Absolute top tier DAC for standard res Redbook CD

Hey Al,
Try some 5751's in place of the 12AX7. GE or RCA any type. My favorite is the 50's version of the GE, which is a triple mica black plate with D getter. This early version can be identified by mica retainer clips above and below the inner 2 mica's. This one is very close to the 10M, if a 5751 works out in your circuit. I'd stay away from the Sylvania's. They are typically forward sounding.

12AU7? Since you have no extra heater current to spare, and you can't use a 12BH7A, I can't think of any that will give you what you want. 7318 is it. Sorry :(

I understand you are worried about reliability and not being able to find more of these rare tubes, but I still recommend the Mullard 10M 12AX7 and CBS 7318 for what you are trying to accomplish. You want what I want, and what most other people want out of their system. Chances are, your CD player is putting the tubes in a pretty light duty situation. They will likely last 30 years or more if you get truly NOS of these. That's how tough these suckers are. Yes, rare and pricey, but will last and be head and shoulders above all others of this type sonically. Spend the money. Don't sweat the petty things, and don't pet the sweaty things :)

Matt - the Overdrive SX will not support DSD. DSD will likely be supported in a new less-expensive DAC I have planned. It will probably not have XLR outs or volume control, but the plan is that it will be DC-coupled.

Steve N.
Empirical Audio

Hi Paul79, you do have a very valid point, and I may just get these tubes any way, If you do not mind me asking, How is it that you know so much about tubes?, maybe you should disclose what audio company you have and what you sale, none of us mind, I have looked a couple of places for the mullard 10m and the CBS 7318 with no success, the couple of places is well regarded as having the real mccoy tubes that most people are looking for, and they have extensive testing equipment, an example of such tube dealers is Andy Bowman of vintage tube services, and another is Jim cross of vacuumtubes inc., and Jim Mcshane, just to name a couple out there, I admitt though, I have not talked to Andy Bowman yet, could not get him on the phone, LOL!, so I do not know what he has or can get, paul, you seem like a good guy, but from what I have been told about the tube market, you can never be to carefull!, who knows, we may still do business on some tubes you sale, you have been very good to me here shareing your knowledge of tubes, that my friend does go a long way with me, cheers.

audioengr, Hi steve, do not laugh!, when you said a player you are going to make is DC-coupled, does that translate to a tube digital player?, thanks steve.

Why NOS Tubes are better:

6moons industry features: A visit to BTB Elektronik

Okay, but you inventory much which would seem of interest to the high-end valve lover. So what’s up with the NOS trend? I mean, really, isn’t it mostly retro? Telefunken simply looks cooler than Sovtek stamped on the glass? Or are there bona fide advantages of quality and sound? Are we really to believe that valve quality and production processes have devolved over time?

The explanation is simple. In the 60s when valves enjoyed their halcyon days, the average German income was about 500 Deutsch Marks and an EL34 of the era sold for 15DM. If you transfer that relationship to 2012, an EL34 still sells for about €15 whilst the average income has come up to €3.000/month. It’s easy to see that tubes today are far more affordable. Hence the inverse is true too – price pressures on manufacturers are much higher today. Because valve production remains about 90% manual, you can’t compensate with automatization. In the past selection was much tighter and rejection ratios were far more generous. Today things make it to market which would have been trashed then. That’s why the quality of vintage valves tends to be quite high to make NOS much more than just a fascination with retro.