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The Solution
The challenge facing GlassWare was this: what to do with the Tube CAD Journal? how to keep publishing it without charging for it? Some possibilities were to stop writing the journal, to charge a subscription fee, or to take on annoying banner ads. None of those options appealed to me. But the idea of writing small and inexpensive companion software, the sale of which would allow me to continue to publish this journal for free, seemed like the ideal solution, as no one is required to buy the software, but those who do will bask in the satisfaction of helping keep this free journal alive.
The downloadable software is incredibly affordable, $12.95 USD -- the price of a budget CD. A disk version is available for a few bucks more. And if you buy either during October 2001, you get an early bird $3 discount: only $9.95 USD. (For Windows 9x/Me/NT/2000.)
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First TCJ Program
This journal's first companion program is TCJ Filter Designer, which lets you design a filter or crossover (passive, solid-state or tube) without having to check out thick textbooks from the library and without having to breakout the scientific calculator. This program's goal is to provide a quick and easy display not only of the frequency response, but also of the resistor and capacitor values for a passive and active filters and crossovers.
While the program's main concern is active filters, solid-state and tube, it also does passive filters. In fact, it can be used to calculate passive crossovers for use with speakers by entering 8 ohms as the terminating resistance. Covering tube-based filters would never even be contemplated at the mainstream EE software mills, but tube crossovers are a major part of this program; both buffered and un-buffered tube based filters along with mono-polar and bipolar power supply topologies are covered.
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