The G9 project is an adaptation of the Gyratec IX dual microphone/line/DI preamplifier to suit the DIY’ers demands. Searching the net, I’ve never come across a complete tube microphone preamp design, so I decided to share this version of our very popular design, the Gyratec IX. It is a classic, conservative design, that easily matches the performance of even the most expensive and esoteric units I’ve been able to compare it to.
I wish to thank Kev and Byron from Group DIY for test-piloting this project, and for their changes and comments on the original design. Without those guys this level of DIY-friendlyness would’nt have been even remotely possible.
Take a look at how Kev Ross builds this project Kev and Byron’s page on building the Gyraf G9.
The G9 contains two channels of real-tube, high-gain, transformer-balanced microphone preamplifiers with additional line and instrument inputs and transformer balanced output. It also features switchable phantom power, high-pass filter and phase reverse, as well as independent controls for input gain and output level – giving the user some creative options to work with.
The signal path contains only tubes, transformers and passive components, to preserve your signal integrety. VERY different from many “tubed” consumer products. But as we are not purists, we incorporate modern semiconductors in the powersupply sections – simply because this is way the easiest, cheapest and best solution available. For power amplifiers there’s quite an audible reason to use tubed power supplies, but for preamps I haven’t been able to spot any advantage so far.