Matt,
The problem with running 0.47 is that it will raise the low frequency crossover point a substantial amount. I have not done he calls as to what the HP freq is with the 2.2 but given that the 2.2 sounds different to a 2.7 I would estimate the lower 3dB point may be in the 5hz-10hz region.
Changing it to 0.47 would lift this by a factor of approx 5.
Ie could lift it to somewhere in the 25-50 Hz region substantially impacting the low freq performance.
Craig
Ps let me know if you have NFI. What I am talking about and and I will elaborate further.
Ditto.
Just to add, in pro audio they generally allow 10 x factor for low frequency cut off point.
For example if a certain product is designed with intent to pass at least to say 20Hz, a LF corner point of 2Hz will be used.
The reason is a/ upward shift of LF point from multiple devices connectivity and b/ Phase shift errors.
For a/ If you have 3 devices connected all with a LF corner point of 20Hz, then resultant LF corner point will be more like 40Hz.
For b/ If the devices are single order LF cutoff design, ie; RC like Killer/ tube DAC then there is phase distortion. The cure is make the LF cut off point much lower
than required.
So getting back to the DAC 2.2uF cap, first question is what is the DAC driving? Typically a tube amp will have something like a 100k IP resistance. At 100k / 2.2uF
LF corner point is 0.7Hz. That is pretty good and easily allows for the 10:1 factor.
You could get away with 0.47uF if the IP resistance of amplifier is 470k or more. This would give the same 0.7Hz CF.
You could probably get away with 220k IP resistance, that would raise the CF up to 1.5 Hz, still very low, but I think
a listening test would be in order to see actually how much difference 470 versus 220 makes. You might be
surprised.
So yes you can use 0.47uF but the amp you are driving should have a suitably high IP resistance.
cheers
T