Stereo API 312 - Finishing touches - Few Questions

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mhuber

Member
Joined
Jul 13, 2007
Messages
5
Location
Plano, TX
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.

API312-1.JPG

API312-2.JPG

API312-3.JPG


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
 
Nice!

About the popping-- we get around this with our SS 110's (using all JLM kits as well) by powering them up and down via our furman. Try using your power conditioner as the master on/off and see if it goes away.

I have an idea how this works, but hopefully someone more tech savy will come along and explain it better than I ever could.

Liam
 
Nice job, not bad at all for your first DIY. Maybe you'll want to get a 25mm chassis punch for your XLR soon.

Oh, and good idea on the transparency to try out your graphics. Can't say that I remember seeing that done here before...maybe though. I can't seem to catch it all myself.

Peace and Happy, Happy DIY!
Charlie
 
I know its lame, but I'm bumping my own thread. Really looking to answers to some of my questions, especially the lit power switch, cause the blue light will definitely make it sound better.
 
about your switch....

It looks like you're having a switch with a 12v DC lamp in it. That's not going to work. You'll need one with a 110v AC lamp in it.

What's the partnumber on your's?
 
Philmore 30-16126

http://www.minute-man.com/acatalog/copy_of_Snap_In_Round_Rocker_Switches.html

Its at the bottom of the page. The package it came in pretty clearly seemed to indicate it could switch 120vac (and it is right now) and just needed a 12vdc supply to run the lamp.
 
[quote author="mhuber"]Philmore 30-16126

http://www.minute-man.com/acatalog/copy_of_Snap_In_Round_Rocker_Switches.html

Its at the bottom of the page. The package it came in pretty clearly seemed to indicate it could switch 120vac (and it is right now) and just needed a 12vdc supply to run the lamp.[/quote]

Well, it can switch 120V ac, but the way the lamp is powered makes it impossible to switch 120V ac while using a 12v DC lamp.
It would have been possible if the switch had 4 terminals (two for the switch and two for the lamp).
 
Thats what I thought, but I was hoping some magic of electronics I didn't yet understand would make it work.... Is it just me or is this a really strange switch?
 
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