Hi guys,
Here's an interesting one....
Noticed last night when using pedals on my Jackson Ampworks Britain 4.0 a popping sound when engaging the looper pedal. At first thought it was the true bypass on the pedal leaking DC but after removing it from the circuit the rest of my pedals make a popping noise when clicked on or off.
Pulled the amp from the cab. It has two inputs which can be cascaded together via volume pots. One channel is an EF86 the other a 12AX7. Two other 12AX7s for gain and PI. Pulled the EF86 still popped. Pulled second 12AX7 and replaced and pop went away for awhile put amp back in cab and pop returned. Pulled chassis replaced second 12AX7 pop still there. Tried all other preamp tubes no avail.
Has two output sections. EL84 or EL34s selectable by switching on back. Pops on both outputs. Tried pedals in another amp no pop.
Any ideas on this one ? I assume DC somewhere but how do I find? Strange how rolling the one 12AX7 made things disappear until remounting into the head shell.
Pedal Issue with Amp
Moderators: pompeiisneaks, Colossal
Re: Pedal Issue with Amp
Try putting a capacitor (I guess anywhere from .001uF to .1uF would be fine) in series with the amp input (after the pedals).
Depending on what kind of guitar cords you have handy, you may be able to just remove the backshells of two cords, and connect them and the cap together using clip leads. Of course you could also put wires and the cap directly between two male 1/4" plugs, if you have some.
This will tell you if it's DC levels from the pedal output affecting the amp, or vice-versa.
If this fixes it, you could permanently solder a cap inside the amp, between the high side of the input socket and the first tube grid.
I once had a friend who swore he always had this problem with pedals, but only if they were plugged into a DC adapter, but not when using batteries. Don't know if that's just BS or not.
Oh yeah, and try another guitar also, if you haven't already
Good Luck,
Ken
Depending on what kind of guitar cords you have handy, you may be able to just remove the backshells of two cords, and connect them and the cap together using clip leads. Of course you could also put wires and the cap directly between two male 1/4" plugs, if you have some.
This will tell you if it's DC levels from the pedal output affecting the amp, or vice-versa.
If this fixes it, you could permanently solder a cap inside the amp, between the high side of the input socket and the first tube grid.
I once had a friend who swore he always had this problem with pedals, but only if they were plugged into a DC adapter, but not when using batteries. Don't know if that's just BS or not.
Oh yeah, and try another guitar also, if you haven't already
Good Luck,
Ken