5E3 chassis with 3 X 12A*7's, what to use the spare preamp tube for?

[RobBozic]

Hi guys,

I have a 5E3 chassis which I've used to build various circuits with. I've decided to take it back to a 5E3 circuit, however I was curious about using the 3rd preamp tube for something, maybe adding a vibrato circuit or a 5879 in lieu of the normal channel.

Has anyone added vibrato or a pentode channel to a 5E3 before?

Thanks
Rob

[Chuck H]

One vote for vibrato.

[RobBozic]

Chuck,

Are there any recomendations for a vibrato circuit? I'm not too familiar with them

[Chuck H]

Me either. But I an including a trem on my next build. After some searching I settled on the reissue bias vary trem used by Fender on various amps. The problem I found was that most of the vintage trems presented a very high, over max spec, heater to cathode voltage. Most NOS tubes will handle this I guess. But I know that many new tubes made by new sensor, and possibly others, will fail in that kind of environment. The reissue style trem amps seem to get good reviews and minimize the problem. You will still want to DC elevate the heater supply for added margin. Here's an example of a vintage trem and the new circuit that Fender uses.

[tubeswell]

5E9A for cathode-biased output (paraphase inverter)

5G9 for fixed bias output (LTP inverter). IMHO the 5G9 trem has the most hypnotic trippy slam

[printer2]

Bassman cathode follower.

[jimboyogi]

How about reverb?

If you sacrifice 1 input channel, and make it the reverb recovery stage. From the remaining input channel take off your reverb signal via a 500pf cap from the top of the volume pot. Feed this signal to a paralleled 12AU7 reverb driver (in the extra socket), cap coupled to a high input impedance reverb tank. For details of the driver check out valve wizard site - The Valve Wizard

Feed your reverb tank return signal to the sacrificed input channel stage, and it's volume control becomes your 'reverb' control.

Might work anyway?!

[EFK]

May I interject here and ask where you got a 5E3 chassis w/ 3 preamp slots? I ask because I've punched a few of my own from blanks, but I would LOVE to get a pre-made chassis like that. ???

[Bruce / Mission Amps]

How about reverb?

If you sacrifice 1 input channel, and make it the reverb recovery stage. From the remaining input channel take off your reverb signal via a 500pf cap from the top of the volume pot. Feed this signal to a paralleled 12AU7 reverb driver (in the extra socket), cap coupled to a high input impedance reverb tank. For details of the driver check out valve wizard site - The Valve Wizard

Feed your reverb tank return signal to the sacrificed input channel stage, and it's volume control becomes your 'reverb' control.

Might work anyway?!

Nuts to vibrato... waste of tube if you ask me. Leave the current tube configuration just the way it is... two channels both with light non-surf reverb.
A little, modest reverb circuit is the way I'd go too... you can use a 12DW7 in that extra socket and tiny low voltage FET amp to mix it all back together before the cathodyne phase inverter. Makes a sweet low wattage amp even better.... especially when you follow the many other suggestions here on this site regarding cutting about 6dB of the bass response from a 5e3.

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