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  1. [SOLVED]Closed: Re: Rookie making an audio step-up transformer

    There are many good quality electret microphones stocked at Digikey. The first one listed costs $.77US and its datasheet shows its fairly wide frequency response and its low noise level. It does not...
  2. [SOLVED]Closed: Re: Rookie making an audio step-up transformer

    A loudspeaker makes a poor microphone because of its strong low frequency resonance. It also does not need a transformer. The cheap old poor-sounding intercom at a gas station uses its speaker as its...
  3. Closed: Re: Zener diode simulation problem using multisim 12.0

    I do not know what you are trying to do.
    1) You have a 5V Zener diode with no part number and no spec's. Nobody makes one but 5.1V is common so my calculations use 5.1V.
    2) You are simulating...
  4. Closed: Re: Zener diode simulation problem using multisim 12.0

    Your attachment cannot be seen because it is invalid.
  5. Closed: Re: Is a tantulum different from a microfarad tantulum cap?

    When an oriental capacitor is marked with "k" then it means its value is +/- 10% tolerance.
    A tantalum capacitor has polarity. If you connected it backwards then it might be damaged and not work...
  6. Closed: Re: humbucker preamp - j201 gain is 1:1, why ?

    The original schematic uses a 6.8k drain resistor and says you do not need much gain for an electric guitar and the gain is only +3dB which is 1.414 times. But you reduced the drain resistor to 4.7k...
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    Closed: Re: Lets take a look on a linear amplifier

    I was called "Audioguru" by a salesman at an audio engineering company I worked for, because a Guru is an expert and master. The salesman and I are not Indian.
    I was born a white Canadian and have...
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    Closed: Re: Lets take a look on a linear amplifier

    The Texas Instruments TPA3220 class-D amplifier IC datasheet shows an output bandwidth of 100kHz and an internal class-D switching frequency of 480kHz. The circuit shows output filters to remove the...
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    Closed: Re: Lets take a look on a linear amplifier

    Most class-D audio amplifiers have an analog input. Some have a digital input. They convert the input signal to PWM inside the amplifier.
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    Closed: Re: Lets take a look on a linear amplifier

    When the signal current is at a peak then it is probably much higher current than a little DC offset current. At 55Hz then the peaks occur at 110Hz.
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    Closed: Re: Driving 140x 3W LEDs

    The datasheets for all ICs show their range of values. The "1.25V" reference of the LM317 is from 1.20V to 1.30V. Then a resistor that is exactly 2.0 ohms produces 600mA to 650mA. Plus a small change...
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    Closed: Re: Portable headphone amp w. batteries

    I noticed that the driver and output transistors are not included in the overall negative feedback loop therefore distortion is produced at high levels into low impedance headphones.
    At anywhere...
  13. Closed: Re: Runtime of clock using alkaline D cells instead of AA batteries

    Some name-brand alkaline D cells have a little C cell inside with the C cell capacity. Few D cells are sold today.
    Some Chinese alkaline D cells have anything that is cheap inside.
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    Closed: Re: Lets take a look on a linear amplifier

    You are using an audio amplifier circuit in another kind of circuit that has output transformers. But audio amplifier circuits have not used output transformers for at least 55 years.
    If the core of...
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    Closed: Re: Lets take a look on a linear amplifier

    Low frequency and high frequency phase shifts caused by a transformer will occur if the transformer is inside the negative feedback loop (when the output of the transformer provides the negative...
  16. Closed: Re: In-ear speaker transducers for hearing aids...

    In the ear hearing aids do not produce the high amount of sound pressure that over-the-ear hearing aids provide, and have problems with sweat moisture affecting the battery and electronics.
    Due to...
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    Closed: Re: Lets take a look on a linear amplifier

    An amplifier does not "sequentially fire gates". Instead it simply amplifies the input signal's voltage and current.

    A linear amplifier has a lot of heating but a class-D high frequency switching...
  18. Closed: Re: In-ear speaker transducers for hearing aids...

    In Google, I asked about "hearing aids speaker transducer" and got many pages of articles, images and history. Most transducers are "balanced armature".
    A hearing aid speaker transducer does not use...
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    Closed: Re: Lets take a look on a linear amplifier

    Your amplifiers are class-AB that waste a lot of power by making heat. The circuit in a class-D amplifier switches on and off at a high frequency with PWM then produce a low amount of heat.
    Class-D...
  20. Closed: Re: What is the conditions for complementary BJTs

    Many complementary transistors have the same range of spec's like 2N3904 and 2N3906, 2N4401 and 2N4403 and 2N3055 and MJ2955. They are not matched so then one might be much more sensitive than the...
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    Closed: Re: Driving 140x 3W LEDs

    I assume that 700mA is the maximum allowed current for your LEDs.
    Then what about the range of reference voltage of the LM317 (1.3V max) and the tolerance of the 1.8 ohm resistor (minus 5%= 1.71...
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    Closed: Re: Driving 140x 3W LEDs

    Without seeing the datasheet for the UV LEDs, I wonder if the 700mA is the absolute maximum allowed current if they have perfect cooling? How will you cool them? With a spray of Liquid Nitrogen? Then...
  23. Closed: Re: Testing LI Batteries with the help of a device

    Your link is in a foreign language.
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    Closed: Re: Astable Multivibrator not switching

    I posted my simulations on the other forum:
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    Closed: Re: Astable Multivibrator not switching

    1) R5 and R6 should be replaced with wires.
    2) R2 and R3 are calculated to cause the transistors to saturate, not to be a linear amplifier, then hFE is not used. Make R2 and R3 about 10 times the...
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