Here is a super simple mod for your Tweed Deluxe. I love my Tweed so I had to try this mod to see if it made it any better.
From Merlin, The Valve Wizard...
Quote:
The much greater problem with the cathodyne occurs when it is itself overdriven. Because it has such a large cathode resistor only a little grid current is required to 'jack up' the cathode voltage. When driven very hard this can cause an inverted copy of the cathode signal to appear at the anode, effectively creating a sort of full-wave rectified or frequency doubled signal at the anode. This is shown in the lower photograph, and it is usually this which causes the ugly 'blatting', 'swirling' or 'grainy' sounds sometimes heard in amps using this kind of phase inverter. Fortunately, the cure is simple. We add a large grid stopper to the cathodyne, to keep this grid current in check. A value of 100k to 1Meg is usually necessary. Before you worry, this will not affect the treble response though, because the cathodyne only has unity gain! Therefore it's input capacitance is extremely low, at about 2*Cga + Cgk, which is only 4.8pF for the ECC83! This is the real 'secret' to obtaining a smooth, consistent sound from the cathodyne, no matter what kind it is. If you are using a cathodyne always give it a nice big grid-stopper. The tonal reward is startling!!! Yes I know Leo Fender didn't use any, but he wasn't designing amps to be overdriven, and this is the 21st century.
So I picked a 1/2W 470K carbon film resistor with the most mojo out of my parts bin and installed it. Easy mod, just desolder the wire on pin 7 of V2 and but the resistor in series with the wire and solder it back in place. Just like any grid stopper try and get the resistor's body as close to the pin as you can.
Anyways longest part of the mod is unscrewing the back panel. I am really liking the change so far. It is fairly subtle and it still has all the great character and qualities of a stock Tweed Deluxe. I found the mod smoothed out the distorted sound and made all the positions on my strat more natural sounding and smooth. Still has a lot of bite and growl. Seems like the amp is a tiny bit more dynamic too....
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