Is there advantage to upgrading the umbilical cable of my Pass Labs XP-32 preamp? Revelation Audio Labs makes an upgraded umbilical cable for the Pass preamps. I would have the cables custom made if it would make sense. Please advise.
Good question. I am wondering the same thing about the XP32 that I have.
I’ve done the RAL umbilical for my XP-22, but some random bits before getting to how it sounds. First, the stock Pass umbilical for the x2 series preamps is way better than the old DB-25 terminated umbilical used for the XP-20 and 30. Second, RAL is not the only company making a replacement for Pass preamps. Tubulus also offers one, which I haven’t tried but also read good things about.
My take on it is the RAL upgrade for the x0 series was more “unequivocally better” than with my XP-22. The RAL for the 22 is better than stock, but it’s also a little different. Not quite the slam dunk choice as with the older series, but that old x0 series stock cable really wasn’t very good, IMO. The RAL on my XP-22, compared to stock, is smoother, more refined, easier to separate the structure of each tone, more natural. But the stock umbilical does a slightly better job of portraying leading edge transients, especially in the low through mid frequency range. Now, these were my initial impressions with the original length umbilical that I purchased. It was ultimately too long for my configuration, since I have the power chassis on a rack shelf about 8” below the control chassis. The RAL was routed across all the ICs going into and out of the 22 just to deal with the extra length. When I spoke to Brad about this he felt a shorter length in my case might sound better. I calculated a .75M length would be about as short as I could get away with. He made one up for me and after giving it some time to burn in and then comparing it to the stock, I’m happy to say that for me I’m satisfied with the degree of across the board improvement with the RAL. I no longer feel the same sense of difference in the transients. I’m still curious about the Tubulus, but right now I’ve got other audio irons in the fire and I don’t really feel the need to futz with this any longer.
I’d say, from my experience, that if you want to try the RAL, get as short a length as you can get away with. I ate the cost on the first one I ordered, but how my system sounds now made it worth it. In case either of you need a 1M length 
, PM me. You’d need two, I guess, but this would get you halfway there. 
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If I were to go aftermarket for the two umbilical cables I would have them custom made. Would silver, silver plated copper or just good grade copper be best? I have a hunch that pure silver would be nice but expensive. The RAL cables are $1000 so it would cost $2000 for my XP-32. Any advice would be appreciated.
Based on my experience with my XP-22 and a RAL cable, which is available dirt cheap, do not waste your money.
If you wish to create some true happiness with that money, send it to me.
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Mitch, I honestly don’t know. Too much of it depends on what your system, as a system, is already doing. One material may sound best for one system, a different material for another. There’s plenty of anecdotal evidence about what the different conductor materials “sound like” in power cords, so one could use that as a rough guide. Although ultimately I’d think the only way to know for sure is to try it in your own system.
And Ron popped in ahead of me, kind of proving my point. Thanks Ron. 
I guess the RAL didn’t do anything to make it a choice for him. In my case it did. 
Having said that, my other posts over the years will tell folks I’m very tempered in my comparisons. None of this stuff is life changing. This was one of those “hey, it’s better” blips on the audio improvement radar. The cost for me wasn’t much of a factor.
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And as a reminder, no signal passes thru those cables, only power.
Agreed, although we know power cables in other instances have been known to make a difference, to some.
Power cables definitely have huge sound characteristics. My pure silver custom dc Neotech umbilical cable between my Keces LPS and Directstream dac mk1 makes a dramatic difference compared to the copper cable I had made for my dac and power supply.
And a good power cable into the XP-22 power chassis will make a nice improvement over the stock courtesy cable.
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Just like to point out that “pure” silver doesn’t mean 100% silver and you have to watch for 99.99, 99.999, 99.9999 etc. The more 9 after the decimal the better and cost a lot more.