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Friday, April 27, 2012

Modified D-Class 555 Audio Amplifier circuit!

The amplifier operates in a way similar to pulse-width modulation. The 555 modulates the Audio input with  a frequency higher than the speaker response capability so the modulating frequency  is dropped (the coil in the speaker acts as a HF filter) and the input signal is being played by the speaker
Note1: Adding a 100n cap between pin 1 and 2 will dramatically increase the volume, distortion and heat up the chip very fast. Also (from original circuit) adding a capacitor across the speaker terminals will increase the volume and distort the output but without heating the chip.
Note2: To add a volume control, replace the 100K connected between the Transistor base and ground with 100K Pot.
Note3: The transistor used in this circuit is BC547, the IC is NE555 and the actual DC supply is 12V.

 Using iCircuit App for iPhone

Sunday, April 15, 2012

LM187 5T 20W Audio Power Amp / Dual Supply setup!

Monolithic power amplifier with a wide supply range (16V - 60V). It delivers 20W into 4 ohm or 8 ohm speaker. Using +/- 30v it delivers over 30W to 8 ohm speaker.

Some important Datasheet Notes:
Note 1: Twist Supply lead and supply ground very tightly.
Note 2: Twist speaker lead and ground very tightly.
Note 3: R1C1 band limits input signals.
Note 4: All components must be spaced very closely to IC.

Thursday, April 5, 2012

Versatile, small power LM386-based Audio Amplifier

 LM386 Audio Amplifier with Gain = 20 

When capacitor is placed between pin 1-8, it will bring the gain up to 200.

LM386 Audio Amplifier with Gain = 200

Monday, April 2, 2012

ThinkPad X30 IIS based Web Server and "" DNS host!

I did set up a Windows (IIS) web server on my old IBM ThinkPad X30 machine and using the DNS host service from I can access the web server over the internet using an URL instead of my dynamic  IP address. offers a client for Windows, Mac and UNIX that checks the WAN dynamic IP address and updates the DNS service with the new dynamic IP! let you create multiple DNS hosts for dedicated services like Http, ftp, .. etc and using their client software i mentioned before you can choose which host (service) you want to activate and also link to the server machine or other machine on the network.