Do these specific PAM8403 boards need a preamp? - diyAudio
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Old 5th September 2014, 01:17 PM   #1
FBMinis is offline FBMinis  Portugal
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Default Do these specific PAM8403 boards need a preamp?

Recently bought a few of these to experiment and learn.

PAM8403 Audio Module DC 5V Mini Class-D digital amplifier board LCD T5 | eBay

Was thinking of using them to power a couple of speakers connected to my portable mp3 player (Sansa Slip +).

Do I need a preamp between the mp3 player and the PAM8403?
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Old 5th September 2014, 01:25 PM   #2
SonyFan is offline SonyFan  United States
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This particular IC has an input voltage range of .5v-1.2v according to the datasheet. I could not find the input Z but given that their test diagram shows a tone generator hooked directly to input I don't think you will need a preamp or buffer. A CD player has a 2v output at its RCAs as a standard, for your reference.
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Old 5th September 2014, 01:41 PM   #3
FBMinis is offline FBMinis  Portugal
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Here are the specs for the Sansa Clip +:

NwAvGuy: Sansa Clip+ Measured

My initial question comes from the fact that I used this same player with a weaker LM386 amp and although it's loud, there seems to be some tone loss.

LM386 Audio Amplifier Module 200 Times 5V-12V Input 10K Variable Resistor DIY | eBay

Would this one benefit from a some sort of FET preamp?
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Old 5th September 2014, 06:06 PM   #4
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Consumer-grade players have an output in the .75 volt range, the manufacturer expects them to drive either headphones or powered speakers, so no preamp should be needed.

The LM386 is an excellent chip for its purpose, but nobody has ever accused it of being hi-fi (except in the Headbanger headphone amp). You can't really make a direct comparison.

EDIT: Or, as SonyFan says, 2 volts. Either way no preamp.
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Old 7th September 2014, 06:54 PM   #5
SonyFan is offline SonyFan  United States
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A preamp would only complicate things more, but you could build an extremely small and simple one with op amps.
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Old 8th September 2014, 12:10 AM   #6
FBMinis is offline FBMinis  Portugal
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Unfortunately I have not been able to test you suggestion this weekend but I just came across this project, which seems to work..

The Single NPN Transistor Audio Preamp | HACK A WEEK
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Old 9th September 2014, 03:26 PM   #7
johnr66 is offline johnr66  United States
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Portable headphone devices will typically deliver a maximum output of 500 mv rms before clipping. Since the music is normally recorded much lower, you may find the 24db gain to be a bit low.
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Old 16th September 2014, 01:40 PM   #8
FBMinis is offline FBMinis  Portugal
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I breadboarded the single npn transistor preamp in front of the LM386 circuit and it distorted easily, which proves your input.
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