[tonyptony]

Hi Frank. Curious - in the DVA 850 is it still necessary to partially disassemble the unit to perform tube biasing?

[avahifi]

Actually you don't need to rebias the amp when changing tubes as long as you stay with main stream 12AT7/ECC81 tubes.  The regulated power supplies on recent products (last 5 years or so) take care of that for you.

On older units, the layout makes getting to the bias adjustment pots pretty tricky unless the back panel is tipped back, but still not a major disassembly project.

Frank

[tonyptony]

Actually you don't need to rebias the amp when changing tubes as long as you stay with main stream 12AT7/ECC81 tubes.  The regulated power supplies on recent products (last 5 years or so) take care of that for you.

On older units, the layout makes getting to the bias adjustment pots pretty tricky unless the back panel is tipped back, but still not a major disassembly project.

Frank

Thanks Frank, but I'm not sure I quite understand what main stream means. I have a lot of NOS AT7 types - TFK ECC801S, Valvo 6201 Blue labels, Sylvania Gold Brand 6201, Siemens ECC81, others... even Brimar 13D9. I'm not sure if any of these fall into the meaning of main stream.

[avahifi]

As long as heat sinks are not getting hot at idle after a tube change you are OK.

Frank

[tonyptony]

Does my 600R fall into this category of power supplies and recent products?

[avahifi]

Yes, but we don’t hear any significant advantage to expensive NOS tubes here.

Frank

[tonyptony]

Yes, but we don’t hear any significant advantage to expensive NOS tubes here.

Frank

Really? I (and a couple - not all - of my fellow audio buddies) can differentiate a TFK from a Mullard from a stock JJ in my system, even if I know which ones are in there and they don't. All tubes I own are checked on my B&K 707 tester. Maybe it depends on what significant means - the differences may not be significant but they are identifiable.

Is your experience the same for the DVA 850?