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06-16-2024, 11:32 AM
Hi Guys
You will notice there are a lot of extra parts in the preferred schematics compared to OEM. Manufacturers want to save money and time, so removing a "nicety" saves the cost of that part, the cost of the labour to install it, and the time to install - maybe they no longer have to inventory it?
Choke-input supplies provide natural current limiting. Chokes were easier and cheaper to manufacture than were high-voltage filter caps of significant value, but then capacitor technology and economics changed and capacitive-input supplies became the norm.
You see current-limiting resistors in older circuits using tube rectifiers and old texts say to add them as do the tube data sheets. As consumer electronics evolved, these resistors were dropped for the above-mentioned reasons. In some amps where parallel low-voltage output stages are used - as in MI and most hifi - parallel rectifier tubes might be used, which effectively increases the current capability of the net rectifier.
Back when I knew less than I know now, I would look at these low-value Rs and Cs and think they are unimportant and exclude them from my rendering. But then you learn more and realise what those parts are for and add them back in. There are some circuit places where I add in a resistor, say, where I never see one in simplified app notes nor in complete sophisticated products. An example of this is a resistive tether to ground at the output of an opamp or direct-coupled solid-state power amp. To me this R helps with reducing DC offset by providing a leakage path for the output stage. It costs pennies. It may not actually do what I initially added it to do, but it does contribute to stability at very high frequencies.
You will notice there are a lot of extra parts in the preferred schematics compared to OEM. Manufacturers want to save money and time, so removing a "nicety" saves the cost of that part, the cost of the labour to install it, and the time to install - maybe they no longer have to inventory it?
Choke-input supplies provide natural current limiting. Chokes were easier and cheaper to manufacture than were high-voltage filter caps of significant value, but then capacitor technology and economics changed and capacitive-input supplies became the norm.
You see current-limiting resistors in older circuits using tube rectifiers and old texts say to add them as do the tube data sheets. As consumer electronics evolved, these resistors were dropped for the above-mentioned reasons. In some amps where parallel low-voltage output stages are used - as in MI and most hifi - parallel rectifier tubes might be used, which effectively increases the current capability of the net rectifier.
Back when I knew less than I know now, I would look at these low-value Rs and Cs and think they are unimportant and exclude them from my rendering. But then you learn more and realise what those parts are for and add them back in. There are some circuit places where I add in a resistor, say, where I never see one in simplified app notes nor in complete sophisticated products. An example of this is a resistive tether to ground at the output of an opamp or direct-coupled solid-state power amp. To me this R helps with reducing DC offset by providing a leakage path for the output stage. It costs pennies. It may not actually do what I initially added it to do, but it does contribute to stability at very high frequencies.
