Help on basic concept!

[DottJ]

Hi all,
i'm trying to undertand the basic concept of this world.
Someone could tell me the difference on this resistor ( specially for the W parameter) and how i could choose the right one?
4K7 CF Resistor 0.25W or 4K7 CF Resistor 0.5W or 4K7 3W Resistor

This way to write is the same? 4K7  or   4,7k ?

this two part are different ? 1n914 1N4148

on this site http://www.bitsbox.co.uk i coudn't find the 1n914

For the resistor i found carbon and metal film type... any difference?

thanks

[bluebunny]

The "W" (watts) is the maximum power dissipation of the part.  It's a product of the voltage (V) across the resistor (in this case) and the current (I) flowing through it.  For pretty much all pedal projects, this value will be very low - less than 0.25W.  So unless the project calls for it, use 0.25W resistors.  They're smaller too.  (Although they would all function correctly electrically.)

And you'll find the value you gave in your example written "4K7", simply because the , or the . might get lost when a schematic bitmap gets resized or scanned or photocopied (or multiple combinations of all these information-losing processes).  It's all the same value, just written that way for clarity.  You'll see the same method used for capacitors, for example, "2u2" rather than "2.2uF".

The 1N914 and the 1N4148 are pretty much equivalent.  There are differences, otherwise both parts wouldn't exist!  But so far as you're concerned they are the same and interchangeable.

Again, there are differences between carbon and metal film resistors.  I won't suggest you can't hear it, for fear of a horrible flamed death.  They might be a slightly different price.  The carbon film will typically have 5% tolerance, compared with the metal film with 1%.  This is unlikely to matter for most projects.  I believe there is more self-noise from carbon.  Again, this is unlikely to trouble your ears.

[greaser_au]

Someone could tell me the difference on this resistor ( specially for the W parameter) and how i could choose the right one?
4K7 CF Resistor 0.25W or 4K7 CF Resistor 0.5W or 4K7 3W Resistor

This way to write is the same? 4K7  or   4,7k ?

The W (wattage) rating tells you how much power the resistor can dissipate (waste) before it will fail. To be able to select intelligently you need to know the current through it or the voltage across it. In most small signal applications even the CF 0.25W will be overkill, but in more demanding  applications you may need a higher rated part.

4.7k (or 4,7k depending on where you're from) = 4k7 = 4700 ohms.

this two part are different ? 1n914 1N4148
on this site http://www.bitsbox.co.uk i coudn't find the 1n914

1N914 and 1N4148 are silicon small-signal switching diodes with *very* similar characteristics. I'd suggest you could likely use them interchangeably in 99.99% of applications!

For the resistor i found carbon and metal film type... any difference?

In general terms and at the hobbyist level:  Carbon film are ever so slightly noisier than metal film.  The CF is less expensive.  Usually CF is 5% (3 band code) and MF 1% (4 band code). The 1/4W CF is usually the same physical size as a 0.6W MF.

hope this helps
david

[mcknib]

Here's a wee PDF I did a while back 'A beginners guide to effects pedal components'

Should hopefully help you gain an understanding of components used in pedal building

I say 'I did' it'd be more accurate to say I added to other peoples work and put it in some kind of order the idea behind it was to stop beginners making the mistakes I made when I started i.e buying capacitors way too big for pcb work etc.

There are links throughout for further reading

http://www.guitarpcb.com/PDF%20Files/A%20Beginners%20Guide%20to%20Effects%20Pedal%20Components.pdf

[deadastronaut]

^ excellent work on that billy,

a must for anyone considering building...