HiZ (MkII)

... impedance converter for electric guitar/bass & passive Piezo elements

A HiZ should be in every guitar case, where a passive pickup can come into play ...


   ... Front      ... Back  HiZ Back

The impedance troubles  ...

Whoever tried to connect an electric guitar with passive pickups to a low-impedance input (e.g. PC, Line-/Aux input of HiFi equipment,...) has experienced these troubles:

  • hazy basses
  • powerless mids
  • trebles without any brilliance

A low-impedance input will simply cut down the "fragile" signal from high-impedance outputs of passive pickups in electric guitars/basses or bare (passive) piezo elements in acoustic guitars.

By interconnecting an 'impedance converter', that provides a high-impedance input for the passive pickup and can drive the current on the output side, that a low-impedance Line/Aux input needs, then the world will be in order again for the passive pickups:

  • crispy basses
  • powerful mids
  • brilliant trebles

HiZ is such a device  ...

An HiZ is equipped with high-grade operation amplifiers (Burr-Brown "SoundPlus" with JFET inputs), that provide exceptional slew rates and extremely low distortion and are therefore also used in high-end HiFi equipment. The characteristics of the JFET inputs are similar to those of tubes thus providing a 'silky' sound characteristic.

Instead of cheap replacement circuitry a high-precision rail splitter from Texas-Instruments provides an exact 'virtual ground' to the circuit.

Burr-Brown "Soundplus" Features
  • Superior Sound Quality
  • Ultra Low Distortion: 0.00008%
  • Low Noise: 8 nV/√Hz
  • True FET-Input: IB = 5pA
  • A high slew rate of 20V/µs
  • Operation voltage down to +/- 2.5V

With a typical output amplification of 1:2.5, the input level from the instrument is lifted, so that even less sensitive inputs can be served well. A HiZ is for that concern also a level shifter to some extent.

An internal 'booster' can be geared to the output signal to push up the output signal's slew rate and lift the corner frequencies. That doesn't make the output louder - but gives a little 'freshness' and 'pinch' in the output sound characteristics.

HiZ Booster small

HiZ has a usual 9-volt accumulator built-in that you can use simply without any power supplies everywhere you need it. To load the accumulator any 12V/DC power supply with a 5.5/2.1mm power jack (ground outside!) can be used. HiZ is delivered without a power supply so you can use one which you already have. If you do not have such a power supply you can find one under 'accessories' in the shop. The accumulators we use on delivery are so-called "Ready-to-Use" (R2U) accumulators which have a significantly low 'self-discharge' and the load lasts a long time if the device is turned 'off' - maybe in your guitar case ...

HiZ deliberately abstains from an operation LED, since even a low-current LED would pull more power from the accu than the entire circuit does when turned 'on' - that's for the benefit of the operations time of the accu. The 'degressive' load circuit gets the accu within an hour to its nominal voltage which is enough for 2-3 hours of operation in a concert or the studio with accu operation and minimal load. The used operation amplifiers from Burr-Brown work stable down to a voltage of 5 volts (+/-2.5V)

After reaching 'nominal voltage' the load current for the accu turns to 'smooth loading' for the benefit of the accumulator's lifetime. The accumulator -practically- cannot be overloaded, so you can have it continuously loading for days, weeks, months, or even constantly. The green "Bat." LED shines brighter than the red LED (which just indicates "power supply connected") if the accumulator is nearly fully loaded. This state takes ~3..4 days to be reached while 'smooth-loading'. The operation time is ~8..12 hours of permanent use if the accumulator is fully loaded - and even far more, if running idle with no input signal.

With a car adapter (instead of a stationary power supply) the device can be loaded while driving your car or in the tour bus, which has a 12V board socket.

Like all devices from musIC, the HiZ also sits in a tremendously high-quality aluminum enclosure. These enclosures can withstand even the roughest circumstances on stage.



Since October 2019, HiZ will be delivered in the HiZ/MkII variant with the following features:

  • Polarity protection "PolProtect"
  • Under-voltage control

Polarity protection - "PolProtect"
With "PolProtect", there is no longer a need to worry about the polarity of the power supply. It is sufficient to adhere to the specification 'DC voltage 12V/250mA (min.)' - regardless of how the '+' and '-' are connected on the power supply plug. This means that HiZ does not simply block power supplies with incorrect polarity, which would only prevent the destruction of the device, but still make it impossible to use the power supply with the wrong plug polarity. PolProtect internally sets the plug polarity 'correctly'. This makes the plug polarity irrelevant, and individual power supplies or "daisy-chain supplies" for effect pedals (9 Volt; outer tip positive; so-called "Boss circuit") can even be used. HiZ still works perfectly even with a 9-volt input voltage.

Under-voltage control
As a mobile impedance converter, HiZ is operated with a "Ready-to-Use" (R2U) NiMH accumulator, making it no longer dependent on a power outlet for a power supply.

During the accumulator charging process, the internal Degressive Charger prevents overcharging of the accumulator, even if the charger is left connected for a long time or even constantly. Degressive charging means that as the charge increases (and thus the terminal voltage of the accumulator), the charging current is continuously reduced until it finally becomes zero when the terminal voltage of the accumulator reaches the charging voltage of approximately 10.6V. This effectively prevents overcharging of the accumulator.

In addition to overcharging, deep discharge of a NiMH accumulator can also severely and irreversibly damage it. This is manifested by the accumulator reaching an adequate voltage during charging, but no longer delivering any current during use.

A 9V (8.4V R2U "Ready-to-Use") accumulator should be considered "depleted" at around 6.8V and should not be further discharged through continued use, as this could lead to deep discharge. With HiZ/MkII, 'under-voltage control' automatically cuts off the current draw rapidly when the accumulator's terminal voltage drops below 6.6V in 'battery operation mode'. This effectively prevents deep discharge and keeps the accumulator's lifespan at a normal extent.



  • Power supply 12V/250mA/DC with power jack 5.5/2.1mm
  • Adapter cable 6.35mm (1/4") socket to 3.5mm jack (Mono)
    [For microphone inputs on a PC - or other LINE inputs with a 3.5mm socket]