DIY Test Equipment for Audio and Ham Radio Enthusiasts:
Harmonic Distortion Tester  
Intermodulation Distortion Tester  
X-Y Datalogger/DataPlotter for use with Microsoft Excel or StampPlot DataLogger
Low Noise Jung Style Super Regulator with PreRegulator (Surface Mount) SMT Jung Regulator
Ultra Low Noise (=<1ppb) Audio Oscillator The Super-Oscillator from Linear Tech's AN67
JFET Tester for the Universal Serial Bus JFET Tester in VisualBasic
Microprocessor Controlled Sine/Triangle/Square and Ramp Generator  
Phase Meter - No Frills This uses off-the shelf comparators for phase-measurement accuracy suitable for mounting loudspeaker drivers, or measuring the phase response of crossovers. 
Phase Meter - 1mHz to 10 MHz, 1% acuracy Don't even think of trying this without our printed circuit board! We implement a phase-meter using very high speed comparators and operational amplifiers.  This is the link to the article on Intersil's website: LINK  Note, the HFA3012B is only available in the JEDEC MS-012-AB package -- use the article as the basis for a comparable instrument.
Phase-Gain Meter for DIY Bode Plots  
The New HP465A - Noise Measurement Apparatus  We take apart  a failed HP465A amplifier and replace the gain elements and power supply for an testing amplifier suitable for testing regulator circuits. Included is a 0.1Hz to 10Hz filter which can be jumpered in to the circuit,  lef t out.hp465_6.jpg (33686 bytes)
Heat Sink Testing Setup To determine the thermal impedance (Co/W) of that bargain heatsink you picked up, use this setup.
High Voltage Data Acquisition Card ISOLATOR LINK
The Isolated MCUTracer - use your PC to characterize tubes, transistors etc.! LINK
PC Controlled High Voltage Power Supply for tube testing and matching This power supply uses StampPlot to control a dual DAC/error amplifier to generate B+ and C- voltages required for tube testing.  It mates with the MCUTracer but can be built on a stand-alone basis.  In the example shown I used a "badly" functioning Heathkit IP-17 high voltage power supply to make a precise computer controlled power supply.
Power Supply "Test Bed" for Amplifier Testing This is more or less an example of how to use the innards of surplus power supplies to create a test-bed for amplifier power supply testing.
An almost "lab standard" voltage reference  
Using the Zetex ZXFL01 bandpass/notch filter chip Digikey still has several hundred of the ZXF36L01 chips in stock -- easy to implement spectrum analyzer.
Hewlett Packard HP3581 "wave analyzer" manual The HP 3581 is an absolutely great instrument for DIYr's -- it has 140 dB of dynamic range and a tracking generator -- couple this with a pen-plotter (or our microprocessor plotter) and you can generate hard copies of the response of any piece of audio equipment.  These are another EBay bargain.
Tektronix TM500 and TM5000 power supply mainframes for your DIY projects. Tektronix TM500 mainframes are available for a small fraction of their original cost.  These provide 
Microphone Amplifier MinnieMikeAmp
Transistor Testing Click here for Link
Impedance Test Article From Hewlett Packard Click here for Impedance Link
Ultra Low Noise Preamplifier (SQUID Amplifier)  
Dual Tracking Lab or Bench Power Supply Despite my exhortation for DIYr's to "buy" rather than make, I have succombed to the desire of those in the community who prefer the opposite.  OK, if you are going to make this supply, you might as well make it as useful and reliable as possible.

This supply uses a high quality thermally controlled voltage reference, good quality error amplification techniques (which have been checked out with the phase-gain meter for their open loop response and stability) to provide + and - 40 VDC at 3 Amps.  

As with our other projects, a microprocessor is used.  You can control the device using a 4X4 matrix keypad or Selmaware's STAMPPLOT !