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The amplifier is the heart of your system.

If you have a mechanical hum, deploy the DC Blocker.

Got big amplifier. Bye bye mechanical hum.

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.

Cute. Clever.

All the benefits of cutting out annoying hum with no drawbacks.

  • Intelligently stops any DC voltage from the mains to eliminate transformer hum
  • EMI shielding is retained
  • Equipment safety is unaffected
DC Blocker from iFi audio

Behind every good component is a DC Blocker.

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.

  • 90-240V
  • Maximum rating >7A, continuous current rating 4A
  • Small size, universal application, won’t block any other connectors, sockets, or cables
Cookie-Cutter ‘Sub-Sonic Filter’

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.

iFi solution:

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.

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

EMI shielding is retained.

The DC Blocker removes such DC and eliminates such mechanical transformer hum, makes the transformer operate at the optimum environment. With the DC Blocker, there is 0 DC pass through.

High-performance glass passivated semiconductor.  High-case dielectric strength of 1500VRMS. UL listed.  Flame resistant IEC socket/connecter/chassis (Fireproof polymers UL94-V0).


ProAudio Italia srl


This product is currently out of stock and unavailable.

ZERO DC Block technologyBlocks incoming DC – up to 1,200mV
Voltage rating90 – 240 volts
Maximum current rating> 7A
Max amplifier power880W or VA on 220v
440W or VA on 110v
Continuous current rating4A
Universal IECHospital-grade IEC connectors
Dimensions68 x 37 x 32 mm / 2.7” x 1.5” x 1.3”
Weight63g / 2.2oz

Excellent Addition to Roon Rock Server

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.


(Click name to read original review)

DC Blocker

“This is an excellent low-cost solution for removing mains DC offsets and certainly offers real sonic improvements for systems.”

HiFi Choice

(Click name to read original review)

Instant silence

“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.”


(Click name to read original review)

DC Blocker – Buzz Blocker! **It worked**

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.


(Click name to read original review)

Annoying noise is now gone!

For two years I have been experiencing an annoying ‘mechanical’ noise, the temporary solution was to increase the volume. Somebody on the forums suggested that it could be the DC voltage in the mains and after some research I found this and so impressed to say the noise has gone! Really pleased- definitely recommend.


(Click name to read original review)

Works well for me.

Very happy with the blocker, it has eliminated the intermittent hum I was getting on my Audiolab 6000A


(Click name to read original review)

DC blocker – not ground loop eliminator

The guy who left a negative review because this device did not eliminate 60hz hum on his guitar amp might not not understand what this device does. This device eliminates DC offset coming in through the AC power line to audio equipment. The problem with DC offset is that it can cause large toroidal transformers to vibrate and cause an audible buzzing/growling sound. This is not a sound that comes through the speakers. Its a sound that can be heard from the chassis of the device itself. 90% of the time if people have “hum” problems with audio equipment, its due to a ground loop. This device is not designed to eliminate ground loops. This has a very specific purpose of preventing toroidal transformers from vibrating and causing buzz.


(Click name to read original review)

Fa quanto dice

Se avete un trasformatore che ronza questo è una delle soluzioni.
Ho un finale dal valore importante e sentire il trasformatore ronzare era deprimente.
Il problema è CC immessa nel circuito di alimentazione. Ci sono svariate soluzioni come condizionatori di rete.. Soluzioni ben più efficaci e dai risultati che vanno ad intervenire su altri parametri ma da altri prezzi naturalmente.
Questa è una soluzione efficace e poco invasiva.
Il prezzo di suo è alto a mio avviso, ma visto che risolve il problema si vale la cifra.


(Click name to read original review)

IFI DC Blocker and GND Defender – A Practical Solution to Power Problems – Review

“IFI’s DC Blocker and GND Defender are two products that take care of the point and solve two problems present in many plants in a direct and immediate way. The cost is not very low, but both work very well and put an end to power problems difficult to solve and in my case they immediately eliminated the vibrations of the power amp, a problem that I had been carrying around for a long time, therefore, I found the money spent on the DC blocker the 150 euros best invested in my systems since the buzz was very annoying.”
Read the full review here…


(Click name to read original review)