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previous: James Frustration with the sound of my Tw... -- 1/7/2000 10:34 AM

Re: Line in on S/F Twin

1/7/2000 6:42 PM
Jim S.	Re: Line in on S/F Twin Chances are, the preamp won't have enough output signal strength to drive the Twin's power stage to full power output. All rack-mount guitar tube power amps that I'm familiar with use a pre-driver stage that brings the signal up to enough voltage to properly drive the phase inverter. Here's my suggestion for a line-in. I've done this before and it works well: Rewire the input jacks on the normal channel, such that when a cable is plugged into jack #2 (which will be the LINE IN jack) the signal from the cable feeds the top of the normal channel volume pot. (If no cable is plugged into jack #2, the jack's shorting connector should connect the output of the treble pot to the input of the volume pot, allowing normal operation with a guitar plugged into jack #1.) With this arrangement, a signal going into jack #2 will be "trimmed" by the volume control and then feed gain stage V1B (acting as the pre-drive stage) which then goes to the phase inverter via the 220K mix resistor. Of course, none of this might be necessary if you can get your Twin's preamp section (and/or power section) to sound better. If it has not already done, maybe recapping and blackfacing might be in order.

1/7/2000 6:42 PM

Jim S.

Re: Line in on S/F Twin

Chances are, the preamp won't have enough output signal strength to drive the Twin's power stage to full power output. All rack-mount guitar tube power amps that I'm familiar with use a pre-driver stage that brings the signal up to enough voltage to properly drive the phase inverter.

Here's my suggestion for a line-in. I've done this before and it works well:

Rewire the input jacks on the normal channel, such that when a cable is plugged into jack #2 (which will be the LINE IN jack) the signal from the cable feeds the top of the normal channel volume pot. (If no cable is plugged into jack #2, the jack's shorting connector should connect the output of the treble pot to the input of the volume pot, allowing normal operation with a guitar plugged into jack #1.) With this arrangement, a signal going into jack #2 will be "trimmed" by the volume control and then feed gain stage V1B (acting as the pre-drive stage) which then goes to the phase inverter via the 220K mix resistor.

Of course, none of this might be necessary if you can get your Twin's preamp section (and/or power section) to sound better. If it has not already done, maybe recapping and blackfacing might be in order.