Hi all,
I'm new to the forum and new to electronics in general. This is a great site and I've spend many hours pouring through the learning material posted here. Thanks to all of you for pulling this together.
I have a project I'm hoping I can get some help with. In short, I'd like to be able to control my guitar amp via a MIDI foot pedal. The amplifier has a foot switch that allows you to toggle the channel, clean channel gain, and reverb. My goal is to build a small box that takes the logical switches available on the MIDI foot pedal and control the amplifier like the foot switch does.
The schematic for the foot switch and foot switch port on the amp are attached. The full schematic can be found here: http://support.fender.com/schematics/guitar_amplifiers/94_Twin-Amp_schematic.pdf (Kudos to Fender for publishing these!)
I bought all of the parts and mocked up the foot switch on a breadboard. 2 caveats: 1) the LEDs in the foot pedal have two lights and three legs and look heavy duty. I replaced these with plain-old LEDs. 2) I left out the reverb switch and associated diodes. Using my mock-up I can switch the channel and the LEDs appear to work, but I cannot get the gain on/off to work.
I measured the foot switch voltage in all positions and here's what I have (1 = on; 0 = off):
The reference voltage is 5V (without the foot switch connected).
Gain Channel Reverb Voltage
0 0 0 10V
1 0 0 9.2V
0 1 0 8.1V
0 0 1 -320mV
1 1 0 7.5V
1 0 1 -1.3V
0 1 1 -2.4V
1 1 1 -3.2
So my questions: is this a really hard project? Seems like it would be simple, but I have no idea what is causing the voltage to jump from 5 to 10 to -3.2. Could I just add a battery and a bunch of resisters and mock up the voltage levels? Does the amperage matter?
Thanks for any advice.
-David
I'm new to the forum and new to electronics in general. This is a great site and I've spend many hours pouring through the learning material posted here. Thanks to all of you for pulling this together.
I have a project I'm hoping I can get some help with. In short, I'd like to be able to control my guitar amp via a MIDI foot pedal. The amplifier has a foot switch that allows you to toggle the channel, clean channel gain, and reverb. My goal is to build a small box that takes the logical switches available on the MIDI foot pedal and control the amplifier like the foot switch does.
The schematic for the foot switch and foot switch port on the amp are attached. The full schematic can be found here: http://support.fender.com/schematics/guitar_amplifiers/94_Twin-Amp_schematic.pdf (Kudos to Fender for publishing these!)
I bought all of the parts and mocked up the foot switch on a breadboard. 2 caveats: 1) the LEDs in the foot pedal have two lights and three legs and look heavy duty. I replaced these with plain-old LEDs. 2) I left out the reverb switch and associated diodes. Using my mock-up I can switch the channel and the LEDs appear to work, but I cannot get the gain on/off to work.
I measured the foot switch voltage in all positions and here's what I have (1 = on; 0 = off):
The reference voltage is 5V (without the foot switch connected).
Gain Channel Reverb Voltage
0 0 0 10V
1 0 0 9.2V
0 1 0 8.1V
0 0 1 -320mV
1 1 0 7.5V
1 0 1 -1.3V
0 1 1 -2.4V
1 1 1 -3.2
So my questions: is this a really hard project? Seems like it would be simple, but I have no idea what is causing the voltage to jump from 5 to 10 to -3.2. Could I just add a battery and a bunch of resisters and mock up the voltage levels? Does the amperage matter?
Thanks for any advice.
-David
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