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DC Blocker

MartinLogan Owners (MLO)

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pegwill

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Hi
I have been reading about DC on mains AC circuits and I was wondering if Ml’s would benefit from the use of a dc blocker. From my understanding it appears they are used to reduce transformer hum. While I have never noticed any, I guess that’s because they are enclosed in the cabinet.

Does anybody use them? have tried them? Or got any they could try and let us know the results? Or is this just a complete waste of time?

Regards

William
 

Speedskater

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Audiophiles often use 'DC blockers' as a solution in search of a problem. There as to be a DC offset on the AC power line for them to do anything. Something big has to be creating the offset and many big AC power users don't run 24/7.
For others: So does the transformer hum change from time to time? Does it change in another building?
 

jda99

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I use a DC blocker. The most obvious improvement was in preventing the noise through the system whenever a hair dryer was switched on in the house.
I see it as an essential tool to prevent crap in the mains getting into my system.
 

spkrdctr

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If you have no transformer hum then it is not needed. But, if you can find a company making one fairly cheap, then it would not hurt anything. Post up if you find any available. Thanks!
 

Brad225

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An electrical engineer audio builder friend of mine has built DC Blockers that work very well.
This pic is one that he built for the front end of my system it plugs directly into a Tripplite Sq sign wave power backup and on the other end it plugs directly into a Shunyata Hydra.
That intern feeds my Pre Amp, SACD/DAC, NAS, network switch, Sonic Transporter and UltraRendu.

He has built quite a few of these over a few year period. He discovered using inexpensive parts only made the sound worse.
If I remember correctly my cost for parts only was about $500 with at least half of that being the 7' of Furutech power cord and plugs for the ends.

I never noticed any noise in my system that led me to believe i needed to remove stray DC from corrupting the operation of the transformers but the in reality there obviously was.
There was a clear improvement in the size of sound stage and spaciousness in the layering of voices and notes.
I sold off my Shunyata power cords and it more than paid for the construction.


IMG_3665.JPG
 
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Brad225

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After the success with the front end he is, probably today, finishing 2 more DC blockers for my mono amps.

Due to the current draw and the transformer size in the amps the parts are substantially larger. On these I chose to make my own power cords from single crystal OCC copper wire with Furutech ends of both.

I don't know the total parts cost yet but I think it will be near $900 for both.
I will again sell of un-needed power cords and put money back in my pocket.

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pegwill

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Hi

Thanks for the replies however I understand about the results on amplifiers but wondered what effect they when connected ML’s electrostics via the mains plug.

Has anybody tried this?

Regards
William
 

jacek-k-wawa

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My 3c to this.

Big transformers (like those in big power amps) sometimes are prone to DC in mains and effect of this is hum which is result of phisical vibration of transformer core. And in this situation DC blocker may help.
Taking about ML speakers there are 2 types of transformers: one in circuit which generate high voltage to panel (but this is very small trafo under small load so hum is very unlikely) and PSU in active bass sections for some of the MLs - but here they use switched PSU and their trafo is not connected directly to mains so mains DC does not have any influence here.

So I would not expect any significant effect of DC blocker with MLs...
 

Stefan_DR3

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I agree. The transformer buzzing caused by DC offset is a mechanical vibration of the plates and has nothing to do with the sound coming out of your speakers. If you can't hear any buzzing when the preamp is muted then stop worrying about it.
 

Brad225

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I installed the DC Blockers on my mono amps today, even fresh from the bench the difference was surprising. As with the blocker on the front end, the sound stage was noticeably deeper and wider. Again the layering of notes was improved with more air around them.

No one needs to agree with my findings. I have never had any noise or hum with my preamp turned up to full volume. It does work in my system.

pegwill, I asked my EE friend today about using them to power your speakers and this was his response.
As long as there are transformers in them and the DC Blocker parts are of good quality more than likely you will notice an improvement.
 

BDH55

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While I've been paying attention to this thread, I didn't think it really applied to me. That was until today!

PS Audio has been trying to chase down a very intermittent problem with the P20 that feeds most of my system. While it has always delivered power to my system, the front panel turns on by itself, and then locks up not responding to any user input requiring a trip behind my rack to do a power down reset. They've been looking at my P20 remotely and today I was told... "I looked over the data and on 2-12-21 around 2am, your P20 shows a large DC spike, which seems to fit the timeline and could explain the issue."

While we plan to just watch the issue for now... I guess I may be looking for a DC blocker of some type as well...
 

Robert D

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While I've been paying attention to this thread, I didn't think it really applied to me. That was until today!

PS Audio has been trying to chase down a very intermittent problem with the P20 that feeds most of my system. While it has always delivered power to my system, the front panel turns on by itself, and then locks up not responding to any user input requiring a trip behind my rack to do a power down reset. They've been looking at my P20 remotely and today I was told... "I looked over the data and on 2-12-21 around 2am, your P20 shows a large DC spike, which seems to fit the timeline and could explain the issue."

While we plan to just watch the issue for now... I guess I may be looking for a DC blocker of some type as well...
What causes that spike?
 

BDH55

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What causes that spike?
No idea, but PS Audio support said it could be just about anything.. from a dimmer, to my neighbors washing machine (although I'd be surprised if they are doing laundry at 2 AM). They recommended I try a DC blocker but I would prefer to solve this on a whole house basis if possible.

