Amp Wiring Overview
As guitar players, most of us will be the first to admit that we're a little different than the average consumer when it comes to what we buy or really how we buy. In general, we tend to educate ourselves a bit more on the products we're interested in, and it is safe to say we sweat the small things a bit more than most folks. This is definitely not a bad thing, in fact, we think it should be considered a point of pride. There is certainly nothing wrong with wanting to have a firm grasp on every aspect of your gear. A good example of this eye for detail is the amount of attention many players pay to not only the features that an amp has, but even how the amp is constructed and what components are used. To the outside observer, the way an electrical circuit is constructed may seem rather trivial or even a pointless piece of information, but to some players it is the deciding factor when it comes to pulling the trigger on a new amp or not. In this article we wanted to look at a few of the different methods used to build tube amps.Before we take a look at the different construction methods, we should probably mention that the purpose of this article isn't to make any sort of qualitative judgement about any of the methods. We have found over the years that it really is hard to draw a ton of conclusions about an amp as a whole by just looking at how the circuit is laid out. In our experience, who made the amp and what components were used have a much larger impact than the construction method of the circuit. The type of construction is just one piece of information to consider. As with anything, there are strengths and weakness to each method.
Construction Methods
When we discuss construction methods it is important to note that theoretically a builder could build an amp with each one of the methods, and as long as the same components are used, the amp should sound the same for the most part. Most amps contain the same basic components: capacitors, resistors, transformers, wires etc. When we look at construction methods, what we are examining is how the components are linked together and organized into a circuit. The three most common types of amp circuit construction are: Point to Point, Tag/Turret Board and Printed Circuit Board.
Point to Point
Point to point (PTP) wiring is the oldest and most work intensive method for wiring an amp. Most early electronics in general were constructed with this method for the simple reason that at the time it was the only practical way to put a circuit together. This is the good "old-fashioned" way to build an amp, many often argue, and some builders still use it today, although due to the work intensive nature of this type of construction, it is a bit more rare than other methods. With this type of construction, there is no board or platform that the components are mounted to. As the name would imply, the components are mounted directly to one another from one point to the next. In some cases, small brackets are used to provide some structure to the circuit, however it is not uncommon to see the actual solder joints themselves form the structure of the circuit coming together in an almost "spider web" type of structure. Due to the structure-less nature of this type of wiring, much more knowledge of electronics is often needed to construct a circuit, not to mention it is also very time consuming to construct.
Proponents of this type of wiring cite its simple nature as one of its strengths. The idea is that since the components are mounted directly to each other a shorter signal path is created and therefor a more pure signal is produced. It certainly seems like a sound theory, however the effect on the tone of the amp may be debatable. Due to the work intensive nature of point to point wiring it is also often difficult to construct very complicated circuits both frequently and cost effectively. For this reason it is not as common as other methods of construction or only used on very simple designs.
Tag/Turret Board
With Tag or Turret board construction you are essentially still constructing a circuit by hand, very similar to point to point wiring, however a pre-made board is used to provide the structure or basic layout. This type of construction is very common both in vintage amps such as most pre-1980 Fenders as well as with many boutique builders of today. Typically the structure that the circuit is attached to is made of either some form of non-conductive fiber board or plastic and either metal tacks or eyelets are pressed or machined into the board. The components are then soldered directly to these tacks or eyelets to form the circuit. There is still a direct path between components as they are actually soldered directly to each other. The board is there simply to provide structure circuit itself.
This type of construction is a little less work intensive than point to point wiring, as the boards can be pre-made to the builders specs which speeds up the process considerably. Having the basic circuit already laid out on the board makes the process a little easier to produce high quality amps in larger numbers. For this reason, this style of construction is very popular among many amp builders who want the pure signal path of point to point wiring yet need to be able to produce reasonable numbers of amps that still have a realistic street price.
Printed Circuit Board
You would be hard pressed to find a modern electronic that does not contain a least one printed circuit board. Honestly, we owe just about all of the credit for our modern conveniences to the efficiency that that the printed circuit board provides. It has truly revolutionized electronics in the last half of a century. It is no surprise that it has also shown up in amp production in the last 30 years as well. PCB's allow much more automation to the production of amplifiers as well the ability to construct circuits that are not really feasible by hand with other construction methods due to the complexity of the circuitry. Some amps now have more in common with a desktop computer than a Fender Bassman. Even with all the flexibility that PCB's bring to the table there are still quite a few players that are very suspicious of them in a tube amp for a few reasons.
It is important to understand what a printed circuit board actually is. A PCB is basically a piece of non-conductive material, normally plastic, with a circuit inlaid into it in the form of copper or other metal tracks. Components are then mounted directly to this board in their proper positions in order to complete the circuit. Think of it as a small road map where the streets are made of copper. Whereas components are mounted directly to one another with point to point wiring, typically the components are only making contact through the metal tracks with this style of construction. Many players worry that there is a detrimental effect to tone due to the less direct path of the circuit as well as issues involving the heat that a tube amp generates and how it effects the plastic circuit board itself. These are definitely legitimate concerns but here are a few things to consider.
- As long as the circuit is constructed correctly and all solder joints are sound, the difference in signal from a point to point wired circuit to that of a circuit board should be minimal. By small, we mean pretty much unmeasurable in most cases. There just is not enough difference in the signal path to really have an audible effect.
- The type of circuit board used makes a pretty big difference in terms of durability. Due to the heat generated by tube amps many manufactures will often use a circuit board that is especially designed to endure heat. Typically these boards are considerably thicker and the material itself is resistant to warping when heated. Some of the military-grade boards can be practically lit on fire before they will fail. They can handle just about any thing a tube amp can throw at them.
- As with anything, the way that the pieces are put together makes all the difference in the world. There are some amps that contain PCB's in which the components are still mounted by hand, not all that dissimilar from a tag/turret board type of construction and many components such as tube sockets and input jacks are still hardwired. This minimizes some heat related issues as well as adding some durability to some of the more "high-impact" components. In our experience it makes a very high quality, durable amp even if it does contain a printed circuit.
Over the years one thing we've found is great amps are constructed in many different ways. There has always been a bit of suspicion with tube amps that contain PCB's among some players, however brands like Mesa, Orange and Tone King are able to make top notch quality amps using some printed circuit boards in their circuits. It really goes to show that it is more about how an amp is made rather than just the method used. Obviously, the type of construction is important but we are not sure it should be the sole deciding factor when you are looking at an amp.
