Hi all,
This is my first post here and first real DIY project. Rascalseven lent a big hand on this project so big thanks to him.
This is a stereo set of API 312 based preamps using Fabio's 2520 op amps, cinemag 75101APC input transformers and Bauer BT-123AL output transformers (same as cinemag CMOQ-2S). The DI circuits, phase+pad+48v, and powersupply are all JLM kits. The LED kits are Velleman project kits with some small modifications to run on 17v. Had I realized what a pain they would be, I would have ordered some of the pico-meters.
Most of you are probably cringing at the front panel XLR inputs. If you take a look at the rest of my rack, I'm a big fan of presonus gear and lots of that have front panel xlr inputs, so for my current setup it makes alot of sense, Eventually there will be parallel inputs on the rear.
All the art on the front panel right now is just a printed transparency laid on there. I've been trying different designs to see what I like before I do anything permanent, this particular design got screwed up at kinkos and everything is 90% normal size.
Some things I still need a little help with:
-The power switch switches 120v AC but has a 12vdc blue LED in it. This may seem like the simplest thing out of the whole build...... but how do you hook this thing up? there are only 3 prongs on the back. I found this product page with hookup instructions but they don't make sense to me:
http://www.minute-man.com/acatalog/copy_of_Snap_In_Round_Rocker_Switches.html
-The preamps sound great but not so great when turned off. Occasionally it doesn't happen, but normally when turned off the channel there is a very loud sound that I can only describe as a zip tie being pulled very fast and then that shoved through a marshall 4x12 (the first time I heard it I was wearing headphones cranked up). I assume this is a cap discharging. What I wasn't sure of is if this is normal, or not normal, or if there's something I can put into the design to take care of this.
-I'm going to have parallel inputs on the rear eventually. Is there any (reasonable) way to use a switch (or 2 switches) to switch between the front and rear inputs (or if not, just disable the front ones)?
Thanks for the input guys,
Mark Huber
This is my first post here and first real DIY project. Rascalseven lent a big hand on this project so big thanks to him.
This is a stereo set of API 312 based preamps using Fabio's 2520 op amps, cinemag 75101APC input transformers and Bauer BT-123AL output transformers (same as cinemag CMOQ-2S). The DI circuits, phase+pad+48v, and powersupply are all JLM kits. The LED kits are Velleman project kits with some small modifications to run on 17v. Had I realized what a pain they would be, I would have ordered some of the pico-meters.
Most of you are probably cringing at the front panel XLR inputs. If you take a look at the rest of my rack, I'm a big fan of presonus gear and lots of that have front panel xlr inputs, so for my current setup it makes alot of sense, Eventually there will be parallel inputs on the rear.
All the art on the front panel right now is just a printed transparency laid on there. I've been trying different designs to see what I like before I do anything permanent, this particular design got screwed up at kinkos and everything is 90% normal size.
Some things I still need a little help with:
-The power switch switches 120v AC but has a 12vdc blue LED in it. This may seem like the simplest thing out of the whole build...... but how do you hook this thing up? there are only 3 prongs on the back. I found this product page with hookup instructions but they don't make sense to me:
http://www.minute-man.com/acatalog/copy_of_Snap_In_Round_Rocker_Switches.html
"This switch has three .187 solderless terminals and is wired as follows:
* Terminal 1: Connect to + 12V DC
* Terminal 2: Connect to your load - switched power coming from terminal 1
* Terminal 3: Connect to - 12V DC. This supplies power to the
internal switch lamp and is switched on when the switch is turned on"
-The preamps sound great but not so great when turned off. Occasionally it doesn't happen, but normally when turned off the channel there is a very loud sound that I can only describe as a zip tie being pulled very fast and then that shoved through a marshall 4x12 (the first time I heard it I was wearing headphones cranked up). I assume this is a cap discharging. What I wasn't sure of is if this is normal, or not normal, or if there's something I can put into the design to take care of this.
-I'm going to have parallel inputs on the rear eventually. Is there any (reasonable) way to use a switch (or 2 switches) to switch between the front and rear inputs (or if not, just disable the front ones)?
Thanks for the input guys,
Mark Huber