DIY STOMPBOX = HUM

[crawler486]

Before all u guys blast me with you violent reactions,
I'm only referring to my own build.

I have finished about 7 stompboxes and all of them
have their own degree of HUM.  Distortions having 4-6
transistors are the worst.

What am I doing wrong? How do I get rid of these annoyance?

I would love to try your suggestions.....

[Ge_Whiz]

No blasting, no violence needed. We've all had this problem with builds at one time or another.

Q1. Are you building in metal boxes?

Q2. Are you earthing the metal of the box itself to the circuit?

Q3. Do you ensure that the earth connection is continuous from input screen to output screen?

Q4. For every part that is connected to earth (input/output jacks, case, circuit board, potentiometer track (sometimes)), there should be only ONE route from that point to the common earth. Multiple runs can cause "earth loops". Are you careful to prevent multiple earth paths?

Q5. Does your environment cause commercial pedals to hum?

[zener]

Are your stompboxes in metal enclosures? Are you sure it's really a hum? It migh be just more of a hiss sound that is somewhat inherent to high-gain distortions. What do you use to power up all of these? If you use an adapter then probably it is (or one of) the cause. Are your input and output wire overlapping each other in the enclosure?

First, I suggest you read GEO's debugging page. It's a very good article. You may want to use a shielded wire for the input and output wires. Be sure to connect one end of the wire's copper shield to ground. You can also try to put a small cap (from pf up to .1uf, try to figure out what's good) between the effect output and ground. It will tame the noise at the expense of little drop in gain/volume.  

What are those stompboxes you've build?

[zener]

earth, earthing, one route etc.

Hey Ge_whiz, Can you elaborate more about those things you said, if you don't mind. All I know is the jacks's sleeve are touching the metal case, making the whole enclosure a "ground box".

TIA :wink:

[crawler486]

No blasting, no violence needed. We've all had this problem with builds at one time or another.

Q1. Are you building in metal boxes?

Q2. Are you earthing the metal of the box itself to the circuit?

Q3. Do you ensure that the earth connection is continuous from input screen to output screen?

Q4. For every part that is connected to earth (input/output jacks, case, circuit board, potentiometer track (sometimes)), there should be only ONE route from that point to the common earth. Multiple runs can cause "earth loops". Are you careful to prevent multiple earth paths?

Q5. Does your environment cause commercial pedals to hum?

1. I build using aluminum boxes.
2. Input and output jacks are all grounded in casing.
3.  ?
4. Not sure. All I know is all parts that need to be grounded
   needs to go to ground (if that makes sense)
   i thought ground loops are created when using only on power
   source to supply multiple effects?
5. My Boss and DOD's hums but my DIYs HUUUUMMMMSSSS....

[spongebob]

2. Input and output jacks are all grounded in casing.

And the enclosure is connected to your circuit ground too? In/Out jacks must have a connection to your circuit ground...

How do you power the pedal? Is the hum eventually coming from an unregulated power supply? If you use a battery there should be no hum (=50/60 Hz line noise) at all, transistor noise (hiss) is a different story...

[Ge_Whiz]

In principle, hum can be induced whenever there are two or more routes between a point and an earth.

I don't know what jack sockets you are using, but I would insert a plug into each and check that you have earth continuity from the PLUG GROUND at the input to that on the output, with both showing continuity to the case. I've had problems with socket bodies not contacting the case properly before.

[crawler486]

I use ULTRA CLEAN power supply from GGG.

[ejbasses]

With my experience ground loops cause hummm. usualy eliminating ground loops will cure humming problems


check for possible ground loops. use only one ground point for the whole circuit. i usually use the back of potentiometers or the ground lug on the output jack.

running a cap from the output to ground will cause some loss of high end because doing this will create a low pass filter. you will lose your harmonics if the capacitors value is too big

[Mike Burgundy]

The Aluminium box is a ground path all on it's own.
If you use metal jacks, take the input's sleeve as central ground point - meaning you wire the circuit ground and misc. other grounds (if needed) to this point. Pot casings are already grounded through the box, as is the output sleeve. If you run an extra wire to the output sleeve, there's two paths from the output sleeve to ground...
Internally, run wires from different bits of circuits away from each other, and cross them at right angles. Don't just twist everything together.
Also, make sure you're not near TV's, monitors, computer-related everything or fluorescent lighting.
hih

[RDV]

More gain = More Hum

It will exploit anything in your signal chain that can be a hum generator.

It's one of the main reasons that stompboxes you buy at your music store tend to be lower gain, middle-of-the-road, types.

Shield your guitars, buy better cords, shorten and make neater your DIY stompbox wiring, and the hum will decrease, but not go away.

Sorry

RDV

[petemoore]

IF you're using a power supply wallwart, try batteries instead, at least for experimental purposes.
 when I tried using wallwarts, the HUMM factor was rediculous for my tastes.

[RDV]

IF you're using a power supply wallwart, try batteries instead, at least for experimental purposes.
 when I tried using wallwarts, the HUMM factor was rediculous for my tastes.

Get a Boss PSA-120

Regards

RDV

[smoguzbenjamin]

I use an ancient, bashed up PSU from many moons ago, works absolutely fantastically, with a schemmo inside... I'll copy that out sometime

[puretube]

watchit!!!

aluminum is a very nice metal to work with mechanically;
however in practice, the enclosures you use may (will) have
a al-(di)oxide layer on it, which is invisible, very thin, and is an
almost perfect isolator (insulator) for low voltages.
Be sure to use the chassis as a common ground only with "biting" sawtooth washers, or thoroughly sand the spots you connect
for grounding purposes!

[petemoore]

I just test the case to check and see if ground is made, as well to jacks and circuit grounds.

[petemoore]

I've had guitars that HUMM.
 Unplugging the guitar is a litnus test for hum, A/Bing guitar hum levels is 'fairer'.
 Unplugging the input of the effects, throughout the chain [one by one] IMO is a good 'determiner' of where the hum comes from.
 A little bit of hum in the guitar, when gained up by effects, can easily become big HUM.
 I find the 'process of elimination' technique indespensible.
 Guitar amp CABles...etc. could all contribute to hum.
 What are you using to supply power to these effects?

[bwanasonic]

I second the suggestion to try batteries for troubleshooting purposes. Just because a PS is noiseless in one situation/setup, it does not guarantee it is not the source of your problem in another. I just recently found this out myself in reference to my DIY builds vs. commercial *over-the-counter* boxes. My particular problem was hiss, not hum, but running batteries was the way I traced the problem.

Kerry M

[Ge_Whiz]

Oh yes, try connecting the signal input directly to earth and see if the hum disappears. If it does, it ain't coming from the box.