Parts Express $10 Amp
I found this amp from a forum post. For $10 I thought the parts alone should be worth more than that so it won't be a total loss if I can't find a use for it.
You can find it at PE through this link here.
PE lists this amp with the following specs:
100watts RMS mono class D
150Hz 12dB/oct LPF
High level inputs
auto turn on using DC offset of high level inputs
As always, I like to disassemble stuff and see what':s inside. Here are some internal pics of the amp.
This is what it looked like when I got it:
Popping the side and bottom cover off, we see the solder side of the PCB:
Removing the clamp, we are greeted with six IRFZ44R MOSFET's:
We can now remove the amp PCB from the heatsink:
Here's the input end of the PCB:
The output stage with the 0.015ohm shunt resistors for short circuit protection:
Another overall view:
Output stage is a full bridge topology so I have no idea how the guy that reviewed it in the PE page was able to "strap" two together. Four mosfets are for the H bridge and I'm still not sure what the other two are for but they appear to be the main power switch.
I did not see any output filters which almost all class D amps have so I originally thought this might be a filter-less class D amp. I took my oscilloscope and tried to check for a PWM signal but there was one!!! It's a class AB amp! Idle current is about 0.2Amp. The offset turn on circuit works ok, it turns on instantly and turns off with a one second delay. Muting is nice and pop free.
There appears to be short circuit protection because there are 0.015ohm shunt resistors on both outputs. There is also thermal protection as there is a thermistor in contact with the heatsink beside the output devices.
A quick calculation showed that it probably won't be able to reach the published 100watts into 1 ohm unless it has 10% distortion or supply voltage is raised to around 15V.
PCB part number appears to be PAM620-02. Board is conformal coated on both sides and has a manufacture date stamp of 2004.11.22
I can see 5 IC's inside. one 555, one dual comparator, two dual op amps one quad op amp and lots of discrete components.
For the price, I couldn't complain. I'm planning to use one for a powered sub using the Tang Band 6.5" subwoofers.
Page created and copyright R.Quan © 11 Feb 2011.