The Secret Society of Lathe Trolls

xjfx · Joined: 09 Mar 2008 Posts: 5

hi

is there someone who knows about an equivalent of the tube 45 triode for presto k 8 amp ?
the 45 is pretty expensive..
thanx
jf

studiorp · Joined: 01 Nov 2007 Posts: 48

You can try to mount on your Presto amp the 2A3 tubes.
This tubes works to 2.5 V voltage as 85.

Perisphere · Posted: Fri Jun 27, 2008 2:02 pm Post subject:

NOTE--Changing from 45s to 2A3s is NOT plug-and-play even though the pin-outs of the two types are the same.

The filament in a 45 pulls 1.5 amps, the 2A3 2.5 amps. Hence the current draw in a push-pull amp will jump up by 2 amps just changing from one pair of 45s to a pair of 2A3s.

Also, the transconductance of the 2A3 is much greater than that of the 45 so there will also be issues with grid and plate current that will need to be sorted, even if the power transformer can tolerate the increased load on the filament winding.