50V on 48V phantom power, yikes!No, there are 50V Elna NP but be careful with fast steps of DC over 15V. Slow transient DC or curre limited, is no problem up to 50V.
That is really pushing it.........
Consider to use Bridge "T" net attenuator?So, finally, I stopped on something like that:
View attachment 1244078
As you can see, the only "0db" mode requires some postprocess EQ in REW FFT. However, as I mentioned above, that mode needed for the DR test i.e. BW20-20k and A-weighted, hence +.69db at 20k isn't really an issue. 18db peak at 70k perhaps may create trouble with chip DACs like CS43198/131, and better to add one more switch to alternate the termination 10k/1k, or keep 30-50ohm as a min resistor instead of 10ohm(I'm greedy regarding the noise so I'd like 10ohm). The R/r resistor divider steps could be different but I like 10 + 1000;600;400, from a total 5pcs 200ohm MELFs(2.5W together).
(or Bridged "H" version for balanced line)
Only 2 R more but beter than L pad?
sorry, I'm not sure if I understand.Consider to use Bridge "T" net attenuator?
(or Bridged "H" version for balanced line)
Only 2 R more but beter than L pad?
That's correct, by phantom power standards, there are two 6k8 resistors in series with the positive and negative of the balanced signal.a mic typically works at 1/2 voltage of the phantom power. More than double headroom for the rated voltage, I think it is 100.00% safe.
Depending on the load of the circuit, the voltage will drop, like you already mentioned.
But it's about the situation when there is no load on the phantom power supply.
48V falls within the tolerances of a 50V capacitor.
So it could work for now, but I don't agree with you that it's 100% safe.
It's not great design practice.
b_force, yeah, I'm just chinese worker but did you read that: https://e1dashz.wixsite.com/index/cosmos-apu
Yes and it would be helpful to quote what you're referring to, but I think you are referring to this:
Question, what will happen when the cable or microphone all of a sudden has a connection issue or a fault for whatever reason?
Do not turn On that power without a mic connected, that may damage the device tied to the APU's preamp input! Please wait for at least 10s after the phantom
power is Off, to safely plug/unplug anything to the Preamp input.
Question, what will happen when the cable or microphone all of a sudden has a connection issue or a fault for whatever reason?
I am still a bit confused.
If it's 100% safe, why the above quoted procedure?
Also, what happens when the connection is all of a sudden broken?
I don't know what PSU is inside?
Looking at the input, probably a flyback (maybe with a coupled inductor).
These sometimes have a tendency to overshoot momentarily when there isn't any load.
I want to be sure my device will be working fine, if my other gear decides to fail for whatever reason?
Otherwise I am happy to replace the 50V cap with a 63Vdc one myself.
If it's 100% safe, why the above quoted procedure?
Also, what happens when the connection is all of a sudden broken?
I don't know what PSU is inside?
Looking at the input, probably a flyback (maybe with a coupled inductor).
These sometimes have a tendency to overshoot momentarily when there isn't any load.
I want to be sure my device will be working fine, if my other gear decides to fail for whatever reason?
Otherwise I am happy to replace the 50V cap with a 63Vdc one myself.
Cosmos APU has a lot lower noise than a condenser mic may require, for that reason, I have to keep a very low input ESR 10ohm. A charged 10u cap may be discharged through that 0603 10ohm into the protection zener, and 0603 resistor likely would be burned.
I have a better idea, in case I'll go for APU-II I gonna throw out 48V power at all. That feature was suggested to me in our discord or maybe forums, and I regret that implemented that. Nobody needs 48V power in Cosmos APU and no one uses it, as I know. The initial idea was using the switch to On/Off 20kHz LPF but I was stupid enough to replace that with the phantom power.
I actually like the 48V phantom power, I don't see why that would be such a big regret?
Makes it a lot more usable this way, otherwise people need a separate 48V phantom power injector.
I did a quick simulation and if you just put a 100k-150k resistor on the output, that will put at least some load on it all.
While bringing down the voltage about 5-10%.
Another idea is just to put a R-zener-R instead of the 6k8 series resistors.
With a 47V zener, the circuit is also always protected
Just curious, but are adequate 63Vdc capacitors so difficult to find?
Makes it a lot more usable this way, otherwise people need a separate 48V phantom power injector.
I did a quick simulation and if you just put a 100k-150k resistor on the output, that will put at least some load on it all.
While bringing down the voltage about 5-10%.
Another idea is just to put a R-zener-R instead of the 6k8 series resistors.
With a 47V zener, the circuit is also always protected
Just curious, but are adequate 63Vdc capacitors so difficult to find?
-87db@1kHz 0db, -99db@1kHz 26db, -83db@20kHz 26db, , -62db@20kHz 26dbIs there a guesstimate on the Scaler's CMRR ?
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