# Need Help With Schematic for Amp

#### bubbagump0

Joined Jul 10, 2007
26
I am drawing up a schematic for a small 1W stereo amplifier, based off of another schematic (Im doing a few minor changes.) I am fairly new at drawing schematics, and I came across a symbol that I didn't understand. It is an arrow going from a pin of an IC to a resistor. I included the link for the schematic, and attached a picture of what the symbol looks like. I am using ExpressSCH. If anyone can tell me what the symbol means and how to replicate it with ExpressSCH I would be very thankful.
http://kitsrus.com/pdf/k87.pdf

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#### spar59

Joined Aug 4, 2007
57
If you are referring to the arrows at P1A and P1B these resistors are potentiometers - variable resistors the arrow is the sliding contact.

Steve

#### spar59

Joined Aug 4, 2007
57
In this instance they are the volume controls the 10k means they are 10,000 ohms measured between the 2 non-sliding contact connections. The log means the characteristic of the resistance track that the slider moves along is not linear but logarithmic - so when an input voltage is applied via IN1 for example the voltage into pin 7 when the potentiometer is at half travel is not 1/2 the applied voltage but a lot less - this particular chacteristic is to match the response of our ears which become less sensitive at high sound (power) levels and hence on the final 50% of travel a lot more than 50% more output is required to make it sound twice as load.

Steve.

#### hgmjr

Joined Jan 28, 2005
9,029
As already indicated it is a potentiometer or variable resistor. spar59 has described the function of such a component nicely.

hgmjr

#### bubbagump0

Joined Jul 10, 2007
26
Thanks, but what I really want to do is replace the potentiometer with two 10K resistors. Once I do that, I don't know how to or if I should connect pin 7 and 6 to the two 10K resistors.

#### spar59

Joined Aug 4, 2007
57
In that case the first resistor is connected between the +ve side of C2 and ground and pin 7 is also connected to the +VE side of C2.

Similarly the second resistor is connected between the +ve side of C3 and ground and pin 6 is also connected to the +VE side of C3.

Steve.

#### nomurphy

Joined Aug 8, 2005
567
In my opinion you should replace the pot(s) with two 5K resistors for each pot (in series from C2 to GND & C3 to GND), which then add up properly to equal the 10K pot(s) being replaced.

The input to the IC, such as IN1+, would be from the center of the two resistors between C2 & GND. This also has the effect, provided the resistors are of equal value and irrespective of their actual value, of dividing the input signal in half.