January 99  Tube Crossover
An active crossover must divide the full audio signal bandwidth presented at its input into sub-bandwidths for each of the four speaker drivers so that their summed output equals a flat frequency response. Two crossover versions: 6 and 18 dB per octave. The 6 dB circuit has been pared down to the essentials only. The 18 dB version is carefully designed to eliminate as many signal path capacitors as possible. 


December 98  Tube Headphone Amplifier   
This month's circuit is a small, single-ended, OTL amplifier for driving dynamic headphones. Some excellent sounding headphones can be had from Grado, Beyerdymanic, and Sennheiser. This amplifier can power all of them, even down to the 32 ohm Grado. 


November 98   Phase Selection & Zero Gain Line Stage Amplifier   
More no gain, no pain. This month's circuit offers the option of inversion of the signal's phase, a low impedance, zero gain, buffered output. Furthermore, the circuit has been optimized to reject power supply noise at its output.   


October 98   Zero Gain Line Stage Amplifier
No gain, no pain. Many audiophiles prefer to use passive attenuators, which have zero gain. However, there are circumstances that demand the use of a high current line stage. So here is the design goal: no voltage gain, but a healthy output current delivery for driving long lengths of cable.     


September 98   Medium Gain Line Stage Amplifier
This line stage uses the Constant Current Draw Grounded Cathode (CCDGC) amplifier topology. A Grounded Cathode amplifier cascaded into a Cathode Follower...what could be more obvious? True enough, but there is a twist. Here is where the twist comes in: the Cathode Follower's output is not taken directly at its cathode.     


July 98   Medium Gain Phono Stage for MM Cartridges
The objective is a two stage phono preamplifier that uses inter-stage passive RIAA equalization for use with medium output moving magnet cartridges.