RuudNL
Well-known member
Any thoughts about this?
http://truephantom.nl/
(Personally I am not really impressed by : "0.06 dB louder"...)
http://truephantom.nl/
(Personally I am not really impressed by : "0.06 dB louder"...)
My thoughts ? Another money-vampire who wants to suck your hard earned money with snows of yesteryear.RuudNL said:Any thoughts about this?
http://truephantom.nl/
.....
The values from the two resistors at the right are 680 Ohm, the other two are 470 Ohm, capacitor is 470pF styroflex. But this configuration doesn't deliver full 10mA (only about 3mA)...Gus said:
Gus said:Now P48 microphones have different current specs so I am wondering at what current the constant current supply is set.
What I mean if the phantom supply circuit is set to 5mA for each leg(10mA total) and the circuit needs 1mA(.5mA each leg) or 6mA(3mA) each leg.
Gus said:So is this a 48VDC series voltage regulated power supply with two summed sense connections with two collector out pass circuits for each phantom resistor circuit like in figure 3b?
In the presence of absolutely balanced symmetrical currents, it should. The common-mode impedance is 3.4K, but the differential mode impedance may be quite high. The claimed benefits are not really obvious in the posted examples; however, it may be interesting to compare with dynamic and ribbon mics, that are usually more sensitive to loading than condenser mics.moamps said:Most likely. And it doesn't work as it should, IMO.
There should be two logical servos, one for absolute value and second for the difference.abbey road d enfer said:In the presence of absolutely balanced symmetrical currents, it should.
The output of the voltage regulator presents very small impedance for AC signals so I doubt it. And this impedance isn't linear in the whole audio spectrum.....but the differential mode impedance may be quite high...
Why? A single servo is needed to make sure the nominal voltage ios 48V. Difference is managed by teh equality of absolute value of AC currents in the two branches. That is the case when the output is transformer balanced; for electronically balanced output, it depends on the actual balance of each side. In particular, some cheap designs that output signal on one leg only (using the other for DC only) may defeat the operation of said power supply.moamps said:There should be two logical servos, one for absolute value and second for the difference.
The common -mode impedance is indeed low (6.8k for each branch), but the differential impedance can be very high. When the sum of AC currents is null, the common-mode impedance is irrelevant.The output of the voltage regulator presents very small impedance for AC signals so I doubt it.
Certainly, but does it need to be optimum in the whole audio spectrum? It depends on the interference signal's spectrum.And this impedance isn't linear in the whole audio spectrum.
The second servo is needed to assure that the DC voltage between outputs is 0V. If it is not, that isn't phantom power. Period.abbey road d enfer said:Why? A single servo is needed to make sure the nominal voltage ios 48V. ..
Why would it be so? Equal DC voltage is not a requisite for good CMRR. Only equality of impedance is required.moamps said:The second servo is needed to assure that the DC voltage between outputs is 0V. If it is not, that isn't phantom power. Period.
It's your opinion and I don't share it. The principle is good; achieving claimed performance indeed depends on actual implementation.This is a lousy design,
Then you should think about it a little more... IMO it's a brilliant design principle with very little practical value.and I don't understand why are you defend it.
But it is very important for mikes with a output transformer. I would never connect this phantom power supply to a 414, U87 and similar.abbey road d enfer said:Why would it be so? Equal DC voltage is not a requisite for good CMRR...
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