Auliya (Hammond AO-43 Conversion)
Posted: Sun 09/08/19 11:41 pm
hello this is my first post here, although ya'll have solved some of the questions that came up during the planning phase without even knowing it... search is a beautiful thing!
i have a hobby of picking up old organs off craigslist. mostly solid state, which for a guy who loves OLD (60s/70s) TO-3 transistor solid state has provided me with a ton of parts for repairs/future builds.
had a hammond 112 show up and i was actually willing to pay for this organ as i had heard that these old hammonds could make great guitar amps.
my normal style with diy effects is "borrowing" modules from various proven designs and hacking them together, so for this it's a take on the vox top boost gain stages but with a baxandall tone stack (didn't want the mid scoop the vox is capable of... and to me the baxandall is just the bees knees) and the power amp section of an orange ad15 (i dig the idea of phase inverter at full tilt and adjusting how much signal hits the power tubes). organ came with a saweet gibbs reverb tank so i knew i needed to use that. thankfully found a one tube reverb and was able to use the 12dw7 that was elsewhere in the organ
i tried to use as many recycled parts as possible. the power supply choke was originally on the input to the reverb of the organ, and a bunch of the killer wirewound resistors came from various organ stripping projects (all new capacitors, pots, and tube sockets though)
besides a couple minor boneheaded moves on the tone control (i initially neglected the coupling cap and had it going straight from the cathode to the resistor and pot... no wonder it was scratchy when i turned it!) i am calling this a success.
reverb is just there enough, not super splashy or surfy but i'm not after that kinda thing
i intended to have a standby switch but didn't have larger than 22k left in the bin in a 2w+ resistor so it's more like a low power mode (i think i got this from merlinb? resistor prior to first filter cap). probably a good thing since full bore it distorted the microphone on my spacephone
quick demo video on 'low power mode'
gut shot
and schematic (redrawn, slightly less messy than what was in my notebook):
my next steps are constructing a box for it and having the old man cut a faceplate/rear plate out of aluminum on the cnc router
thanks again for all the help ya'll didn't even know you gave me!
i have a hobby of picking up old organs off craigslist. mostly solid state, which for a guy who loves OLD (60s/70s) TO-3 transistor solid state has provided me with a ton of parts for repairs/future builds.
had a hammond 112 show up and i was actually willing to pay for this organ as i had heard that these old hammonds could make great guitar amps.
my normal style with diy effects is "borrowing" modules from various proven designs and hacking them together, so for this it's a take on the vox top boost gain stages but with a baxandall tone stack (didn't want the mid scoop the vox is capable of... and to me the baxandall is just the bees knees) and the power amp section of an orange ad15 (i dig the idea of phase inverter at full tilt and adjusting how much signal hits the power tubes). organ came with a saweet gibbs reverb tank so i knew i needed to use that. thankfully found a one tube reverb and was able to use the 12dw7 that was elsewhere in the organ
i tried to use as many recycled parts as possible. the power supply choke was originally on the input to the reverb of the organ, and a bunch of the killer wirewound resistors came from various organ stripping projects (all new capacitors, pots, and tube sockets though)
besides a couple minor boneheaded moves on the tone control (i initially neglected the coupling cap and had it going straight from the cathode to the resistor and pot... no wonder it was scratchy when i turned it!) i am calling this a success.
reverb is just there enough, not super splashy or surfy but i'm not after that kinda thing
i intended to have a standby switch but didn't have larger than 22k left in the bin in a 2w+ resistor so it's more like a low power mode (i think i got this from merlinb? resistor prior to first filter cap). probably a good thing since full bore it distorted the microphone on my spacephone
quick demo video on 'low power mode'
gut shot
and schematic (redrawn, slightly less messy than what was in my notebook):
my next steps are constructing a box for it and having the old man cut a faceplate/rear plate out of aluminum on the cnc router
thanks again for all the help ya'll didn't even know you gave me!