My latest audio design. A dual triode vacuum tube microphone preamplifier for recording applications employing an embedded microcontroller to remotely control the device from a distance via WiFi. A motorized gain potentiometer and series of relays allow settings to be changed and recalled using a phone, tablet or computer. By placing the preamp closer to the mic and returning at line level, better signal integrity is possible.

A feature-rich interface, custom audio transformers, the clarity and headroom of vacuum tubes, plus keen attention to ergonomics make this exciting combination of old and new perhaps my best effort yet! Time will tell.

The nature of vintage audio transformers is that their popularity is sometimes based on their imperfections. Things like shifting HF phase response, different core materials and various parasitic reactances can subtly alter the sound in a pleasing manner.

In the ongoing effort to learn more about this Art/Science of Audio Magnetics and quantify these elusive traits, I designed an audio transformer analyzer with a 1 MHz USB scope and LabVIEW to characterize things like Amplitude, Phase, THD, Group Delay, Impedance, Turns Ratio, Voltage Ratio plus a host of others and deliver a full report of the data in HTML form. 

First Product: Designed in 2005, the Tube Equipment Corporation SR 71 is my take on the infamous Fairchild 670 tube compressor from the 60's. With 17 tubes and weighing in at nearly 50 pounds, this $7000 tube beast has many happy customers and well-known popular recordings to it's credit! 

Using a common 4 channel Focusrite USB home recording interface and the DSP power of LabVIEW, I was able to create a 24 bit Audio Analyzer to rival professional products at a fraction of the cost. I use this analyzer every day to create and refine audio designs. It delivers a full report of all the measurements in HTML

During the production of the Tube Equipment Corporation SR 71 Compressor, it became crucial to obtain large quantities of the main Remote Cutoff gain reduction tubes and hand select them for best THD and plate curve matching. Even with a Tektronix curve tracer, doing this manually was terribly inefficient so I designed an automated tube curve tracer of my own which would select batches of 8 tubes at a time for one unit. Automating the process cut this task time down dramatically.

Buoyed by the results of the massive SR 71 Tube Compressor and also looking to go beyond old 60's designs, I tried to embark out on my own and do something new in the tube audio recording gear market. That something was to take my basic circuit from the previous product and automate it using motorized controls and a Microcontroller to manage things. WiFi remote control and storage of preferred settings made it easy to recall previous sessions, a requirement in the modern studio.