Audio Research CA50 + tube rolling


I recently purchased an ARC CA50 which I like a lot. It betters the Cary SLI-80 sig IMO but that's beside the point.
My question is about tube rolling. Has anyone tried rolling either power or driver tubes in the CA50 and what were the results ?

The only info on the net regarding this is somewhat paranoid thread on diyAudio advising against this and suggesting that ARC designed this amp around Sovtek/EH 6922s
Personally I don't buy it.

I contacted ARC and spoke to some bland dude who I don't think even knew what the CA50 was.
He blurted out something about adjusting the voltage on the side panels of the amp if I want to change the driver tubes.

Anyway, your thoughts, suggestions, advice and experience (good or bad) with tube rolling in this amp will be greatly appreciated.

Thanks in advance to all replies.
akanrg

Showing 6 responses by geraldm121

I have owned my CA50 for the last 3 or so years and I am very happy with the amp. I currently use it full range driving fairly high efficiency speakers and a pair of add-on ribbon tweeters and the sound is very neutral.
You perhaps should have checked here or any of the other audio boards before getting upset as it is fairly common knowledge the CA 50 is not a good candidate for tube rolling.
I tried both JJ 6922's, Amperex Orange Globe and Bugle Boy 6DJ8's and it ate all in short order. The JJ's (which are nice warm sounding tubes in most amps) actually shorted and damaged the Amp while the Amperex's merely became noisy. This gets expensive in short order. Audio Research and Audible Illusions really stress the 6DJ8/6922's in their products and the Sovetek, Electro Harmonix and some versions of the NOS 6h23 (the 6h23EB I believe but you should check)are all that will last long term in the amp. See Jim McShanes website for his take on the subject. The EH69222's that ended up replacing the original Soveteks are not bad with a smoother less strident sound. I have heard that 7308's may work and I have some Valvo's and Tunsgrams I may try when I get brave (and perhaps foolish).
On the other hand the CA50 seems to tolerate different output tubes with just the normal re-biasing. Currently I am using the Tungsol 6550 Re-Issues with good results.
Sorry, I did not mean to be so definitive :<}, I was more referring to the numerous discussions regarding Audible Illusions and Audio Research's problems with Various 6DJ8/6922 tubes when used in their equipment.I very much agree that when used within the restrictions imposed by it's power rating the CA50 truly gives you the Audio Research Sound.
Yes I still have it (and it is up and running) what questions can I answer for you.

Jerry
When you turn the CA50 off you do hear a brief moment of the program material just before final shutdown. It's almost as if the muting circuit powers down slightly before the amp. As to all the input the lights flashing I believe that they do. I know some of the LED's flash but I cannot remember if all do (I am actually on vacation at the moment and cannot check to be sure). I will confirm this when I get back home in about 10 days.

Regards, Jerry
Sorry for the long delay but on my CA50 only the mute switch led blinks on start up.
Yes,it's a mid-level Monster power conditioner(nothing to get too excited about)that was a gift from a friend.