Problem with home made guitar amp

[Rob Strand]

through the 10Ohm resistor in parallel with the 100nF cap as stated at fig.3

OK so there is one of those networks hidden in there after all.  The way it's drawn on fig 3 isn't a clear as it should be, it's better for the transformer and and network to join at the junction of the two large caps.   It's minor point where this connection goes, I wouldn't worry about it too much unless you get problems (which I doubt).  I just like connecting the cap at least near the input socket.

i saw that that their track is connected directly to the filter caps ground point

It must connect at some point, presumably the PCB wiring matches figure 1B and wiring the PCB in this manner should be OK.  The main point I was trying to make before was that the high speaker  currents shouldn't pass through the ground involving R2 and R6.  At that stage I wasn't sure what layout you were using but it's now pretty clear you are following the ESP layout.  There shouldn't be a problem with speaker currents since R26 is off the PCB.

[dj_death]

Hi, I rebuild the preamp board, because it was impossible to make all these shielding modifications with the previous pcb. I want to ask the shield under the preamp should be grounded to preamp's ground or to the main's earth. In this week i think that i will be finish the amplifier. Thank you in advance !

[dj_death]

Yessssssssss!!!!!!! It finally works there's not such screaming anymore. I don't know if shielding saved the day , because i rewired the pots and rebuild the preamp board. But the amp is know much much quieter and i think that shielding helped very much. I also used shielded wire at the input and output of the preamp and everywhere i could when i was
wiring the pots. I connected transformers body to mains earth and i put a metal sheet connected to mains earth under the little board where i put the filter caps and supply zeners. I connected the metal sheet under the preamp with preamp's ground point and the front metal panel, too. I did't isolate input jacks so the front panel was grounded by the jacks. Do you think that is bad? The only connection between mains earth and the
ground of the filter caps is with the 10Ohm resistor paralleled to the 100n cap. Now i will put a shield over the preamp and to the jacks as ESP suggests.Now there's only some hum, which increases when i put master volume at max. Hey i forgot to ask where to mount R26 and if i should put a shield under this resistor. I mounted R26 between preamp and the transformer on the wood and of course it's away from these boards.I want to thank everybody in this forum and "espessially Rob" for your valuable help and recommendations.

[Peter Snowberg]

Rob saves the day!

Congrats on your new amp!

-Peter