What are the advantages of having a pedal or amp that is point to point wired as opposed to one that is built on top of a printed circuit board? Are there any disadvantages of PTP?
Advantages to the user of PTP: you can maintain it much more easily. You can simply see the signal path and often component spacing is less fiddle.
Potential advantages in PCB design is often easier to make robust circuits. Broad generalisation, but a well made circuit board can be very resistant to drop damage, whereas a larger layout PTP may suffer from more of a bending moment if dropped. Analysis tools for PCB design are also readily available.
I always prefer to PTP in prototype and finalize on PCB.
Theoretically, there's not necessarily any difference.
Practically speaking, however, there's a fairly fundamental difference: air has a much lower dielectric constant than epoxy (which is what most PC boards are made out of). This means even a fairly small gap of air between PTP wires reduces the capacitative coupling to a very low level. Achieving exactly the same (or even less) capacitance between traces on a PC board is always possible, but often quite impractical.
As already noted, however, that all goes out the window if you bundle wires together -- the minute you have direct insulation-to-insulation contact between the wires, you're dealing with the dielectric constant of the insulation rather than of air (and it's typically in the same general range as epoxy -- much higher than air in any case). The higher dielectric constant of insulation is why some people actually use uninsulated PTP wiring -- as long as you assure against the wires touching, it (nearly) minimizes capacitative coupling (though, of course, there is that oh-so-minor detail that catastrophic problems change from "if" to "when").
You're going to pay more for PTP than PCB and that is the only difference. I challenge anyone to post an audio clip where you can discern the difference between PTP and PCB of the same design, because there will be no audible difference if the boards are laid out and made properly.
Additionally, even observing w/oscilloscope or running noise analysis on the board vs point-to-point should give you nearly exactly the same results.
PCBs were really expensive back when Fender was making the Deluxe, that's why it was all PTP. Now they're cheap, so there's no reason to go through the extensive labor.
Also there's talk about parasitic or inter-channel capacitances and other phenomenon like that. Analog stuff found in electronic warfare at extremely high frequencies like 6GHZ+ work great on PCB and they are astronomically more sensitive to noise than a guitar signal is - you'll never find that stuff wired PTP because I suspect you'll actually start to hit more unknowns in workmanship such as inconsistent contact being made. In fact, the one trick they use for RF analog designs is to use large ground plane "pours" on boards. If there's any improvement over a standard PCB it isn't to go PTP, it's to design a very well grounded board.
That said I've owned a 5E3, but that's just because they are awesome :) Get what you like, but don't be fooled by the pseudo-science
I'll give you the answer from an electrical engineering perspective:
- PTP can be easier to service when the problem is with the interconnects between components. If you've got a bad lead from one component to another it's an straight forward matter to unsolder a wire and replace it with a new one. Bad leads on a PCB design aren't impossible to repair, but they aren't as easy either.
And that's it.
As for disadvantages:
- It's a harder thing to lay out a PTP amp because you don't get to lean on software to ensure that your signal routes are sane. With a PCB-based amp you can use software to ensure that parasitic capacitances in parallel traces aren't a problem, that traces are sized properly for the power they're expected to handle, that components are spaced adequately and so on. And it's an easy thing to change the layout, in software, and simulate new designs for problems without having to resort to a time-consuming prototype build.
And that's it.
It's pretty minor stuff really.
There's a nice article called "PCB vs. HANDWIRED" at The Pro Guitar Workshop's site.
Basically it says a good PCB can be as good as good PTP.
The way I look at it, super-high-end audio circuits like we'd find in expensive stereo amps and radios, recording equipment and synthesizers, among many other devices, which have a lot higher frequency and sound accuracy demands than guitar, use PCB. So, a printed circuit board has the capability to move audio around at least as well as point-to-point wiring. It comes down to the components and care taken when designing it all.
Without going into too much technical detail (since it is a bit over my head...) One very good thing about a PTP amp is that they are easy to maintain and repair compared to a PCB... The biggest disadvantage of building a PTP amp is cost, since it takes a lot of planning and wiring by hand compared to a PCB!
As for the differences I think a well planned and well built PCB will be as good as a well planned PTP (and a lot cheaper to make).
I find it much easier to modify a PTP circuit than a PCB, even for simple mods that only involve adjusting the value of a preamp cathode resistor or capacitor.
You might like to draw a distinction between a PTP "rats nest" circuit with a dozen resistors hanging off valve sockets and PTP circuits built around an eyelet board or turret board. Personally I prefer eyelet or turret boards for their tidiness, which to me is an advantage when servicing or repairing.
If you don't plan to modify your amplifier much, get the PCB. I have played both types and can't tell the difference. If you are building one, it will be a lot easier to change and modify the circuit to get "that sound" YOU want to hear with PTP wiring. I would reccomend using a turrret board or tag board to build the next one, if you are planning to duplicate the amp for sales or a stereo guitar setup.
Certain components, especially paper capacitors, have characteristics that are dynamically affected by variations in the mechanical forces on their leads and/or the ambient air pressure. If a paper (and foil) capacitor sits with a certain loosely-maintained level of bias voltage, forces that would squish the foil layers together will tend to reduce the voltage, while those which would pull them apart would increase the voltage. It would be difficult to engineer an amplifier so that this would have a particularly predictable and controllable effect, but if one builds an amplified speaker assembly where the board is subjected to vibrations produced by the speaker, the interaction between the speaker and the capacitors could color (distort) the sound in ways which would be difficult to characterize or produce by other means, but which might be reasonably consistent among amplifiers constructed in the same fashion from the same kinds of components.
A point-to-point-wired circuit would likely subject its components to mechanical vibrations in a fashion different from a printed circuit board. Questions of which was "better" or "worse" would likely be influenced more by subjective aesthetic factors than technical ones. What's most important is not the way in which a particular amp is constructed, but rather whether the person using it likes the sound it produces.
A point to point wired amp will generally have a rectifier, a nice big transformer, simple but high quality components, and be connected to a decent speaker; anyone with a PTP amp probably has a decent sounding axe. This will sound better. Rectifiers have nice natural compression. Seems a lot of people haven't heard old amps much. There's a reason they're expensive. They sound better. I know transistors can be good, but I also know old hard wired amps can be great.