HAIRBALL AUDIO Elements Mic Pres

Using our experience from DIY500 we helped Hairball Audio design the Elements series of mic preamps and DIY kits. In addition to the universal module motherboard we provided an optional daughterboard for using a rotary switch in place of the pots.

Hairball stocks all of the necessary components and provides all of the necessary support, making Elements Silver much more affordable and accessible than DIY500 ever was. Upgraded features include an active DI which travels through the entire mic input path, transformer included, and a buffered output fader for Gain–>Master-Volume style overdrive variations. Moreover, we are confident that these Hairball Gold, Copper, and Bronze preamps meet Eisen Audio’s very high standards for sound quality and build longevity.

HAIRBALL AUDIO Raindog Discrete Operational Amplifier

In order to complete the Elements Bronze mic preamp design and make best use of their LA-3A transformers, Hairball Audio needed an op amp in popular 2520/990 footprint which would imitate the unique sonic signature of an LA-3A makeup gain amplifier section, and so Eisen Audio was recruited once again. Raindog is what we call the result, which makes strategic use of a hybrid surface mount approach (some components sound better in SMT and others do not) while including an inductor and electrolytic capacitor in a unique bias arrangement.

PURPLE AUDIO LILPEQr Program Equalizer

Purple Audio was impressed with the tone and usability of Eisen Audio’s LILPEQr LE60 and asked to reissue it as a Purple Audio product. Ed Anderson was tasked with creating an authentic-sounding replica of the vintage input transformer, which ended up taking a very long time. Jens would not let this reissue be finished until it sounded just like the original batch.

While re-drawing the PCB, the “Input – Direct” feature was removed, based on customer feedback, and a selectable input fader mode was added in its place. This allows for attenuation so that maximum boost (which still sounds great) won’t overload, and means that a rack full of Purple LILPEQr modules can be used as the front end of an analog mixing solution. Another new feature is the Purple-designed tri-color LED signal level metering.

Visit for details and sales.

HAKANAI DC8 Hybrid Lunchbox

Eisen Audio contributed to the development of the Hakanai, LLC DC8 by drawing its backplane PCB.

DC8 is a lunchbox enclosure housing four 500 series modules alongside four 200 series modules. Provisions for TRS insert jacks were made. Hakanai designed the metalwork, and a third-party designed the internal power supply.


Peterson Goodwyn at DIY Recording Equipment developed the Colour 500-Series Palette Kit and invited Eisen Audio to create a hardware “plug-in” for this open source signal processing platform. Our first contribution, manufactured and sold by DIYRE, is the TM79 Colour, which you can read all about.