DC blockers - what's your experience

yes, they work wonders when needed -- ifi, van alstine, audiolab, ps audio, they all make them

@tunehead what DC voltage are you measuring your incoming power at?

Do you actually have a DC problem?  Can you identify the source and remove it?

If you turn off everything else in your house and you still have DC it's time to call the power company.

I'm using a Long dog audio one inline to my power conditioner.  it makes a positive effect in my opinion in my system but it does limit my power cord to 12 gauge.

my issue is a fish tank with variable DC pumps and variable LED lights.

one day I'm going to try blocking the DC at source (other side of the room)

Then taking it out of the system, I get no hum on my transformers without but I find the tone sweeter with it.

Thanks all.

@holmz  I don't necessarily have a problem. Don't know if I have a problem or the equipment to test if I do. Was more a general question after viewing reviews of DC blocker products and the positive affect for minimal investment.

@tunehead  - Avoid them unless you have an issue. One more piece of gear to break. 

DC should almost never happen in a home, and usually it's caused by things like LED power supplies and dimmer switches. Usually best to deal with the source of the problem and only if that can't be dealt with due to WAF and budget or being a tenant then a DC blocker is in order.

A better idea IMHO is to monitor your AC voltage near your rack and see how much it varies.  If you see too much a voltage regulator may be a good idea.

https://amzn.to/40AoTWG

Should point out that the thing DC blockers fix the most is mechanical transformer hum.  99% of the time it does not affect the electrical output.

Should point out that the thing DC blockers fix the most is mechanical transformer hum.  99% of the time it does not affect the electrical output.

this is correct and consistent with my experience

reality is, dc in the powerline is a reality for most, in modern homes, with modern electronics, lighting and appliances...

My experience of using a few different DC blockers is they seem to choke the transient impact, bass and speed of the power amplifier.

If you have DC issues, like I did in my last apartment, they can make the sound cleaner and clearer, but with the above mentioned negatives. So they give and take away.

If you have no DC issues, like in my current house, they just become a net negative and your system is better without them.

I have noticed that in my area the DC on the line situations come and go, when they occur they persist for a few weeks. Whenever there's a holiday, that's when it starts and persists.... the cause is most likely overloading of the entire neighborhood, and it got much, much worse since the outbreak of the pandemic with most people staying at home / working from home / losing jobs & full time at home watching TV and hanging on all times to their electronic devices.

The most practical solution I found is to bleed the DC when it happens with a parallel inductor (Richard Grey - RGPC makes such device, for example). Then I get a major improvement in sound quality in all areas.

However, when there's no DC on the line, I keep the RGPC off.

This way I can avoid the negatives of a series DC blocker...

DC causes my amps toroidal transformer to buzz fairly loudly. The only time it happens is when my wife uses this one particular space heater.

I think DC on an AC circuit in the US is very rare and is often blamed for buzz when it is something else.  

Your audio should be on dedicated 20-30 amp lines 

and I had  had awg 10 copper wire and to make more quiet my audio electrician friend installed 4 wire 1 common ground ,the other a separate is plated ground 

Going to its own small buzz bar  it sounds dead quiet day or night .

I use iFi on my NAS and fiber transmitter….they work excellent and are extremely affordable. 

I had major problem with transformer hum that lasted for years, this along with over voltage issue(124-126v). Never could get rid of transformer hum, bucking transformer for the over voltage. Suddenly one day I come home no more transformer hum, voltage down to 119-121v, this has remained for years now. Seems electrical grid was finally repaired.

Power is primarily clean here where I live do have an LessLoss 640x on my LessLoss DAC and audiolab dc blockers on my digital and analog FEU. More for assurance than anything else. Amps are right into the wall. 

 

 

Also new hook up terminations. Aluminum wire terminations start to corrode and loosen over time when exposed to the outdoors environment. Sun’s rays, heat, cold, rain, wind. All will break down a tight, clean, low impedance termination. A poor termination can and does cause excessive harmonic distortion on the mains.

I do not think that UV and heat affects aluminium, unless the global worming is higher that I believe it to be.
And there is no “clean connection” with aluminium, as the stuff naturally gets a layer of alumina on it in a hurry. The pickle it with hydrofloric acid before it is bonded… so it always has the tunneling happening…

But then again, which does, or what do, harmonics have to do with DC blocking?

