Peter Millett’s DIY tube microphone preamp is designed around a Lundahl input transformer and ECC88 and 6DJ8 tubes. The PCB includes a switching power supply, designed so that the noise it generates is beyond the audible frequency range. PCBs are available from eBay and the designer’s website.

• Lundahl LL1690 input transformer
• ECC88 and 6DJ8 tubes
• Harmonic distortion below 0.5% within the linear range
• Up to 58dB of gain
• PCB fits in a LMB-Heeger EAS-500 box

Price: $30 for PCB

Adjusted Price: The creator estimates $400 all told to build a channel.

More info:

• Specs and schematics at PMillett’s website