4863 amplifier connected directly to Pedalshield

curado
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8 years 3 months ago #416 by curado

4863 amplifier connected directly to Pedalshield was created by curado

To keep a long story short, I wired a pair of computer speakers (Walmart brand) directly to the Pedalshield. They were of poor quality, and contain a 4863 amplifier chip. The first attempt simply fried the 4863 chip after a few minutes of playing (smelly smoke :lol:

).

I investigated with a second set of speakers of higher quality (Logitech), and the same situation develops. The 4863 chip gets very hot, only when playing, with the gain turned up past about 40%.

Is it possible to output unamplified/line level from the Pedalshield? So I don't keep frying speakers?

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Ray
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8 years 3 months ago - 8 years 3 months ago #419 by Ray

Replied by Ray on topic 4863 amplifier connected directly to Pedalshield

Hi there, pedalSHIELD output is not particularly high, but its true that is not line level... a bit over it.

If you want to reduce to level ar the output of the pedal this is the best way:
- If you look at the schematic , the last op-amp is a summing amplifier (it adds the original guitar signal that comes trough R15 and the modified signal that comes trough R16).
- The Summing Amplifiers output is Vout = Rout/Rin (V1+V2) where Rout=R17=100K, Rin=R15=R16=100K, V1= original signal, V2=modified signal.

So the output voltage of the pedal Vout = 100K/100K(V1+V2), if you want to reduce the output voltage just reduce the value of Rout=R17

In a nutshell: If you want an output voltage half the size make R17= 47K, or even lower 22K.

Last edit: 8 years 3 months ago by Ray.

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