So far we have two things that are not known, or shown to exist on the OPs power that need to be fixed.
It is like an SNL skit of an AA meeting with testimonial stories of what was done to fix these “problems”.

Personally I would be spending $100 on an electrician before fixing a problem that has a chance of being non-existent. There are many real problems that likely need fixing that could happen first.

holmz Said:

I do not think that UV and heat affects aluminium,

In response to this statement of mine;

"Also new hook up terminations. Aluminum wire terminations start to corrode and loosen over time when exposed to the outdoors environment. Sun’s rays, heat, cold, rain, wind. All will break down a tight, clean, low impedance termination."

TERMINATIONS... Repeat. TERMINATIONS...

@holmz Said:

And there is no “clean connection” with aluminium, as the stuff naturally gets a layer of alumina on it in a hurry.

When the outdoors 120/240V aluminum connections are first made-up at the utility power transformer and the utility overhead lateral triplex to the electrical service weatherhead service conductors the connections are clean and tight. With the passage of time, possibly many decades of service the terminations are subject to the Sun’ UV rays, rain intrusion, snow intrusion, heat, freezing moisture in the termination, and wind. High wind can whip the heck out of the wiring terminations.

As for the sun’s UV rays it will break down the insulating, waterproofing, material(s) that was originally installed over the terminations with the passing of possibly decades of time. It also will cause the deterioration of exposed THWN insulation covering the bare conductor. I've seen it first hand.

 

@holmz Said:

But then again, which does, or what do, harmonics have to do with DC blocking?

My post was in response to this post:

sns

2,947 posts

02-03-2023 at 08:50am

I had major problem with transformer hum that lasted for years, this along with over voltage issue(124-126v). Never could get rid of transformer hum, bucking transformer for the over voltage. Suddenly one day I come home no more transformer hum, voltage down to 119-121v, this has remained for years now. Seems electrical grid was finally repaired.

Best regards,

Jim

Thanks @jea48 - but I can read, so I was sort of expecting something added and not a rehash of the thread.

Which parts did I get wrong? Or which parts don’t conform to your understanding?

On the SNS part, it seems like the power grid was fixed and the voltage lowered, and all that @sns did to fix it was to come home suddenly. We don’t know if the power company had a DC offset, nor harmonics, we just know that he said that the voltage went down the same day that the hum went on walkabout.
Nor do we know that if he can home less suddenly, that the system wouldn’t still be humming.😋
(I sort of doubt that the suddenness was causal to fixing the problem.)

I move slowly.

@tunehead ,

Here is a thread that may help you better understand DC on the mains.

DC Offset Blocker/Killer - where to buy in the USA

more useful info on the subject for those who care to learn

Just bought the Audiolab DC blocker. I have two dedicated AC outlets feeding my system. Since I expected there to be possibly some DC seeping through and the EMF filtering, it was worth a try at $150. First off it created what sounded like a cleaner sound throughout. Crisp revealing but what little 'hum' that was residual in my system was also much clearer. At first I reasoned the enhanced clarity was worth the trade off but then I noticed something else troubling. The entire presentation had lost something. After giving the unit a week to break in (although it was a demo unit and hence should have had some miles on it) I pulled it out and listened again. Without overtly realizing it, the presentation had lost the warmth, organic, musical, 3-D quality to it. WOW, my system's magic was back. I'm a bit unsure what actual effect the Blocker had. Seemingly clearer but flat OR pinched I might say. And that extra 'hum' was gone receding into the faint background as I am OCD about the smallest trace of system sound of any kind. Unit has been returned for full credit. Lesson learned. Same result with "power conditioner" by Furman.  

@allears4u it is redemanded to use on source equipment such as DAC, Phone Pre, Streamers/servers. Not recommend for amplification. I bought a couple of these for my Daughters system as they live in a condo and worked quite nicely cleaned here system up, used on Analog and Digital sources. 

Good tip! I now wish id tried it on my other components. What caught my attention was this line in Audio Advisors description of the DC Blocker.....Quiets "modern high flux toroidal transformers" . Well, thought I, I have two of those humming along on top of my tube amp which always could be a little quieter. So....live and learn (and loose $15 for return shipping!)