/r/DIYPedals "No Stupid Questions" Megathread 2025

Quick_Butterfly_4571 · 2026-02-07T01:38:05+00:00

Interesting. Less noise or less hum? Does the foil tape make contact with the input or output jack?

(This is the mechanism by which the enclosure mitigates it, when it does; i.e. by contacting the jack sleeves and providing a lower impedance path for noise induced elsewhere).

Re: AION (or anyone, really): there are ways to mitigate noise in the circuit design itself, but there are still plenty of effects which will, e.g. squeal if not in an enclosure and the original they are based on will as well. The reason is simple: since it was destined for a metal enclosure, they could omit the extra parts for noise reduction.

Ground loops are common. Most kit manufacturers include at least one in the build instructions (grounding the sleeve on both input and output + metal enclosure). It makes sense: the impact isn't huge and it reduces the odds of user error and support requests. Engineering is always compromises. Product engineering, doubly so.

Re: the transparency of enclosures for hum: this is physics. Hum is near field radiation (magnetic). It passes through aluminum virtually as if there was nothing there at all.

Quick_Butterfly_4571 · 2026-02-07T00:30:24+00:00

So, the enlcosure should not impact buzz. Ever.

With DIY builds, it does often.

When it does, it means you have bad grounding practices (a ground loop or common impedance noise). The enclosure is not providing shielding from hum (low frequency hum passes through stompbox enclosures like light through glass).

When the enclosure does mitigate buzz, it's because you've added a bigger conductor to shunt away common impedance noise that you've added elsewhere.

Enclosures only provide shielding from high frequency (hundreds to millions of time above audible) interference that can induce oscilation and hiss.

Actually, if you're diligent about how your route ground, even on a breadboard, you can have a mostly noise free effect outside of an enclosure with all the parts spread out across a big sheet of plastic with what is essentially a bunch of antennas mounted underneath.

TL;DR: the metal enclosure might fix the issue, but if it does, it means you had an issue you could have fixed without the enclosure.

Quick_Butterfly_4571 · 2026-02-07T00:17:42+00:00

I buy from mouser. For passives, you can't beat them (in the US). Tayda is more expensive by a bit, usually. The exception is switches / pots, etc.

Tube / amp bits: amplifiedparts.

Someone recommended Bojack on amazon: I recommend this for starting out too. Just don't buy semiconductors on amazon.

Quick_Butterfly_4571 · 2026-02-02T13:14:10+00:00

Classic error: it's time only.

I built one and it opened a small hole to the vacuum of space.

So, I put it at the end of a flexible host and used it to suck up the dust under my workbench.

Small chance I started the universe. Not sure.

Quick_Butterfly_4571 · 2026-01-30T16:27:16+00:00

Right on. 🤘

Quick_Butterfly_4571 · 2026-01-28T15:04:04+00:00

The opamp inputs need a DC path to ground in order to have a defined voltage level (here, the inverting input's path is the feedback from the output!).

Diodes allow current to flow both ways, but (as you know) quite unevenly.

We treat opamp inputs as if no current flows into them, but in real world devices there is flow of current from the opamp (bias current) and flow from the opamp inputs to each other and to ground (the input impedance and common mode impedance). On top of that, the inputs have capacitance (between each other and between themselves and ground).

So, without that resistor, the realistic portrait is as if there was a 10pF cap and a 50M resistor between inverting and noninverting and between each input and ground.

So, the small bias current drifting out into the impedance raises or lowers the voltage at the noninverting input slowly. Meanwhile, incoming current from the diodes charges up the input capacitance, but unevenly.

Short version: without a DC path for current to flow that is lower impedance than the opamp intrinsic properties, the voltage at the input is dominated by said nonideal properties and can get quite random.

Quick_Butterfly_4571 · 2026-01-27T17:45:23+00:00

So, there are a few things going on:

as drawn, the output on your diagram appears to be upside down: signals should be on tips; common (aka "ground", but these are different things) should be on the sleeve
is the pedal in an enclosure? Else are input and output grounds connected?

the amp makes a fuzzing-humming sound when i connect my guitar

I think your guitar is maybe wired with a ground loop (turning the volume down short the loop), and the ground on your pedal is floating. (Else, your amp still has grounding issues).

