Wreck Express questions for clone builders

9/25/2000 12:42 AM

Mark Abbott

Wreck Express questions for clone builders i think the best way to address the various question regarding this amp is stage by stage.     The input stage of this amp is fairly standard in various versions, though some people felt the need to use a grid stopper resistor, what purpose did the grid stoppers serve?   Gris stopper values used;(33K in the A5 lite, 68K in the A3, 47K in the A4 version and 47K and a 1M trim pot for grid leak.)     The option for the tone stack seem to be either using a 500pF cap with a 250K pot, or a 50pF cap with a 1Meg pot, the later being used for blues sounding amps.   I am curious about the variations of midrange controls, the mids control is either a 25k pot wired as a variable resistor, with the 0.022uF cap on the hot side of the pot or the hot side of the pot attached to the bass control and the mid cap attached to the wiper of the mid control, what is the tonal difference between these two circuits?     I am curious about the 820ohm resistor after the volume control, what purpose does it serve?     The next area of tweaking is the coupling cap after the tone control recovery stage, and following grid leak resistor. Once again from the circuits I've seen this too is divided into two catagories, firstly a 0.001uF cap with a 56K resistor, or a 0.002uF cap and a 150K resistor.   What is the difference in tone between these two circuits?     The driver circuit was also an area where some people chose to use 0.1uF for input and output coupling, while other went for 0.022uF caps, was this driven by bass response problems, or tonal response?     The power supply seemed standard, I'm curious here too as some of the resistor values seem quite large, is this as per the original design, or chosen for tonal response?     Why wasn't a choke used in the power supply circuit?       Okay thanks for reading all the questions, your replies are very much appreciated.       Yours Sincerely       Mark Abbott.