JT-10KB-D Isolates and Converts Speaker Drive to Line Level
Our senses, especially our eyes and ears, are remarkably precise instruments. We can distinguish the slightest gradations in intensity, color, frequency, etc. Nonetheless, eyes and ears are also easily fooled.
The first 2 stages are auto biased. So the only variables are bias 1 and 2 of the output stage. Using an ECC88 the optimal bias for the minus pole is around 1.5 Volts leading to 15 mA of current in the lower half of the ecc88. So BIAS 2 = 1.5 Volt. For the plus pole the optimal bias is around 2 Volts leading to a quiescent current of 12 mA for the upper half of the ECC88.
This project grew from several conversations that I had with John Broskie of the TubeCAD Journal. I was looking for a good headphone amp and John and I discussed some of the advantages and disadvantages of several of his published circuits.
Is this a project or an article? Since you may have arrived here from either index, you might be a little confused. This is fine, as it has elements of both, but lacks the in-depth analysis of other articles, and also lacks the application of a final design that is common to my projects.
At some stage, we will all find ourselves pushing hi-fi equipment just a little too hard, and if lucky, will just find that the sound has become "dirty". If this happens too often or is too severe, tweeters are the first to go
In another of my project pages (see 14 - Power Amplifier Bridging Adapter), there is a design for a simple add-on bridging adapter for stereo power amplifiers. There is, however, an even simpler way, provided you have (or can trace out) the appropriate section of the amplifier circuit.
See upper side of the figure! It is called the pure-complementally-push-pull-amplifier. I made it and the maximum power of it was 110mW. See lower side of figure.
The Zen - along with Zen improved, son of Zen, Bride of Zen, Second cousin of Zen (or did I imagine that one?) Class-A amp designed by Nelson Pass seems to have become popular.
It can be easily demonstrated that doing your final mixes with headphones can produce stellar mixes when the mixing engineer is familiar with the practices of mixing with headphones. But how is this possible?