Short Battery Life Fix: GREEN Rev 1.6 LHZ Preamps

We have received a small number of reports from users indicating that their battery life is extremely short. In normal use, with the bass unplugged when not playing, a 9-volt battery will typically last a year or longer. In these cases, batteries would be depleted within days or weeks.

CAUSE OF BATTERY DRAIN: Certain installations can bypass the ground switch in the barrel jack by shunting the negative battery power via a the control cavity walls lined with foil or highly conductive cavity paint. If the cavity walls are sufficiently conductive and the volume and/or blend pots have grounded housings, battery ground can be picked up by a potentiometer to completing the circuit so the pickups are always under power regardless of the jack being plugged in.

RESOLUTION: The resolution is to swap the RING and SLEEVE wires on the output jack on the GREEN Rev 1.6 LHZ-01 and LHZ-02 preamps.

TECHNICAL DISCUSSION: The LHZ, like most active preamps, relies on the RING connector in the barrel jack to act like a switch so that power is only supplied to the preamp and pickups when a standard guitar jack is inserted as shown in the following diagram:

The LHZ preamp has 3 output pads marked as “T R S” to indicate connections to the barrel jack. On the initial run of preamp boards (GREEN circuit boards marked as “REV 1.6”) the R and S markings were inadvertently transposed. This results in the battery negative being connected to the SLEEVE (S) instead of the RING (R) terminal.

If the cavity lining is sufficiently conductive (eg. using a foil liner) the SLEEVE (S) connection will carry the battery negative to a grounded potentiometer complete the circuit, effectively bypassing the switch.

GREEN REV 1.6 REMEDIATION: The current LHZ-01 and LHZ-02 installation manuals for the GREEN Rev 1.6 preamps have been updated to show the R terminal from the LHZ connected to the SLEEVE (S) terminal on the barrel jack, and include a red warning drawing attention to the reversed connections as shown below:

We have updated the printed circuit board with corrected printing, and have transitioned to the new boards in late September 2023. The new boards are BLUE and are marked as Rev 1.7g.

To reduce the potential for confusion, the BLUE Rev 1.7g boards have a separate installation manual that shows the correct wiring and does not include the red warning text. The website was also updated so visitor first select their board version (GREEN Rev 1.6 or BLUE Rev 1.7g) to get to the the appropriate installation manual for their preamp.

IMPORTANT: There is no functional difference between the BLUE and GREEN preamps aside from the printing correction. The circuit is the same, and the components are the same.

APOLOGIES AND APPRECIATION: This project has been a journey of learning as the LHZ was never intended to be a commercial product. With the amazing feedback and suggestions from our users, we have streamlined the packaging, options, and vastly expanded the installation manual. We’ve also learned what it takes to support a business, and have relied on our long-time clients for their feedback and guidance along the way.

The simple truth is that the misprinting was a simple oversight, not much different than a typo in a document or email. The acronym TRS has a couple distinct meanings in electronics. One TRS meaning is TIP / RING / SLEEVE for wiring cable connectors. Another TRS meaning is TRANSMIT / RECEIVE / SEND for communications lines. I was thinking in terms of the second example when designing the board, but created the early Installation diagrams assuming TIP / RING / SLEEVE.

Unlike a typo, it takes a lot more work to correct a printing mistake on a circuit board! It is my hope that quick individual responses, updating the manual with corrected wiring, and making this information readily available will help existing users who are potentially impacted find quick resolution.

I sincerely appreciate everyone’s patience and communication as we identified the root cause and set out to solve it!