CAL Alpha DAC: Stock vs. 24/96 upgrade

I recently purchased a used stock (I believe 18-bit) CAL Alpha Tube DAC. I'm considering the 24/96 upgrade. Those of you who are familiar with the sound of both, please weigh in. Also, tubes that you like with either version, what sound do they produce? My DAC came with the Eico/Mullard brand 12AX7/ECC83. Thank you in advance.
How are you planning on getting the 24/96 upgrade? To my knowledge, that hasn't been offered since 2002-ish, since California Audio Labs has been out of business for several years.

As for the tubes, my favorites so far are the Sylvania 5751's. (It's a lower gain version of the 12AX7.) Not cheap, but definitely a big upgrade putting those tubes in.

Michael, I emailed Approved Audio Service in Litchfield, CT. They emailed back and said they can do it for $500.00 + shipping.
Routeman, I considered doing this myself as I had a Cal Alpha original DAC. The general feedback that I received on this same mod (about 15-18 months ago) was some liked it better modded and others didn't.

Overall though, the concensus was not to pay for the upgrade but instead to just buy the 24/96 version and see which you prefer. Sell the one you don't like more. The difference in value between these two DACs is only about $150 (then, 15-18 months ago), so based on this, it is more cost affective approach.

FWIW, I never got the 24/96. I eventually went with a Kora Hermes (which I loved). But that Cal Alpha is a great DAC, especially for the price! Be very careful when shipping that unit, you need to place a piece of foam on the transformer to support it. It has a tendency to crack at the connection point and then you have a couple hundred dollar repair.
Ckoffend, How about that! I never heard about supporting the transformer when shipping. Thank you for that info.

I have 2 "stock" Alphas and just last week purchased an upgraded Alpha on Audiogon. I did what CKOFFEND suggested above and bought an upgraded version to compare. After listening for a week I have to say that there is a difference but not a $500 difference. If you invest in good tubes you will get more bang for your buck (IMHO). I used the Mullard CV4004s that came with my new DAC in my original Alpha and was floored (approx. $180 at Upscale Audio). I use Telefunkens and Mazdas in my other 2 DACs and am very happy with the results. These DACs respond well to NOS tubes and I highly recommend tube rolling before dropping $500 + shipping. I am very happy with both versions and can't believe the bang for the buck they offer.
Buda, Thanks for the info. Are you saying the Mullard CV4004's sound great in your stock AND upgraded Alpha? When I purchased my Alpha it wasn't being used by the previous owner for quite some time so it didn't sound that good the first couple of days I used it. On the third day something happened: It smoothed out & just sounded wonderful. So for now the Eico/Mullard tubes are staying in it. That doesn't mean I won't tube roll.
The eico/mullards are tough to beat as long as they test strong. 5751's will definitely have a different personality.

