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G Weber's Tweed Deluxe Line Out Mod

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6/29/1999 2:54 PM

G Weber's Tweed Deluxe Line Out Mod

Has anyone tried the mod outlined in Gerald's book? It involves replacing the wire from the regular speaker jack to the extention speaker jack with a 2.2K resistor, then adding a 100 ohm resistor across the extention speaker jack.

I myself would be attempting this a tweed deluxe style amp, running it into the bar's P.A. (tonight, so prompt answers would be greatly appreciated. Joe

6/29/1999 3:27 PM

This kind of approach is standard on many mesa boogie amps. It can also be found on early gibson amp schematics in the Tube Amp book. You shouldn't have any problems with it.

The resistor values you gave are probably good for 1/2 volt signal level input to a board or power amp. You'll need different resistor values for a smaller signal if you're going to input another guitar amp (preamp). I use about a 47k series, and a 500 ohm or 1k pot as the shunt to match circuits with a sensitivity higher than "line".

6/29/1999 4:56 PM

You may not be very happy with the tone coming out of the PA (or floor monitors, for that matter, if you're also trying to hear yourself better on stage). Keep in mind that there won't be a speaker and a microphone in front to add coloration and introduce some serious high-end rolloff. When going direct, you really need to use a speaker emulator (such as a Hughes & Kettner Red Box) to accurately mimic the effects of the speaker/mic combination. (By the way, the line-out trick works really well, without using any extra outboard gear, when slaving amps, such as when connecting the line-out signal to the effect loop input of a much more powerful amp.)

I think you'd be better off just sticking a microphone in front of your amp for now. If you do still want to experiment using a line-out signal, then you'll be at the mercy of the soundman's skill at using the mixing board EQ controls to approximate the frequency response of a 12 inch guitar speaker. A relatively flat board EQ will result in a tone that's too bright and raw-sounding, especially when the amp is overdriven.

6/30/1999 6:00 AM
tracy	I tried this mod on my tweed Deluxe and had the results Jim discribed. The PA man complained that sound was trebley and buzzie. I didn't care for the sound in the monitors either. However running the line out into my 50 watt marshal made it sound great. It was kinda like a giant tweed sound with a little marshal flavor. There's probably a way to smooth out this circuit to get a better PA out.

6/30/1999 1:09 PM

The simplest thing to do is to add a shunt cap on the resistor to ground. This will give you a 6dB/8av slope rolloff. The frequency where the cap's reactance = the resistor is the -3dB point if my memory is working this AM..

You should try a bunch and just listen IMHO. Math is fine, but what is going to sound the best is not always obvious.

keep in mind that guitar speakers don't have much of any response over 5 or 6K, and very little below 100Hz(save mud), particularly in an open back cab like a 5E3.

6/30/1999 4:45 PM
Benjamin Fargen	Speed, Do you add the shunt cap to ground before or after the 2.2K resistor? or is it after the 100 ohm resistor? Thanks, Benjamin

7/2/1999 1:50 AM
anonymous	The cap should shunt (parallel) the 100 ohm resistor: from speaker hot --///--\|-\|---- to line-out jack 2k2 \| \| > _ 100r > _ cap > \| \| \| \|-\| \| --- -

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