Which is better, point-to-point (PTP), or printed circuit board (PCB)? You will find manufacturers arguing both sides, some quoting outlandish claims to support their argument, others claiming PTP is much better, then, when they start using PC boards, they claim PCB is better. What is the truth?
First, exactly what is point-to-point?
Point-to-point wiring is the term given to a style of construction where the components are mounted on the tube sockets and/or terminal strips, and the connections between components are then hand-wired together to complete the circuit. Perhaps the best-known example of point-to-point is the Matchless amplifiers, which had the parts mounted on terminal strips and wired together. Carr amplifiers also use this type of construction. The term is also commonly used when referring to amplifiers with parts loaded on eyelet boards or turret boards, with the connections hand-wired between them, although these are technically not "true" point-to-point. Old Fenders are examples of eyelet board construction, with the eyelets installed in a wax-impregnated cardboard board. Hiwatts are examples of turret board construction, with all the components neatly layed out between two rows of turrets on a piece of phenolic board.
Matchless John Jorgensen (point-to-point using terminal strips)
Hiwatt DR504 (turret board)
Fender '65 Vibrolux Reverb (eyelet board)
What is a printed circuit board?
A printed circuit board is a piece of copper-clad phenolic or glass-epoxy board with portions of the copper etched off, leaving copper traces that connect the components together. The components are soldered to "pads" at the ends of the traces. This type of construction is well-suited to high-volume production, because the components can be auto-inserted by machines, and all connections can be soldered at once by passing the loaded board through a wave solder machine. Most of the cheaper modern amplifiers are PCB construction, including all new amps by Mesa Boogie, Peavey, Fender, Marshall, etc. Surprisingly enough, some very high priced "boutique" amplifiers, such as the Soldano SLO-100, are also PC board construction.
Soldano SLO-100 (PCB)
Peavey 5150 (PCB)
Okay, so which is better?
Either construction method can be good or bad, depending upon the way in which it is done. Neither is inherently good nor bad on their own.
Properly layed out, a point-to-point amplifier is a work of art, and is virtually indestructible. Improperly done, they are a veritable "rat's nest" of wires, impossible to troubleshoot. The main advantage to point-to-point is ease of maintenance and modification. Components are simply desoldered from their eyelets or terminal strips and new ones are put in their place. There is no disassembly of the unit, and the repair is quick and easy. The main disadvantage of point-to-point is the intensive labor needed to construct the amplifier. This is why it is only used by low-volume boutique manufacturers who have lower overhead costs, and whose amplifiers usually command a premium price that allows them to cover the cost of the extra labor involved.
Properly designed, a printed circuit board can be every bit as reliable as a good quality point-to-point board. However, most manufacturers do a very poor job of designing the PC board. They skimp on quality in order to lower costs, by doing such things as making the board single-sided, where the traces are only on one side, which means the pads tend to be rather flimsy, and usually pull up the first time a part is replaced. In addition, these types of boards tend to have solder joints that break loose very easily under vibration, as there is only a very poor mechanical connection on one side of the board. A proper PC board should be double-sided, with plated-through holes, which allows the parts to be soldered in much better. In addition, some manufacturers also skimp on the soldermask, which is an insulating coating (usually dark green, gold, or blue) that protects the bare copper traces from solder shorts and other unintentional short circuits. Some manufacturers even go as far as not providing a silkscreen, which is the ink layer that indicates the component reference designator as an aid to troubleshooting. The hallmark of a very cheaply built amplifier is one that uses single-sided boards with no soldermask and no silkscreen. Incredibly, some very high priced amplifiers use this type of PC board construction.
A good hybrid method, in my opinion, is to use a thick, 1/8" G10/FR-4 epoxy circuit board, but instead of just plated holes to mount the component leads in, turret terminals are mounted in the holes. If the board is manufacturing using heavy 2-oz double-sided copper, with plated-through holes, the turrets can be swaged in to allow a tight mechanical connection on the top and bottom pads, and then soldered to the bottom pads for absolutely reliabable conductivity. This type of construction allows for extremely consistent wiring, a full ground plane on top of the board if desired, and ease of component removal or servicing or modification. Components can be soldered and desoldered from the turrets indefinitely without the possibility of lifting a circuit pad trace, because the swaged-in turret itself holds the top and bottom pads and inner plated-through core in place. In addition, a soldermask can be added to protect the traces, and a silkscreen can be added to allow easy identification of components during servicing. The disadvantage to this type of construction is that it is still time-consuming, and cannot be automated for machine-assembly, so it is not suitable for mass-produced amplifiers. It is also expensive to have the turret boards manufactured, so smaller companies may not be able to justify the added cost.
Aiken Invader MK I
(turret boad with full ground plane, soldermask, and silkscreen)
As to which is better, you can argue PTP may be the better choice from a repair/modification standpoint, however a properly designed PCB amplifier can be just as reliable, but slightly more difficult to work on if you are replacing individual components. Ignore the hype put forth by the "gurus" who claim PTP "sounds better" than PCB for various unsubstantiated and unprovable reasons. You will find many of them extolling the virtues of PTP, claiming PCB amps "rob tone", then, when they start making PCB amps to improve their profit margins, suddenly PCB amps no longer "rob tone". Make an informed decision on which to buy based on quality of construction, not hype.
Copyright © 1999,2000, 2001,2002,2003,2004,2005 Randall Aiken. May not be reproduced in any form without written approval from Aiken Amplification.