You'll never get the $500 back out of it if you sell the unit. So, do you intend to keep it forever? Alpha are nice but I have never missed mine. A modded music hall or denon dvd will crush the alpha's sound.
Kevin, if you send in the alpha to the service company (Kevin there) will tell you to do this. Repairing these is a big part of his servicing of the Alphas.
Elevick, What personality do the 5751's have? I own a stock Denon 2930 DVD player. Have you heard one modded? Let me know. Thanks,
Ckoffend, I don't understand what you're saying. Please explain in more detail. Thank You!
I think the mullards have very smooth mids and really clean, crisp highs. Telefunkens seem to get a little better bass. In my experiences, 5751's rock a little better. They do not smooth over any sound. 5751's can handle more plate voltage which is why the can "crank" a little more. CJ pre-amps always came with 5751's and I hated it. They would cook mullards but I felt they sounded a little more "tubey" with mullards in them (I've had a PV-5, PV-9 & PV-10).
Yes, I tried the Mullards in both Alphas with very pleasing results. If I had 3 sets, all my Dacs would have them. The Telefunkens and Mazdas have more air in the highs but the Mullards vocals are crystal clear (most of my music is vocal and acoustic). I have not heard modified players compared to the Alpha but saying they "crush" the Alpha may be pushing it. The Alpha is very hard to beat for the money. Plus with the next wave of audio being music server based, a nice tube DAC will come in handy. My neighbor already uses his SigmaII with an AppleTV in a 2 channel set up with Dali Helicon 400s and a Prima Luna Dialoge integrated. WOW! Both audio and video are outstanding. Plus the simplicity of a music library at your finger tips. I am planning on that next leap with my systems (which is why I have 3 Alphas).
Buda, When I read your posts you sure do make a case for the Alpha. As stated before, I'm still getting used to it. It really does have some characteristics I like a lot. I also own a CAL Icon Mk.II Powerboss which I really like too. Of course, I'm finding it's a different animal than the Delta/Alpha combo. I will probably tube roll before I decide on the 24/96 upgrade. I don't want to spend too much on tubes but it would be a good idea to at least try some out. Thanks for your help.
I tried the Mullard's and didn't like it. Very syrupy, lacking in details. The Sylvania 5751's, though, provide a very clean, full, airy sound that was a revelation. I agree with the idea of playing with tubes before you throw down $500 for an upgrade that you will never be able to recover.
Kevin, When you take the cover off of the Alpha, there is the large metal piece/part inside. This is the transformer and is noticeably the most heavy part in the case. It is tall, comes about 1" short of where the top cover would be if the cover were back on. You should use a piece of styrofoam or even better a softer foam. This should be thicker than the space between the top of the transformer and the cover when it is put back on. This piece will then compress with the cover installed and hold the transformer in place to prevent its heavy wait from receiving shipping impact. Since the cover slides on it is fairly easy to do this.

What is known to happen without this is during shipping the box and components takes some real impacts when it is being tossed around and dropped. Due to the weight of the transformer these impacts cause cracks or total breaks to occur at the contacts or base of the piece.

If you ship the piece, you should always do this, but you also need to let the buyer know to remove it before playing. Many people don't know to do this and this is why so many of these units have been sold in good working condition, only to arrive not working at all - no power. I will check my office computer to see if I have a photo of this.
Kevin, I did some checking at my office to see if I took a picture of the support for the transformer - all packaing pics, but not of the unit opened with the support. I early stated it was Kevin with Approved Audio, it was really Larry. This is what he wrote to me when I sent mine in (and by the way, the unit will power up and even seemed to lock onto the signal - just no output):

". . . prior to shipping, i suggest removing the screws from the cabinet (4 on bottom, 3 on rear,
3 on top front) and sliding back the cabinet. you will see a large black thing in the front left corner-this is the power transformer.
take some cardboard or something similar and place some pieces on top of the transformer so that when you slide the cover back on, the cover will press against the transformer holding it in place. cal used a transformer which is not screwed to the chassis, it is held by the solder connections and some glue between the transformer and the circuit board. if the box gets dropped just right, the transformer can break loose. this is not a good thing. it doesn't happen often, but i've seen a couple. i always do this when i return ship them, and haven't run into a problem. it's cheap insurance. box it up, insure it for $1000 and send it in. it's a great sounding dac, i use one in my system."
Ckoffend, I understand completely what you're saying. I know what to do if I have to ship. I didn't understand your post from 2/20. It makes total sense now. I thought you were talking about something other than the proper packing for shipment. Thank you very much for the detailed explanation.
I'm not sure what direction I plan to take (keep or sell). There are so many posts from different listeners with different perspectives. One thing I learned; The Alpha is still a well appreciated piece of equipment to many in 2008. As mentioned to Buda, I will do some tube rolling before jumping into the $500.00 upgrade OR purchase of a used 24/96 Alpha. In the past I didn't have to think as much with SS units.
Thank you everyone for your posts.
Kevin Billig
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,
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.
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 $.
Noelpastor, Thanks for your input.
The following webpage contains a chart that will tell you what to expect from some popular 12AX7 varients ( 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). (
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.
I don't know what you're using for an interconnect. If it's not something outstanding- this will vastly improve your combo's musicality ( I owned an Icon II, and when I went to the Delta/Sigma- my son inherited the Icon. When I got the Alpha(and installed the Telefunkens), it was another audible magnitude of improvement(toward the sound of live).