I’m well underway with my first VP26 preamp. So far, everything has been smooth sailing. The instructions from Classic API are very thorough, and parts are well labeled and packaged. As someone who is used to building things from a schematic that I made myself, it’s been a pleasure to build from a kit.
The only puzzle I’ve had to solve was the gain switch. When I ordered the VP26 kit, I selected the option for Stepped Gain. This allows gain matching of two VP26 preamps, so I can get a true stereo image when recording things like an X-Y room mic pair.
The gainswitch board, stuffed with resistors
The instructions mention a special mounting procedure for the Bourns 25K gain pot, which I couldn’t find anywhere in the kit. I did find a bag marked “VP26″ with two small PCBs, some resistors and two Grayhill rotary switches. It took me a while to figure out that these were the stepped gain switches, and that I didn’t have the Bourns pot because it was replaced by this assembly. I found an email that Jeff Steiger at Classic API had sent me with thorough documentation on assembling the gain switch. That got me up and running again.
Here’s a shot of the main board for the VP26. Note the large cutouts for the input and output transistors, and how simple this circuit board is. There really aren’t that many parts to the API console pres, but as the kit instructions say, “High quality, sometimes custom component selection is crucial to achieve this sound.”
Main board of the VP26, a vintage API console-style preamp
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While I move forward with testing and implementing new ideas for the Spectrum, my digital preset switcher for analog pedals, I’m also doing some kit building. I’ve got four kits for 500 series microphone preamps, including kits for discrete op-amps, and two kits for console-style faders. In case you’re unfamiliar with the API 500 series format, it’s a DIY builder’s dream. The idea is to centralize the power supply and routing for studio effects units, which saves me time and money. I can use a standard API Lunchbox, which comes assembled with the power supply, routing and enclosure, and add preamp kits as I build them. The effects are modular and mounted to a faceplate with a standard card edge connector that plugs right into the power supply / routing unit. This makes assembling a custom setup easy. The modular idea works a lot like the Colorbox, and I immediately found it attractive from the user perspective.
My first kit is the VP26, from Classic API. It’s designed to replicate the sound of preamps from API consoles of the mid-70s, which are largely responsible for what people call the “LA sound” on drum recordings. They’re supposed to be aggressive and gritty in the midrange, perfect for snare and toms. Sounds good to me!
The first step of building the VP26 kit is assembling the discrete op-amps. These are parts which can be subbed out for integrated circuits, but most people agree that the discrete versions sound better. I keep making this discovery in audio electronics: when circuits are built from the best possible parts, and kept as simple as possible, they sound better. In this case, the more advanced technology of ICs, though it may reduce the parts count and keep the cost low, is not as desirable in terms of tone.
Here’s a photo of my first gar2520, the opamp I chose to build for my VP26s. I’ll post more as I go along.
gar2520 discrete op-amp
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