Why Use Standby

From mgarvi–(at)–anix.com Wed Oct 18 12:32:54 CDT 1995
From: mgarvi–(at)–anix.com (Mark Garvin)
Newsgroups: rec.audio.tubes
Subject: Another reason to use STANDBY switch
Date: 18 Oct 1995 12:33:07 -0400

I just posted this to a.g.amps but realized it may be relevant here
as well. Pardon the dual post.

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Cathode stripping occurs when current gets pulled thru the tube
before the tube is warmed up. Most techs know this.

But consider what else happens. Tubes that are not warmed up will
draw appreciably less current. This means that there will be very
little voltage drop across resistors in the power supply. And that
means that the full unloaded B+ voltage will be applied to the poor
low-rated electrolytics in your preamp section.

In other words, if the main B+ is 450v and your preamp supply is
320v, the preamp will usually have electro’s rated at 350v or so.
If the tubes aren’t warmed up when the standby is flipped, the
preamp will get a shot of 450v!

How about that for motivation?

Regards,
Mark Garvin