EEVblog Electronics Community Forum
Electronics => Beginners => Topic started by: Frank the dish on April 02, 2021, 04:13:05 pm
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Hi Guys, Im trying to internally amplify a guitar, ive got hold of a tiny card from the net and need a bit of help wiring it, I understand most of the connections but the power supply confuses me. I have 3 grounds which I presume are common , At the bottom I have the speaker connections , no problem there , and at the top the stereo input connections, no problem with those either . Im left with the centre 3 marked Sw, +5.v and gnd. The 5 v I presume takes the positive from the power supply but where would the negative go? Does anyone know the purpose of the switch connection and how that should be wired , if at all. Ill say thank in advance to anyone who can help me with this.
Regards
Frank
Just found shot on you tube, the switch wire is not used, so I can now start my project.
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Negative of the 5V supply goes to GND, presumably the intention is to use the GND hole directly adjacent to the +5V hole. But, maybe I'm misinterpreting your confusion.
SW could probably be configured a few ways, depending on the circuit. Do you have a schematic? The seller didn't mention anything? The switch is probably connected between SW and +5V, or between SW and GND, if I had to take a guess.
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Hi, yes thats the way I see it, I couldn't see the way the SW connection would be used . Im going go put an inline switch in the positive 5v to switch my circuit off.
Thank you
Frank
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Check the text on the amplifier chip, then download the datasheet for it.
The chip will have an enable pin or on/off pin and the datasheet will say if the sw has to be connected to gnd for the chip to work, or if it has to be connected to voltage (and if so, if you need a resistor or something between the switch pin and the voltage)
If you can't figure it out, maybe take a picture of the other side and show it here.
I suspect it's PAM8403 as this amplifier chip is very common and runs on 5v , the datasheet is here: https://www.mouser.com/datasheet/2/115/PAM8403-247318.pdf (https://www.mouser.com/datasheet/2/115/PAM8403-247318.pdf)
IF this is the chip, it has a pin called SHDN (shut down) and a MUTE pin ... so one of those could be your SW pin :
Mute Operation The MUTE pin is an input for controlling the output state of the PAM8403. A logic low on this pin disables the outputs, and a logic high on this pin enables the outputs. This pin may be used as a quick disable or enable of the outputs without a volume fade. Quiescent current is listed in the electrical characteristic table. The MUTE pin can be left floating due to the internal pull-up.
Shutdown Operation In order to reduce power consumption while not in use, the PAM8403 contains shutdown circuitry to turn off the amplifier's bias circuitry. This shutdown feature turns the amplifier off when logic low is applied to the SHDN pin. By switching the SHDN pin connected to GND, the PAM8403 supply current draw will be minimized in idle mode. The SHDN pin can be left floating due to the internal pull-up.
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Hi, ive found it wired this way on you tube , and it works like this . This is fine the way I want fo use it.
Thank you all for the information
Frank