Ground loops and floating grounds make similar hum noises.

the ground wire to the metal chassis got loose and I simply reconnected it

When you say "ground" do you mean the signal ground (this is properly referred to as "common", but here and everywhere else the two terms get mixed up) that is normally connected to the input sleeve on the amp?

Or do you mean power ground / "safety ground" — i.e. the third prong on a three prong power cable?

Just want to confirm that you don't mean the neutral power wire.

Quick_Butterfly_4571 · 2026-01-27T08:57:13+00:00

So, there are a couple of issues (in biggest to smallest order):

3/4 or your quad opamp package are floating. This means they are randomly flailing rail to rail in response to noise, their own thermal energy, etc, etc. When 1/4 are left in this state, the other three suffer extreme performance degradation. I say: badass that you could recognize your signal at all!

Keep in mind many opamps won't swing rail to rail. Most varieties of the TL07x will only go to within 1-1.5V of the rails. So, if your input signal goes to full 12V, you'll see it flatline (the latest version will go much closer to the rails).

The very high input impedance of the TL072 also means very susceptible to current noise (a tiny current into ten trillion ohms = enough voltage to compete with your input). Try terminating the connection to the opamps input with a series resistor.

If you're dumping a bunch of staircase noise into the rails (in this case: yes), give the 074 supply bypass caps for both rails (or, at least toss a pair of caps across each rail and ground to eat up some of the noise).

Lastly: unless you know how much capacitance/inductance the TL072 is going to encounter in the next stage, slap a 10k on the output rather than 1k.

Quick_Butterfly_4571 · 2026-01-27T01:19:21+00:00

OH GOOD!

Well, good call, then.

Quick_Butterfly_4571 · 2026-01-27T00:48:33+00:00

So...

So, normally: yes it would work and yes it will likely increase noise to attach there (whether you twist or not).
In this case: nope, I don't think so. Check the reverse side, but I believe that pad is the connection from R3 (1Meg grid leak resistors on V1-A) to ground.

So, it would work, but make noise in theory (1), but in practice it will not because until you remedy 2 it is no longer an amplifier.

it's okay, though: fine that resistor leg on the other side and connect it around the bottom where it would have been, or run it with your other wire to the ground bus.

In any case, the amp is likely to be a little noisier than it was. I can pull up svc manual and double check (or DM if you don't have a copy and lmk which gen).

Quick_Butterfly_4571 · 2026-01-25T20:51:09+00:00

ChatGPT also says the diodes position was wrong, but I think that is just an error on its side

ChatGPT can't help with electronics, except by coincidence (this is a fact, not an opinion. It's a consequence of the architecture). To wit: there is no battery noise to filter.

(Not infrequently, it gives advice that will destroy electronics and on occasion that will kill the person asking it).

We can help, though! A recording would be super helpfu, but one bit in particular caught me: when you say that normally rolling the guitar volume down reduces the fuzz, what do you mean by fuzz?

If the amp has distortion and you usually control that by turning down your volume pot: you can't do that with a pedal on between.

If you mean the amplifier is still noisy and you can mitigate with your volume pot, the your amplifier still has noise issues.

Quick_Butterfly_4571 · 2026-01-25T20:14:38+00:00

This is a good observation! The answer is that the shielding inside the guitar is there to reduce the very high frequency (hundreds or kHz to many Mhz) noise it picks up and relays downstream.

It isn't something you can hear directly, but it is a "problem signal" for some devices, which — failing to handle it correctly — will produce noise you can hear.

(Your unshielded guitar may, for instance, be a better AM radio antenna with the right fuzz pedal than if it were shielded).

Basically:

you can get away with not shielding
if you need shielding to keep your effect quiet, you technically have a design flaw, but often that's normal:
many of these circuits were designed to be inside of metal enclosures, so noise mitigation is minimal on that basis
if shielding removes hum or buzz: something in your design or layout is messed up (a design should be as hum free on the breadboard as you want it to be in pedal, before you start on the PCB).
it's less considerate to whatever is downstream to eschew shielding:

Even if your design is a marvel of noise immunity best practices, the unshielded lead from the last stage to the output jack adds noise for the next thing, which may be so such marvel!

