A Perceptual Evaluation of Audio Transformer Colouration

This paper explores the perceptual impact of audio transformer colouration, a phenomenon often described anecdotally as "warmth," "fullness," or "smoothness" by audio professionals. Despite these widespread subjective perceptions, empirical evidence supporting such claims remains largely anecdotal. We implemented a rigorous controlled listening experiment comprising of a double-blind triple-stimulus with hidden reference method where listeners were asked to identify audio stimuli passed through a Lundahl LL1582 transformer stage. Eleven subjects participated in the tests, with each test comprising 12 repetitions of each condition (15 samples/conditions) per subject, distributed across four sub-sessions, resulting in 45 trials per session and a total of 180 trials per subject. Results indicated that whilst transformers can introduce measurable objective differences such as total harmonic distortion and phase change, the perceptual impact of such variations is generally imperceptible to listeners. Notably, only stimuli with lower spectral weighting were detectable, therefore the perceptual impact remains minimal and is largely programme dependant.