CAL Alpha DAC: Stock vs. 24/96 upgrade

I currently run an Alpha (non 24/96), and have a Sigma II as well, both run with CAL Delta Transports.

I'll second what I've found with using Mullard CV-4004, as I tried a good pair of Platinum graded Upscale Audio Tubes, that were donated to me to try, by a very kind agoner here, "zinfan", and it was just too lackluster, dull, and killed detail.

Jan/Phillps 5751 Tubes that came in this DAC ( I bought it used) were the exact opposite, like fingernails on a Chaulkboard.

I contacted Kevin Deal, decided to try 3 pairs, NOS '50's RCA Triple Mica Blackplates, the GT Mullard 12AX7M re-issue, and a pair of JAN/GE 5751. All sounded very good, with the RCA's coming out the clear winner. All were platinum graded. The GT Mullard was close second behind the RCA. Lastly, the JAN/GE 5751, but not at all bad either, being a wee bit more forward in the mids.

I did not long ago, buy 3 pair of New Sensor/Sovtek Mullard Long Plate re-issues from The Tube Store, and while these Tubes initially seemed to sound a little darker than both the RCA, and GT Mullard, these New Sensor Mullard re-issues seemed to really come around with a little run time, and I've found provide very nice sound indeed!

I am currently running these now for the last few months, and they give good sound top to bottom, good even detail without being over-analytical very nice bass weight, and tone to the sound, and so far, appear to be holding up, no problems. This I feel is a great Tube to try, without breaking the Bank.

Another great "cheap" Tube that also might be worth considering, that will have a different sound than the New Sensor Re-Issue "Mullard", but may work very well in a particular system, would be the Sovtek 12AX7LPS.

I've tried to read every available post out there about the Alpha, and there's two camps in which some like the 24/96 upgrade, and others that didn't. You may get more favorable results by Tube Rolling.

Re-Capping, and changeout of other parts to superior components, would/can be another option, but again, won't be exactly a cheap option.

As for the vintage NOS 5751 Tubes in the Alpha. Although I've never tried them, I'd probably concur, that the Sylvania Triple Mica Blackplate (with D-Getter I believe) would probably be the ultimate "holy grail" choice, and if one can find a good pair cheap, then god bless you, but I had to shy away when I seen the asking prices. Just can't see shelling out $140+ ea for a tube, that not many years ago you probably could've gotten for $12-$20 each.

I've also heard from one strong personal proponent of the Sylvania TM Blackplate 5751, that although a fantastic sounding Tube, they are not a long lasting Tube.

Hope this helps, Mark

Mark, Thank you for your input. You gave me a lot to think about. I'm new at this tube thing. In a nutshell, this is what I want to do: My Alpha came with the Eico/Mullard tubes. They sound warm, rich & smooth. They lack in the detail I'm looking for. I'm looking to buy a nice pair that has higher resolution & clearer detail. The Sylvania 5751 (from previous posts) sounds like a tube I might want. However, your mention of the New Sensor/Sovtek Mullard Long Plate peaked my interest. Are they improved detail & resolution tubes? I looked for them at the tube store but couldn't find them listed. Is it a Sovtek/Mullard (together) brand or separate Sovtek & Mullard brands? Please weigh in if you would. Thank You,
Kevin

I have an integrated CDP from norh which is a clone of the CAL Delta - Alpha (w/ upgrade) in one box. It used to be made (already discontinued) by the same Thai manufacturer that CAL used to outsource the Delta-Alpha.

I've had this player since Y2000 and have done mods on it (replaced the cheap opamps) plus tube rolled. I tried these tubes - Telefunken 12AX7 (both ribbed and smooth plate), Svetlana 12ax7 (supposed to be very similar to the Mullard CV4004), GE 1960s 5751 3Mica Black Plates, Sylvania 1950s Gold Brand 5751 Grey Plates, Sylvania 1950s Gold Brand 5751 Black Plates. The Black Plates Sylvania gave the best balance and most textured presentation. Mids are just to die for. 2nd place is the GE 3mica black plate, which I believe is cheaper and easier to source. All the 12aX7s I tried are way below these two in performance.

Either the Sylvania or GE tube brings this player up a level in performance. If you wish to go another level or two replace the opamps with decent ones. I've done these many years ago and recall using OPA627s and OPA2111. My tech told me the original opamps were really el cheapo crappy variety.

Noelpastor, Thanks for your input.
Kevin

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 $.