Let’s begin by discussing the similarities between the two Whitestone P331 models available, the standard model and the EVL version. Just like the original Whitestone P331, the Whitestone P331 EVL version also utilises digitally controlled analogue components for all controls. The precision of left/right coherence remains unchanged and intact.
The solid-state output amplifier, which is fully-differential, remains consistent across both versions. The LIFT circuit, present in both units, is identical as well. However, it’s worth noting that the harmonics generated by the LOADING section impact the frequencies affected by the LIFT circuit. Consequently, the LIFT feature on the Whitestone P331 EVL might exhibit differences in sound compared to the original P331.
The fully differential tube LOADING amplifier in the EVL starts from a notably distinct starting point. Although the LOADING control serves the same function as it does in the original P331—regulating the operational state of the 6SN7 tube—it’s subjected to more aggressive manipulation right from the outset. It’s important to clarify that this isn’t akin to the distortion found in a guitar amplifier; the manipulation maintains its appropriateness for mastering purposes. The alteration results in a distinctive and more prominent “feel” compared to the original Whitestone P331.
The area of greatest divergence lies within the XFORMER section. In the Whitestone P331 EVL model, considerably greater current is directed towards the transformers, significantly driving them into deeper saturation. This modification yields a heightened presence in the lower frequencies, delivering increased force and impact without sacrificing clarity or becoming muffled.
To achieve genuine amplifier excellence, a foundation of pristine, clean power is imperative. In the case of the P331, its linear power supply emerges as the paramount element for upholding audio integrity, ranking closely alongside the inherent gain structure and circuit configurations within the amplifier. Operating as the vital backbone, the high-voltage plate/anode tube power supply commences at approximately 320V DC.
This power is meticulously refined through multiple stages of filtration (up to six times), accompanied by active regulators. Notably, the integration solely involves film capacitors and authentic inductors (chokes) that meticulously expunge disturbances, ripples, and noise from the realm of high-voltage power provisions.
The LOADING circuit constitutes an integral component of the fully differential (balanced) Class-A tube amplifier. Its purpose revolves around guiding an audio signal to interact with different points on the response curve of the tube. As the signal progresses through the tube, the gain incrementally diminishes in a uniform manner. This strategic attenuation contributes to maintaining a delicate equilibrium between audible level changes, preventing substantial gain fluctuations or losses. This preserves the ability to assess the impact of tube enhancements without dramatic alterations in volume.
Two distinct operational modes govern the LOADING circuit:
- “CLEAN” Mode = Feedback Mode – This mode leverages feedback manipulation to influence internal tube gain, introducing nuanced non-linearities and harmonics of even order.
- “BLOOM” Mode = Feedforward Mode – In this mode, the manipulation of plate loading comes to the fore, impacting internal tube gain along with slightly less overt non-linearities and even order harmonics.
The Whitestone P331 operates on a foundation of entirely digitally controlled analogue architecture. Every individual parameter can be replicated with utmost accuracy and can be retrieved using front-panel rotary and toggle switches, which oversee a comprehensive array of over 80 impeccably sealed precision relays. The audio route to the P331’s front panel is void of any audio transmission, and the audio pathway exclusively incorporates the highest-quality components available.
