Twinline™ Development

For years, guitarists have been asking us to solve the age-old problem of sharing a single pedalboard between two amps. Although this almost seems like a simple request, if you think about it, the solution is not so easy to come by. The point here is that we are not talking about using a pedalboard in front of a couple of amps… we are talking about connecting the pedalboard to the effects loop in the amplifier's rear panel and then having the effects magically switch to a second amp automatically.

Traditional 'two-amp' set up with pedals at the 'front' of the signal path. Adding delay at the pedal board and then distortion to the guitar and delay is not always preferred.

Moving the pedals to the 'back' of the amp or the end of the signal chain requires connecting the pedals to each guitar amp's effects loop. This way, the amp's distortion can be sent through a clean delay.

There are several reasons why using the amp's effects loop can be beneficial:

  1. Tone
    When connecting a guitar directly to an amp, you can really maximize the tone of the amp's preamp section. Using the effects loop or the preamp output to feed pedals will often result in cleaner and more distinct notes. Pedals often sound fuller and more natural when used this way.
  2. Noise
    When you send a buffered signal into pedals, the impedance is often lowered which reduces susceptibility to noise. High impedance circuits tend to act like antennas – so lowering the impedance solves problems. Further, since the signal is already amplified (buffered) you are no longer boosting the background noise that may be introduced by the pedals.
  3. Delays
    Delay pedals are usually placed at the end of the signal chain on a pedalboard. This is done because delaying a distorted tone sounds better than applying distorting to an echo. Notes remain distinct. The same applies to guitar amps. If the amp's preamp section is generating distortion, placing the delay after the distortion will sound better.

When using rack effects, matching the impedance can also be a problem as many studio effects are equipped with balanced line inputs that need a higher output signal to work properly. This means that you need to use a preamp of sorts to boost the signal and then once processed, drop the signal back down to go into the amp at a level that will not cause the loop circuit to distort.

Once all of this is understood, you then need to consider switching the two loops in such a way that you do not end up with a bunch of popping noise and introduce some form of remote controllability so that you do not have a spaghetti mess of cables going from your amp to the pedalboard and back. This is why the Twinline is so cool.

For all of you completely mad scientists, consider using the Tonebone Headbone™ as part of your setup. This unique device lets you switch between two heads sharing a single cabinet on stage. In other words, you can use a Marshall™ head for crunch and a Mesa Boogie® head for solos. Easy enough… however, when switching heads, you cannot have a long trailing echo in an amp that is not connected to a speaker as it requires a load for safety. This problem has been one that guitarists have had to contend with for years.

The Twinline presents a solution as you can automatically route the delay to the active amp, eliminating the chance that a long, trailing echo can harm your amp.

Establishing the feature set

Lets start by following the block diagram of a typical Twinline setup. This shows six cables whereby the two amplifier effects loops are brought together in the Twinline and they both share a central effects loop. Anyone that has tried connecting amps together is well aware that in most cases, the amps will buzz like crazy due to ground loops. The Twinline solves this problem by isolating the two amp effects loops from each other using transformers. This is supplemented with three ground lift switches on the top panel that can be toggled on or off to find the quietest setting.

The next challenge is keeping signal levels in check. Both of the Twinline amp effects loops are equipped with send and receive level controls to match the signals going to the pedals and back to the amp for optimum signal to noise. This is supplemented with polarity invert switches for each loop to ensure the two amps play in phase. The Twinline goes one step further by offering a choice between a typical unbalanced guitar signal for pedals or guitar processors and a pro +4dB balanced line level signal for use with studio effects.

Switching amps and loops

There are several ways you can set up your system to switch amps and have the Twinline follow. Some require extra foot-stomps, others are more seamless. For instance you can connect your guitar to a typical ABY switcher like the Switchbone™, Twincity™ or BigShot ABY™ to feed the guitar signal to your two amps. You can use a remote footswitch to route the pedalboard to the active amp. For this setup, the Radial JR2 is a great option as it can select between the active loops and bypass them both using the two footswitches. It also receives its power for the LED indicators from the Twinline, eliminating the need for batteries or a power supply connection.

You can also remotely switch the Twinline using a contact closure such as found on most MIDI controllers or connect it to the Slingshot remote output from another Radial pedal. Another option would be to use the Radial SW2™ Remote footswitch. This has two Slingshot outputs that can switch the Twinline and the Slingshot-equipped Headload simultaneously.

As the end of the day, the development of the Twinline is to provide the more tone-demanding guitarist with better switching options that will at once improve the tone and maybe spur on creativity.