Basic terminology and circuit symbols

[tjgarcia88]

Hey,
I'm in the process of using a schematic for the original tubescreamer to build my own variation, http://www.schematicx.com/view-schem...pro-schematic/
When I put in my Op amp, how can I tell (by looking at the chip itself) which of the 8 leads is what (4 on each side)? This schematic breaks the IC down by the two sides as two triangles, does it matter what lead connects to what?. also, when a resistor says 4k7 (R6,23) what exactly is the value? Im guessing V+ means a sort of "common" path that,s positive.....and does Vr mean variable resistor, i thought the symbol was an arrow to a resistor. Lastly R19 says 500k log.... what? Any help would be appreciated, I'm very knew to circuit stuff and just want to know how to connect the dots.

[Techknowman]

The chip will have a dot or depression near pin 1. it may also have a u shaped notch at one end. with the notched end up the top most left pin is 1. This is with the chips part numbers face towards you pins pointing away from you.
Numbers go counter clockwise from pin 1

1| ' U |8
2|=== |7
3|=== |6
4|____|5

4K7 means 4.7K or 4700 ohms though I have seen it mean 4K 7Watt {4000 ohms 7watt}
(R6,23) is the part designation number. meaning R6 and R23 are 4.7K values.

Vr (variable resistor) potentiometer ect.
500K or 500000 ohms "Log" means logrithmic its the resistance curve of the potentiometer.
There are 2 types "LIN" Linear "Log" logrithmic.
Logrithmic is also sometimes called audio. Which is used as Volume controls. as the knob is turned clockwise the value of the resistance changes in a non linear fashion. usually alowing easy small adjustments at lower volumes and more agressive closer to the full Clockwise direction.

[defaced]

The schematic doesn't link properly. I get a 404 error.

The op amp data sheet will tell you what legs are what. Each pin has a specific job and if you don't connect the pins to the proper place, you can blow up the op amp. You need this info, so get ahold of the datasheet and do some reading.

4k7 is 4.7k. The decimal tends to get lost (especially in coppies), so an old time way of doing it is to move the unit to where the decimal goes. You'll see this with many different values in electronics. 4u7 for a 4.7uf cap. 4R7 for a 4.7 ohm resistor, and so on.

V+ is probably battery voltage positive. So yes, a common positive voltage.

Don't know about Vr since I can't see the schematic. Maybe a reference voltage, but I've never bothered to digest the tubescreamer workings so I'm just guessing.

500k log is a 500k, log taper pot. In the USA that's typically called out as 500KA, while in Europe is usually 500KB. And to make is confusing, in the USA linear taper pots are B and in Europe they're A.

You might want to also check out the stompbox forums. DIY Stompboxes, Free Stompboxes, and Build Your Own Clone all have very active and helpful forums. These guys breathe stompbox solder fumes, so you should get some good help there.

[Techknowman]

On the triangles question.
the triangle is an operational amp(op-amp). your chip has 2.
each op-amp has a +(plus) and a -(negative) input and an Output.

You must keep the "triangles" shown on the schematic the same.
the + and - for a givin output must be used. However you can use one sides "triangle" in place of the other as long as you use its +, - and output.
But its best to follow the schematic as it is.

[Enzo]

He PM'd me with this yesterday, and on his schematic, the pots are just R numbers - R19 etc - his Vr was the reference voltage at half battery formed by two 10k resistors.

[Enzo]

Oh, and welcome to the forum, tj, glad you could join us.