Something to consider with Rectifier amps

Anonymous · Jul 4, 2012

I read this post by Scott Lerner on TGP talking about screen grid resistors on his Fuchs amps:

The usual values are 470ohm for 6L6 tubes and 1K for EL34 tubes.

IF you have 1K on a set of 6l6 tubes, reducing to 470ohm will run the tubes a little hotter assuming that you do not readjust the bias.

This is moot really.... You should rebias it while it is open.

I personally much prefer 470ohm on 6L6 tubes. For me, I notice more mud and lack of articulation in the bass notes when using 1K.

Some guys use 560ohm or 680ohm on the 6L6 tubes to increase longevity... I would not bother changing a 560ohm. It is pretty close already.

For the record, I can always feel and hear the difference from 1K down to 470ohm. So, anyone who claims there is no difference is smoking this>. :bong

The Rectifiers are set up with 1k screens so that you don't burn up EL34s when using them. I noticed myself preferring EL34s in my Rectifiers, so out of curiosity, I decided to switch the screens to 470 with 6L6s and see which I liked more.

First, I'll say I don't notice a huge difference from EL34s with the 1k to 6L6s with 470. It seems there's more of an even frequency spread with 6L6s. But 6L6s from 1k to 470? It's there. The amp responds a little better; it's more direct and sounds more clear. Not night and day, but definitely a better amp IMO than before. If you like EL34s and have 5 minutes to spend with a soldering iron, I'd definitely recommend trying this!

YellowJacket · Jul 4, 2012

Hmm. So if you do this mod 6L6s sound better but you can no longer use the EL-34s for any sort of gigging situation? It seems to me that Mesa made a completely legitimate design compromise with flexibility in mind. I prefer EL-34s in a Recto but I'd probably use them to record. For any sort of practicing or gigging, the more robust / reliable tube wins in my mind.