My eight space 500 series rack has had only one module in it until now. It was the Sound Skulptor MP573 Mic Preamp kit I built several months ago. My ultimate plan is to get a second one of those and a pair of something else. After a lot of consideration, I decided that the something else would be the Lola from Hairball Audio in Seattle.
The kit arrived a few days agon, and I managed to build it in three sittings. And.. it actually works! Other than the discrete op amps (see below), the build is pretty simple and straightforward.
The main board in the vice ready to populate (sorry for the blurry pic. I had my high-mag reading glasses on at the time)
The main board build is actually pretty easy. It's a very good quality circuit board with decently sized and spaced pads. Resistors, caps, diodes transisitors and relays are all packaged in a series of bags referenced by the build guid. It's very buildable by anyone with decent soldering skills. The input and output transformers are very easy to mount. I added a little bit of blue locktite on all fasteners for the transformers and other mechanical connections..
Discrete OP Amps
The Lola takes two discrete op amps because it maintains a fully differential signal path through the whole amp.Hairball offers several options for amps - including a DIY version of their own JE990 amp - but you can put any standard footprint DOA in here you want. I went with the Hairball DIY option and that was my one regret. It's a very challenging build which probably doubled the overall build time. There are 30-ish parts on a 1 sq inch circuit board with very tiny solder pads. I have pretty good soldering skills, but while I was working on the DOAs, I was thinking that the chances of both of these actually working is pretty slim!. If/when I get another Lola, I will certainly not build the OP Amps myself.
Installing the second Discrte OP AMP
So far, I've built kits by Sound Skulptor, Mic-parts and Hairball. I'm battting a thousand (so far) at having stuff work right off the bench, but that says as much about the quality of the kits as my ability. In terms of parts inventory, the hairball kit was perfect - nothing missing and nothing extra. The build-guide is pretty good, but slightly not as good as the other companys' kits I've built. The guide is written with a little light hearted dead-pan humor which I appreciate. I don't own a printer so I was reading the guides on my phone while building. There were a couple times when I should have scrolled down just one more half inch for a warning or tip before I soldered something. The one part of the build guide that stood out as being sub par was for the LED Meter board. The image in the guide for that build is very low res and quite unreadable. The silkscreening on the board is so tiny, it is also unreadable so the image for that board is especially important. I found myself installing the resistors I could read first and then doing the rest when there were fewer choices to guess between.
Finishing the LED board. The idea is to get the LEDs all pointing straight up.
LED board mounted to Driver Board. The guide for this board was particularly not so good.
500-series stuff presents a challenge for a designer. There is very limited space (in three dimensions), limited power supply rail voltage and limited heat dissapation. Sometimes to get everything to fit, the parts are very difficult to physically put together. Not so with the Lola. The main board fastens to the back plate with four stand-offs. The back plate wraps around so that the front panel sits against it making alignment of the controls very simple. The LEDs sit behind the panel and a series of clear plastic light pipes are used to get the light outside of the box. It's a very well-done design overall!
Final assembly complete
Fully baked and ready to test
In the rack and working!
Mic setup for the a shootout using the matched Mic-parts kit mics
Well, mainly the fact that it worked at all was a big (and somewhat unexpected) thrill. I was encouraged after the main board and DOAs were done that an initial smoke test in my rack yieled none (smoke, that is).
The Lola has the familiar Grayhill rotary switch for input gain and an output +/- variable trim control. Unlike most of these style preamps, it has a 10 segment LED meter so you can really tell how hard you are hitting it. My one complaint here is that the meter is on the final output. I think it would have been much cooler to have it strictly showing how hard the input was being driven (My UA 4-710d preamps have a pre/post switch for the metering). I already have plenty of ways downstream of seeing the output level from the pre-amp. I would rather see the input.
The input gain switch on the Lola is awesome - it's rotates over 270 degrees and covers steps from 17 to 65 db of gain. That 65 instead of the usual 60 is due to the differential signal path. My MP573 by comparison has a switch that is only about 180 degrees with bigger steps. The Lola will definitley be more tweakable in terms of pushing it into saturation with more fine control.
As I was finally installing it in my rack, I heard some birds chirping outside. I put one of my modified 990s out the window (with a tee shirt over it as a wind screen), floored the gain on the Lola and recorded a bit of ambient neighborhood sound. It doesn't really matter how cool a preamp sounds if it's noisy, but this thing is really quiet. That was supposed to be one of the Lola's strong points (wth the fully differential signal path) and it certainly is.
I set up my matched pair of modified 990s - one feeding my Sound Skulptor MP573 and the other the Lola - and recorded some acoustic guitar. Neither preamp was pushed into saturaiton at all (for this test). At first, I had the mics side by side (very close). I recorded one pass and then swapped preamps and recorded another pass. What that showed was that the two inch difference between the mic position had much more of an effect than the preamps (the one toward the headstock sounded much better than the one toward the body).
I re-oriented the mics over/under (see photo) and did the test again. I've added the results to my soundcloud "shootouts" playlist below.
The first Lola vs MP573 track is the entire track alternating back and forth every two measures. The differences are subtle (to me). As always, to make the differences really pop out, it helps to do a short repetitive loop. The "Loop MP573-Lola Alternate" track does exactly that. The loop plays twice for each preamp. The differences are much more apparent. Interestingly, the differences are even easier to hear after soundcloud did their horrible compression than they were on the original 24bit bounces!