you guys already put in so much time making layouts and helping people out when things go wrong.

Build, debug, learn, repeat!

[Neil mcNasty]

Jack Orman's site http://www.muzique.com is a wonderful resource when it comes to learning about stuff like this.
I would also recommend R.G.Keen's http://www.geofex.com
Specially Keen's Law is essential reading. http://www.geofex.com/effxfaq/keenslaws.htm

I have learned a lot by spending time on these sites!

[Frank_NH]

"Build, debug, learn, repeat!"

Actually - since you mentioned "build" let me heartily recommend using a breadboard for prototyping and experimenting with circuits.  I did this with some projects this year and it's so easy to switch out parts and test what they do.  You can even do this for projects you're not sure about building - if you like it, then you can build the project with the parts from the breadboard.

[PMowdes]

Frank_NH wrote

"Build, debug, learn, repeat!"

Actually - since you mentioned "build" let me heartily recommend using a breadboard for prototyping and experimenting with circuits.  I did this with some projects this year and it's so easy to switch out parts and test what they do.  You can even do this for projects you're not sure about building - if you like it, then you can build the project with the parts from the breadboard.

Funny you should say that.  I ordered a few at lunch time.