Rick -
Heater voltage can affect noise, lifetime, and characteristics; here's a
link (translated) that shows changes in characteristic curves with
heater voltage changes:
http://honyakuinfoseek.infoseek.co.j...onyakuinfoseek

Here's the origianl japanese
page:http://www2.famille.ne.jp/~teddy/datalib/heater.htm



Rick Ralston wrote:
What is the +/- % of deviation that can be applied to heaters on say 12ax7
tubes. I am rebuilding a small single ended 7695 amp and after I got the
heater supply wired the voltage on the 12ax7's is in the 13 volt range. Any
help would be greatly appreciated.