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mboxler

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About mboxler

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  1. The manual for your Parasound A23+ seems to contradict itself. The balanced input section mentions the 6 dB increase, yet the specifications page implies a 0 dB increase. Total gain 29 dB Input sensitivity for 28.28 Vout Unbalanced 1 V Balanced 1 V per leg This implies that once the non-inverted and inverted legs are subtracted from each other, the resulting single-ended voltage is then cut in half. Confusing.
  2. Looks like they do, as long as the caps on the board stay at .015uf. http://www.xkitzconnect.com/files/Linkwitz-Riley-2Way-Calculator.htm
  3. Bumping this 13 year old thread. I'm testing an adjustable Type-A crossover. The attached schematic shows the basic circuit. The T2A will be replaced with a Bob Crites 3636. More importantly, the input wire to the autoformer will be terminated with a female quick connect, and can be connected to taps X, Y, or 5. The autoformer end of the wire to the 26uf cap will also be terminated with a female quick connect, and can be connected to taps 1, 2, 3, or 4. This will allow midrange attenuation of -1 to -12 in 1 db increments, without any change to the crossover frequency (419 hz using a 14.6 ohm resistor in place of the K-55). I built a prototype of the midrange portion of the crossover, and it appeared to work flawlessly. I also tested a 20 hz 6.75 volt signal across 0-5. The voltage across 0-4 measured 4.8 volts...pretty close to the 4.75 volts I expected. It's been said that this circuit will not work well due to the high voltage of lower frequencies. However, the current through the autoformer is identical to the stock Type-A circuit at all frequencies. Is autoformer saturation a product of high voltages, high current, both??? Thanks, Mike
  4. A while back I decided to buy ALK's Universal kit. It was my first soldering experience, and even though it looked awful, it worked. Like you, though, I had trouble understanding how it all worked. Forward many years, and I think I finally understand most of it, although I still have a lot to learn. @Deang bumped a thread on inductors. I think that's great, and I think many would like to understand how a passive device that opposes changing current would also act as a low pass AC filter. Likewise, perhaps a thread on capacitors would be helpful. It wasn't until recently that I understood how a capacitor works. Again, I think many would like to understand how a passive device that opposes changing voltage would act as a high pass AC filter. I found the fact that a capacitor blocks DC and allows AC to pass confusing, to the point that I thought they were invented for both purposes. Once I realized that this is not the case (the capacitor was invented long before AC was "invented"), my understanding of crossovers became much clearer. It seems that capacitors are only discussed in crossover upgrades, and then it seems to turn into a discussion on which brand of capacitor is best. I'm sure many don't care about the how's and why's of a capacitor, but perhaps there are many others who do. It might be interesting to discuss plates and dielectrics instead of brand A vs brand B. Then again, maybe not. Apologies to the OP. This was not meant to hijack your thread. Mike
  5. 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.
  6. 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.
  7. 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.
  8. 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.
  9. I assume you like the last track on the cd, Epilogue and Hymn. It is also one of my favorites.
  10. 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!
  11. 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.
  12. 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.
  13. Could you take a picture from further away so we can see the ends of the other cable?
  14. 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
  15. 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.
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