Like many reissues, this Super Jet sounded great when it was new but over time started to develop intractable issues. It was no longer reliable enough for gigging or recording and was becoming a real headache for it’s owner. It was a prime candidate for a rewire.

Every rewire is unique, this Ampeg’s design dictated a couple of special features. Though it originally ran 12AX7s, the old tubes were PC board mounted. The holes where the tubes past through the chassis were too large to install miniature 9-pin sockets so we decided to expand them and go with octal-based preamp tubes taking advantage of a decent supply of NOS 6SN7 and 6SL7 preamp tubes. These tubes are much more prone to inject AC hum into the signal then standard 12A_7 types so we worked a regulated DC heater supply into our rewire plans.  With the DC heaters this amp’s noise floor is dead silent, perfect for recording applications.

Another problem that had to be addressed was what to do in place of the amp’s original integrated circuit reverb. With only two preamp tubes and no real room to expand a true tube spring reverb was out of the question. It so happened that this musician preferred a nice TC Electronics rack mount system for his ambient effects anyway. In place of reverb we opted to install a simple effects loop to interface with his rack gear. It was fortunate that the reverb mix control had been given the creative label: “Dimension”. After experimenting with numerous ways of redefining this control’s function we finally settled on a post phase-inverter “Matchless-style” master volume.

The amp was wired with a mind toward maximizing loudness and clean headroom. Our custom Synaptic EQ provides smooth highs, precise bass control and full ranging mids. A simple foot switchable boost circuit gives the option of a soft compressed tone or a punchy in-your-face sound.

Fender  Strat:

Gibson ES-339:

This rewire project came in from a musician who felt like he was in a constant struggle with his amp to get his sound.  As reissues go this ’59 Bassman had a lot going for it: a beautiful tweed cabinet, four very nice 10″ AlNiCo drivers, a heavy duty chrome plated chassis and a massive transformer set… It just didn’t have the sound.

Here’s the before picture:

The first step in the rewire was to pull the chassis out and disconnect all the quick connect terminals from the board. The whole circuit board pops right out just as easily as it was installed by the underpaid 3rd-world laborers who assembled it. With the chassis all cleared out we machined all the new holes we needed for our new circuitry and then began lining up our components for the rewire. The next step will be to design and manufacture the turret board for our circuit.

After carefully planing our circuit and layout the board is cut to size, drilled and the turrets are staked by hand on a drill press. With the board ready to go it’s time to begin remounting all the chassis components and then move on with the wiring.

The power supply always seems like a logical place to start the wiring process…

Followed by the main filter capacitors…

Then we’re ready to start populating the turret board and begin wiring it into the chassis.

The average rewire takes about 25 hours of labor from start to finish but the end result is an amp with the kind of rugged reliability needed to last a lifetime. The final steps of tweaking and modding the circuit to hone in the amp’s sound and feel to the musician is what really makes the difference between the assembly line reissue we started with and our custom rewire.

The Twin Reverb is a favorite for musician’s who just want their amp to be loud and clean. Unfortunately modern reissues lack the reliability and repairability players require for a serious road-worthy amp. If endless repair bills and frustration have you on the verge of ditching your reissue amp, consider the possibility of a rewire.

Rewiring an existing amp is often the least expensive way for a musician to step their rig up to modern boutique quality. While the main weakness of reissues lies with the cheap PC-board circuit design inside, the major costs of the amp as a whole are tied up in the cabinet, chassis, transformers and speakers. By salvaging these items and rewiring the internal circuitry new life can be breathed into a tempermental reissue at a fraction of the cost of a whole new amp.

The Twin shown above offers a typical example of what you can expect to find inside a modern reissue amp. This particular amp has all the qualties that make a good candidate for rewiring. The most essential characteristics are its all tube design (no solid state reverb circuits or boost nonsense) and chassis mounted tube sockets.

It’s pretty quick work pulling the old board out. The bulk of the time is in cleaning the old leads off the tube sockets and cleaning the old solder of their pins to prepare them for reuse. It’s nice to try to salvage as many components as possible such as the original pilot light housing and switches but anything of questionable integrity has to go.

With all the major components removed from the chassis we can get a clean new start. Dismounting the transformers helps maneuver the chassis on the drill press in order to machine all the new mounting holes we’ll need for the power supply capacitors, circuit boards, etc…

Every rewire starts at the drawing board with a custom circuit design, schematic and layout. We can follow as true to an amp’s original design as is desired but it’s usually nice to take advantage of the opportunity to customize and voice the amp to better suit the musician. Once an initial schematic is finalized we produce our turret boards which you can see getting dry fitted above. If everything checks out it’s time to get the wiring underway:

In working with amps one at a time it’s nice to be able to invest a little more time in lead dress than would be possible in an assembly line process. Neatly routed leads aren’t just intended to be sexy to look at… the goal is to control interference between signals and minimize hum and noise. There’s nothing quite like hand wiring a Twin to make you understand why all the major manufactures have gone to PC board construction… the process is super labor intensive requiring many hours of patient steady soldering to bring it all together.

Finally we have a fully wired amp ready to power up and bring to life. An extensive process of ear testing and modifying is what makes the difference between an assembly line amp and a custom tuned “boutique” amplifier.  Our end result is a truly unique sounding Twin Reverb with a couple twists:

• Reverb and Vibrato on both channels.
• Dumble-style EQ for wide ranging mids, smooth highs and precise bass control.
• “Sag” switch for mild compression and reduced hum.
• Custom voicing for tighter bass, extra clean headroom and lowest noise.

This custom reverb head was designed for a musician that shares the stage with a variety of acoustic instruments including violin and woodwinds. The need to maintain a low stage volumes dictated a moderate wattage design to enable access to a full bodied clean tone that yields gently to a gradual breakup when pushed.  We opted for a class A single-ended 6L6 output stage with a transformer set wound for slightly higher voltages. The amp runs in pure class A putting out about 15 watts of clean power. The controls are simple: Volume – Tone – Reverb. Bright and Bass switches on the front panel give additional control of the amp’s voicing allowing it to be adjusted to suit a wide variety of instruments and playing styles. The amp is housed in a mahogany dovetailed cabinet featuring our standard figured maple face.

Here’s a look at what’s inside:

This stand-alone reverb unit started life as a reissue with a cheap PC board construction that simply wasn’t cut out for the abuse of modern rock and roll. We gave it a full overhaul salvaging only the original chassis, transformers and cabinet. Hand wiring the circuit on a custom turret board with new panel mounted jacks and pots resulted in vast improvements in ruggedness and reliability. Additionally, the hand wired circuit provided a wide-open door enabling the extensive modifications needed to hone in on the “dripping wet” reverb tones this unit’s owner were seeking.