PCB vs Point to Point Wiring
By Phil O'Keefe |
Examining the advantages and disadvantages of each
By Phil O'Keefe
Occasionally you'll find a topic that's hotly debated by musicians, and certainly one of the bigger ones is the subject of printed circuit board construction verses point to point wiring in amplifiers and effects. Once electronic circuits go beyond the simplest forms and use more than just a handful of components that can be directly soldered together, some sort of substrate must be used to help facilitate organizing and mounting all of the parts. Printed circuit boards and various substrates combined with point to point wiring can both be used for this purpose, and each approach has its fans, but what are the differences between them, and is either one really "better" than the other?
Point to point wiring
In older electronic devices (including most vintage Fender amps), vulcanized fiberboard eyelet boards were often used to mount the electronic components. They require hand insertion of the various parts and hand soldering, so considerable human labor is involved with this manufacturing approach. Fiberboards have their share of issues. They can warp over time, which can lead to stress on components and solder joints, which can cause them to fail. They can also absorb moisture from the air over time, which can lead to micro-voltage conductance and leakage between components across the board. This can sometimes have an adverse effect on the sound of the amp - the 100k plate resistors leaking to the 68k grid resistor issue that frequently leads to soft popping, ticking and "bacon frying" noises on vintage Fender amps is a well known example of this. Some feel that in certain cases this subtle micro voltage leakage can actually contribute positively to the sound of vintage style amps, and many companies still use these types of boards, even on modern amplifiers.
Perfboards are also commonly used as a substrate for point to point wiring. A perfboard is usually made of laminated paper and phenolic resin, or fiberglass and epoxy, and has multiple holes laid out in a grid pattern, with the holes typically spaced about 0.1" apart. This hole spacing facilitates the insertion of a wide range of electronic components. Each hole is copper-clad, with individual metal pads for each hole. Nicer perfboard usually has pads on both sides of the board. As with eyelet and turret boards, components are hand mounted, and the wiring is routed by hand from one component to another, so care must be taken to assure correct wiring by the builder.
Printed circuit boards
Today, printed circuit boards (often referred to with the initials "PCB") are the most commonly used substrate for electronic circuits. PCBs use a non-conductive substrate on to which conductive copper pathways or "traces" are etched. Copper clad holes in the board are also included for the insertion of individual electronic components, if the PCB was designed for such parts. Some PCBs have their metal pads and traces on just one side of the board, while others have the metal soldering pads and traces on both sides of the board.
One significant advantage of PCB construction is the ability for much more of the construction process to be automated, thus decreasing assembly costs substantially. Surface mount technology allows for even more extensive automation in construction. Whether such automation results in an increase or decrease in quality is debatable, with detractors saying hand-assembly allows for more individual inspection, care and quality assurance checks, while proponents note that automation reduces the possibility of human error in parts installation and soldering. Using a PCB also insures consistent parts placement relative to other parts, and a pre-routed wiring configuration on the PCB that reduces the potential for wiring errors.
Which approach is best?
Once again we're looking at a situation where there really is no clear winner. Both printed circuit boards and point to point wiring remain popular in the world of musical electronics. There are plenty of benefits with both printed circuit and point to point construction, and ultimately it usually comes down to weighing the advantages and disadvantages and deciding which method best suits the design that's being built. Circuit complexity and the device's target price point are both key considerations; the more complex the circuit, and the higher the parts count, the more expensive and time-consuming point to point construction becomes, and the more crucial the skill level of the builder(s) becomes as well. Automated printed circuit board construction and soldering methods remove a lot of the potential for human error and can greatly increase manufacturing efficiency, and thus lower costs.
While there are things to avoid when using either approach, there is no reason why a PCB build has to sound any worse than a point to point wired unit. Ultimately it comes down to the particulars of each individual product, and while other factors such as serviceability and ease of modification still bear consideration, a well designed and built PCB product can sound every bit as good as a well designed product that uses point to point wiring. Ultimately you'll need to consider a lot more than whether a product utilizes point to point wiring or a printed circuit board before you can really judge it fairly, so don't automatically disregard a product over the way it was built. There are plenty of good products that use printed circuit boards, and loads that use point to point wiring.