Vox AC4 Hand-Wired Guitar Amplifier
In the search for the essence of the classic vintage AC30 amp sound, we conducted a detailed analysis and study on mint condition AC15 and AC30s from the 1960s to truly uncover and understand the inner workings of these legendary amplifiers. The culmination of these efforts has resulted in the emergence of the new VOX AC Hand-Wired Range of amplifiers: the greatest VOX amps we have ever produced.
The rarity of vintage amplifiers contributes significantly to their high value, but equally impactful is the distinctive sound inherent in vintage amps. Despite the AC30 being manufactured with nearly identical circuitry since the 1960s, the character of vintage units is often described as being almost beyond description, possessing a rich and musical quality that i s equally unmistakable and mysterious. We aimed to unravel the secrets of this sound, bringing the vintage magic to the musicians of today.
The Hand-Wired series reproduces the vintage VOX tone through meticulous research. A diverse lineup caters to the individual preferences and needs of discerning guitarists. The series includes a AC4HWR1 compact combo amp, designed for lower output use.
1. Searching for the classic VOX Vintage Sound
1.1 Revision of the Power Supply Circuit
Contemporary power supplies aim for stability by minimizing voltage fluctuations, resulting in a reliable power source. In contrast, vintage amplifier power supplies exhibit fluctuations that respond to the large movement of speakers, giving the distinctive “compression” and “sag” sensations associated with vintage amps. In our research, we measured the power supply circuit of many vintage AC30s and used these to help design an entirely new power supply to replicate these vintage tone and performance characteristics.
However, merely mimicking the vintage characteristics can lead to the generation of undesirable tones, particularly”ghost notes”–extraneous pitches unrelated to the actual played notes especially at high volumes. Faced with the dilemma of prioritizing sound quality or addressing ghost notes, the previous AC30CC2 model incorporated a switch to toggle the power supply’s smoothing circuit. With the newly designed power supply circuit, the new VOX Hand-wired amplifiers address ghost notes without compromising sound quality and responsiveness, navigating the delicate balance between the two considerations in a truly musical way.
1.2 Output Transformer
The output transformer contributes significantly to the classic vintage VOX sound. Even if the specifications are the same, saturation distortion in the transformer section can add to the pleasant harmonic components of vintage amplifiers. However, as this distortion cannot be precisely measured by the specifications of the transformer, we embarked on a program of extensive prototyping to develop custom transformers with the essential vintage sound characteristics required
1.3 Cabinet
We carefully examined the thickness of the materials used, as the vintage AC30 employed slightly thinner cabinet materials, contributing to a rich and expansive midrange. Our new cabinet design employs the same thickness of material as the vintage amp, helping to deliver a faithful sound reproduction.
2.Practical Features
While it was important to get as close as possible to the specifications and sound of the 1960s models, our approach was to maintain simplicity while incorporating practical features for contemporary guitarists.
2.1 Spring Reverb
In contemplating what could enhance the immersive quality of a guitar amp, a very high-quality spring reverb unit was considered a “must-have” to achieve that magic vintage sound.
2.2 FX Loop
Modern guitarists love to combine various effects to create their individual sound. However, issues can arise when combining distorted amps with spatial, modulation, and pitch-shift effects. Distorting these effects can muddy the sound. To address this, an FX loop was integrated, allowing for a clean output of effects.
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