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shp's picture
Last seen: 1 year 3 months ago
Joined: Nov 18 2007 - 4:57pm
Tube advice for a VAC 80/80

I bought my VAC 80/80 used in 1999.  I replaced the 4 KT88's in 2001/2002 with Ruby Tubes but never the 12AU7A.'s  The unit was in storage from 2003-2008 so the tubes aren't quite as old as they'd seem.  But I think it's time for new - better :)! - tubes.

I have a Sonic Frontiers SFL-1 pre-amp (just ordered a Siemens 12AT7 from Parts Connexion).  And Focal Profile 918's.

I've read good things about the EAT KT88's but the price is out of my budget.

I can just get the ones VAC is offering through their site.  But any other suggestions?





commsysman's picture
Last seen: 2 years 4 days ago
Joined: Apr 4 2006 - 11:33am

Be aware that the 12AT7, 12AU7, and 12AX7 are distinctly different tubes with different impedances and gains.

There are ignorant people who seem to think they can play around with interchanging them, and this is not smart at all.

You should NEVER replace one of these tubes with one of the others, because you are putting it into a circuit that is not designed for it and distortion will result in most cases.

As someone who designed circuits with these tubes for a number of years, I know what I am talking about.

They each have a very different transconductance and require very different plate currents to operate properly.

They are not interchangeable.

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