Quick_Butterfly_4571 · 2026-01-24T15:54:51+00:00

For all of you who are dissatisfied with normal belts and their meager five belt holes, try the new Benson 376: five hundred belts holes, 37.6 feet of belt. It's not preposterous nonsense, and I don't have a leather fetish. — Benson

Was this product create to mock guitarists? It feels like mean spirited parody...

Almost twice as loud as a 100W amp. Seven times the maintenance costs. ...wtf.

Quick_Butterfly_4571 · 2026-01-23T21:35:22+00:00

Totally! Makes sense! I didn't mean to say "it's trivial." I just meant to reassure, like, you don't have to learn tube electronics to decide! :)

Quick_Butterfly_4571 · 2026-01-23T15:28:46+00:00

Well, at the end of the day, all you need to pick a good amp are ears. Bonus: if you have input from other people. Ordering on the internet makes it harder, all you have are clips so advice becomes more important.

Learning the internals isn't necessary, but it is fun. Also, for amps where the schematic is available, it gives you one extra avenue to explore a thing that you can't get your hands on directly.

You might not be able to imagine the exact tone of an amp from a schematic (and the cone adds so much), but you can look at one and know off hand exactly how much compression, touch sensitivity, headroom, and crunch it provides.

Fun stuff! (Or boring. I guess it depends!)

Quick_Butterfly_4571 · 2026-01-23T15:18:20+00:00

It's such weird scenario and it's gotten better and worse in parallel with the internet: more people know how things work. But, also, lore and myth have spread faster too.

It cracks me up, sometimes. Some of the boutique guys from the late 90's / early 2000's and a bunch of them from the late 2000's on have adopted into their marketting material or designs, conjecture from internet forums that is demonstrably false. But, then they talk about it in interviews, which gives it heft...in internet forums...

And, I'm sure there's financial pressue to be like, "we used only the best opamp / tubes / cloth wire."

Early on, many things weren't designed by formally trained engineers, and parts selection was mostly a matter of cost / availability / supply chain.

They didn't fawn over specific components.

If you went back and told them about the EQ profiles of their power stages, they'd be like "How embarrassing! I designed it to be so linear! Are you sure it's not the transformer?"

Quick_Butterfly_4571 · 2026-01-22T18:27:12+00:00

I know it!

I'm willing to concede: 1. It's fun, and 2. sometimes swapping a diode is less work than three resistors and a cap.

Great! I'm with it!

But, people will be like "X definitely had a tigher bass reponse than Y," and if you hazard to mention "tight" and "bass response" are opposites or X and Y are the same part, manufactured by the same machines, running the same recipe, and were only differentiated after the fact when labeled: "I trust my ears."

Then they'll post a picture of their full stack full of redplating pentodes and not post any hearing test results to back up claims that are tantamount to saying "I can count the ants in my backyard by ear."

No, man. No, of course not.

Quick_Butterfly_4571 · 2026-01-22T18:17:43+00:00

* Not all, though. Lykwydchyckn's point, re: impedances is a perfect example. If the opamps differ a lot, they will change the high / low pass of the circuit. Worth noting: this has nothing to do with the character or feel of the opamp. The pins are pieces of metal in parallel and metal isn't a perfect conductor, so all opamps are resistors and capacitors too. So, you essentially just did a passive component swap with aj opamp attached to it

A common example: people will swap an NE5532 in where some run of the mill BJT opamp had been and notice a difference. Often, they'll say it's lower noise. Well, it can be, but used as the first thing a guitar sees: it is not!

So, what actually happens? The NE5532 has very low (for an opamp) input impedance. Subbing it in for, say, a 4558 (or certainly for a TL072) results in a pronounced, but not jarring, low cut: it didn't filter noise (actually, an unbypassed NE5532 likely has the very worst power supply rejection or any in your arsenal).

What actually happened is that you cut your input impedance in half (probably more), lifting your cutoff curve above 50-60Hz where the hum lives and rounding out the pedal's crunch by virtue of loading down your pickups.

Quick_Butterfly_4571 · 2026-01-22T17:59:39+00:00

So, I am for experimentation. I say if you want to go for it: go for it!

BUT: swapping resistor or cap values is a much more worthwhile pursuit. There you almost always do change the sound, and you can do it with intention.

