jusin3am's Lola preamp build

[justin3am]

When I started looking for a pair of preamps for my 500 rack, I didn't start out looking at DIY options. But thanks to some advice from my friend Eric Beam (rhythminmind, vieris), I found that the Lola Preamp from Hairball Audio had all of the features I wanted and it's available as a complete kit. You can find a lot of good information about the preamp and it's origins, here: Story of Lola

I got a pair of these kits and just finished building the first. I have some pictures of the process to share.


My first impression was very good. This is by far, the project with the most detailed documentation, I have ever worked on.


The parts are packed with the parts itemized on individual boxes for each portion of the build.



First thing to do is install the op-amp sockets.


I don't have a vise, so I used masking tape to temporarily hold the sockets to the PCB.



Then the gain resistors.


Then the rest of the resistors.


Followed by the diodes and transistors.


Relays.


Capacitors.



Most of this has been familiar territory for me so far, and the board isn't very dense. A pretty easy build.
I've never built anything with a multi-position switch like this, so I was very careful when placing the stop pin for the greyhill switch.




When building synths, I usually mount switches, jacks and pots to the front panel, before soldering them to the PCB. But this build calls for carefully positioning those parts on the PCB before mounting the hardware. Luckily most of the parts snap snugly into place.


The 1/4" D.I. input jack needs to be mounted, so that it's not flush with the PCB, which wasn't too difficult. Luckily I was following the build guide carefully!



That's it for tonight. I'll post some more, tomorrow.

[justin3am]

There are two large transformers. An EA-10468, based on the Marinair 10468 used in the Neve 1073, for the input transformer and a EA-1166 output transformer, based on the LO1166, also used in 1073 preamps.

This is the EA-10468


This is the EA-1166


That's the main board, finished. Only the meter board and the two discrete op-amps remain. These are much more densely populated and the PCBs are much smaller, requiring extra care.*

First the DIY JE-990 DOAs. This op-amp is based on the Jensen 990. More about that here: JE-990



On this board, I start with the diodes, because all of the other parts are taller than they are.


Then resistors.


Transistors and capacitors.


This was a new one for me. Diodes need to be thermally coupled to these output transistors, to reduce distortion with low-impedence loads.





There are two transistors like this. *But it's very important to note that they are not the same part! When I built the second of these DOAs, I managed to put the NPN (MJE181) transistor in the PNP (MJE171) position, though I swear I triple checked! . As a result, I let the magic smoke out of a few 10ohm resistors when I first powered it on. Mike at Hairball Audio was super helpful and pointed me in the right direction.


Last there are two inductors which need to be wound.


There were also a few surface mount parts which were already populated.

[justin3am]

With the discrete op-amps installed, all that's left is the meter board.



Starting with Diodes and ICs. Usually I would socket the ICs but I was lazy.


Then other stuff.


I assembled the LED board without taking any pictures. It was a pain in the ass to get them mounted straight without the fixture I use at work.



Yes! Final assembly!





It sounds fantastic. I've mostly been running my bass through the DI input, just for testing. I'll do some recording with them once I have the second one built. It was a pretty easy build but it's critical to read through the build guides ahead of time. I had fun with this one and would certainly recommend it to anyone who is interested in getting into DIY audio equipment. I may build one of their FET compressors next.

[vurt]

nice work

i don't trust myself building anything that plugs in
battery builds only for me

but im soooo tempted to go eurocrack

[justin3am]

Definitely better to start with stuff that can't kill you.
As long as you aren't building your own PSU, Eurorack is pretty safe. I'm sure you have seen the Thonk website. Lots of cool/easy kits to get you started.
I wrote about my experience building Eurorack modules, here: justin3am's DIY eurorack adventure.

This was easier in some ways, than the modules in that system but there are some pretty expensive parts which I was worried about blowing up. Luckily, it mostly went together smoothly.
Building stuff, I find is very easy. Troubleshooting a problem, when you f**k it up, is the difficult part. Tracking down the mistake and desoldering parts is a huge pain in the ass. It pays to be patient and methodical and test everything along the way.

[whyterabbyt]

Another impressive build Justin...

[whyterabbyt]

...and of course the other thing abut Justin's build threads is that they make me get around to stuff on my own 'to build' pile.

So today I dragged some kits of their baggies and finally built my second Music Thing Radio Music, as well as a pair of Nootropic Video Experimenter arduino shields.

I'll leave programming the firmware and testing them (and the Bastl GranPa/SPA I built a couple of weeks ago) till tomorrow though, Im a bit frazzled now.

[cuppa]

Great post, thanks for this !!!

[justin3am]

...and of course the other thing abut Justin's build threads is that they make me get around to stuff on my own 'to build' pile.

That is awesome to hear! Have fun!

[vurt]

It pays to be patient and methodical and test everything along the way.

i think i can see where i fail

[whyterabbyt]

Have fun!

Cheers, Justin. The Radio Music works perfectly, and I also updated the old one to the newest firmware and the current 8gb sample bank. Hadnt realised i had a -really- ancient and tiny 270Mb set on the SD card.
Plus I also swapped out the panel on my Mikrophonie to one of the new black ones. Purty.

And had a too-lengthy panic while I spent 30 minutes looking for the two SD cards that came with my TG ONE. 8cmx5cm silver antistatic bag, really unnoticable, eh? :doh:

GranPa aint working though. I'll have to have a look at that.
And I think I need to update the firmware on my (non-DIY) Knit Rider too, it seems to be doing extra steps. Got a micro-SD extender cable to fit to that anyway.

Not bad for a weekend. Particularly good for me on a weekend. And more than enough random-sample goodness to have fun with.

[knockman]

Very nice! What impresses me most perhaps, is your ability to stop and take a photo at every step. I often start with that intention but soon forget or simply get too impatient.

[justin3am]

Very nice! What impresses me most perhaps, is your ability to stop and take a photo at every step. I often start with that intention but soon forget or simply get too impatient.

It takes about three times as long to populate parts when I'm documenting the build. But then, I'm much less likely to make mistakes (or more likely to catch the mistakes I've made) when I'm stopping to take pictures every minute or so. So I get some of that time back in the end.

I build prototypes at work and I document that process as well, so that we can show the people at the factory where they need to pay extra attention during assembly. I just naturally reach for the camera now, when I'm building stuff.

I feel like I need to learn more about lenses and I need to get my lighting situation and figured out before I do this again, though. The pictures I got look okay but the area that's in focus is very small, making the pictures more artistic than informative. I know so little about cameras, I'm not sure which kind of lens will help me with that.