ZERO DC Block technology – stops DC from getting into your amplifier and eliminates amplifier transformer hum.

Tom Evans who makes very nice phono stages made the following astute comment:
A rumble filter simply adds to the bass cut making your already “cut” records sound bass light. Plus, it “time-steps” the bass in relation to the higher frequencies (where our hearing is most sensitive) so much so it can confuse the ear into believing the bass is playing out of tempo.
Since the very first iPHONO launched in 2012, we have used our own in-house ‘Subsonic Filter’. It made it into the iPHONO2 and the iPHONO3 and now, the ZEN Phono which is the very first time this filter is seen in such an affordable price level.
As there is only minimal vertical modulation remaining at very low frequencies with an an actual cut LP that is playable, we know that “vertical modulation” at low frequencies must be warp.
So we designed a filter to take advantage of this.
This is not artificial but real knowledge. By understanding fully how LPs are cut and replayed, it is possible to filter record warp strongly without at the same time attenuating low bass or adding group delay.
If you have a mechanical hum, deploy the DC Blocker.
Many large amplifiers have a really annoying mechanical hum (emitted from the toroidal transformer itself).
You can hear it when you place your ear close or next to the chassis.
This is caused by a small amount of DC voltage in the mains which makes its way through to the mains transformer, it will become ‘saturated’ and start to hum like a trooper.
The DC Blocker is a clever device that you place at the IEC (at the rear power inlet) and as its name implies, it stops DC from getting into the amplifier. It therefore eliminates amplifier transformer hum.
All the benefits of cutting out annoying hum with no drawbacks.
The bigger the amplifier, usually, the larger the toroidal which is susceptible to residual DC voltage. JUst add the DC Blocker at the IEC to stop DC from getting in.
ZERO DC Block technology | Blocks incoming DC – up to 1,200mV |
Voltage rating | 90 – 240 volts |
Maximum current rating | > 7A |
Max amplifier power | 880W or VA on 220v 440W or VA on 110v |
Continuous current rating | 4A |
Universal IEC | Hospital-grade IEC connectors |
Dimensions | 68 x 37 x 32 mm / 2.7” x 1.5” x 1.3” |
Weight | 63g / 2.2oz |
I added this device to my PrimeMini4 Roon Rock Server’s 19v switch mode power supply.
It is a fit-and-forget dongle that simply attaches to my Server’s PSU.
It has a subtle, yet significant, effect on any mains-borne noise that might otherwise be present in my system.
“This is an excellent low-cost solution for removing mains DC offsets and certainly offers real sonic improvements for systems.”
“Annoying loud intermittent humming coming from my Simaudio Moon 600i amplifier. Established the cause as DC Offset. Ordered the IFI DC Blocker, arrived next day, plugged in and no more humming. Complete silence.
Great little device.”
I have a BK Electronics XLS200 subwoofer that has a really annoying intermittent loud buzzing hum. (but only at certain times of the day) After much fiddling around with extra grounding, ferrite cores, special leads & much online research I narrowed down the problem to the power transformer making a mechanical noise caused by DC offset.
So I decided to try one of these little gizmos. ** It worked **
So, if you have a humming/buzzing amplifier where the noise is NOT coming through the speakers give one a try. It’s much easier than trying to trace the cause of the DC offset in your mains supply.
Very happy with the blocker, it has eliminated the intermittent hum I was getting on my Audiolab 6000A