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Τετάρτη, 6 Απριλίου 2016

Mains hum in DIY amplifiers.

Mains hum is a major problem in almost homebrew amplifier project.I run across this problem all the time.I haven't figured out how to solve it yet.

My DIY amp with two TDA2030s and  preamp.



You can clearly hear the mains hum in my speakers.




Possible causes of mains hum in speaker.

  • power cables too close to audio cables.
  • no shieled cables for preamp out/amp in
  • preamp too close to its transformer
  • preamp too close to power button
  • RCA in contact with casing
  • no ground wire from mains socket to metal casing
  • power button wrong position




Here are a couples of things I changed that seem to reduce the hum significantly.


  • shielded wires for audio
  • preamp transformer moved away from preamp.This reduced the hum a great deal.
  • preamp moved away from power button.
  • ground wire from mains to metal casing 




I still got some hum but much much less than initially.
Any suggestion regarding what I did or to reduce the hum more?


arximastoras.blogspot.com
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Σάββατο, 30 Ιανουαρίου 2016

Basic safety advice for beginners in electronics.



As a beginner in electronics you should follow some very basic principles to avoid risk of electric shock ,injury and even death.





As a beginner in electronics you should NEVER-EVER start with circuits that use high current such as power supplies.You never open home appliances such as a TV,or microwave oven.These two are the most dangerous home appliances.They can hold current long after they have been unplugged.One should know exactly what he is doing before opening a TV.You should always start with low current circuits such as a small battery operated amplifier like the LM386 amplifier.I repeat as a beginner in electronics never touch circuits that use mains power.There is great risk of electric shock.Electronics is a nice hobby but it can be deadly and like playing with fire if you do not know what you are doing.
Enjoy electronics and -above all- stay safe!


arximastoras.blogspot.com
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Κυριακή, 20 Σεπτεμβρίου 2015

VGA cables not all the same!!

VGA cable pinouts can vary.
"Classic" VGA:
1 Red (Analog) 
2 Green (Analog) 
3 Blue (Analog) 
4 Reserved 
5 Ground
6 Red Return 
7 Green Return
8 Blue Retuen
9 No Connect
10 Ground
11 (ID0) GND (Color)
12 (ID1) NC (Color)
13 Horzontal Sync
14 Vertical Sync 
15 No Connect 

newer standard 

"VESA DDC2"
Pin 1 RED Red video
Pin 2 GREEN Green video
Pin 3 BLUE Blue video
Pin 4 N/C Not connected
Pin 5 GND Ground (HSync)
Pin 6 RED_RTN Red return
Pin 7 GREEN_RTN Green return
Pin 8 BLUE_RTN Blue return
Pin 9 +5 V +5 V DC
Pin 10 GND Ground (VSync, DDC)
Pin 11 N/C Not connected
Pin 12 SDA I?C data
Pin 13 HSync Horizontal sync
Pin 14 VSync Vertical sync
Pin 15 SCL I?C clock

source 

arximastoras.blogspot.com
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Δευτέρα, 7 Σεπτεμβρίου 2015

LED Vu meter circuit (LM3914)

This is a simple LED Vu meter circuit based on the LM3914 IC.


You can use either the LM3914 or the LM3915.The difference between the two is that the LM3914 is analog while the LM3915 is logarithmic.

The input comes for your audio amlifier the speaker out (+ and -).

Feed this circuit with 9 to 12 volts.

Here is the schematic.



And here is an easier way to read the schematic.









arximastoras.blogspot.com
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Τρίτη, 25 Αυγούστου 2015

Very good variable power supply kit by banggood.

This is a quite good variable power supply kit moneywise and specswise by banggood.It puts out 0-30 volts and 0-3 amps and it costs 10.39 bucks!Not bad at all.


This kit does not include the transformer and heatsinks for the lm7824 and the D1047.

I made little modification though-a 24 volt fan is difficult to come by so I replaced the lm7824 with a lm7812.



arximastoras.blogspot.com
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Παρασκευή, 7 Αυγούστου 2015

How many volts are needed to light up switch button?

I think one needs 40 volts at least to light up this red switch button.

I usually connect it in series with one of the mains wires (240volts(Danger of electrocution!)).


arximastoras.blogspot.com
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