schematic help

i am going to build a guitar effects pedal, i have found the site to buy peices off and a good schematic plan. the only problem is i can understand things like, where to atach the earth and more importantly, where do the '+' & '-' contacts atach.
and, when you look closely at the plan, you will see, 250k a-drive, near a switch. is this a pot or resistor or even just the whole switch.
at the in and outouts there are numbers, 1n and 22n, what does this mean?
and finaly, at the output, why does it point to a resistor.
thanks dudes.

caleb said:

i am going to build a guitar effects pedal, i have found the site to buy peices off and a good schematic plan. the only problem is i can understand things like, where to atach the earth and more importantly, where do the '+' & '-' contacts atach.
and, when you look closely at the plan, you will see, 250k a-drive, near a switch. is this a pot or resistor or even just the whole switch.
at the in and outouts there are numbers, 1n and 22n, what does this mean?
and finaly, at the output, why does it point to a resistor.
thanks dudes.

Click to expand...

Usually, that symbol with the 1n and 22n means capacitor... so I'm pretty sure 1n means a 1nf capacitor. The grounds go to battery ground (the - on the battery) and the + is where it says +V. So, again the + attatches where it says +V and the negative attaches to ALL the leads that point to ground. The 250k-A means 250kohm adjustable resistor (I'm guessing in this case, its adjusting the drive). You'll also see a 100k-A volume, which is a 100kohm adjustable resistor for the volume.

ok, i seem to get all except a bit unsure on the ground still, are you saying all the grounds connect to the negative '-' on the battery.

yes, ground is negative in this case. Ground is not always the negative terminal however.

A potentiometer has three leads on it. One at each end of the resistor and one lead that changes resistance as the knob is turned. In the case of this circuit your output volume is defined by the changes in the potentiometer.

anything that looks like this: --/\/\/\-- is a resistor, measured in ohms... if the schematic says 1M5 it means you need a 1.5 megaohm resistor.
anything that looks like a resistor with an arrow pointing to it is a potentiometer, or a variable resistor.

anything that looks like this: ---||--- is a capacitor, measured in farads... if it says 3n3 it means you need a 3.3 nanofarad capacitor. The greek symbol "mu" (funny looking "u") means "micro" btw.
the capacitor that looks like this: ---|(--- is a capacitor where polarity matters.. the curved side of the diagram is negative and is indicated by a stripe on one side of the cap.

I'm not quite sure what the purple things in the schematic are, some sort of transistors. consult the part sheet.

in any schematic where V- isn't specified, it can generally be assumed that gnd connects to the negative terminal of the battery... and in the case of a guitar pedal with no input specified for the negative side of the headphone jack, you can assume that connects to gnd too.

Also, I believe that the 250K Ohm A pots are audio taper (non-linear) and the B means linear taper.  All the grounds go to a common case (earth) ground.
What is this a "fuzz tone" ?? The arrow on a pot denotes the wiper not polarity.

Mike

Good catch Mike, they would have to be non linear.

FC --
Yah --  I'm an OLD audio man.  I still have my clone Fender tremolux amp I built in high school !!  2- 6L6's in the final amp  

I think those "purple things" are n-channel J-fets

Mike

its overdrive.
is there 3 switches, that alot, or are some integrated into the in/output?
and 4 pots?
where do the three terminals go on the pot, is on positive, one negative and the other something else?

caleb said:

its overdrive.
is there 3 switches, that alot, or are some integrated into the in/output?
and 4 pots?
where do the three terminals go on the pot, is on positive, one negative and the other something else?

Click to expand...

The "switches" aren't switches, they're transistors.  Hemlock Mike said N-channel Jfets (personally I don't know the type).

There are typically 3 terminals on the potentiometer, usually the middle (or pin 2) is the wiper, which is shown as the arrow head portion going to the middle of the resistor symbol on the schematic.  The other pins, 1 and 2, are either end of the resistance "track" that the wiper runs over to produce a resistance.

On the ones that show the wiper arrow connected to the one side of the resistor, that means pin 1 and 2 are connected together to whatever is on the one side and 3 is connected to whatever is on the other side.

On the schematic components that show just the arrow pointing to the middle of the resistor, that means it's being used as a potentiometer or voltage divide, where the wiper (pin 2) is connected by itself to something, while pin 1 and pin 3 are also connected to whatever is on either side of them.

The "pins" I refer to are the common arrangement, so you should be sure of which pins are connected to the resistance track and to the wiper to be sure.

Also, do you have a parts list for this schematic?  It would be a good idea have one, as it will probably be difficult for you to build this circuit without knowing exactly what you need.

EDIT: I see the creator listed recommended transistors at the bottom "Use J201, MPF102, or 2N5457". Thought I'd also point out that the V+ is the power source positive, "IN" is your audio signal positive input, "OUT" is your audio signal positive output, and the striped headed arrows pointing down at the bottom are ground, to which the power source negative and audio input/ouput negative should all be connected.

Caleb --

Now there's a ton of info --- Now build it

Mike

is also says adjust trimpots to 1/2 voltage. do i just turn them half the way round?
resistors
1M X2
1K
22K
1M5
10K
3K

Pots
100K 'trim' X2
100K-B
100K-A
250K-A

Capacitors
1N X2 (is that 1 nanofarad?)
3N3 X2(3.3 nanofarad?)
6N8 (6.8 nanofarad i guess
22N

And so how many switches, one i guess?
and 2 transistor, anyone know what type?

thanks dudes, i should be building by the weekend! hopefully!

Your parts list looks good, and you are correct on the nano-farad measurement of the caps. Unfortunately I cant help you with the transistors, as I really don't know enough about their schematic notation to comment :-[

The 3 n-channel JFETs could also be replaced by BF245B,C

caleb said:

is also says adjust trimpots to 1/2 voltage. do i just turn them half the way round?

And so how many switches, one i guess?
and 2 transistor, anyone know what type?

Click to expand...

I don't know about the trimpots, you may want to contact the original maker of the design about how exactly to set it up.

As for the other questions, have you read mine and others' posts?  :

There are NO switches shown in the schematic... if you want to add one to turn the power on/off, that would be a good idea.  I'm guessing you'd also want a switch for turning the effect on/off as well?  For the effect, I'm guessing you'd need something that was a push on/off switch that would just pass the audio signal through when "off".

Also, you may want to take a look at this for your reference, it shows a board layout:

http://www.runoffgroove.com/odie.html

i found a better one, it has the schematic (with every part listed), a wiring diagram and the checklist of all the parts.
ooh.. and an LED. and the switches.
but, you didnt waste your time, you helped me heaps.
il tell you if it worked or not.