I built an Austin microphone preamp from a kit! It’s for use with ribbon mics, and also dynamics – it doesn’t supply (and cannot be hooked to something which supplies) phantom power, so it’s pretty special-purpose and will never leave the studio. But given that I’m about to have a ribbon microphone, it’s useful! And hopefully fun. Anna made me promise not to blow anything up; when I told her that horse had left the barn, she added “today,” and upon checking the clock I found I could agree.
The kit came in a bunch of components and a few machined parts in an assortment of bags. You also get a PDF with extremely detailed directions. See that printout to the right? You get a bunch of those, along with step-by-step instructions.
Must be Sunday
Building is therefore pretty simple, as long as you know how to solder, can keep your solder under control on a fairly but not screamingly small experimenter’s board – you’ll want a good soldering station, mine certainly earned its keep – and can follow directions carefully.
The supplier even provided all these little jumper wires already cut and stripped! Everything else needed cutting and stripping, though.
Eye recovery makes this a very slow job. Still doable; just… slow.
The supplier said it should take about four hours; it took me rather longer, mostly because of the current limitations in my vision slowing me down. I was also very careful and methodical, for the same reasons. Even with all that, it’s still just a one day project.
Paul asked me right about here whether I was making any headway on that dematerialisation circuit.
No. Stupid time lords.
This is what it looks like when you’ve finished the converter array and have the power rails all set up.
Time to test for magic smoke leaks.
The manual has you do testing at this point, and provides several key warnings. The checkbox-as-you-go system really makes it harder to miss things or to get things wrong, as long as you keep up with their grid system. Thanks to my still-recovering vision, I was checking every solder joint under magnifiers.
First try PASSES!
The kit has two ICs: THAT and OPA chips. I don’t really know why I find that hilarious, but I do.
THAT chip! OPA!
Once the chips have been installed in their sockets, it’s time to start adding I/O ports! This one has balanced microphone input, unbalanced line-level output, and external power connector socket. There’s no power switch; it’s just plugged in to turn it on, and you connect power FIRST – before plugging in to any other hardware like the microphone or the input card – and then remove power LAST, when taking down. This is opposite to my current hardware; I’ll have to add reminder labels.
That, and the whole phantom power thing. It’s an odd beast, for an odd sort of microphone.
Input is boosted enough and output is loud enough that you can test it with headphones; no separate amp required. At the highest power levels, I was honestly kind of astounded at how much gain it had, and quite pleased with the noise levels even at maximum boost. First test of the complete assembly passed just fine.
Yep! That’s a power light!
The printed control panel looks rather smart, I think. It only has the one control – a stepped gain control knob – but it has a good range of boost steps.
All done; all tests passed first try!
I can’t say a whole lot about performance yet – but I can say it’s very low noise at very high gain, and had a nice natural sound on my quick SM-58 tests. The real test will be the ribbon microphone I intend to use with this amp, which is also a kit. Despite fewer pieces, it’s a longer build – there’s materials time, and unfamiliar processes.
But I’ll get there. I’m just hoping my studio is up to gear this shiny. ^_^