The Audio Geek!

DC Blocker

Headphone System 1
I finally met Bryan Fletcher from Audio Note Australia / Finn Technology for the first time at the recent Melbourne Audio Show, although I have enjoyed the AN sound at several previous shows. The AN sonic signature for me is always holistic, engaging and pure. Even with a more cost-effective set of products, this year was no exception and we got talking about music, audio, wine and food in general and then more specially about the impact of noise on the power line on audio systems Well, to be honest, Bryan did most of the talking!

Bryan has done much analysis and testing and determined that the residual DC on the incoming AC line was responsible for an audible degradation of the sound outputs of audio systems, and visual outputs of LCD screens and panels. According to Bryan - 'D C on the A C line comes from solar inverters, switch mode power supplies, electronic transformers for halogen lights, anything using a half power switch like hair dryers and the great thing is it doesn’t have to be in your house, could be the neighbour 2 houses away or the transformer up the pole or buried in the ground.'

I am in no way technical nor do I have any electrical engineering expertise, but we do have 26 solar panels on the roof and an inverter to feed the juice back into the grid, plus electric fences for the horses (to keep us out or them in, not sure which) and various other technologies and machinery that co-habit our semi-rural environment. So if the DC Blocker was going work anywhere it should be here.

After some further discussion, and an unnecessarily long reference check on my character, Bryan kindly decided to loan me a sample of his DC Blocker to try at home. He seemed very confident of the outcome.


The unit contains two AC receptacles as outputs, with one IEC input from the wall. The chassis is surrounded with a pleasantly machined aluminium case and rests on four rubber feet. I placed mine on an old, spare amplifier stand just to protect the loaner product and get it up off the floor. All downstream devices should be plugged into the unit so that no stray DC can infiltrate from other connected components. The only system I have that would fit this requirement is my headphone system, and upon further thought, would be an excellent test to determine if any undesirable DC impact was removed from the output.

With several other competing priorities here at Humphries HQ, I have only just got around to installing the DC Blocker into the power supply chain for my headphone system, replacing a well-regarded Gary Cawsey 'PowerBox' filter.

IMG_4268 (1)

Probably worth mentioning the rest of the headphone rig at this point. I have a Benchmark Media Systems DAC1 USB, which does double duty as a DAC (!) and a solid state headphone amplifier; a Yamamoto HA-02 tube headphone amplifier with RCA input from the Benchmark DAC; Sennheiser HD 600 headphones with a Stefan Art Audio 'Equinox' single ended after market cable. Front end is a mid 2012 Apple MacBook Pro (using only battery power for listening tests) running OS X Yosemite, the Fidelia Digital Player, with the Advanced module enabled. Output is via USB to an Audiophilleo 2 USB transport passing the reclocked signal via a S/PDIF connection to the Benchmark.

I sat down to listen with some enthusiasm but with a totally open mind. Probably best to start with some well known tracks (ripped and stored with the Apple Lossless CODEC) and I cued up various tracks to sample and, hopefully, enjoy. It took only a few songs to realise that I really was enjoying the iTunes-sourced material. A clear, clean and extended musical presentation from top to bottom at moderate gain levels producing a most acceptable sound to my ears.

Then I started to think about what I was hearing. Previously, my system sounded good from mid-range upwards, although requiring the volume control of the Benchmark to be wound around to the 1 or 2 o'clock position. Or more… Here I was listening at less than 12 o'cock levels, hearing excellent dynamics, instrument / vocal separation and tonal balance with minimal blurring or 'sonic confusion' in the music. Just clean, clear, smooth and balanced across the frequency range.

I deliberately did not reference Bryan's website before I sampled the product. But here now is his take on the sonic impact -'The surprise however was the substantial improvement in sound. It was like the system had a layer of grunge removed from the frequency range in the bottom end that you never even knew was there. We are not talking subtle here, faster dynamics and real bass'.

Perhaps due the headphones and related equipment I didn't necessarily hear DEEPER bass but I certainly heard clearer and more spacious bass. I absolutely agree that there is a benefit and change in the lower mid range down, but I also heard some smoothness or reduced 'flare' in the very upper register as well. These two improvements made the overall sound more musical, balanced and listenable. At no stage during a three hour listening session was I fatigued or tempted to listen to my library of high resolution music. I was simply enjoying 44/16 source material too much!

This result is frankly quite shocking. That a relatively small and simple (but well built) 'box' could produce such a sonic improvement was indeed a revelation. I would highly recommend a listen to the DC Blocker if you suspect DC contamination is a problem in your system / environment.

I will beg to retain the DC Blocker for a few more weeks of listening, comparing and testing, but I suspect that it will not be making the long road trip back to SinCity! Many thanks to Bryan Fletcher for the opportunity to sample the DC Blocker and hear it's benefits in my system and my congratulations to him on the development and delivery of such a well realised component.