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  1. audioguru2

    Electronic Stethoscope

    Hi Dazza, I dislike multiple volume controls. The main volume control might be set too low and someone will turn-up the R4 gain causing clipping distortion of the preamp.
  2. audioguru2

    Self-powered Fast Battery Tester Circuit

    Hi Tom, As I said earlier, The TLC555 probably won't work with a supply voltage of 1.5V, it needs at least 2.0V. Maybe the values of your capacitors are incorrect. 10nF is 0.01uF and sometimes is marked "103". 100nF is 0.1uF and sometimes is marked "104". C8 should have a whopping voltage...
  3. audioguru2

    Electronic Stethoscope

    Hi Dazza, It is great to hear that it is working better.  ;D You probably used 3.3nF (not uF) for C3 and C4 for a low-pass cutoff frequency of about 1.4KHz. Changing the equal values of R5 and R6 changes the low-pass cutoff frequency the same as changing C3 and C4. You could try a 100K stereo...
  4. audioguru2

    ignition circuit

    Hi Kouha, Welcome to our forum.  ;D It is good that the project's author put the warning label. Many circuits on the web should also have the label. Maybe the author's circuit blew-up and he doesn't yet know why. Some of the "beta" software on my computer have a similar warning label.
  5. audioguru2

    Self-powered Fast Battery Tester Circuit

    Hi Tom, There's your problem.  :o The NE555 is the original one that is not Cmos. Its minimum supply voltage rating is 4.5V. You need LMC555 Cmos ICs that are guaranteed to work with a supply voltage as low as only 1.5V. The ICM7555 and TLC555 Cmos ICs are guaranteed to work with a supply...
  6. audioguru2

    Electronic Stethoscope

    Hi Dazza, I am sorry to hear about the "surgeon". I hope that everthing is alright. You have a great idea!  ;D Of course the baby's heartbeat will be hard to hear, but maybe the bloodflow is better heard. Try decreasing the value of C3 and C4 for a 1KHz low-pass cutoff frequency, and decreasing...
  7. audioguru2

    Self-powered Fast Battery Tester Circuit

    Self-powered Batteries Tester project: http://www.electronics-lab.com/projects/power/012/index.html
  8. audioguru2

    Another INVERTER we can talk about..

    Hi Blitznet, Which inverter circuit did you build?
  9. audioguru2

    Self-powered Fast Battery Tester Circuit

    Hi Tom, The circuit looks OK to me. C8 should charge to about 4 or 5 Volts when the circuit is powered by a 1.5V new battery cell. It probably won't work if the battery cell is rechargeable, used or a button cell. 1) What size of battery cell did you try? 2) What is marked on your Cmos 555's...
  10. audioguru2

    Another INVERTER we can talk about..

    Hi Alun, Maybe he was feeding a 40A sine-wave into his Mosfets. Then they will make lots of smoke!  ;D
  11. audioguru2

    3V LED Chaser project

    Hi Daemon Frank, You could power this project with two N cells or even two AAAA cells for small size. There are many 3V lithium "coin" battery cells that will work and are also very small. I have seen small battery holders for them at my local electronic parts shop. A little car remote 9V or 12V...
  12. audioguru2

    Low-pass Filter?

    Kevin, A Butterworth active filter is the same as discrete RC filters except is much better. Two cascaded RC filters affect each other because the 2nd one loads-down the 1st one. If you buffer the input of the 2nd one so that it doesn't cause loading, the combination of the two filters cause...
  13. audioguru2

    Transistor distortion and reducer circuit

    Hi Alun, A FET-input opamp is less noisy than a BJT-input opamp usually only when they have a very high source impedance. With a low source impedance their noise is about the same and is determined by their design. The transconductance of FETs is called "Square Law" because their voltage gain...
  14. audioguru2

    Transistor distortion and reducer circuit

    Kevin, The graphs show a transistor circuit with nearly half its positive-going waveform missing. It is nowhere near full output but its distortion is an extremely high amount of 15%. Distortion might be 50% at full output. Nowadays, an amplifier with only 0.5% distortion at full output is...
  15. audioguru2

    Another INVERTER we can talk about..

    Maybe the Mosfets are both turning on at the same time. Maybe the Mosfets are trying to pass too much current for their rating because the load current of the inverter is too high.
  16. audioguru2

    Electronic Stethoscope

    Hi Dazza, Do you want it to "beep" like heart monitors in hospitals? They pickup electrical impulses to trigger the beep, not the actual sound from the heart. First you must eliminate the friction crackling noises.  ;D
  17. audioguru2

    fm tranismiter

    Hi Alun, This 10.7MHz ceramic filter controlled FM transmitter won't be able to change its RF frequency much away from the 9th harmonic at 96.3MHz. I'm surprised that Sazi got some very high frequency output out of his transistor's collector, because it is swinging at 10.7MHz, isn't it? The...
  18. audioguru2

    Transistor distortion and reducer circuit

    Hi Alun, In an opamp the changing base-emitter impedance is minimized by using an extremely high impedance current source instead of a collector resistor so that the change of impedance of the base-emitter is negligible. A series emitter resistor is also used to minimize the change. Multiple...
  19. audioguru2

    Transistor distortion and reducer circuit

    Hi Alun, Isn't that a neat way to cancel a transistor's distortion by making it more linear?  ;D The transistor's gain decreases when it conducts less current because the impedance of its base-emitter junction increases. The diode in the circuit conducts more current when the transistor conducts...
  20. audioguru2

    Low-pass Filter?

    Hi Heey, Welcome to our forum.  ;D There is nothing special about the 2SC1061 transistor except it is available in the orient. Any 40V, 3A to 6A medium power transistor will replace it. I would use a TIP31 but maybe you could find a BDxxx equivalent.
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