Hi
@cykin ,
20V I may have mentioned as the maximum voltage range the analogue stage can supply, which is correct, but this is not the 0dBu RMS output level.
Output levels can be specified in multiple ways, let me try to explain the differences by an example:
View attachment 148966
This photo shows a measurement of a 1KHz @ 0dBu output (maximum level) from a DAC analogue output..
The Peak-to-Peak Voltage (Vpp), the total voltage swing from the maximum positive peak to the maximum negative peak, is 8.46V.
The maximum positive peak amplitude is 4.24V.
The maximum negative peak amplitude is -4.22V.
There is a DC offset of 0.012V causing a difference in the positive and negative peak amplitude.
The RMS Voltage (Root Mean Square) is 2.99V (which you can also calculate by dividing Vpp by 2sqrt2).
What is RMS voltage: A type of "average" voltage that represents the equivalent DC power delivered by an AC signal.
The 2.8V RMS output voltage I specified for the current XDMI analog, is 7.92 Vpp.
Some Context:
Type Voltage (RMS) Reference
Consumer Line Level ~0.316 V -10 dBV
Professional Line Level ~1.23 V +4 dBu
Headphone Output (varies) 0.3–2 V Depends on device & load
The -10 dBV standard (common in home audio gear) means that 0.316 V RMS is the nominal output.
So as you can see typical audiophile equipment utilises significant higher output voltages than consumer level, or even studio equipment, and even the 2.8V RMS output of the XDMI DAC is already a very high output level which will typically need to be attenuated by a preamplifier for most power amplifiers, though some audiophile recordings can be at such low levels, and some power amplifiers have very low input sensitivity, so you could still end up in a situation where you'd need an active pre-amplifier to actually further amplify this already very high level....
And yes balanced can give you double the voltage swing but that does completely depend on the design