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  1. Audioguru

    Building an EKG analog front end circuit

    Most ECG circuits have the patient connected to an inverted common-mode AC and DC signal that cancels most hum and muscle movement pickup like this:
  2. Audioguru

    Battery Pack Conversion Project

    The 11.1V Li-ion battery will be 12.6V when fully charged. Replace it with 9 name-brand AA Ni-MH cells in series.
  3. Audioguru

    Difference in battery capacity between Alkaline and NiMH cells

    Are 6V lead-acid batteries made anymore?
  4. Audioguru

    Need a dummy load

    The Lutron datasheet for the dimmer shows that it is used for approved bulbs (yours are not approved) or a minimum 10W load.
  5. Audioguru

    Difference in battery capacity between Alkaline and NiMH cells

    Some D size Ni-MH cells have a little AA cell inside, because nobody complains and nobody uses a D size battery anymore..
  6. Audioguru

    Need a dummy load

    The resistance of the 10W light bulb is easily calculated. If the voltage is 120V then a resistor value of 1440 ohms draws 10W, because P= 120V squared divided by the resistance. A 10W resistor will be very hot so use a 20W resistor. Paying for 10W of electricity for a year will cost more than...
  7. Audioguru

    Klipsch ProMedia 2.1 subwoofer circuit help

    I looked up the Klipsch ProMedia 2.1 speaker system to see what it has. Tiny 3" woofers in the satellites that are supposed to play down to 48Hz! A 6.5" small "subwoofer" that cuts off its bass at 48Hz! The spec's claim response from 31Hz on up but with no dB's. I suspect that it booms at about...
  8. Audioguru

    power supplies in parallel?

    Please post the datasheet or a link to the LED strips. 12V LED strips have 3 LEDs in series, not parallel and each series group is probably 20mA or less. Then the total current for 2736 LEDs is 18.24A or less, not 164.16 Amps.
  9. Audioguru

    Klipsch ProMedia 2.1 subwoofer circuit help

    Here is the lowpass filter shown on the Klipsch I/o board. Its slope is not very steep.
  10. Audioguru

    Klipsch ProMedia 2.1 subwoofer circuit help

    The Chinese circuit board ad has no audio spec's and does not say which opamp is used. I wonder why their translation says it is "overweight"?
  11. Audioguru

    Klipsch ProMedia 2.1 subwoofer circuit help

    I repeat: The filter circuit from the Klipch manual that is outlined in red is not a lowpass, it is a highpass which is simulated here:
  12. Audioguru

    Modify car amplifier power supply.

    The Alpine MRV-1507 car amplifier obviously has a stereo amplifier that produces 150W to 225W per channel into 4 ohms with a supply to its DC-DC converter of 12VDC to 14.4VDC. It is probably class-AB (not class-D) so with 300W of total output its heating is about 200W so its power supply must...
  13. Audioguru

    Voltage on a white LED.

    Here are parts of the datasheet for the white LED:
  14. Audioguru

    Voltage on a white LED.

    The white LEDs are 18,000mcd with a 30 degrees viewing angle and their "white" is very blue.
  15. Audioguru

    Large project, speaker help needed

    My son-in-law found a nice little speaker system that was cheap and it sounds pretty good. But its rechargeable battery charge does not last long very long. I hope you find cheap little speakers that sound good and find out how to connect everything together.
  16. Audioguru

    Large project, speaker help needed

    A speaker must have a sealed or ported enclosure to prevent the sound from its rear that is out-of-phase with the sound from its front from cancelling low frequencies. The datasheet for most half-decent speakers (but there is no datasheet for that very cheap Chinese one) show a recommended...
  17. Audioguru

    Klipsch ProMedia 2.1 subwoofer circuit help

    The subwoofer lowpass filter circuit you found will work but you will be missing the matching stereo highpass filters for the mids and highs speakers. The circuit outlined in red before is a highpass filter, not a lowpass filter.
  18. Audioguru

    Large project, speaker help needed

    The tiny speakers you selected will sound awful (no low frequencies) with music, even if their enclosures are fairly large. They will sound like a cheap clock radio. There are class-D bridged amplifier circuit boards available that provide about 1.5 Watts or 3 Whats to one 4 ohm speaker, use...
  19. Audioguru

    Voltage on a white LED.

    Please post the manufacturer's name and part number of the very bright LED or its datasheet. I suspect it is an ordinary fairly dim LED in a case that focusses it to make a very narrow beam. I have a cheap Chinese LED flashlight (a torch but without a flame) that can adjust the focus of its...
  20. Audioguru

    Klipsch ProMedia 2.1 subwoofer circuit help

    One TL074 has 4 opamps in it. You need the entire controller circuit, not just the parts outlined in red. The lowpass filter must be fed from a very low impedance like from the outputs of the amplifiers shown on the left side of the lowpass filter.
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