First Build Issues

[yeahyeah]

Hey all, i'm new to amp building. And my first one has some issues.

Its a fender 5e3 clone, with a switchable negative feedback loop.

If i play something then switch off the standby, the sound swells in like its going to work like it should, then the sound cuts and is quiet... wisper volume. what is really weird is when i switch the negative feedback loop in it gets louder and is at normal talking volume.

its also very muddy.

What could be causing this? what part of the circuit should i be inspecting?

i'm glad nothing blew up.

[Bob-I]

Sounds like you're missing a grid load. That's the resistor that goes from the grid to ground. Without that you'll charge up the tube when the power is applied but it'll bleed out quickly.

Check out the grounds on the input jakcs through the 1M resistors, the grounds on the 2 220K resistors on the power tube grids, and also the grounds on the volume controls. While you're at it check out the filter cap grounds too.

Good luck, let us know how that works out.

[Bob-I]

I missed the part about the NFB loop. I'd guess that you've connected it to the PI triode. That grid connects to a 1M resistor, then to the cathode between the 1.5K and the 56K resistors. I'd check this first. It sounds like the NFB is grounding the grid through the output transformer secondaries, which would account for the little bit of sound bleeding through.

[yeahyeah]

Ok its working right now, everything was wired correctly, but i had used three 1M resistors where three 1.5k's should have been. both cathode resistors and one in the phase inverter.

i'm experimenting with the tone stack and de-farting it now.

[Bob-I]

Check out this tone control mod. Worked great for me but you'll need a dual ganged 1M pot. It really opens the amp up and each channel has a unique voicing.