ZRTN Speaker cable filters - AVAILABLE NOW

NEW - Zero Reflection Termination Network (ZRTN) for use with speaker cables, now available from DNM.

The DNM speaker cable ZRTN is a series and parallel design for use with DNM Stereo Resolution Speaker cable and DNM Stereo Solid Core Precision speaker cable.

Note : you can save £100 if you wish to part-exchange one pair of speaker cable HFTNs for one pair of ZRTNs - just buy the next product on this page.

We strongly recommend ordering your ZRTNs with two short cables (made up by DNM Design) to connect to your amplifier - these are shown as LINK CABLES below and versions with 2mm/ 4mm/ spade/ bare wire terminations are available plus a choice of DNM Resolution or Precision 2 cable. These link cables are soldered directly to your ZRTNs for the best connection quality.

The photograph at the top of this document shows how each speaker cable ZRTN of a pair is supplied by DNM Design.
The pair of ZRTNs is fitted with 4mm speaker sockets as standard but can be soldered directly to speaker cables ordered at the same time if this is preferred. Each ZRTN measures 29mm high by 85mm wide.

You need only one pair of ZRTNs for a normal amplifier but two pairs are needed for a balanced output amplifier - more details in the "Full ZRTN fitting and connection information" PDF linked below.

The ZRTN is series/parallel connected to the speaker cable - part of its network is in series with the cable and part is in parallel. This enables the ZRTN to precisely control the cable's termination impedance, eliminating external interference with the amplifier's feedback system. The ZRTN is purpose-designed to be fitted close to the amplifier and it gives a very substantial performance improvement.

The exploded view of the ZRTN PCB group above shows that it requires a complex assembly of parts to achieve very high performance filtering at very high frequencies.
When assembled the ZRTN boards fit together in a tightly packed stack of 4 layers which is 8.4mm thick.
The two inner layers are each 2.4mm thick double sided, thru-hole plated with gold plated surfaces and extra heavy copper. These boards are intricately shaped to hold the four 4mm sockets and accept copper inserts to enable 25 amp continuous current handling capacity.
The two outer layers are used as component covers, one of them takes six press-in 3mm self-clinch nuts that allow the whole assembly to be held together.

If AIRSURE shipping is available to your country (or Special Delivery in the UK), we strongly recommend using it when buying ZRTNs, for faster, tracked, more reliable delivery with better compensation for lost goods.


If in doubt about what to order (for example if you need an odd number of Speaker cable ZRTNs or if you are unsure about postage), please email DNM Design or use the Contact Us button at the top of this page.

Full ZRTN fitting and connection information
(Connecting just a pair of HFTNs initially)

NEW - Zero Reflection Termination Network (ZRTN) for use with speaker cables, now available from DNM including a part-exchange allowance for speaker cable HFTNs

NOTE : DNM recommend that customers with just 1 pair of HFTNs keep them and ADD 1 pair of ZRTNs (please see the previous product).

Customers who purchase 1 pair of the new ZRTNs are offered a £100 price reduction in exchange for the return of their other pair of DNM speaker cable HFTNs to DNM Design.

To take advantage of this offer, select the exchange ZRTN option (this product) and then return your other pair of speaker cable HFTNs using a secure insured postage method.

You need only one pair of ZRTNs for a normal amplifier but two pairs are needed for a balanced output amplifier - more details in the "Full ZRTN fitting and connection information" PDF linked below.
(Just one ZRTN is shown above but this product is always supplied as a pair.)

We strongly recommend ordering your ZRTNs with two short cables (made up by DNM Design) to connect to your amplifier - these are shown as LINK CABLES below and versions with 2mm/ 4mm/ spade/ bare wire terminations are available plus a choice of DNM Resolution or Precision 2 cable. These link cables are soldered directly to your ZRTNs for the best connection quality.

If in doubt about what to order (for example if you need an odd number of ZRTNs or if you are unsure about postage), please email DNM Design or use the Contact Us button at the top of this page.


