Will upgrading Umbilical cord power supply to preamp improve sonics

Yes, umbilicals pass the Law of Efficacy; it is easy to hear how they impact/improve a power supply. Do not neglect working with the power cord feeding the power supply, as this, too, influences the result. 

I do not find that the umbilical has among the most powerful of influences of cables, but it is distinct, nevertheless. 

I tried WyWires and Clarity Cable umbilicals on the Plus Power Supply for the Exogal Comet DAC. Each has a distinct sound signature. The WyWires was leaner, and the Clarity Cable fuller/thicker. 

This is an old thread but if someone comes across this like I did, be very,very careful about dealing with Revelation Audio. They took my money over 40 days ago and I cannot get them to answer emails, return phone calls etc. This is not uncommon from what I have read. It seems that those who had some luck with Brad sing his praises but there are many more who paid Brad and never got their product shipped to them, or if it was shipped, it took eight months to a year. I was promised an umbilical by early March, it is now the second week in April, and I get no replies from them no matter how I try to make contact. I have finally had to file a dispute with my CC company. Buyer beware!

After several false starts and chargebacks with Brad I finally achieved success by purchasing through Ebay and got a good discount too.

Ebay will steer him in the right direction. 

My umbilical for my Musical Fidelity Titan and my Viola Sonata pre-amp have been nothing short of amazing.

A digital XLR however was decent but for the price ok.

What about Bryston preamps? (BP series)