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Automatic Saturation Compensation (ASC — the Smart Audio Transformer Solution
Automatic Saturation Compensation (ASC) – the Smart Audio Transformer Solution
By Electro-Voice
Automatic Saturation Compensation (ASC) is a patented Electro-Voice technology that delivers outstanding audio performance from transformer-isolated loudspeakers on 70V/100V systems. ASC preserves lowfrequency performance while presenting a stable load to the amplifier – regardless of the number of loudspeakers connected in parallel. As a result, ASC-equipped loudspeakers – including subwoofers – sound virtually identical, whether they are used with a transformer or without. The video above and the article below give an overview of how it works.
The Problem:
As a drive signal increases, every audio transformer will reach a point at which its core begins to saturate, especially at low frequencies. When this happens, the load impedance can fall low enough to cause the amplifier to shut down or fail. When multiple loudspeaker transformers are connected in parallel, there’s an even higher risk that the impedance will drop so low that the amplifier just won’t work. When driven fully into saturation, a transformer is really no different than a dead short across your amplifier terminals.
A common industry practice is to use a high-pass filter with a cut-off frequency – nominally around 50 Hz – that affects the entire system. This reduces the risk of core saturation by blocking some of the low-frequency energy delivered to the transformer. And 50 Hz is low enough that it doesn’t affect perceived bass response for most types of music and in many applications. As more transformers are connected together, most manufacturers recommend higher cut-off frequencies to maintain amplifier stability. But a higher cut-off means less bass and less warmth in the sound.
TK-150 inserted via rear input panel
The Solution:
ASC takes a different approach by automatically inserting a high-pass filter with a variable cut-off frequency in each loudspeaker. The ASC circuit senses the low-frequency current in the drive signal and changes the filter cutoff just enough to keep the transformer from saturating. This gives you the warmth and fullness of a 50 Hz highpass with a level of amplifier protection that would otherwise require a filter set to 100 Hz.
ASC is a standard feature for all models in the new EVC series of fixed-install loudspeakers, and is optimized to pair with our high-quality TK-150 audio transformer. In addition to all EVC models, ASC is a standard feature on the transformer-equipped versions of the Electro-Voice ZX1i. The combination of ASC and the TK-150 makes it almost impossible to tell whether the speaker is connected through a transformer or not. And because the TK-150 is flat within ± a dB from 35 Hz to 20 kHz, you can even get full, rich sound through a transformer-isolated subwoofer.
It doesn’t matter how many loudspeakers you need to connect in parallel, ASC preserves the richness of your system’s low-end while keeping the load impedance in a safe range for your amplifiers.
