I'd like to add a low gain switch

[hifitoaster]

After the Crack, I was hooked. So build the S.E.X., it sounds awesome! I really like it with the LCD-X headphones (20 ohms, Sensitivity: 103 dB/1mW). However there's some hum with those headphones and I can BARELY turn the volume up from 0%.

I'd like some advice on how I could wire a low gain switch in the amp. Perhaps adding some resistors and a switch?

Thanks for the help!

 

[ccmccull]

I've done a couple of versions of this with PB's guidance

https://forum.bottlehead.com/index.php?topic=14385.msg130935#msg130935

I ended up using a switch but you don't have to. See the thread linked to from there to see the switchless version.

 

[Paul Birkeland]

Be sure that the nut near terminal 36 isn't touching terminal 36.  If those two touch, you'll get some hum.

 

[hifitoaster]

Be sure that the nut near terminal 36 isn't touching terminal 36.  If those two touch, you'll get some hum.

Thank you Paul, I did check terminal 36, I even placed a bit of card stock paper between the nut and terminal 36 as an insulator. The funny thing is, I don't think I noticed a hum before the C4S upgrade. It seemed like the output was higher after the upgrade. Or maybe I did something wrong during the upgrade to introduce the hum.

 

[Paul Birkeland]

If the volume control is all the way down, is the noise there?

 

[hifitoaster]

Yes, still a subtle hum with the volume all the way down.

 

[Paul Birkeland]

The padded output would be a good idea for your situation.

 

[hifitoaster]

Thanks for the help Paul!

I'll order the parts to get a switched L-pad setup added. I'm going off the setup you helped ccmccull with.