Viva Analog 360+


Viva Analog

I build a high-quality compact pedal version of the Acoustic 360 Bass Preamp. The unit is roughly 1" in height so the pedal will fit in most gig bags. The guts use robust amplifier-grade construction (Alpha 24mm Pots, Switchcraft JACKS, Lorlin, C&K, Carling Switches, ...) and the Variamp filter circuit is built using a great sounding audio-grade inductor custom-wound for me by Cinemag USA. The preamp costs $500US - this includes the AC adapter, a custom finish, and air shipping to US/Canada.

The Fuzz BLEND control is new and original in design, allowing fully independent mixing of fuzz and straight signals, the FUZZ bypass switching is also re-designed to minimize switch pop/noises. The fuzz circuit uses selected 2n1306 Germanium devices providing a fairly faithful reproduction of the 360 distortion qualities - and with the BLEND control any amount (up to x3 over-unity) of clean signal can be mixed in for a heavier and fuller sound.

On the inside there are two user adjustable trim-pots. The one near the center of the board sets the gain of the output amplifier. This needs to be set carefully since the output amplifier circuit can put out around 22volts (pk-pk) signal. The 360+ comes with an instruction sheet that describes how to best adjust this trimmer.

The pop-less MUTE function is achieved through an original constant-current optical switching design. Since class-A circuits are sensitive to sudden variations in rail current and typically passes on the variation as a click noise to the output it was necessary to devise a switching circuit that leaves the rail currents constant. The MUTE circuit has no effect on sound quality when disengaged.

The power supply circuit features an over-kill design that rivals battery operation in terms of noise/ripple output. The new PSU circuit combines passive and active filtering where the 60Hz and 120Hz components find themselves lying below the -96dbV threshold of my 24-bit soundcard (with gain full up); and that's when using an ordinary unregulated AC adapter.

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fx pedal stompbox stomp box guitar effects pedal amplifier amp amplification preamp pre-amp volume/amplification fuzz distortion/fuzz/overdrive dirt grit
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