Need help reading an electrical diagram for CMOY amp.

[Specop 007]

OK, thinking of doing an at home project. Decided to do a headphone amplifier, the Chu Moy design. Nice beginner project right?

So I found a diagram here

And a picture here

Now in the schematic it shows the amplifier section and says duplicate for both channels.
In the picture is where I start to get confused. If you look at diagram #3 it shows the project nearly finished. I assume the middle vertical row is the shared ground, left side is right channel right side is left channel.

Now the part that confuses me... The top left shows a + in, the top right shows a - in. Wouldnt both sides need a + and -? Based on what I see it looks like the left channel is positive and the right channel is negative, but I would think the right channel would have both a positive and negative which would then be mirrored across the left channel.....

So, can anyone help out a confused n00b?

Thanks! 🙂

 

[jmcoreymv]

The dual op-amp only needs one pin for positive power, and one pin for negative power. It is branched out internally within the op-amp IC so both channels get positive and negative voltages.

 

[Specop 007]

Originally posted by: jmcoreymv
The dual op-amp only needs one pin for positive power, and one pin for negative power. It is branched out internally within the op-amp IC so both channels get positive and negative voltages.

Thats what I was wondering, if the op amp wasnt the bridge between the two.

Cool, thanks 🙂

 

[mrrman]

also look at the C1 +, it is in line with the batt +, the same goes for the C1 -, in line with the batt -

 

[Specop 007]

Originally posted by: mrrman
also look at the C1 +, it is in line with the batt +, the same goes for the C1 -, in line with the batt -

I feel fairly comfortable with the power section, its just the amp section thats tripping me up. I think if it were a single channel amp so both sides were mirrored I would pick it up faster, but the dual amp thing is throwing me off a bit.

 

[jmcoreymv]

Check out the datasheet for a basic dual op-amp http://www.national.com/ds/LM/LM1458.pdf

It shows how pins 4 and 8 are shared between the two amps.

 

[Specop 007]

Originally posted by: jmcoreymv
Check out the datasheet for a basic dual op-amp http://www.national.com/ds/LM/LM1458.pdf

It shows how pins 4 and 8 are shared between the two amps.

Ahh, that helps. Thanks 🙂

Hope to order the parts this weekend and work on it next week. I bought my son one of those electronic snap kits here so figured it would be fun to do a "grown up" project with him. Since I already have some nice Senn's, and the CMOY amp is billed as a beginner project I figured that'd be just the thing.

Thanks everyone 🙂