Your favourite (line level, low noise) preamp circuits?

[Regebro]

So, I'm thinking about making two 19" racks with a bunch of preamps, at least 20dB, 30dB would be nice, variable even better. It's going to be for synths, I don't need to plug guitars or mics into it, it's basically a -10dBu to +20dBu boost.

So, any suggestions, experiences? I've found a few circuits online, some simple, some stupidly complicated, some discreet, some opamps.

And is making this with -90dBu noise realistic? I mean, even the Tascam LA-80mkii has only -90dB noise, and that's without the +30dB boost you seem to be able to have. I'd like at -80dB after the boost.

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The whole story, if you have questions:

I got a uTrack24 audio interface, and having 24 channels in and out for that price comes with cut corners, obviously. And the cut corners on the uTrack24 are two. The first is that it's +20dBu, and that's it. No preamps, no levels. The second drawback is that it's pretty noisy.

Yeah, it's 24bit, but the noise floor is actually around 90dB. That's fine for me, buuuut, with clipping happening at +20dBu, then a typical line input at -10dBu will have -60dB noise, and that's NOT OK. Which means you need to use a preamp in front of it. Which is fine.

Buuut, I have 24 input channels. And one clean preamp with 2 channels. So that makes 22 channels pointless. So, maybe I could plug my synths directly into those channels, so I can: 1. Use more than one stereo synth at once. 2. Skip one patch bay. And shitloads of preamps is expensive. And very few rack preamps have inputs on the backside.

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Why build something myself? Well, because anything except the Behringer DI800 is too expensive, and the Behringer DI800 is a Behringer. Also, it has inputs only on the front, which I definitely don't want. (I'm planning to have inputs on the front as well as on the back, at least for some channels, because that will save me a patch bay). The Tascam LA-80mkii would probably do, but I can't find one single one with 220V power for sale second hand. And it has no inputs on the front.

Let the flaming begin.