critterkllr
Well-known member
I'm hoping to get some advice on this. I have a Rev D 1176 clone (Mnats/Hairball). I'd like to also have access to a Rev A. Even though there are a number of different value components on different sections, it seems that the preamp is the biggest difference between the two revisions. So, I'd like to try to make the two different preamps switchable in my compressor.
Rev A schematic: http://mnats.net/files/1176REVA_125_VOLTAGES.pdf
Rev D schematic: http://mnats.net/files/1176REVD_VOLTS.pdf
I was wondering if the preamp can be switched in and out using a 3PDT switch. The three points that I would be switching are from:
1) The input (#8 on the schematic).
2) The negative side of C7 (this would be lifted from the pcb and wired to the switch).
3) The meter output (#7 on the schematic).
The wire from the input transformer would simply be removed from the PCB connector. The switch would then be wired to select between sending back to that connector on the main PCB, or to the input of the mod PCB.
The output would work by desoldering and lifting the negative side of C7. A wire from the switch would be soldered to the empty pad where C7's negative lead was. The switch would then be wired to selected between the negative lead on C7 or the output of the mod PCB.
For the meter, C22, R7 and C6 on the Rev D PCB would need to be lifted from their adjoining ends. They would then be soldered together. A wire from the switch would be connected to one of the empty pads from C22, R7 or C6. The switch would then be wired to select between the soldered C22, R7 and C6 leads, or the meter out on the mod PCB.
Ground and +30V would simply be taken from their respective points on the main PCB and not switchable.
The schematic of the preamp mod is attached. I'm still pretty new at this stuff, so I'd appreciate any input on the project.
EDIT: There are a few errors on the attached schematic. R17 is missing. R6 is mislabelled.
Rev A schematic: http://mnats.net/files/1176REVA_125_VOLTAGES.pdf
Rev D schematic: http://mnats.net/files/1176REVD_VOLTS.pdf
I was wondering if the preamp can be switched in and out using a 3PDT switch. The three points that I would be switching are from:
1) The input (#8 on the schematic).
2) The negative side of C7 (this would be lifted from the pcb and wired to the switch).
3) The meter output (#7 on the schematic).
The wire from the input transformer would simply be removed from the PCB connector. The switch would then be wired to select between sending back to that connector on the main PCB, or to the input of the mod PCB.
The output would work by desoldering and lifting the negative side of C7. A wire from the switch would be soldered to the empty pad where C7's negative lead was. The switch would then be wired to selected between the negative lead on C7 or the output of the mod PCB.
For the meter, C22, R7 and C6 on the Rev D PCB would need to be lifted from their adjoining ends. They would then be soldered together. A wire from the switch would be connected to one of the empty pads from C22, R7 or C6. The switch would then be wired to select between the soldered C22, R7 and C6 leads, or the meter out on the mod PCB.
Ground and +30V would simply be taken from their respective points on the main PCB and not switchable.
The schematic of the preamp mod is attached. I'm still pretty new at this stuff, so I'd appreciate any input on the project.
EDIT: There are a few errors on the attached schematic. R17 is missing. R6 is mislabelled.
