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mboxler

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About mboxler

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  1. This is pretty good. https://en.wikipedia.org/wiki/Bridged_and_paralleled_amplifiers It was hard for me to understand the concept that each of the bridged amps "sees" one half of the speaker's impedance, until I worked backwards from a mono amp. 1) A single-ended mono amp with a +-50 volt power supply delivers the same power to an 8 ohm load as two bridged amps with a +-25 volt power supply. 156 watts. 2) If the two bridged amps combine to deliver 156 watts, then each amp must deliver half the power, or 78 watts. 3) Each amp is applying 17.7 volts rms and 78 watts to it's side of the 8 ohm driver. 4) Ohms = Volts squared / Watts. 17.7 squared / 78. 313.3 / 78. 4 ohms. Not sure if that's the correct explanation, but it worked for me.
  2. Sorry, but can't seem to let this go. The 100 volt comparison is misleading. It's true than bridging two amps with a +- 25 volt power supply can deliver the same voltage across a load as one single-ended amplifier with a +- 50 power supply, but it's not the same circuit. Again, each of the bridged amps (+- 25) can apply a 17.7 volt rms signal to it's side of the load, with the second amp's signal inverted. The single-ended amplifier (+-50) can apply a 35.4 volt rms signal to one side of the load and will apply zero volts to the other side. Notice I said "can" apply. The D75 has a voltage gain of around 20, so a .5 volt rms input signal will be amplified to 10 volt rms to drive one side of the load. 10 volts rms equals +- 14.414 volts. Since the power supply can deliver up to +- 25 volts, your good. The extra volts are not wasted or lost, they are just not used. A 1 volt rms input signal, of course, will be amplified to +- 28.29 volts, and clip. Likewise, just because an amp can apply a certain voltage doesn't mean it supply the current. That's why the D75's 4 ohm rating isn't twice the 8 ohm rating.
  3. Your Crown D75 is a perfect example of current limiting. It's 40 watts into an 8 ohm load, but 55 watts into a 4 ohm load. This tells me that it's limited to 3.7 amps per channel, not the necessary 4.5 amps required for 80 watts. Your loaded +- 25 volt supply equates to 35.35 rms volts bridged, more that the 30 volts required for 110 watts into an 8 ohm load. If the doubling of the voltage when bridged concept is still confusing, consider this. When driving a speaker single-ended, when the + side of the speaker has +25 volts, the - side has 0 volts, a 25 volt potential difference. When bridged, the + side of the speaker has +25 volts, the - side has -25 volts, a 50 volt potential difference.
  4. How many watts can the amps put into a 4 ohm load when run single-ended? I wonder if there's a current limiting issue.
  5. I assume you like the last track on the cd, Epilogue and Hymn. It is also one of my favorites.
  6. As with all transformers, watts in equals watts out, so let's use Ohm's Law. As an example, let's use a T2A autoformer, and apply 2.83 volts to taps 0-5. Taps 0-4 will connect to a 14 ohm K-55 driver at 2.00 volts (-3db). 2 volts into a 14 ohm load equals .2857 watts (watts = volts squared/resistance, or 4/14). Since there's .2857 watts output, there's got to be .2857 watts input. 2.83 volts at .2857 watts equals 28 ohms (ohms = volts squared / watts, or 8 / .2857). As you can see, taps 0-5 appear to be a 28 ohms load. Hope that helps!
  7. The turns ratio squared of the 3507 is around 6.4, so the series load on the 3uf cap will always be 6.4 times the impedance of the driver in parallel with the inductor. If the cap were on the other side, it would need to be 6.4 times larger to get the same results.
  8. Talk about cool! https://positive-feedback.com/reviews/hardware-reviews/agd-production-vivace-gantube-monoblock-amplifiers/ Didn't know GaN transistor based amps were available. Pricy.
  9. Could you take a picture from further away so we can see the ends of the other cable?
  10. Did you ever try to connect the transformer outputs to the audio interface board, bypassing the input op amps? I sold my EVM before trying this out. Mike
  11. Without knowing the crossover schematic, let's assume a 1 mh inductor in series with a 4 ohm load. At 637 hz (the -3db point), the impedance would be 5.66 ohms. 8.95 at 1274 hz. All I'm saying is that I wouldn't classify this as a 4 ohm load on the transformer.
  12. On top of that, splitting the crossover does not create separate 4 ohm and an 8 ohm circuits, if I understand what is being implied.
  13. I assume the 20 volt preamp output would be for a current amplifier instead of a voltage amplifier.
  14. The miniDSP 2 X 4 input max is .9 volts or 2 volts, depending on a jumper setting. The output voltage, however, is set at .9 volts. If the input setting is 2 volts, the output has a 7 db insertion loss. Mike
  15. Interesting! Someday I'll re-install my ALK Universals into my K-horns and experiment. I have a pair of 1.0 mh inductors that I can put in series with the 1.3 mh in the crossover. I assume the yellow graph is the woofer, with the woofer current lagging the mid driver current by 90 degrees? Thanks for the info! Mike
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