Little Green Scream Machine questions

Bubba Kester

Bubba Kester

New member
Hi,
I have been looking at the schematic of the Little Green Scream Machine and have questions about 3 components and their values.

C11 47uF Electrolytic: I have often seen the cap in this position specified at 100uF, but did find a few instances of the 47uF value. I am wondering what thoughts influence the choice of value.

C12 100nF: This seems like an addition to the traditional circuit. Has this been added to shunt high frequency noise from a power supply to ground? If not, why has it been included?

R1 2M: I have seen resistors placed at this position with the intention of loading to prevent a "popping" noises from occurring during the switching. Is this why R1 is included? In other examples I have seen 510k used in this position. Is the value important?

Thank you!
 
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C11 is the main filter cap and can often be anywhere from 47µF to 220µF. 100 is possibly the most common. In some circuits I swear that using 100 rather than 47 will let more low end through but this is highly contentious and I have been ridiculed for suggesting it! The 100n at C12 is a fairly common addition to help filter the entire frequency range. I've been known to leave it out sometimes and I can't hear any difference. It's considered "best practise".
 
Thank you for the info about the capacitors. I am somewhat familiar with filter caps in linear AC to DC supplies, but have not thought much about their role in designs that are based upon an external AC to DC supply. I am just beginning to appreciate that these filter caps have been added to circuits originally designed for DC B+ sourced directly from batteries, but these circuits are now more often powered by a variety of external converter appliances.

Thank you!
 
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