Very Simple Single Stage Op Amp Preamp

[scottjoplin]

Between pins 1&2 and between 6&7 on the chip

 

[Altecboy]

bypass caps

I put 0.1uF caps from pin 8 to ground and pin 4 to ground. I did it on the bottom side. Pretty small board. I needed magnification to see what I was doing. You could put 10uF from each supply side to ground at the input. It won't be pretty. But it's a buck. Cannot get much cheaper than that.

 

[Altecboy]

corrected schematic

BTW, mine came with different resistors than shown on the ebay site.

r1: 39k
r2 558
r3 1k
r4 3k
r5 68
c2 and c3 are not included and no dedicated solder pads are present.

as delivered, gain of around 4x

 

[Pirmin]

I got one of theese, if I simply short R5 and R6 it will be unity gain? Im slow
1Pcs Power Supply 12-35V Ne5532 Preamplifier Preamp Board Dc Single Ic New D | eBay

 

[scottjoplin]

Trace which pins on the chip they link http://www.remotefactory.com/images/8-pin-dip.png

 

[Pirmin]

Seems like R5 is between pin 2 and pin 3
R6 between 6-7 both in paralell with a cap

 

[scottjoplin]

Check the pin numbers against this diagram http://circuits.datasheetdir.com/37/FAIRCHILDSEMI-NE5532-pinout.jpg
Have you a multimeter?

 

[Pirmin]

Used my mulitmeter, R5 pin 1 and 2. R6 pin 6 and 7. Both in paralel with a cap

 

[scottjoplin]

They are the feedback resistors from the outputs to the inverting inputs. If you short them you'll have your unity gain buffers

 

[Pirmin]

Wohoo!

 

[scottjoplin]

Ha ha!

 

[Altecboy]

the schematic

R4 connects the output to the inverting input. R3 goes from the inverting input to ground. I think you want to remove R3 and short R4. But even if you leave them as is, the gain is very low. The pcb is not really too terrific for rework. Why don't you try it as is?

 

[scottjoplin]

What schematic? He verified R5 and R6 as the feedback resistors