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Old 12th June 2013, 01:48 PM   #1
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Default Match Electric guitar output to PAM8403 Amp input

Hi Guys,

I have got a PAM8403 mini amp. It is a sterero 2x3W class D amp. I want to use it as a portable chipamp for my electric guitar, but I am afraid of damage it if the signal level of the pickups are too high for this little amp. Do you have any advice on how to match the signal? Do you recommend some kind of buffer or attenuator? or do you think it is ok to plug it directly?

Thanks in advance,

Frank.
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Old 12th June 2013, 04:46 PM   #2
Minion is offline Minion  Canada
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Your guitar has a instrument level output that is of a high impedance (if it is a guitar with passive pickups) and your class D amp expects a line level lowish impedance signal at it"s input .....
To achieve this I would suggest you simply put a guitar effects pedal between your guitar and amp , this will buffer the guitar signal and bring it up to line level .....
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Old 12th June 2013, 05:36 PM   #3
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Hi Minion,

Thanks for your response. But I am trying to build a small portable amplifier. Do you recommend a simple JFET buffer?

I have been reading about JFET Buffers but I don't know how to adjust the resistors values for this case with a power supply of 5V.

My first bet is some of the buffers explained here: Basic Buffers

But I am not sure what is the best option.
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Old 14th June 2013, 05:35 AM   #4
gootee is offline gootee  United States
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If you need to increase the level, then you would need a buffer amplifier but with some gain > 1.

You should probably just use an op amp amplifier. That is the easiest way to get extremely good results. Look at AN-31 and AN-20, at national.com or ti.com .

Whatever you use, make sure to add some local power supply decoupling capacitances, and some high-frequency bypass capacitances.
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Old 14th June 2013, 06:32 AM   #5
Minion is offline Minion  Canada
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Quote:
Originally Posted by mnesarco View Post
Hi Minion,

Thanks for your response. But I am trying to build a small portable amplifier. Do you recommend a simple JFET buffer?

I have been reading about JFET Buffers but I don't know how to adjust the resistors values for this case with a power supply of 5V.

My first bet is some of the buffers explained here: Basic Buffers

But I am not sure what is the best option.
A Buffer would give you a low impedance output which would interface with the input of the class-D amp well , but the signal level coming from the guitar would still be low level , If you build a Gain stage with an opamp it will also act as a buffer .... You could use a pot to get an adjustable gain ...

There are a lot of jfet buffers but if you are talking about a jfet buffer called Tillman then it is an okay buffer but it ads very little gain and you can get it to break up by hitting your strings hard , the tillman wouldn't be good at 5v either ...
There are some fet opamps that can run on 5v .....
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