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Why is transformer isolation so important?

When two amplifiers are connected together, they invariably will share the same electrical ground. This leaves them open to stray DC currents circulating between them which, more often than not, will cause hum and buzz. This effect is commonly known as a ground loop. Transformers allow AC to pass but are extremely efficient at stopping DC noise. By bridging the audio signal through a transformer, the stray currents are reduced and so is noise.

What’s the difference between the Twin-City and the more expensive Switchbone?

The Switchbone is a 100% discrete, class-A device that is equipped with a tuner output and variable gain power booster. The Twin-City is basically a pared down version of the Switchbone that is both smaller and more affordable.

What is EIS Electronic Impulse Switching?

Although the switches on the Twin-City look like regular switches, they are in fact special non-latching momentary switches that activate an internal electronic circuit which does the actual signal switching. Because this avoids mechanical switching, problems such as wear and tear, or contacts sticking, are significantly reduced. The result: you get longer trouble-free switch life.

Can I use the Twin-City with a battery?

No. Batteries are painful! They go dead and then are tossed into landfill sites. This is not environmentally friendly. To power a Twin-City you need to either use an external 9V power supply or multi-pedal power brick. Consult your dealer for the best option to suit your needs.

How do you use a stereo chorus with the Twin-City?

Most artists use a chorus ‘mono’ in between the guitar and the Twin-City as the stereo effect cannot be heard by the audience. You can use it after the Twin-City and your two amps but you may lose the benefit of transformer isolation.

Why do I get hum with my Whirlwind ABY box when connected to my Fender and a Vox amps?

This is a common problem with most ABY boxes. The Twin-City employs a buffer and an isolation transformer to eliminate this problem.

What is a class-A buffer?

A buffer is a unity gain amplifier that drives the signal. There are various types of buffers available. Discrete class-A buffers are preferred by audiophiles as they sound more natural than chip based buffers. This is what is inside the Twin-City.

Can I use the B output on the Twin-City as a direct box output to feed the PA system?

Direct boxes are normally Lo-Z balanced outputs while the Twin-City output is Hi-Z. If you want to use the second HI-Z output from the Twin-City as a DI box, then you would have to limit the distance to about 15 meters (50′). You could take the output from the ABY and run it into a Radial ProDI™ which would then balance the signal and enable you to run it 100 meters (300′).

Does the Twin-City recall the last setting used when reconnecting the power?

No. There is no ‘memory’ in the Twin-City, you will have to select the setting you want to start with.