SMD vs. THT parts

Ask the DudeToday, more and more circuit boards are assembled with cost-effective SMD parts.
But what are the advantages and the disadvantages of SMD technology?
Why does it make sense to use in some cases THT technology?
And what do the acronyms SMD and THT actually stand for?

SMD and THT

SMD is the acronym for surface mounted devices. All parts are mounted directly on the surface of the circuit board.
THT means thru hole technology. For this technology, a circuit board with small drilling holes is necessary.

Cost-effective and fast assembly

The installation of SMD parts can be operated by machines. For the machines can deal easily with the small parts, the manufacturing of a circuit board is done in a few seconds. Thereby, it is a very cost-effective way to produce a circuit.
The parts are long-lasting. But if there is a defect, a repair is almost impossible. Accidents can happen so fast: you have assembled a really huge pedalboard but unfortunately, you have connected the wrong power supply, what definitively can do harm to some parts of your effect pedals.
At my workshop I have also seen pedals with SMD parts, arriving clattering and rattling. A capacitator came loose. The legs of a SMD capacitor are as thin as a single hair. If they are not stucked or glued to the circuit board, even a little spill can crash the whole pedal.

If the pedal needs a repair, you will have to pay for the whole manufacturing again. For it is almost impossible to repair SMD circuit boards or the repair will be very expensive, the complete circuit board must be replaced.
Especially, when the warranty has already been expired, this is pretty annoying.
Actually, the cheap production costs will in this case become quite expensive for the end-consumer.

Space-saving circuit boards

Many digital effects have one or several big, mostly double-sided assembled circuit boards, that fill the enclosure completely.
If you want to produce such a circuit with THT parts, the pedal will become quite big.
Some time ago, you could find many big box Deluxe Memory Man delays on pedalboards all over the world. No guitarist paid attention to the needed space on a pedalboard. At those days, even extensive circuits produced with TH technology would not have been a problem at all.
But today, the pedals get smaller and smaller and many guitarists are looking for extensive digital effects in mini enclosures.

Availability of parts

The production of many old parts has been stopped and therefore, they are not available anymore. Or you will only find remainders that are pretty expensive.
Especially, if a manufacturer has developed a certain circuit, it can be pretty annoying if these special parts suddenly run out.
While the market mostly offers a limited number of old germanium transistors, SMD parts are normally available in a great number and for a longer time.

The sound

Regarding the sound, there are different opinions.
SMD parts mostly produce less hiss and have a more limited range of the variation of values. Therefore, all pedals of one batch will sound the same.
In my opinion, the sound of pedals with SMD parts is different to the sound of a pedal with a THT circuit board.
But for the higher tolerance regarding the values of THT parts, two pedals built up via true hole technology might sound completely different.
Regarding the sonic differences of Mythos effects with SMD or THT parts, there is a nice demo video on the internet. There you will find a comparison of two pedals that only differ in the respective technology of the used parts.

Alternatives

To be honest, I think, that some advantages of SMD parts (like costs, availability or the need for space) cannot be denied.
But the lack of the chance to repair a SMD circuit and the sonic character speak against SMD technology.
Thus, the combination of both technologies might be the answer.
Where ever the sound matters, manufacturers could use THT parts.
The protection circuit against electrical surge and reverse polarity of the power supply should also be built up with THT parts to facilitate a repair.
For everything that is relevant for the control (midi, LFO, switching) the manufacturers could use
SMD parts.
Thereby, you would get a high-quality pedal that combines the advantages of both technologies.