Output tubes for ARC Ref 110


I am getting ready to replace the tubes in my ARC Ref 110.
I will be buying set of KT120 as main output tubes but was wondering if I should also replace at the same time the 6H30 stage tubes ?
I have done just a bit of reading and see that many people run the 6H30 much longer than the main power tubes.

What's the recommendation here ?

thanks!
ether

Showing 4 responses by ether

Thanks !! 
Most people said the same thing as you but one person said to replace all 12 tubes in my amp.
HI Mechans

Do you mean I should get 6H30EB rather than 6H30 but that EB version would probably last half as long as standard 6H30 ?
One more question but regarding output tubes and bias.
My amp came with 6550 and the manual says to set the bias to about 65mA
Now that I have KT120 - do I still adjust to the same bias of 65mA or should it be adjusted to a different value ?
OK....so just finished replacing the tubes and re-adjusting the bias.
The instructions say to adjust bias at the V5 tube to 65mVDC and then measure V7 to make sure it falls between 55 and 75 mVDC and do the same for other pairs.....

What I noticed is that  the mVDC at the main tube in the pair is showing as positive number (always 65mVDC) but when I check the voltage at the slave tube - I get negative reading...( ex: -60mVDC)
I was able to adjust the tubes and everything is as it should except for that reverse voltage for every slave in the pair.... I made sure I am not reversing the probes....
The manual doesn't say anything so I am just surprised.....