Full ZRTN fitting and connection information

These short link cables (built with no construction charge by DNM Design as part of your ZRTN order) are plugged into your DNM PA3 or PA3S power amplifier using the included 2mm plugs (spring body type). The other ends are soldered directly into your ZRTNs.

It is possible to make up your own link cables but this would need twice the number of plugs and means another non-soldered joint in the path so we strongly recommend ordering these link cables instead.

This covers TWO linking cables so you just need to order quantity ONE for normal stereo use. (This applies to both normal and balanced amplifiers.)

These short link cables (built with no construction charge by DNM Design as part of your ZRTN order) are plugged into your amplifier using the included 4mm plugs. The other ends are soldered directly into your ZRTNs.

It is possible to make up your own link cables but this would need twice the number of 4mm plugs and means another non-soldered joint in the path so we strongly recommend ordering these link cables instead.

This covers TWO linking cables so you just need to order quantity ONE for normal stereo use. (This applies to both normal and balanced amplifiers.)

These short link cables (built with no construction charge by DNM Design as part of your ZRTN order) are plugged into your amplifier using the included spade terminals. The other ends are soldered directly into your ZRTNs.

It is possible to make up your own link cables but this would need extra 4mm plugs and means another non-soldered joint in the path so we strongly recommend ordering these link cables instead.

This covers TWO linking cables so you just need to order quantity ONE for normal stereo use. (This applies to both normal and balanced amplifiers.)

One end of hese short link cables (built with no construction charge by DNM Design as part of your ZRTN order) is plugged into your power amplifier. The other ends are soldered directly into your ZRTNs.

This covers TWO linking cables so you just need to order quantity ONE for normal stereo use. (This applies to both normal and balanced amplifiers.)

These short link cables (built with no construction charge by DNM Design as part of your ZRTN order) are plugged into your amplifier and your ZRTNs using the included 4mm plugs (8 off).

This covers TWO linking cables so you just need to order quantity ONE for normal stereo use. (This applies to both normal and balanced amplifiers.)

ZRTNs are always supplied with a pair of 4mm sockets at each end of the ZRTN.

If you use 2mm plugs with springy bodies to connect to your DNM PA3 or PA3S power amplifier, you will need to buy a set (quantity ONE) of these adaptors to connect your springy-bodied 2mm plugs into the ZRTN.
Alternatively, if you are happy to solder your cables, you could order 4 off 4mm LEAF plugs and solder these onto your speaker cables instead of the 2mm plugs - but that is a little more expensive.

Please note : these adaptors will NOT give a reliable contact if used with solid-bodied 2mm plugs, please see the adaptor below for use with 2mm solid-bodied 2mm plugs.

If the ZRTNs will need to plug into 2mm sockets in your amplifier, we strongly recommend ordering your ZRTNs with the optional short cables soldered to your ZRTNs and ending in 2mm plugs, this will cover your amplifier connections.

ZRTNs are always supplied with a pair of 4mm sockets at each end of the ZRTN.

If you use 2mm plugs with solid metal bodies to connect to your DNM PA3 or PA3S power amplifier, you will need to buy a set (quantity ONE) of these adaptors to connect your solid-bodied 2mm plugs into the ZRTN.
Alternatively, if you are happy to solder your cables, you could order 4 off 4mm LEAF plugs and solder these onto your speaker cables instead of the 2mm plugs - that is less expensive.

These more expensive adaptors are NOT needed (or recommended) if you use springy-bodied 2mm plugs, please see the adaptors above for springy-bodied 2mm plugs.

This version uses internal springs to grip plain SOLID-bodied 2mm plugs securely and so this more complex construction makes it more expensive. If you look inside the adaptor in the photo above, you can just see the internal springs needed to suit the solid-bodied 2mm plugs. (The comparable photo of the version for sprung plugs shows the plain internal construction.)

If the ZRTNs will need to plug into 2mm sockets in your amplifier, we strongly recommend ordering your ZRTNs with the optional short cables soldered to your ZRTNs and ending in 2mm plugs, this will cover your amplifier connections.