Connecting input and output sockets ground together and adding a direct ground to mains ground in between may help reduce noise.
Then you would have a second ground wire direcctly to mains, directly to ground of amp ground.
If the amp is large and Left Right ground spaced far away from each other you will need to directly ground both Left and Right to mains.
You really want to have the ground star return point somewhere overhere as in picture, then you will have one wire that connects to the ground of b+ supply on other side of pre amp.
Also you need a cap here of 1uF or larger somewhere from Pre AMP B+ to Ground.
Without 1uF and the wire length the power supply is not quite a short circuit, signals may appear on b+ and maybe negeltible sound quality reduction.
Also I've noticed your not using coax cables for input and output, that will make you pick up noise, you need to atleast twist your signal or output signal to its ground to make twisted pair to help reduce noise. From exprience even twisted pairs pick up some noise is best to use coax.
Is your pot connected directly at outputs, if pot connected at input that means at 0volume the power amp input is not shorted to ground and some noise is normall.
Also if you connect your pot wrong way arround then the pre amp is short circuit and the power amp input is not short circuit to ground at 0 volume which will cause noise.
So it seems like the pot is connect at inputs, this means with some small noise at 0 volume its normall.
Gab wrote:
Jakub wrote:
Can I be interested in a wiring diagram? Would you like to build by your (:
I’m not shure if I understand exactly what you meant, but here is the link for the power supply schematic and I have uploaded the shematic for the amp and buffer sections.
http://diyaudioprojects.com/Tubes/Universal-Tube-Preamplifier/4S-Universal-Tube-Preamplifier-Power-Supply-Schematic.pngOriginal 4S writeup :
http://diyaudioprojects.com/Tubes/Universal-Tube-Preamplifier/