LXH2 "Marshall" Simulating Preamp Schematic
Includes both preamp and speaker/cabinet simulator sections.
!!!!! IMPORTANT WARNING !!!!!
Do NOT connect this circuit to the speaker output jack on your amp. Serious damage can occur to both your amp and this circuit and can cause a fire hazard. This is a line level device. Use only with preamps, effects processors, and other line level equiptment. Line level refers to the output level of most mixers, preamps, and effects processors.
FILTER DATA TABLE:
1. Connect all [peaks] MFB filters together in paralell where shown.
2. Connect all [dips] MFB filters together in paralell where shown.
3. Keep all leads as short as possible to prevent oscillations.
4. All power supply connections are not shown in this drawing.
MFB FILTERS FOR PEAKS
In all MFB filters below, C represents C1 and C2.
MFB FILTER 320 HZ 800 HZ 1.2 KHZ 1.8 KHZ 2.5 KHZ
R1 270k 270k 180k 120k 330k
R2 4.3k 3.0k 2.2k 1.2k 5.1k
R3 110k 150k 82k 68k 180k
R4 12k 12k 12k 12k 11k
C .022uF .01uF .01uF .01uF .0022uF
MFB FILTER 5 KHZ 8 KHZ 11 KHZ
R1 247k 390k 68k
R2 5.4k 4.4k 1.15k
R3 202k 270k 570k
R4 18k 16k 15k
C .001uF 560pF 560pF
MFB FILTERS FOR DIPS
MFB FILTER 600 HZ 1.45 KHZ 2 KHZ 7 KHZ 9 KHZ
R1 220k 120k 330k 220k 56k
R2 6.8k 1.2k 1.5k 9k 8.2k
R3 120k 100k 180k 202k 39k
R4 11k 10k 22k 10k 5.6k
C .01uF .01uF .0047uF 560pF .001uF
1. All op-amps are TLO84.
2. The "cabinet" and "damping" circuitry in the lower portion of this schematic provides an adjustable resonant boost around 100 Hz for use with guitar speakers powered by high damping factor solid state amps. The total low frequency response is more like the resonant response of a sealed 4-12" guitar cabinet powered by a low damping factor amp such as a distorting tube amp.
3. For best results, all potentiometers should be audio taper except the 250K treble control which should be linear. For best results, the 10k "damping" control should be audio taper, using the "low" and wiper leads (left two leads if you view the front of the pot with the leads pointing down). This makes the resistance increase more slowly as you increase it, for best taper in damping. Counterclockwise rotation decreases damping (increases bass resonance). Otherwise, make this potentiometer linear.
Copyright (C) 1997, 1998 LXH2.