Active, serial FX-Loop for a subsequent installation in an existing tube amplifier
The FX-Loop works with two LND150 in the send and in the return stage. The send and return level can be adjusted to their optimal value with two potentiometers. The Loop works with the present high voltage of the amplifier.
It has two inputs for low and high signal levels.
Input Levels:
InA: 30 - 60 Vpp, max. 65 Vpp
InB: 10 - 15 Vpp, max. 18 Vpp
The FX-Loop utilize POTENTIALLY FATAL HIGH VOLTAGES.
Seek help from a competent technician if you are in any way unfamiliar with high voltage circuits.
Use at your own risk.
Files:
- Power voltage taken from B4
- Changed the 22k resistor for B4 voltage to 18k, to keep up the tube plate voltage
- True Bypass switch installed on rear panel
- LND150 board installed at rear panel. Inside the amp it is just above the rectifier diodes = 50Hz noise, so I enclosed the LND150 board on 5/6 sides with a steel EMI protection box from Bürklin. Noise gone!
- I used the Fat capacitor config (as I play bass), a hint less high treble but could compensate with tone controls.
- Noise is quite low and I could adjust the trim pots to have a great pass-through equal to the amp's internal signal volume. from B4
- Changed the 22k resistor for B4 voltage to 18k, to keep up the tube plate voltage
- True Bypass switch installed on rear panel
- LND150 board installed at rear panel. Inside the amp it is just above the rectifier diodes = 50Hz noise, so I enclosed the LND150 board on 5/6 sides with a steel EMI protection box from Bürklin. Noise gone!
- I used the Fat capacitor config (as I play bass), a hint less high treble but could compensate with tone controls.
- Noise is quite low and I could adjust the trim pots to have a great pass-through equal to the amp's internal signal volume.
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