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Author Topic: hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm  (Read 2801 times)
hendrixrules
Posts: 22


hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm
« on: January 28, 2004, 02:57:33 PM »

i wired up the breadboard on saturday but when i turned my amp on i got this really loud low pitched humming noise and when i turned the volume down it stayed a the same volume and pitch :cry:
so i experimented with different componants and i discovered that its the resistors that cause it to hum the higher "K" the resistor the louder the hum :?  is this normal :!:  :?:  :!:
also is it possible to use a polarized 1uF instead of a film :?:
i found this film cap in a old walkman/radio its about 10mmx7.5mm, its dark green and it ses 2A102K on one side, WHAT IS IT?Huh?? :evil:
what difference does it make if i use a 100uf p cap instead of a 10uf, i picked up the wrong one in the shop! :oops:
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aron
Administrator
Posts: 10227

Aron Nelson


Re: hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm
« Reply #1 on: January 28, 2004, 03:14:19 PM »

Quote from: hendrixrules
i wired up the breadboard on saturday but when i turned my amp on i got this really loud low pitched humming noise and when i turned the volume down it stayed a the same volume and pitch :cry:
so i experimented with different componants and i discovered that its the resistors that cause it to hum the higher "K" the resistor the louder the hum :?  is this normal :!:  :?:  :!:
also is it possible to use a polarized 1uF instead of a film :?:
i found this film cap in a old walkman/radio its about 10mmx7.5mm, its dark green and it ses 2A102K on one side, WHAT IS IT?Huh?? :evil:
what difference does it make if i use a 100uf p cap instead of a 10uf, i picked up the wrong one in the shop! :oops:


Sounds like you had DC voltage on the output, that's your hum.

The 102 cap is probably 1000pf or  .001uF.

The 100uF will work. It will pass more of the signal, but should be ok.

You can use a 1uF electro  instead of film,  but you need to orient it properly. The plus side goes to the side with the higher voltage.

Aron
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smoguzbenjamin
Posts: 2718

Ben Allen


hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm
« Reply #2 on: January 28, 2004, 03:17:22 PM »

Yup, don't forget the DC blocking capacitors Wink
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hendrixrules
Posts: 22


hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm
« Reply #3 on: February 03, 2004, 01:24:08 PM »

i forgot to mention that this is my first ever pedal so i dont know anything about 'DC' (except that it has somehing to do with a battery) or about how to stop it, could u explain? :?
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smoguzbenjamin
Posts: 2718

Ben Allen


hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm
« Reply #4 on: February 03, 2004, 03:12:54 PM »

There are two forms of current, Direct Current (DC) which has the current flowing in one direction only like from a battery, and Alternating Current (AC) which is like what comes out of the mains outlet. The current, or flow of charge, goes one way first, and then the other.

A capacitor blocks DC, but will pass AC above a certain frequency. Smaller cap = higher frequency. Because a guitar signal and all other audio is AC, the capacitor will pass the guitar signal, but not the DC current. You can sortof think of them as a wall to stop DC from going places you don't want it to.
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aron
Administrator
Posts: 10227

Aron Nelson


hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm
« Reply #5 on: February 04, 2004, 02:23:20 AM »

Here is an easy way to think about it. Each stage in a pedal - op amp, transistor etc.... should have a capacitor "separating" each stage from each other. This is how it is typically done.

However, there are many cases in which a design will use the existing DC on the signal to bias the subsequent stage.

Anyway, for beginners, think of it as a "wall" separating DC from one stage to the next so that you don't throw off the bias of the next stage.
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hendrixrules
Posts: 22


hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm
« Reply #6 on: February 13, 2004, 02:45:26 PM »

when i tested the resistors and it hummed i didnt have a battery wired up with it
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smoguzbenjamin
Posts: 2718

Ben Allen


hummmmmmmmmmmmmmmmmmmmmmmmmmmmmm
« Reply #7 on: February 14, 2004, 03:53:54 AM »

Then that's your problem, you need to power the circuit  if it has any active components in it Wink
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