Point To Point vs PCBs In Tube Amps

FAQS with The Amp Doctor

We often hear of the pros and cons of constructing tube amps with either Point- to-Point (P2P) wiring techniques (Tag or Turret boards) or with printed circuit boards (PCBs). So, which is better? Does P2P make a superior sounding tube amp? What if we constructed two amplifiers with the same schematic and same tubes, speakers, and other components, but one using P2P and the other using a PCB? Would they sound different? To be honest, I don’t think there would be much difference.

So why use P2P if there is no significant advantage in sound? Well, we are dealing with tubes that are, let’s face it, outdated, inefficient, oversized and power hungry, and require an external power source just to turn them on! But, they just happen to sound fantastic, and they look good too - so, we keep using them. Tubes need to be plugged into sockets mounted onto a chassis along with usually three, rather large transformers, some pots, sockets, and switches. Components like resistors, capacitors, diodes etc. can be mounted on simple tag board as used in earlier amplifiers and boutique amps today. Compared to solid-state amplifiers that have a much higher component count, constructing them on tag boards would be too laborious and costly so a PCB would be a better choice.

 

P2P is a very reliable construction method, and also figuring out the schematic for repair is a lot easier because the circuit is pretty much laid out in front of you. However, in construction, each component has to be individually placed on the board and hand soldered which is time-consuming. One disadvantage of some P2P tube amps’ designs is from an electrical point. You have a circuit (wires, components, etc.) that runs back and forth all over the chassis. Therefore, careful wiring and placement of components is critical. Hav- ing many stages like this can pick up hum and noise and could also be prone to self- oscillating if correct wiring techniques are not used. Therefore, PCB designs have an advantage over this type of P2P construction due to the circuitry being located in a smaller area. The tighter construction of a PCB decreases the need to run wires all over the chassis, therefore, keeping all con- nection to and from the tube and other comps as short as possible. The result is a circuit that sounds great with low noise and is very stable and not prone to oscillation. I use PCBs when constructing complex multi-stage and multi-channel amplifiers that have a greatly increased component count, and for simpler amps I use P2P turret boards.

 

We often hear of the unreliability of PCB designs, and this is true only to a certain extent. Single-sided PCBs, (tracks on one side only) that are wave soldered are the worst offenders. It is common for the wave sol- dering machine to skimp on the amount of solder required for larger components, and over time these solder joints break and the amp fails due to the lost connection between that component. Double-sided PCBs have tracks on both sides of the board that connects from side to side with plating through the holes where the component leg is inserted. Because of this, when soldered correctly over the same wave-soldering machine the PCB will have very reliable solder joints. One of the main reasons manufacturers started to use PCBs was to build a more cost effective product because PCBs by and large are much easier to assemble. However, as part of the cost-saving measures, the qualities of the other components in the amplifiers were compromised. This cost saving measure resulted in an overall lack of quality compared to the earlier style amps where the emphasis was more about tone than cost, and many of them also happen to be P2P wired. 

Comments