Here's some useful information for all owners of the Hiface (stock or modified) & maybe the upcoming Evo?
Use an RF attenuator on the SPDIF cable to reduce jitter!! These are only $12 & best bang for the buck you can get, I believe.
RF Attenuators have been know about & used for many years. A recent discussion about their use on the SPDIF output of the hiface is to be found here:
http://www.diyhifi.org/forums/viewtopic.php?p=43397#p43397While there look in on this thread which also discusses them ( I'm the schmuck & troll referred to)
http://www.diyhifi.org/forums/viewtopic.php?f=19&t=2062&p=43639&e=43639 These particular attenuators are in-line adaptors that can be connected at the start or end (or both?) of your digital cable. The idea behind using these attenuators on a digital cable is to reduce in strength the inevitable signal reflections that travel up & down the cable. These reflections are one of the many sources of added jitter in every digital system. Reducing the strength of these reflections should result in a reduction in the jitter generated by the transport to DAC connection. There are many situations where this should result in better sound, for instance, it may be a good way of reducing the sonic penalty usually incurred in using a BNC to RCA adaptor. So this could mean that by using these attenuators an RCA input on your DAC should now be about the same sonically as a BNC input.
These are premises based on how the attenuators work - real world results may be different although I have tested a BNC to RCA adaptor with & without one of these attenuators & the sound was noticeably smoother & without edge with the attenuator in-line.
Here is the cheapest place I have found on the internet for these attenuators at $12 each - there are other places that will charge you >$30 for eactly the same thing - I've even seen them for >€100 in RS which I thought must be a mistake! I believe this is cheap enough to allow experimenting with the range of values available.
http://www.minicircuits.com/products/attenuators_coax_fixed.html Scroll down to the bottom of the page - it's the BNC 75ohm variety that you want. They come in 3, 6, 10, 15, 20dB versions - the 3 & 20dB ones could probably be ruled out as too low & maybe too high an attenuation. What we want to aim for is enough attenuation to suppress signal reflections BUT not too much to reduce the signal voltage to too low. You will know if you have done this as the DAC will not lock to the SPDIF signal.
Why buy expensive digital cables when using the high output Hiface & similar transports - these simple & cheap devices can be used to achieve a better solution. It's better solution because of the fact that a good digital cable if well made (expensive!) will have controlled impedance from end to end & will be a close match to the desired 75ohm. Outside of the cable at the DAC end or the transport end the cable cannot ameliorate any impedance anomalies that are encountered by the digital signal so these will give rise to reflections travelling down the cable. The attenuators, knock down these reflections to insignificant levels making them no longer important !
