"Sound is a mechanical wave that is an oscillation of pressure transmitted through a solid, liquid, or gas, composed of frequencies within the range of hearing."
The act of producing these oscillations is degraded over the distance or medium it must travel to before it is received by the end receiver (in most cases, an eardrum). This is how we perceive sound over distance.
If one wishes delay, suspend or archive the sound for later listening, much effort is required to keep the original sound "signal" as true to the source as possible. The holy-grail is to be able to playback that suspended signal with as least distortion as possible. One could get close to a zero distortion system, but that would be physically impossible.
This project is a comprehensive understanding of signal processing with audio and component level analog electronics. The goal was to develop a line pre-amplifier to accompany a long-playing phonograph machine to attempt the zero distortion playback goal. For the amount remaining distortion in this goal, vacuum tubes are selected over MOSFETs to help manage even order harmonics to produce a more "natural" result with the remaining distortion at hand.
Utilizing performance high-gain triodes in a Mu-Follower 2-stage Full Class-A operating system with a separate power supply caged in a Faraday cage grade copper interior, this arrangement will provide a signal gain of 370 to bring the phonograph cartridge output signal up to an audible level for listening with the least amount of distortion introduced with the quietest sound floor available.
Left and Right channel input signals symmetrically enter the amplifier furthest from the power supply to minimize EMI clouding. High current heater lines are isolated from the High voltage B+ rails and are arranged to have the least amount of electromagnetic coupling with the signal lines.
This completed amplifier functions appropriately. Power Cable is handmade.
The above slideshow shows the CAD involved for the component level design arrangement. In small signal amplification, component and wire arrangement is critical. Inductance coupling from "noisy" sources such as transformers and RFI are one of the largest causes of signal degradation so extra care is taken to design the most appropriate layout to eliminate as much signal to noise interruption as much as possible.
This layout partitions the stabilized high voltage rails and valve heater lines from all signal side processing by distance as well as using a large copper ground plane to help further drain extraneous EMI to ground. Also important to eliminating an unwanted sound floor is designing an appropriate grounding configuration. Taking advantage of the "star-grounding" scheme as well as the popular "ground plane" technique, cathodes of each stage are grounded hierarchically to keep heavy output stages and power supply ground currents from interrupting the more delicate low-level input stages.
Once the component hierarchy arrangement has been defined, CAD could be utilized to help layout the components in the most organized, clean, and easy to access as possible given the limited space. Although the majority of the finished product is sealed closed, the beauty in the design will make general maintenance in the future logical.
