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The ZMX is an automatic impedance matching device for the KHE ACS Amp/Cab Switchers. It is designed to eliminate impedance mismatches between the amps and cabs in the KHE ACS system (speaker-level signals). Automatically, safely, and transparently.  

The ZMX is designed specifically for the KHE ACS and does not work with other amp switchers or without an ACS.

How it works:

To match impedance, the ZMX uses a custom auto-transformer (single-phase transformer with multiple impedance taps). The transformer taps are switched by a relay matrix, according to the programmed impedance values. Example: If you have an 8Ω amp with a 4Ω or 16Ω speaker cabinet, the ZMX will automatically transform the impedance, so both the amp and cab are matched. It can even match uneven values like 5.3 / 3.2 / 2.6 Ω. The ZMX auto-transformer is custom-made in the USA, rated for 150W RMS, and built for the highest quality and pure signal integrity.

Connection & Setup:

The ZMX connects to the ACS Attenuator Loop, between the amp outputs and the speaker cabs or load boxes, using speaker cables. The ZMX has no power adapter. It gets phantom-powered by the ACS, by connecting it to the ACS CTRL IN port with the included DIN-5 cable. This connection provides phantom power for the ZMX, and enables the units to communicate together to exchange commands and status via CAN Bus. Attenuators can also be used with the ZMX—see the attenuator section in this manual for details. 

Impedance Programming:

During the initial setup, the ZMX is programmed with the impedance value for each amp and cab on the ACS. Once programmed, the ZMX automatically matches and compensates for any impedance mismatch. The ZMX constantly communicates with the ACS and checks which amp and cab are active. Whenever amps or cabs are switched on the ACS, the ZMX automatically selects the correct transformer tap for perfect impedance matching.

Impedance Values:

For each amp or cab on the ACS, the ZMX can be set to 16 / 8 / 4 / 2 Ω. The ZMX can also handle all uneven impedance values (like 5.3 / 3.2 / 2.6 Ω) that occur when running two mismatched cabs in Dual-Cab mode. Simply put: never worry about impedance again.

Bypass Modes:

The ZMX can be manually bypassed by the BYPASS button. This completely removes the ZMX from the signal chain. It also has an automatic bypass mode, which bypasses the ZMX if the amp and cab impedance already match. It also had an automatic bypass mode for transistor amps, and manual impedance control modes.

Compatibility & Safety:

A single ZMX can be used with up to 15 linked KHE ACS switchers. The ZMX works with any mono amplifier: tube, solid-state, or class-D (including bridged-mono), and supports all load types (reactive and resistive). It’s built in a robust steel enclosure and includes rack-mounting brackets for easy rack installation (2U). The ZMX is completely safe to use: It ensures there is never a «no load» scenario for the amps and automatically switches a temporary load during switching. The ZMX is extremely transparent and preserves the amp’s tone and dynamics (use the bypass button to hear the proof).

Do you need the ZMX?

If you use multiple amps and cabs with different impedance values, the ZMX is the ultimate solution for automatic and reliable impedance matching. If your amp and cab impedances already match, or if you are happy with a mismatched setup or prefer manual cable plugging, the ZMX isn’t necessary. If you use an active attenuator with solid-state power amp, such as the Boss TAE Core or Two Notes Reload II, matching the speaker cab is to it is not required as those units work universally with all load values. If unsure, send us a message. See the ACS Impedance Guide for alternative solutions: www.khe-audioelectronics.com/impedance-guide

IMPORTANT NOTES

• The ZMX is designed exclusively for use with KHE ACS Switchers and is phantom-powered via the ACS CTRL INPUT port. It does not function as a standalone device and cannot be used with other amp switchers.

• The ZMX is compatible with all KHE ACS-Series switchers that have the CTRL IN port. If unsure, send a message.

• The ZMX is not a load box for silent recording. It requires at least one speaker cab or load box as a load device.

• When using attenuators, the ZMX can only match one side of the attenuator.

SHIPPING & DELIVERY

• Payment: Credit Card or PayPal in CHF (Swiss Francs). For Bank Transfer (IBAN), send us a message.

• Stock units are usually shipped within one or two working days

• Price excluding VAT. Import charges may apply for the customer on import.

• Shipped from Switzerland (non-EU)

• Worldwide shipping available (check the shipping costs during checkout)

• Shipping Delivery Time: USA 2-5 days, EU 5-8 days (UPS Express)

• The shipment is fully covered by insurance.

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