mrface2112
Well-known member
So, I finished building a Classic API VP25 mic preamp a couple nights ago and thought I'd document the build process.
For those of you uninitiated, the Classic API VP25 is a 500-series compatible mic preamp which is firmly in the family of the old API 312 mic preamp. The Classic API site sells the kits, and there is a strong tie-in with the GroupDIY forum.
The build was super easy, with the opamp excepted. That required some tight soldering under a magnifying glass. I don't know what my pics can provide that the excellent build instructions that are included with the kit does not.....but these days I can't seem to build anything without taking pictures, so what the hell.....
First, we have the bare circuit board:
Then we add the resistors. I find it's easiest to use an online resource for mapping the color bands to resistance :
Add the diodes, being sure to get the polarity correct!
Add the capacitors and switches. Again, pay attention to the polarity where necessary.
Solder in the sockets for the opamp.
Add the transformers. Make sure to line measure your output transformer leads twice before cutting them, and be sure to account for stripping when cutting. Using heat shrink around the output transformer leads to group them will tidy things up.
Closeup on the 2503 output transformer:
Closeup on the "new style" T-Pad adapter board for attaching the attenuator. This is the one thing that's different than the instruction manual.
Add in the 48V Phantom Power Switch. Again, make sure you've got enough lead:
Mount the board in the chassis:
And attach the faceplate. If you followed the instructions properly, everything will line up perfectly:
Here's a shot of the finished mic preamp:
And a front shot with the knobs installed:
Here are two shots of the GAR2520 opamp. I didn't document that process as it's basically "stuff the board".
So.....how's it sound? In a word, fantastic. Big low end, aggressive/forward mids and a really nice, airy high end that isn't strident in the least. It's really nice on my vocals, and i haven't had a chance to put it on a drum kit yet, but i bet this thing would slay on kick and snare as well as guitar amp and powering a bass DI.
I've got another one enroute.
cheers,
wade
For those of you uninitiated, the Classic API VP25 is a 500-series compatible mic preamp which is firmly in the family of the old API 312 mic preamp. The Classic API site sells the kits, and there is a strong tie-in with the GroupDIY forum.
The build was super easy, with the opamp excepted. That required some tight soldering under a magnifying glass. I don't know what my pics can provide that the excellent build instructions that are included with the kit does not.....but these days I can't seem to build anything without taking pictures, so what the hell.....
First, we have the bare circuit board:
Then we add the resistors. I find it's easiest to use an online resource for mapping the color bands to resistance :
Add the diodes, being sure to get the polarity correct!
Add the capacitors and switches. Again, pay attention to the polarity where necessary.
Solder in the sockets for the opamp.
Add the transformers. Make sure to line measure your output transformer leads twice before cutting them, and be sure to account for stripping when cutting. Using heat shrink around the output transformer leads to group them will tidy things up.
Closeup on the 2503 output transformer:
Closeup on the "new style" T-Pad adapter board for attaching the attenuator. This is the one thing that's different than the instruction manual.
Add in the 48V Phantom Power Switch. Again, make sure you've got enough lead:
Mount the board in the chassis:
And attach the faceplate. If you followed the instructions properly, everything will line up perfectly:
Here's a shot of the finished mic preamp:
And a front shot with the knobs installed:
Here are two shots of the GAR2520 opamp. I didn't document that process as it's basically "stuff the board".
So.....how's it sound? In a word, fantastic. Big low end, aggressive/forward mids and a really nice, airy high end that isn't strident in the least. It's really nice on my vocals, and i haven't had a chance to put it on a drum kit yet, but i bet this thing would slay on kick and snare as well as guitar amp and powering a bass DI.
I've got another one enroute.
cheers,
wade