Excellent condition Seymour Duncan combo made in early 80s. 5 - 100 Watt variable power control. 

Modular Preamp Design

The Convertible could sound like any amp in any setting. In addition to its all-tube power section, there were five slots for specially designed preamp modules; a global input stage and two more for each of the amp’s two channels. You could have a vintage-voiced clean platform or a fire-breathing high-gain monster with ease by mixing and matching modules.

The Convertible 100 shipped from the factory with the following modules installed:

• 2 x Classic
• 1 x High-Gain
• 1 x Normal
• 1 x Presence

But the company offered a ton of different additional modules for purchase separately, capturing every voice from JC120-like cleans to modded-Marshall roar. These included the Classic Distortion, High-Gain Hybrid, FET, IC, and many more. We even offered versions of the modules with additional EQ onboard for tweaking every aspect of the circuit.

Always ones to lend some advice, the Convertible’s manual even came with some great-sounding combination suggestions to get players started.

Today, tube amps with modular preamps are relatively common. Everyone from Synergy, Randall, and Egnater has shown what such a flexible rig can do. But in 1980, the Convertible started it all.

Variable Power Control

Power attenuation and power scaling are other features found on tube amps all over today’s market. But, as with the modular preamp design, the Convertible was there first. We called it the Variable Power Control. It lets you take the amp’s output from a massive 100 watts down to a practice-friendly 5 watts. And the control is 100 percent variable to set it to the exact level required for your situation.

As if that weren’t enough, the control features a Variable Power Jack, which lets you control the whole thing via any passive volume pedal! Power attenuators are everywhere these days. But not many people have caught up to that one.

Most important, the Variable Power Control sounds terrific throughout its sweep. And again, we’re not honking our own horn. Bonamassa agrees. When speaking to Beller, the amp’s designer, he said, “The power attenuator alone you guys should make. It’s the coolest and most natural-sounding one.”

A Whole List of Player-friendly Features

An all-tube guitar amplifier from the 1980s with modular preamps and variable power is enough to put the Convertible on the list of all-time greats. But these amps were loaded with even more tools gigging guitarists continue to need to this day.

1. The head version can be removed from its shell and rack-mounted
2. Load Resistor Input: Included load resistor plugs optimize the amp’s input for different pickups.
3. AC Convenience Outlets: 2 x 9V outlets for plugging in additional equipment.
4. Variable Damping: Speaker output that lets you loosen or tighten the feel of your speaker response.
5. Effects Loop with level control.
6. Slave Out: Sends attenuated, line-level signal from the amp’s output stage to F.O.H., interface, etc.
7. Accutronics spring reverb
8. Custom output transformer allows for mixed/matched cabs and impedances (just like the PowerStage pedal amplifiers).
9. The power section works with EL34, 6L6, or 6550 tubes (Rebiasing required).
10. Pentode/Triode Switch selects between 100- and 60-watt max power.

A True Classic

If the Convertible amps had one drawback, it’s that all of these boundary-pushing features were hampered by the technology of their day. This led to some of the amps overheating and other less-than-desirable on-the-gig events. That’s why it’s not uncommon to find as-is versions on the used market.

Thankfully technology has improved in leaps and bounds since then, creating mods and upgrades for the old Convertibles, bringing them back better than ever. And you can still find plenty of the original preamp modules for sale. There’s never been a better time to get one of these classics for yourself. But you’ll want to move fast. Word is out on these game-changing amplifiers, and prices are on the rise.