Zesto Audio Bia 120 Stereo Power Amplifier

Design Philosophy

With my pro audio background in the recording studio and live concert mixing,
I wanted to build an amp that allowed me to hear music the way I know it should sound.

I wanted it to be easy to use, reliable and with plenty of power to drive the speakers. In short, I wanted power without compromising the music.

Class A Design

The tubes are always on, so you have power when you need it. Class A is fast and responsive. There is no lag, providing your music more punch, transient response, better dynamic range and transparency.

Circuit Topology

I choose a Class A Ultra-linear, Push-Pull circuit design to deliver the most precise, enjoyable and faithful reproduction possible.

Unsung Hero

The unsung hero of a power amp is its power supply. That’s why my design incorporates a custom Toroid power transformer and a choke-based, dual-mono power supply to deliver all the “slam” you can handle.

Easy to use

With Auto Bias, you need no adjustments. It’s safe, consistent and the settings are always perfect so you can enjoy your music.

What is Bia?

In Greek mythology, Bia is the Titan Goddess of force and power.

Key Features

• Plenty of power to drive your speakers
• Pure Class A power is fast and musical
• 4, 8 & 16 Ohm taps give you options for your speaker preference
• Dual Mono gives you less crosstalk and better stereo imaging
• No adjustments with Auto Bias. Its safe, consistent and settings are always perfect
• Provides enough gain for most standard preamps and accommodate most speakers
• Choice of either Single Ended RCA or Balanced XLR to suit your needs or cable preferences
• Transformer balanced XLR input offers true noise rejection and isolation from the preamp
• Left and Right ground switches on the XLR balanced inputs to help eliminate ground hums
• No Negative Feedback provides for virtually no compression to your music
• Custom Toroid provides lower noise with plenty of available power
• The global mains power supply can work all over the world
• KT120 compatible
• Push-Pull circuit design gives you more power
• Ultra-Linear circuit design provides lower distortion
• Low noise levels allow really dark black quiet musical passages
• Non-inverting polarity retains the same phase as the input (so your trumpets blow and don’t suck)
• Gold pin sockets are more reliable because gold doesn't oxidize when it heat cycles
• Matched quad output tubes retain the stereo balance
• It’s ready to enjoy with 50 hours of factory burn in on all circuits and vacuum tubes
• Elegantly designed, heavy duty 14 &16 gauge zinc plated steel enclosure
• Each unit is hand built “Made in the USA”
• The wide frequency response allows you to hear the finest passages in your music
• High-quality gold-plated RCA, XLR connectors and 5-way binding posts
• All fuses are easily accessible

Specifications

Output

• Pure Class A
• 60 Watts per channel
• 4, 8 and 16 Ohm output taps
• 8, 5 and 4 Amp Slow blow fuses for outputs
• Eight 5 way binding post
• Non inverting output polarity
• Push-Pull and Ultra-Linear design

Inputs

• RCA single ended inputs Left and Right with an impedance of 100K Ohms
• Transformer floating XLR balanced inputs Left and Right (pin 2 hot)
  with an impedance of 12K Ohms
• Independent ground lift switches on left and right balanced inputs
• 2 Volts RMS input to reach rated output

Detailed Specs

• Dual Mono
• Auto bias
• No negative feedback
• Frequency response 20Hz to 50Khz ~ 2db
• Total Harmonic Distortion ~ 0.22% at 1W output into 8 Ohms
• Gain of 23dB
• Noise level > 0.2 mV RMS into 8 Ohms with input shorted
• 1% metal film resisters throughout
• Polypropylene capacitors throughout the audio path

Power

• Custom Toroidal power transformer with global mains
• Choke based power supply design
• 120 Volts AC mains
• Optional factory installed 220V, 230V, 240V 50/60Hz
• Power consumption at rated output 300 Watts
• On/Off switch conveniently located on front panel
• 3 pin IEC power connector with fuse

Active Components

• Matched quad set of four (4) KT88’s vacuum tubes
• Four (4) Gold pin ECC82s (12AU7) vacuum tubes
• High quality gold pin ceramic sockets

Other Features

• Each unit is made by hand
• 50 hour factory burn in on all circuits and vacuum tubes
• Dimensions 17″ W X 20″ D X 10 ” H
• Weight 66 lbs. (30Kg)
• 16 and 14 gauge Zinc plated steel enclosure