Audio Research I/50

Check the manual and get to the installation page.

It said you need get assistance from the dealer or technical guy to get tube bias.

So it is definitely not auto bias.

Besides, they said tube 6550we has about 2000hours. 

And I think it is pretty shorter than normal. But I do not know why.

@dweller  You said 6550 in your amplifier last about 2 years,it is matter how long time you run the amplifier and how hard the sound make,right?

If some one maintain in low sound level,the lifespan could be much longer.

@dweller  your calculation is right.  

I have  vt100 mkiii and the tube is from period owner, 

Recently I changed all 6550 tube and 6h30 tube, but the old one is not dead. I am wondering how we can found the tubes are almost end and got swapped out?

If I do not prepare in advance,does that damage the amplifier?

@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.

@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.

@mezzanine 

       I have a question for you. If the power tube 6550 bias is very stable. Is that to say, the tube is ok for use and not even near the end of lifespan?

I get the reply from Audio Research regarding I/50,

"Dear James

Summary: The I50 is not auto bias. The tubes should rarely need to be biased on this product but if it needs to be checked, the unit needs to be disconnected, turned upside down ,and the bottom cover removed, then there will be points to connect a voltage meter and read the settings. There is a small pot to turn with a plastic screwdriver that will adjust the bias. We are working on written instructions for this as well as a short video. Those will be available in the near future."

With my vt100 MK iii, we adjust the bias while the amplifier is connected.

Why for I/50,it need disconnected and do adjustment? I do not know.

Don't worry. They are on listening and I guess they will get the SE version pretty soon.

600 hours is talking about the amplifier break in and it is the one time event.

I am sure there IS tube break in, but it is not 600 hours.