CAL Alpha DAC: Stock vs. 24/96 upgrade

There are three CAL DACs in our house right now. A beloved Alpha (non-24/96)in the bedroom system; a Sigma II (non-24/96) in the TV room, doing great things hanging off a DVD player; and a 24/96 Sigma II that is in a cupboard gathering dust. The regular Sigma II sounds more musical to these ears, regardless of which system I A-B them in--fuller, warmer. I don't know if this experience is mirrored in the Alpha realm because I've never heard a 24/96 Alpha, but I can say that the Alpha is very tube sensitive (more so than the Sigma II) and you can get a lot out of it, as others have observed here, by putting in favorable tubes. Telefunken 12ax7s and Mullards CV2004's didn't do it for me--too flabby--and they had me wondering if I had made a mistake in buying the darned thing. Thankfully, I get experimenting. I agree that the Sylvania 5751 blackplates make this unit sing. Raytheon 5751 blackplates are really good in it too, and can be found for less $.

The following webpage contains a chart that will tell you what to expect from some popular 12AX7 varients (https://www.tubeworld.com/12ax7.htm). I don't like the Btitish coloration of the Mullard CV4004 personally. My favorite was the Telefunken ribbed plate(NOS) in the Alpha and Sigma. I owned both for a number of years to go with my Delta. I'd also suggest tube rolling and trying a cable like the the Kimber Orchid before the upgrade. If you do get an Orchid: be certain to get one of at least 1m. For some reason the shorter lengths don't get it(personal experience). (http://www.kimber.com/Products/DigitalCables/Orchid/Orchid.aspx)

Hello Kevin, Goto The Tube Store, The heading "Tube Type" on the main page, click "12AX7". Scroll down in alphabetical order till you get to
"M" There you will see this Tube under "Mullard 12AX7", it of course is not a "real" vintage Mullard, but the New Sensor Clone made in Russia.

Great Tube, I really like them in my Alpha, and as I said previously, won't break the bank, and will hopefully stop your search, and desire for futher money being spent on your Alpha. Mark

Approved Audio Service may be the only act left in town, as far as acquiring specific CAL Audio Parts, but may not be the last act for doing Mods-Upgrades.

Great Nothern Sound was one who regularly did substantial upgrades on Cal stuff. I've got a CAL Delta Transport fully modded by them, Blackgate Caps throughout, high speed Rectifiers, and Bybee Filtration.

I did business once with Approved Audio, for a pair of Drawer Belts for one of my Delta's, thinking it was bad, and needed replacing (It wasn't) $5 ea, and $10 to ship them in a little brown envelope. Postage was actually like .72 cents. God forbid what they'd charge to ship back an Alpha to sombody? I got an excuse from them, that it cost thier guy a lot of time to ship that envelope out to me. Mark

Mark, Thanks for getting back. Also, thanks for directing me to the right tube at The Tube Store. I will order a pair of the Mullards. The price is right for me. The cost for a pair is $41.85 incl. shipping. A lot of tubes suggested in the previous posts (Specifically Sylvania 5751 black plates) sound like the real deal but not the price. WHEW!! I found a couple pair of the Sylvania 5751's on ebay & elsewhere. They are hard to find in pairs.

As an aside, I'm curious about how current or previous owners of the CAL Alpha DAC feel about CAL solid state CD players, specifically the Icon II Powerboss. I own one. I've owned SS players pretty much exclusively since I've been buying digital. I'm fairly new to the tube DAC thing. Have you ever owned or currently own a CAL SS player, comparisons to the Delta/Alpha combo, etc. Tube & solid state lovers please weigh in.