Few Questions On Components For A Pedal

[JoJo T. Magnifficent]

hey, I got a PCB printed out at university for the 4-transistor modified electra distortion pedal (just as a fun project, dunno how it sounds, but i can get most of the stuff for free at uni, including the PCB ) and i was just wondering about a few of the components:

Resistors: I could only get 1/8 watt for the 470 ohm resistors (no idea why, all the others are 1/4 watt ), will this be enough? I figure running of 9v that means the would only like sub 20mA currents, which may be cutting things a bit close.

Diodes: I could only get 1N4148's, the schematic says to use 4x 1N4001's and 4x 1N34A's, is this likely to have a signifficant effect on anything other than the tone/gain levels?

and finally,

Transistors: The schemtaic used a 2N3904, ive never even heard of that kinda code for a transistor, im only familliar with BC named ones, had quick look this afternoon at a eletrical supplies store and couldnt find any, so if anyone knows of an alternative code that would be helpful, and also again, if using any other NPN transistor would effect anything other than tone/gain (I think we have BC337's or sumthing at uni that are NPN)

cheers for any help you can give guys

-nick

[lovekraft]

The 1N4148s will sub for the 1N4001s fine in this case - the 1N34s are gp germanium diodes, and can be sub'd with 1N60s, 1N270s or any other general purpose germanium diode. The 2N3904 is a general purpose medium gain small-signal NPN transistor, and there's nothing special about it, so any model matching those specs should work fine. That circuit is pretty wel-designed, and it'll tolerate a fair amount of tweaking without turning into total rubbish. Once you've got it built, you can start modding it if you want a little more of anything (like gain, bass, or whatever).

Edited October 6, 2005 by lovekraft

[JoJo T. Magnifficent]

The 1N4148s will sub for the 1N4001s fine in this case - the 1N34s are gp  germanium diodes, and can be sub'd with 1N60s, 1N270s or any other general purpose germanium diode. The 2N3904 is a general purpose medium gain small-signal NPN transistor, and there's nothing special about it, so any model matching those specs should work fine. That circuit is pretty wel-designed, and it'll tolerate a fair amount of tweaking without turning into total rubbish. Once you've got it built, you can start modding it if you want a little more of anything (like gain, bass, or  whatever). 

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Thanks heaps, i should be able to get some germanium diodes easy, aswell as the NPN transistors.

What about the 1/8th watt resistors? Im guessing the should be ok, because the transistors would go aswell if there was sufficeint current to burn the resistors (more than 20mA). So Im guessing that it will run ok, just mayb a little hot

[lovekraft]

By my calculations, 1/8 watt in 470 ohms takes only about 16mA, which is unlikely, but not unheard of - can you link me to the schematic, so I can figure out how much juice that resistor is pulling?

[JoJo T. Magnifficent]

http://www.geocities.com/j4_student/4trans.gif is the one im using

I just realised i got the diodes backwards in the PCB schematic, so ive fixed it up and ill re-submit it later, hopefully theyll print it out again (although i was surprised they did it in the first place).

cheers for all your help lovekraft

[lovekraft]

Uh, JoJo,.... there's not a 470 ohm resistor in that circuit. If you're talking about the 470 kilohm resistor(s), 1/8 watt should be no problem!

[JoJo T. Magnifficent]

lol, my bad, thanks for pointing that out. i wonder if i actually used 470 ks or not :S thanks for pointing that out. I managed to get some 1n60s aswell.it may take a while to get the working PCB back, if I can get one at all. If not Ill just have to settele for the 5 year old bit of veroboard I found in my closet thismorning

my brain dont seem to be working too well, too many assignments due, not to mention the duck project ( we basically have to make an IR gun that can track one of 3 plastic ducks that generate pseudo random binary code, find it and kill it. they made it quite challenging though, by making the prbs clocked at 133hz so we get ALOT of noise from mains hum and the flourecent lights on the prbs reciever).

Thanks for all your help lovekraft.