THE CIRCUIT BOARD
This is a transistor amplifier not a tube version like it's big brothers. The design is well laid-out with excess wiring zip-tied out of the way. The output op amp is heat-sinked with thermal grease. Parts quality is very good for this price point. The board is marked with the orientation of components, nice touch.

CAPACITORS
There are 8 small polarized electrolytic capacitors (.47 to 47uf) on the board. The power supply holds a pair of 2200uf 35V and a pair of 220uf 25V. To round things out are four green 224J (.22 5%) film caps in various places. The electrolytics are all Sanwha SGs listed as "Standard series for general purposes, high performance and high reliability". I will be upgrading all the caps.

RESISTORS
The resistors all look to be 5% carbon films. A pair of carbon composites are used in the power supply.

OP AMPS
- Three JRC 4558D "high performance monolithic dual op amps" are visible. These chips are well-known in the guitar industry and are frequently used in effect pedals. Given their provenance I'm leaving these alone.
- The main output device is a 5-pin TDA2030 14W hi-fi audio amplifier. Its rated for high output current with very low harmonic and cross-over distortion. Again, given its quality I see no need to mess with it.

DIODES
To the right of the large power supply caps are four diodes creating a bridge rectifier. These generic types can be upgraded to Schottky's to eliminate rectifier switching noise.

LEDS
The volume/gain circuit uses a pair of red LEDs in the Boost circuit to add distortion as the volume gets turned up. A popular mod is to remove the LEDs but I decided to leave them to retain the factory circuit.

THE MODS
My goal was to make the amp as musical as possible by making the signal path more linear. While this amp is well-regarded because of its tube-like sound, it doesn't appear to be due the factory selecting unusual parts. Filled with general purpose caps and resistors it meant I could upgrade the parts quality with no guilt. Keep in mind that the range of an electric guitar is a narrow 80-1200HZ.

- To begin I changed all the small electrolytic caps to brown Elna Silmics of the same value. I like the Silmic sound, an open, warm, dynamic presentation I use them in signal paths when an electrolytic is needed.

- The amp only puts out 14W so only mild power supply updates were needed. I changed the 2200uf 35V caps to 3300uf 35V Nichicon PWs. The 220uf 25Vs I changed to a 330uf 25V. This added a modest increase in capacitance, helps filtering and beefed up power reserves slightly. Nichicon rates the PW series as "Low Impedance, High Reliability for Switching Power Supplies". I also added film bypasses to each electrolytic to filter out noise.

- The stock green .22 film caps are general purpose polyester. I replaced them with Russian K73-11 .22 160V PETP caps.

- To lower switching noise I replaced the four diodes in the power supply with 1A 60V MBR160G Schottkys.

THE WIRING
VOX created a wiring oddity (below). A 22 gauge (#1 in photo) speaker wire carries the high-level signal to the jacks on the back panel. This is standard practice to let you use the head to power a separate speaker cabinet.

The oddity is that an even skimpier wire (#2) returns from the rear jacks to carry the signal down to the 8" speaker. This return wire is very thin, half the diameter of the other. I realize the Pathfinder only outputs 14 watts, but choking down the wire gauge going to the driver doesn't make sense. Why add unnecessary resistance and inductance to the output signal? Considering the attention VOX paid to the rest of the amp this is a puzzler. Did they use a tiny wire to alter the frequency response intentionally?

So I bought a length of Marshall Sound Runner W8116 16 gauge speaker wire. Its features are listed as " High density, non-plated, oxygen-free copper (OFC) strands with low capacitance provide extremely low power loss, wide bandwith, and excellent transient response. Low wattage signal will be enhanced from this series of cables by assuring good dynamic range and damping factor of the amplifier". I like how the last the last line reads. An easy mod, all I did was replace both with the Marshall wire.

I used K73-17 1.0uf PETP bypasses on the main 3300uf power supply caps. K73-11 .1uf bypasses were used on the 330uf caps.

BELOW:The final layout with Nichicon PW, Elna Silmics, Schottky diodes, and K73-11s.
This upgrade went very smoothly.

RESULTS
I hadn't used this amp in a decade so I didn't have a reference sound to compare with the modded version. However replacing capacitors with sonically better versions, beefing up the power supply, reducing rectifier noise, and correcting the wiring are all well-known mods that produce audible results. Using my Les Paul I found the sound very musical. Dynamics and overtones are clean with accurate, round-edged dynamics. Transients are correctly rendered in a quiet envelope with no hyper-detail. This is consistent with my other mod projects that involved upgrading parts quality.

 

	NOTE: The 54 watt rating on the back is for power consumption not output. The amp only outputs 14 watts.