So I decided to tag the guys at Audio Advice as I've always found them helpful. Their take was that while they could sell me something, I would be better off contacting my power company and putting this on them. They said that it would be much better to have them clean up the power coming into our house, than to try to deal with it inside our house. While I agree, the challenge is what does the power look like six months after they come out??

Anyway, since I had another DC spike last night, I'm going to have to deal with this. So, I'll call Duke Energy tomorrow and see just what they can do for me. With a heavy winter upon us I doubt I'll get a warm response, but I am going to give it a try...
 

Robert D

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No idea, but PS Audio support said it could be just about anything.. from a dimmer, to my neighbors washing machine (although I'd be surprised if they are doing laundry at 2 AM). They recommended I try a DC blocker but I would prefer to solve this on a whole house basis if possible.

So I decided to tag the guys at Audio Advice as I've always found them helpful. Their take was that while they could sell me something, I would be better off contacting my power company and putting this on them. They said that it would be much better to have them clean up the power coming into our house, than to try to deal with it inside our house. While I agree, the challenge is what does the power look like six months after they come out??

Anyway, since I had another DC spike last night, I'm going to have to deal with this. So, I'll call Duke Energy tomorrow and see just what they can do for me. With a heavy winter upon us I doubt I'll get a warm response, but I am going to give it a try...
Let us know what they say. I'm worried they won't do a thing and blame it on your home or equipment.
 

pegwill

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Hi

I built three dc blockers following the circuit given in the link below


The circuit is towards the end of the article figure 8. They are now installed one in each speaker (Aeon) and one for the amps, DAC etc. I only used cheap capacitors 6 4700uf for about 5.00 uk pounds + 6.75 for three 35a rectifiers and the same for the plastic boxes, the cable I already had. So each one cost about about7 uk pound each.

I have no reason to suspect that you would get better quality if you spent more on the capacitors.

For little outlay you might give it a go. If it solves your problem then, you might consider better quality capacitors, if it makes you feel more comfortable.

It is quit an easy circuit to follow and make one.

Mine have been running for two days now and as far as I can tell no adverse effects. Whether I was actually suffering from dc in the first place, I don’t know, but chances in this day and age I would say yes. But i’m Happynow nowing that everything is running more efficiently.

Regards

William
 

BDH55

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Let us know what they say. I'm worried they won't do a thing and blame it on your home or equipment.
That's kind of what I expect, but I've got to at least try them as according to PS Audio I had yet another spike last night. PS Audio has been helpful as I don't have a way to see that I actually had a DC spike, and at what time (they can remotely pull data off my P20). I'm hoping that they will continue to help me out so I can build up a week or two weeks of data. I think if I present Duke Energy with 'I have had DC spikes on these dates, and at these times' I may have a better chance of them at least getting someone to listen to me.
Hi

I built three dc blockers following the circuit given in the link below


The circuit is towards the end of the article figure 8. They are now installed one in each speaker (Aeon) and one for the amps, DAC etc. I only used cheap capacitors 6 4700uf for about 5.00 uk pounds + 6.75 for three 35a rectifiers and the same for the plastic boxes, the cable I already had. So each one cost about about7 uk pound each.

I have no reason to suspect that you would get better quality if you spent more on the capacitors.

For little outlay you might give it a go. If it solves your problem then, you might consider better quality capacitors, if it makes you feel more comfortable.

It is quit an easy circuit to follow and make one.

Mine have been running for two days now and as far as I can tell no adverse effects. Whether I was actually suffering from dc in the first place, I don’t know, but chances in this day and age I would say yes. But i’m Happynow nowing that everything is running more efficiently.

Regards

William
Thx for the info, but I would prefer to either a) have our power company resolve this, or b) buy something from a manufacturer. However, this does give me one more option... (y)
 

Brad225

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Hi BDH, I was with my EE friend yesterday and told him of your issue.
He said his gut feeling was it is more than likely something in your residence that is causing the spike. Motors are apparently one of the worst offenders for DC current pollution.
Good luck let us know what you find out.
 

Robert D

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Hi BDH, I was with my EE friend yesterday and told him of your issue.
He said his gut feeling was it is more than likely something in your residence that is causing the spike. Motors are apparently one of the worst offenders for DC current pollution.
Good luck let us know what you find out.
Hum, so what motors are running inside a home? The fan on the central heating/ air duct is one. The fan on the outside air conditioner, but not during the winter. Appliances.
 

BDH55

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Hi BDH, I was with my EE friend yesterday and told him of your issue.
He said his gut feeling was it is more than likely something in your residence that is causing the spike. Motors are apparently one of the worst offenders for DC current pollution.
Good luck let us know what you find out.
Thx for running this by your friend. What's weird about this is if it wasn't that my PowerPlant P20 occasionally locks up and I had been working with PS Audio to resolve it, I would have never known about something called a DC spike (other than seeing a post up here and thinking it didn't apply to me). My conversation with the CEO of Audio Advice really encouraged me to go after the power company to try to clean up the power entering our home.

Everything is underground near us except the big green power box that feeds us as well as our immediate neighbor. While this certainly could be something inside our home, from what the PS Audio guys are telling me, these spikes are usually hitting in the middle of the night. If it is coming off a motor of some type, it would seem to have to be off our HVAC system. At this point my main concern isn't that I have to reset my P20 as I know it is protecting the equipment connected to it... it's more about I have no idea what this DC spike may be doing to other electronics in our home...
 
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