ZOTL Pre One Audio Preamplifier


Pristine, Powerful, Advanced

The ZOTL PRE ONE is a stereo vacuum-tube single-chassis preamplifier that uses the output transformerless ZOTL technology (US Patent 5,612,646).

The ZOTL PRE ONE provides for five input sources plus one processing loop source. On units equipped with the optional RIAA phono stage, input number 1 is used as the phono input and there are four high-level inputs. Two main output jacks and one 1/4 inch headphone jack are provided. Except for the headphone jack, all audio connections are via single-ended RCA jacks. The ZOTL PRE ONE can be powered universally (100 V - 240 V) from the AC mains or from an external 12 V source.

As to the controls in the preamplifier, volume adjustment is via a 24-step switch that uses precision resistors. There are also separate eight-position step attenuator switches for each channel to allow balance adjustment. Source selection is made by a rotary switch or processing loop toggle. Other switches include mono, phase invert, and mute.

David Berning ZOTL Pre One

  • The ZOTL PRE ONE is equipped with Stillpoints TM OEM Universal Resonance Dampers. A unique wrap-around shield prevents undesirable signal bleeding from the controls or from the input/output jacks to the audio circuit board. Routine tube replacement on the ZOTL PRE ONE should not be needed with normal usage, and 10,000-hour lifetime should be expected.

    Other features and specifications include:

    • Dc-coupled line stage with dc offset null servo.
    • Dc output protection shutdown.
    • No negative feedback used in either the phono or line stage.
    • Non-magnetic chassis prevents skin-effect induced distortion.
    • Power consumption: 35 W ac powered, or 24 W dc powered (12 V @ 2 A).
    • Line voltage required: (universal) 100-240 VAC, 50-440 Hz.
    • Signal to noise, high-level stage, 20-20 kHz: 90 dB referenced to 1 V RMS input, unweighted.
    • Signal to noise, phono only, without MC step-up transformer: 60 dB ref. 10 mV RMS input @ 1 kHz, unweighted.
    • Signal to noise, phono only, with MC step-up transformer: 56 dB ref. 1 mV RMS input @ I kHz, unweighted. Transformer configured for 1:8 ratio.
    • Distortion, almost all 2nd harmonic: High impedance load ~ 0.5 % @ 2 V RMS output; 50 Ohm load ~ 2 % @ 1 V RMS output.
    • Maximum output: Hi-imp.- 5 V RMS @ 3 % THD; 50 Ohm- 2.5 V RMS @ 7.5 % THD.
    • Frequency response @ 2 V RMS output both High- imp load and 50-Ohm load: -0.5 dB at 20 kHz and + 0.2 dB at 20 Hz. Ref 0 dB at 1 kHz.
    • Output impedance: 50 Ohms.
    • High level gain: 12 dB maximum.
    • RIAA phono gain @ 1 kHz, no transformer: 48 dB. Additional 17 dB with transformer set to 1:8 configuration. 1:12 and 1:24 configurations also available.
    • Phono overload: 110 mV RMS @ 1 kHz no transformer. 14 mV with transformer (1:8).
    • High-level input impedance: 56 k? max, can be as low as 12 k? with balance attenuators set to minimum and volume control turned full clockwise.
    • Tube complement: (4) 12AU7 high-level stage; (2) 12AX7 + (2) 12AT7 phono stage.
    • Size: 42 cm wide, 33 cm deep, 15 cm high, (16.5 X 13 X 6 inches), including connectors and feet and knobs.
    • Net weight: 6 kg (13 lb); Boxed, 8 kg (18 lb).
    • Finish: silver anodize


  • Ships in approximately 1-2 weeks

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