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My JJ 6V6 and ECC83S's are here for the HRD and I'll be putting them in tomarrow. This is my first tube swap. Do I have to do the burning in of the tubes. I think I read somewhere to leave the amp on for 48 hours or keep a low music signal running through the amp during that 48 hours or something like that. I've pulled the power tubes out so I'm guessing the preamp tubes just pull out like the power tubes also?

From everyone I've asked, they said to bias it after getting the new tubes in. I called Bob at Eurotubes cause I was kinda confused when he said I wouldn't need to have it biased. He said I don't need to bias it since he is sending me a matched pair grade #30-#32 power tubes. So I'm guessing that means that the tubes I'm getting are made to run at where the HRD is set at from the factory. Though I've read it all depends on the tubes you get, one set may sound great at the stock bias point and another set of the exact same tubes may need an adjustment of the bias to sound their best, don't know if that's true or not but I read it somewhere. So what do you think? From what I've heard, Bob knows his stuff, so I wouldn't think he would give me bogus advice.

Here is that part of the email:
Your HRD is an adjustable bias amp but it has a narrow window of adjustment so for this application I would go with a matched pair of the JJ 6V6's that are a grade #30 to #32. These will work nicely to plug and play or you will have room to tweak the bias if you want to.

I'd take Bob's word on this, but most techs would tell you it doesn't hurt to check your bias ANY time you get new power tubes. It sounds like Bob's saying he gave you tubes that fall somewhere in the middle of the range on that amp

the one thing you haven't established is where your current tubes are biased.

the JJ 6V6s are very sturdy and do seem to bias at a different point than other tubes ... the same is true of their 6L6

if your concerned about the expense of biasing tools, or having a tech check it, we can give you some inexpensive solutions ... Gearjoneser also has a method of tuning it by ear

I'm not concerned about the expense to have it done or do it myself. I'd like to learn how to do it so I have the opertunity to experiment with different tubes and not have to pay someone to bias it everytime. I've seen the multimeter method but I really don't like the idea of working right next to those parts that will shock the hell out of you. And is there any like breakin period with the tubes or can I just plug them in and play? Thanks guys.