We had the opportunity to compare the circuitry, components, EQ response, and audio artifacts between our LHZ-01 and LHZ-02 preamps and a vintage HazLabs preamp (serial number 2029). We also had a KHaz clone and ran the same comparisons as well.
THE RESULTS
| Testing | Process | HazLabs S/N 2029 | KHaz |
|---|---|---|---|
| Circuit Wiring | Compare schematic against PCB traces. Passing grade indicates all components are connected in the same manner. | PASS | PASS |
| Component Marking | Compare component marking. Passing grade indicates stated values and types match or are functional equivalent. | PASS | PARTIAL |
| Component Values | Compare component values to marking. Passing indicates components match marked values. | PASS | FAIL |
| EQ Response | Visualize EQ when fully boosted and fully cut. Passing grade indicates unit exhibits the same EQ response. | PASS | FAIL |
| Audio Artifacts | Visualize audio artifacts. Passing grade indicates unit exhibits the same audio artifacts when preamp is driven hard. | PASS | FAIL |
We are happy to report the the LHZ is a component-level clone of the HazLabs preamp and exhibited the same EQ response and audio artifacts. The only variance was that the LHZ uses a 100uF power capacitor where the HazLabs uses a 33uF. This capacitor is strictly for the power supply and does not impact the audio performance.
The KHaz unit we tested had a several discrepancies in the circuity and operation:
- Used 1M voltage divider resistors instead of the 100k used in the Haz & LHZ preamps.
- An output resistor measured 6.8k but was marked as 100k. The resistor did not appear to be damaged. The low resistance significantly reduced the preamp output volume lower than the Haz &LHZ preamps.
- The KHaz used an 072D op-amp instead of the LF442CN used in the Haz & LHZ.
- EQ response was different. (This is likely due to mis-labeled capacitors as the wiring match the Haz.)
- Treble control was shelf to 20kHz instead of bell curve.
- Bass boost was approximately 3dB lower, and slightly lower range.
(This is likely due to mis-labeled capacitors as the wiring match the Haz.)
- Audio artifacts were different (likely due to op-amp used).
The differences in the EQ response of the KHaz is likely due to mis-labeled or failed capacitors as the wiring correctly matches the HazLabs preamp. The difference in audio artifacts is related to the use of the 072D op-amp instead of the LF442CN as used in the HazLabs as each op-amp responds differently when driven hard.
IMPORTANT: The observations about the KHaz performance is specific to the single unit we tested, and is not intended to be a blanket statement about all KHaz preamps. We are confident that if the KHaz were repaired using the same components found in the HazLabs, it would offer identical performance.