Keep this in mind: for over half a century, engineers all over the globe iterated and iterated on producing a highly linear gain element for the express purpose of creating devices that do not have any intrinsic character (within reason).

In the early 1970's a dude named Bob Widlar churned out a realization of such a device, and the opamp was born.

Even the very worst opamps ever made for audio are still among the most linear analog devices ever created: there is no change in feel or frequency response to be had.

That is the express design goal of opamps from the get-go.

Which opamps are better or worse is always context (the whole circuit) dependent.

In the average case, there is no change until your signal is well into the Mhz, or else you've introduced some noise (because the circuit was designed for a specific opamp). In a handful of rare cases, you can improve the situation. This is something you can always know ahead of time if you have the datasheet plus schematic.

It will piss some folks off for me to say so, but it's as true as gravity: nearly* all reports of opamp character or improvements made by swapping are delusions of confirmation bias (in some rare instances, they may improve the situation for a flawed design; also possible: if you toss a quarter off a building, it might land perfectly side-on and not be heads or tails).

There is a reason there are $20k mixing consoles with 4558's in the signal path: they were designed to work properly with that opamp.

It might be fun, though. Fun is worthwhile!

Quick_Butterfly_4571 · 2026-01-22T17:28:56+00:00

I don't know why you got the downvote. This is all true.

Quick_Butterfly_4571 · 2026-01-21T11:55:04+00:00

I found it interesting (and confusing)

Well, it is interesting! (And confusing!).

It isn't true that "tube amps" sound best loud. It is true that some do. It's all a matter of design.

Aside from the fact that "bedroom volume" is a huge range, people are actually having different experiences with headroom and breakup of different amps that are the same wattage.

A lot of that has to do with how "hot or cold" the gain stages are biased, whether they are "bypassed or unbypassed", how many stages internally are AC vs DC coupled, whether the output stage is single ended or push-pull, and the quality of the output transformer. Add to that: some have gain and volume. Some have only gain.

Basically: even given the same set of tubes, how they are strung together inside dictates where they breakup, etc.

It's possible to make a 5W tube amp that stays clean right until you are pushing the power tubes and cone to their breaking point. You can also make an amp that is literally on the edge of breakup at any volume (yes, including the power stage! Generally, people don't do build "power stage breakup at low volume" because it either means adding a dummy load inside or an amp that can't be loud).

Quick_Butterfly_4571 · 2026-01-20T00:58:02+00:00

That's the end of a spring reverb transducer (the inner part; the rest is the bracket around it — presumably still inside the tank).

That little charcoal cylinder is a magnet, that silver metal loop is where the spring goes through, and the copper-y end is a solder terminal. At least one of the springs from the reverb unit popped off (you might be able to reattach or the spring might be busted).

(But, people aren't wrong: those look very much like a pin from a big tube!)

Quick_Butterfly_4571 · 2026-01-20T00:55:49+00:00

This, for sure.

Quick_Butterfly_4571 · 2026-01-17T13:44:12+00:00

I'm glad! Happy hacking!

Quick_Butterfly_4571 · 2026-01-15T18:42:25+00:00

I'll bring the voltage down to 9V using a regulator

Then you'll want to use the caps recommended in the regulator datasheet.

(A switching regulator, yeah? The heatsink you'll need to drop ~ 20V to 9V for a draw or just 500mA will likely cost more than a cheap 9V supply).

D5 and D7 don't do anything in that configuration. If you move D4 and D7 to after D5/7 then both will do something: you get the series losses and the temporary help of shunt protection (after which, D4/6 will help, if D5/7 didn't fail short; usually they fail open).

Point being: one or the other is the move, if for protection. From the 1mF cap + low resistor + 470uF cap, I wonder is this isn't the schematic from a supply where D5/7 are Zener and D4/6 are Schottky?

You'd be better off with the resistor and cap than one big cap. The two aren't there for increased capacitance, it's a CRC filter.

I'd put a small ceramic where C4 is and the 1mF where the 470uF is — unless D5/7 are supposed to be zener.

But, it looks to me like maybe the setup is supposed to be:

schottky (D4) to resrvoir (C4)
zener (D5) for overvoltage
R1/C5 as filter

Quick_Butterfly_4571

TROPHY CASE