Audio Research I/50

@runwell - I too owned the VT-100 III. Also the Mk-I and a Classic 60 (the good old days!). I never used them with a preamp that matched their quality, however so never heard them at their best. If you are worried about tube failure, just replace the 6550s after two years. You can send the old set to someone who does testing (like Upscale Audio in L.A. California) and keep the good ones for spares. The 6H30s last a lot longer than 6550 (ask ARC about lifespan). BTW, I had a power tube go out on my ARC Classic 60 and didn’t even notice it (I listen at conservative levels and use a subwoofer). Discovered when I traded in for the VT-100 Mk I.

@dweller Good Point. 

It is really trick things to handle how the power tube is dead or not. 

The most difficult things is the handover amplifier from the prior owner, as I even do not know how long they used it. I want to replace 6550 set this time, as the sound is way beautiful as some one tell me the status pro of the tube will be best just before they die.

For 6h30 tube, Audio research official one is not good for the  sound,I will change it to EH 6h30PI GOLD even the machine is new like my REF 75se.

By the way,I had Classic 120 many years ago, beautiful  sound, just have maintain problem as I was in China that time, so I have to sell to a Engineer who can handle it  by himself.

I was thinking of buying one as well but then I read that it needs to be biased by a trained technician. That really has made me consider not buying it. It makes no sense that a product in this price range, made by a manufacture with such a long history of making tube amps, would offer their latest product like this. Audio Research needs to clarify this. There are some points/questions I'd like to bring up.

1) Why can't Audio Research offer either automatic bias or user adjustable manual bias? Prima Luna offers automatic bias. Rogue and most other companies at least offer user adjustable manual bias. Trim pots next to each tube. Companies like Rogue even include a multimeter readout dial on the amp. Very easy. Four words: User Adjustable Trim Pots. Why not AR? 

2) I've owned tube amplifiers before with manual user bias. I usually checked the bias at least once every 3 months. I can tell you they were always a little off and I always had to readjust the bias to get it back to the optimal bias level. Not all tubes are equal. Some fade out over time quicker and some can even stop working. For AR to basically say the bias is fine for 2000 hours or about 2 years is odd to say the least. Is Audio Research certain the tubes won't drift out of bias within 2000 hours or about 2 years? 

3) Where to send it in to get the new tubes biased? Does AR do it or do we need to find our own "qualified technician"? Some of us may live far away from one and need to box it up and ship it off to one. Very inconvenient. Not to mention the extra cost for the user and possible shipping damage each time. What if a tube goes bad early? More hassle.

As I write this I am more convinced than before that I'm not buying one. It's a shame because I'm sure it sounds great, it does look awesome and it's made in the USA. Perhaps the biasing issue won't matter to some of you. Especially if you have an AR dealer close by with a technician. However, for others I think it will be an issue. 

i also will not buy an amp that  can't control the bias , auto or manually, but i think that this subject still need to be checked.
i don't think you'll have to send it for biasing.
think that the meant is when you replace the tubes, let say after 2000 hours of playin, which to my opinion it's not much, it can be to me after 1.5 year, you can bias it using a technician at your place.
but, yes, if it like that ,it's disappointing. 
 

@mezzanine +1

We must have the ablity to bias by ourself or auto bias,it is bottom line.

Otherwise,the Tube drift,especially for the new tube. How we can ask the technician mutli times for the same issue? 

I am asking this point to Audio research and hopely they will reply me soon.