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Posts posted by faizanbrohi

  1. Everthing is working fine but there is one problem the Attenuation is still low . i can still hear music when the pot is fully turned off , i think a higher value potentiometer would solve the problem , a 200K or 300K Pot should solve the problem , well i am going to check it in my university because they have big high wattage pots , seems that they should work fine . and one more thing when not playing any sound or music there is a very annoying hum , how to stop this ??

  2. Hello Audio Guru , i have built the units together in one PCB they are complete . there is only one problem , the speakers are howling because of the microphone. is there any method i can apply to remove it

    One more thing is that the volume when set to zero . i mean 100Kohm , it is still giving a amplified output at the speaker . i want volume at zero to be implemented where at zero no voice is there at the output what should i do , see the figure i think i should should add a resistor.


  3. The Power amplifier uses bipolar capacitors , and they were hard to find . why are bipolar capaictors , why not use simple polar capacitors when there is an option.
    and the input transistors are okay , i have a assembled version of the power amp which i bought as a guide and it is working. no problem with the input tranisitors . Just Hope the amp works .

    One more thing i tested the assembled version of the power amp with a computer and it ran fine. don't know if it will work with the TL071 Preamp

  4. Hello Audio Guru , i have almost built the PCB and refined it , for the 80W Stereo That i posted the first time . i am making only a mono version for the university project. so i also need to make a preamplfier . So i had a preamplfier i made some time , but it had very bad distortion , it was made using a AN7116 Power amplfier IC , had awful distortion. I also tested it with the Power amp . didn't work good for my need.
    SO here is another schematic . THere is a graph for THD also . I am making a PCB for it . Will this work for my Power Amplfier ?



  5. IF we make a sine wave inverter with making sine wave instead of square wave and and use mosfets in our design 4 parrallel mosfets oen side and 4 parallel mosfets other side, IT willl minimize heat dissipation and we will have a sine wave inverter.
    BUt making a modified sinewave wave , a digital which has steps in it , would be easier , but will it run a TV or Computer . The UPS I had , if it produces a stepped sine wave , then , i used it to run a computer , full with CRT monitor also and a TV also ran fine .

  6. Well amazingly i found a UPS Inverter . and well it is quite complicated , dual layer PCB and all that stuff . i cannot use the parts in it , beacause it is my dad's office UPS and it is dead . so here are some of the things i found .

    * 4 mosfets IRF240 , 2 sets in parallel .
    * BUZ11 mosfet
    * Transformer ( Don't know if it is a ferroresonant Transformer or not )
    5 wires coming out of the input side , one is connected to battery directly. 4 wires coming out from the Input side .
    * 4 Logic Gates IC , like CD4077 , CD 4093 , TC 4093 and MC14081
    * One Quad amp LM339

    Now condsidering the following components , i think the Logic gates produce a approximation sine wave and then is filtered into sinewave with a LM339 Quad amp and then Mosfets are used to increase the current , THen THe transformer does the step up .. All in all it is producing a approximation sine wave , i think
    what do you think ? comment

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