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  1. audioguru2

    0-30 Vdc Stabilized Power Supply

    You can look up the spec's for those old opamps to see if they will fail with a supply voltage from this project that is higher than the max voltage allowed for them. The OP37 and NE5534 are de-compensated and therefore would oscillate in this circuit. Since you cannot get modern parts then use...
  2. audioguru2

    The caps surrounding the LM7812 regulator?

    The actual output resistance is about 1 ohm. The high gain and high amount of negative feedback make it function the same as if its output resistance is only 0.008 ohms. With a load of 1.5A then its output voltage would drop 1.5V across its actual reistance of 1 ohm. The gain and negative...
  3. audioguru2

    0-30 Vdc Stabilized Power Supply

    Heat is caused by power dissipation. Power= volts x amps. You have a 24VAC transformer that has a peak voltage of 40.0V. The rectifiers will drop it to an unfiltered positive supply of 38.0VDC at full output current. If your transformer is rated at 120VA then it will be able to supply the 40V...
  4. audioguru2

    multiple electret mics connected to pro audio gear

    thanks. I am on most of the electronics chat forums on the web. Some guys post the same question on all of them.
  5. audioguru2

    The caps surrounding the LM7812 regulator?

    No. Read the datasheet. A 7805 voltage regulator keeps the output voltage very close to 5V if the input voltage changes from 7.5V to 30V and/or if the load current changes from zero to 1.5A. The output resistance is spec'd on the datasheet at 0.008 ohms for a 7812 an is less for a 7805. The...
  6. audioguru2

    Voltage Regulator LM317 to 120ohm or to 240ohm

    The transformer in the 30V/3A project is too small. With it the project has a max output voltage of 25VDC at 2.1A when the transformer is at its max power rating. Its supply voltage for its opamps is higher than their max voltage allowed. Some parts get too hot and fail.
  7. audioguru2

    The caps surrounding the LM7812 regulator?

    The load has nothing to do with a high gain regulator that has lots of negative feedback. It works perfectly until the max load current is limited by the regulator. Its output resistance at DC is only 0.008 ohms so the load resistance is much higher (1A at 5V= 5 ohms which is 625 times higher...
  8. audioguru2

    multiple electret mics connected to pro audio gear

    Hi Viper, Nice try. The signals from your mics were shorted by the power supply and the opamp was amplifying noise from the power supply. Try this mixer circuit:
  9. audioguru2

    Electronic Stethoscope- Project PCB

    Con designed a pretty good pcb for my fixed version of the project.
  10. audioguru2

    Voltage Regulator LM317 to 120ohm or to 240ohm

    The extra votage will make a lot of heat if there is any load current. You have the wrong transformer.
  11. audioguru2

    white led

    The current regulation is pretty good. From 300V to 345V is an increase in voltage of 15% but the current increased from 26.4ma to only 27.3mA which is an increase of only 3.4%. EDIT: The current regultion is even better than that because the actual circuit voltage is nearly doubled.
  12. audioguru2

    0-30 Vdc Stabilized Power Supply

    That is why I recommend using two output transistors on two separate heatsinks to share the heat. A 24V transformer is used like in the original project. Then it is set to a low output voltage and set to 3A or its output is shorted. Then the 2N3055 output transistor must dissipate 32V x 3A= 96W...
  13. audioguru2

    TV Signal Amplifier ?

    It is complicated. You must tune in the weak signals before the amplifier to avoid other stronger stations from overloading the amplifier. The tuned circuits might not be sharp enough. Then you must mix the amplified signal into the STB somehow.
  14. audioguru2

    white led

    I don't know how good or how poor is the current regulation. When the rectified voltage is as high as 366VDC then you don't want the current to be higher than the max allowed for the LEDs which is 30mA.
  15. audioguru2

    0-30 Vdc Stabilized Power Supply

    It is too bad that you can't get stuff in your country. I just order parts from a neighbor country (USA) online and they are delivered to me the next morning.
  16. audioguru2

    multiple electret mics connected to pro audio gear

    Electret mics pickup sounds from all around them. Directional ones are directional only at high frequencies unless they are very long. Your 30 to 40 mics will all pickup the same sounds so why have so many of them so close together? The Jfet in an electret mic has a pretty high output...
  17. audioguru2

    0-30 Vdc Stabilized Power Supply

    Where are you where common parts are not available? Come over to this part of the world where everything is available.
  18. audioguru2

    0-30 Vdc Stabilized Power Supply

    The old LM143 and SG143 are very slow and their output voltage swing is limited. Their offset voltage adjustment is different. The circuit would need many changes for them to be used.
  19. audioguru2

    TV Signal Amplifier ?

    If you live anywhere near a TV station then this very simple circuit will be overloaded and won't amplify another weaker station. It is not tuned like the input of your TV. If you live away from any TV stations then your TV will be operating at its max gain and this very simple circuit won't do...
  20. audioguru2

    Voltage Regulator LM317 to 120ohm or to 240ohm

    The output voltage will not go to 0V with diodes in series with the input. If two diodes are connected in series with the output then their output will go to 0V sometimes, but the voltage regulation will be ruined and the output voltage will change with output current and temperature as the...
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