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Old 5th November 2012, 08:45 PM   #31
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The attached file: CompoundAmp A7.pdf shows another schematic/diagram of a Compound Power Amplifier [CPA] whereby its VSA and TCA are electrically isolated. In this application the VSA [one channel of THRESHOLD S/150] drives one voice coil of a woofer/subwoofer, and a diy TCA drives the second and independent voice coil of the same woofer/subwoofer. The amplifiers drive the voice coils in phase. This experiment is in progress. I'll report results for these 2 unique cases:
  • A free hanging 10" dual voice coil woofer driver.
  • An enclosed 10" dual voice coil woofer in a commercial box designed for subwoofer duty. The voice coils are preceeded by a crossover network.
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Old 5th November 2012, 11:08 PM   #32
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Quote:
Originally Posted by Antoinel View Post
The attached file: CompoundAmp A7.pdf shows another schematic/diagram of a Compound Power Amplifier [CPA] whereby its VSA and TCA are electrically isolated. In this application the VSA [one channel of THRESHOLD S/150] drives one voice coil of a woofer/subwoofer, and a diy TCA drives the second and independent voice coil of the same woofer/subwoofer. The amplifiers drive the voice coils in phase. This experiment is in progress. I'll report results for these 2 unique cases:
  • A free hanging 10" dual voice coil woofer driver.
  • An enclosed 10" dual voice coil woofer in a commercial box designed for subwoofer duty. The voice coils are preceeded by a crossover network.
I may add that one coil of the two maybe a stationary field coil instead of a moving voice coil like in the new Lowther [BAF 2012] or Supravox drivers.
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Old 25th November 2012, 07:59 PM   #33
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Default A Mini Compound Power Amp Using the LM386 Chip

The above posts taught using powerful amps [e.g Threshold S/150] to implement compounding. The attached schematic shows a Mini Compound Power Amplifier [MCPA] which uses two LM386 IC chip amps as a starting model for this application.
  • The upper LM386 is wired as recommended by its maker. Its output port must have a Zobel for stability. It simultaneously functions as the output port of the MCPA and the [+Vs] port for the lower LM386.
  • The lower LM386 is thereafter connected as recommended by its maker. Curiously, its output port [pin 5] must be connected via a capacitor [0.1 uF film to 1000 uf electrolytic] to + 12 VDC so as to make the net MCPA work right.
  • Note the phasing on the secondaries of the transformer driving the inputs of both LM386 chips.
  • Vo/Vi = 15 or ~24 dB at 1 KHz. A 1.5 Vp-p energized an ADS L730 loudspeaker of 6 Ohm impedance for this voltage gain test.
  • Sound of music was fully satisfactory within the milliwatts capability of MCPA.
The NPN output transistor of the upper LM386 works as a voltage source amp [common collector]. The NPN output transistor of the lower LM386 works as a current source amp [common emitter]. Its output emanates from its collector node which is at its +Vs pin. This is the same topology like that in the Classic parent of Mr. Pass's F6; but with localized loop feedback in the output stage of the chips.
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Old 26th November 2012, 06:47 PM   #34
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I have an error in the lower LM386 diagram of the above schematic. The top lead of its transformer's secondary winding goes to the [+] or non inverting input at pin 3. The grounded bottom lead of the winding goes to the [-] or inverting input at pin 2.

Note that LM380 has a similar circuit topology like LM386; but with a higher output capability. It is highly likely to operate well in my schematic of the previous post. LM380 requires additional heat sinks to work properly.
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