My other mic pre build thread seemed to interest a few people around here, so I thought I'd post another one for my most recent project: a pair of Hairball Audio Lola mic pres. (Here's the Tape Op review that got me interested in these in the first place:
http://tapeop.com/reviews/gear/93/lola-500-series-mic-preamp/)
So after waiting patiently for these to make their way to Brooklyn from Seattle, USPS finally delivered these to me:
Let's get to work. There are three PCBs that go into making one of these: one large one that comprises the audio portion of the mic pre, and two smaller ones to make an LED meter. Pictured here is the main PCB, populated with all of the passive components:
Note the cluster of standing resistors in the top left - these set the gain levels for the Grayhill rotary switch that'll come a little later. You may remember these Grayhill switches from the Classic API VP28 build. What else is going on this board? Input and output transformers, op amps, phantom power/phase/line switches, Bourns t-pad attenuator, DI jack, relays (for the three switches and DI jack), a ribbon header (for connecting the meter assembly), one very large 1000 uF cap (which goes underneath the left alligator clip), and two 1k resistors that were accidentally left out of the kit. Mike at Hairball sent those resistors to me via two-day delivery on his own dime - an extremely classy move.
Enough talk - let's add those missing components.
You'll notice that the board is now also mounted to an L-bracket for final placement in the Lunchbox. While the main PCB is actually complete now, this mounting is temporary. You need to do this to ensure that the t-pad and the DI jack will align properly with the faceplate. They don't sit flush to the PCB, so you need to get them aligned before you can solder them in. This means that you need to solder just a couple of pins to hold them in place, then remove the L-bracket for final soldering. If you guessed that this step is the biggest pain in the ass in the entire build, you guessed correctly.
After testing, it's time to move on to the meter assembly. Here's the brains of it:
All standing resistors, again. I'm starting to understand why some people hate them. All of those ICs get soldered directly to the PCB, too. Slightly nerve-wracking. This photo is zoomed in, so it looks huge, but the board is pretty small. There's a 2.2 uF electrolytic cap towards the left side that's one of the smallest I've ever seen. The holes above the large IC are for a header that mounts the LEDs to this board. And speaking of LEDs:
It looks simple, but you really need to take your time and be sure your LEDs are flush to the PCB and aligned in a straight line. Once you're set there, you can put it together with the meter PCB...
...and then mount the full meter assembly to the main PCB:
And it's done! There's a ribbon cable that connects the meter assembly to the main PCB, which I didn't get a picture of for some reason. Here's my current Lunchbox situation:
I didn't get a picture, but the three pushbutton switches are illuminated with pleasant blue LEDs. The meter LEDs are white up until 0 dB, then three orange ones, and a violet one at the top of the meter.
All in all, I'd say these were easier to build than the VP28s were. They took about the same amount of time, but the Lolas have fewer components. I haven't gotten to really check them out yet beyond the basic "all controls function" test, but I'm going to be breaking them in on a long tracking session next weekend. Needless to say, I'm really excited.
