HiZ Pre
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The "Vacuum"
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Acoustic Instrument – Tube Preamp – EQ – Active D.I.

The HiZ Pre is a vacuum tube driven active direct box with a Baxandall two-band equalizer. 

There are two versions of the HiZ Pre, Guitar or Bass w/ the equalizer tuned for:

  • Guitar/Violin/Cello with a center frequency at 1kHz
  • Bass Guitar/Bass Viola with a center frequency at 500 Hz

1st and 2nd production runs sold out!!!

Hi Z Pre and HiZ Pre Bass are discontinued due to being too busy with a great daytime gig. 

We have the raw materials to build a few more.   Please contact us if necessary. 


  • ¼ inch input jack w/ultra-high input impedance
  • 12AX7 vacuum tube preamp for warm harmonically rich sound
  • 2 band Baxandall shelving equalizer
  • Input signal clip indicator
  • Output volume control
  • Power switch and indicator (to preserve tube life)
  • Balanced XLR output
  • Unbalanced buffered ¼ inch jack output

Hear the HiZ Pre difference

The HiZ Pre unlocks the frequency response of an acoustic-piezo electric instrument by coupling the guitar into your PA or amplifier.  The ultra high input impedance provides a very low noise floor and preserves the full bandwidth and bass response of a piezo element pick up.  The shelving equalizer enables ultra clean boost or cuts of treble and bass frequencies. The buffered output allows simultaneous drive to a stage amplifier and a balanced XLR input on your console or mixer.

Hear the wood of your acoustic instrument!

Produce ultra clean recordings of your guitar, bass, or stringed instrument...piezo or magnetic pickups!

See the HiZ Pre difference

The HiZ Pre is constructed of heavy duty 16 gauge steel. The chassis is finished in a scratch resistant, textured powder coating designed to combine an eligant look that withstands the wear and tear of a working musician.  The HiZPre rugged construction takes abuse while performing to specifications.

2 Band Shelving Equalizer

The 2 band HiZ Pre shelving equalizer boosts or cuts frequencies independently above and below the center frequency.  The standard model has a center frequency of 1 kHz, while the bass model has a center frequency of 500 Hz.

The standard model plot below shows the frequency response of the bass (left side) and treble (right side) frequency bands.  The bass and treble act independently on the frequency bands below and above the 1 kHz cut-off frequency to boost or cut up to +/- 20 dB.  A mid-range boost can be accomplished by cutting both the bass and treble to below 0 dB.  A mid-range cut can be accomplished by boosting both the bass and treble to above 0 dB. 

HiZ Pre Front Panel Controls

Hi Z input – High impedance input matched to piezo electric elements such as undersaddle and soundboard transducers.

Bass –  Sets low frequency shelving equalizer gain to +/- 20dB.

Treble – Sets high frequency shelving equalizer gain to +/- 20dB.

Clip – Monitors the instrument input and indicates the input is being driven with a signal that is too hot. The clip indicator has been finely tuned to illuminate when the input signal level reaches an amplitude that may cause the harmonic distortion of the output of the HiZ Pre to reach an undesirable level. This is particularly useful for instruments which have an integral battery powered pre-amplifier.

Volume – Sets the output level. Ideally, set this to the maximum level before clipping the input to the console or mixer, while minimizing the input gain of the console or mixer.

Power – Power switch.

Power Indicator – Indicates the unit is powered on.

HiZ Pre Rear Panel Connectors

Unbalanced output – Buffered ¼ inch output to drive a monitor or stage amplifier.  The buffer allows both the 1/4 and XLR outputs to be used simultaneously without loading down the output stage of the HiZPre. 

Balanced Output – XLR output to couple to a console or mixer. Use this for highest quality sound and for long cable runs (through a stage snake for example).

Power Jack – Connect the 16VAC, 1000mA wall transformer.

Download the User Manual


HiZ Pre User Manual

HiZ Pre 2U Rack Mount Kit (Holds 2 HiZ Pre units)

Example with Rackmount Case:

The HiZ Pre Rack Mount accessory allows two HiZ Pre units to be rack mounted side-by-side in a 19" equipment rack or case.  The Rackmount kit includes everything to mount the HiZPre into a studio rack or road case: 

  • 1 Each, Rackmount plate
  • 4 Each, Clip nuts
  • 4 Each, Washers
  • 4 Each, Screws
  • 5 Each, Mounting screws