Class D amplifiers are much more efficient than other classical amplifiers, but their high efficiency comes at the expense of increased noise and distortion. You can assess the frequency- and time-domain characteristics of a Class D amplifier, including the output filter, using online simulations.
You needn't look further than Class D audio amplifiers to find a technology whose proponents tend toward exuberant advocacy at best and bald-faced hype at worst. Although these ICs are not yet the be all and end all of audio amplification that their makers would have you believe, they are remarkably good-certainly more listenable than the clamor about them.
Most audio outputs have some standing DC voltage which is separated by a capacitor. The capacitor will block this DC voltage while allowing the AC or audio to pass. Audio components using transformer coupling are not affected.
This relatively simple mixer was designed for three dynamic microphones, but can be re-designed for more or less. Level and tone controls are available to tailor the sound to your needs.
When showing my first DIY headphone amplifier to a friend of mine, who happens to be an engineer, the result was very unsettling frown.
Followed your recipe of mods on my 69 YBA-1 and single channeled it by lifting a 100k resistor, changed the common cathode resistor to 1.5k and tried lowering the capacitance there from 100uFd but the amp wanted to regenerate at high gain settings, so I put back the 100u cap.
In the the valveamp schematic below you see that the amplifier is built with only 5 vacuum tubes!
The circuit is a classic push-pull amplifier using an output transformer with a center tap.
This topology is widely used for tube amplifiers, because it is impossible to make a complementary P-type tube:
you cannot make holes in vacuum as you do in semiconductor materials.
This project is finalized, that means it is no longer experimental. This amplifier, altough limited in output power (20W), has been designed to give the best listening pleasure.
The volume control in a hi-fi amp or preamp (or any other audio device, for that matter), is a truly simple concept, right? Wrong. In order to get a smooth increase in level, the potentiometer (pot) must be logarithmic to match the non-linear characteristics of our hearing. A linear pot used for volume is quite unsatisfactory.
I am amazed at the number of amplifier designers who have, for one reason or another, failed to take some of the well known basics and pitfalls of amp design into consideration during the design phase. While some of these errors (whether of judgement or through ignorance is uncertain) are of no great consequence, others can lead to the slow but sure or instantaneous destruction of an amplifier's output devices.