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Naive questions re d-i-y

98.70.62.10
Posted on July 28, 2009 at 15:09:02
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006



I just bought all the parts to make a four-outlet "felix" power conditioner with dc-blocker (a la Audio Circle), in a double-insulated chassis, and I have some naive questions for the room -- some of which are probably *really* naive, so forgive me.

1) I can figure out how to connect everything except the bridge rectifier for the dc-blocker, and its associated caps. The diagram that gets reproduced in the audio circle from time to time shows a bridge rectifier and caps but not in such a way as to enlighten me regarding where to solder the hookup wire, and where not to. (I'll attach the diagram as a jpg)

2) I'm going with a double-insulated chassis to reduce the risk of electrocuting myself: all-aluminum inside and plastic of some sort (buddy industries) on the outside. Which means at some point I'll need a nudge in the right direction as to how to machine the holes to exacting tolerances, and also how to connect the two chassis to each other. Glue?

3) Can mounting bosses be added after-the-fact to a project enclosure that doesn't already have them? If so, how are they sized by the hobbyist to make an ideal fit and how are they affixed to the inside of the enclosure?

4) Is there anything like heat shrink that can be used to cover a non-radial area of exposed wire? Say, for example, one ends up with a T-junction that has been soldered, and wants to insulate the whole junction -- is there something that can be "wrapped" around the t-junction and then sealed, a la heat shrink?

5) Can I use glue to hold the capacitors and the cmc's to the perf boards? If so, what kind?

6) I bought fuses (three 3-amp slow blow and 1 10-amp fast blow) and now I'm wondering whether to place them in series between the power inlet and the caps, or between the caps and the outlets -- which?

7) Will isolation transformers from Action Electronics be additionally efficacious, and if so, do they go between the felix modules and the wall, or between the felix modules and the equipment?

8) Are any of you free two weeks from this coming Saturday, to deliver the eulogy?

 

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RE: Naive questions re d-i-y, posted on July 29, 2009 at 00:15:34
zanash
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Posts: 1031
Joined: August 23, 2001
 to question one .... the snubber caps as there known should really be connected across each diode ...but why bother when schottky diodes produce no switch related reverse current?

if your not clear what your doing then don't do it !!!

mains can kill the unwary ......

live long and proper

 

Less-dad-more-answer, anybody? :-), posted on July 29, 2009 at 06:40:52
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 Hey, folks -- I could still use a constructive reply to the specific questions I posed in my OP, seeing as how I haven't gotten one yet. (Actually, in a tweakers' forum, I'd go so far as to say that "If you don't know what you're doing, you shouldn't do it," isn't just non-constructive, it's flat-out wrong: If you don't know what you're doing, you should find out -- BY ASKING. HERE. But hey, maybe that's just me.)

Anyway, the parts are here and I'm ready to do the project, and I hereby explicitly and freely acknowledge an awareness of, and full personal responsibility for, the safety issues involved. All I need are seven relatively mundane answers about d-i-y electronics and I can get cracking, and "Oh my God, AC mains are dangerous!" is not one of them. Thanks again, y'all! ;-)

 

RE: Less-dad-more-answer, anybody? :-), posted on July 29, 2009 at 07:02:56
HumanMedia
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Posts: 421
Location: Sydney, Australia
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 I have considered answering a few times but have hesitated as there are so many issues you raise which indicate that the end result may well be an unsafe mess that makes your equipment sound worse.

Sorry if that offends so I will try and answer a couple of questions.

Fuses - use a single fuse on the active line directly after the input from the wall and before anything else. I would go with the single 10A one assuming the rest of your components in the filter are rated for that.

Isolating Transformers - sort of do the same thing that the filter does, but IMO they only sound good for digital front ends and limit dynamics of amplifiers. And you wouldnt want them one after the other anyway. Try the balancing transformer on your CD player only and the Felix filter just on your preamp only, with no filter on your power amp.

Chassis - insulation isn't going to help if the internals are not wired correctly and you start a fire. Maybe you haven't got the right sort of chassis if its not clear how its supposed to go together and glue is a definite no-no (bolting or pop-riveting might be an option) Probably good to have your chassis tied to earth/ground as well.

Mounting bosses (?) - I would drill holes in the chassis, use standoffs and brass bolts to hold the boards away from the chassis.

 

RE: Less-dad-more-answer, anybody? :-), posted on July 29, 2009 at 07:05:50
HumanMedia
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Location: Sydney, Australia
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 And make sure to test the end result on a table lamp before plugging any audio or video equipment into it.

 

A helpful and proportionate answer -- PERFECT!, posted on July 29, 2009 at 07:16:59
author@escapeclause.net
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 I'm not offended as long as the preface is there, so let me say that first -- thank you for prefacing this with a sort of, "you sound like you've decided you want to try" kind of thing. There's a fine line in a thread like this between voicing earnest doubts, and stealing power, and I appreciate a man who can tell the difference!

The answer on isolation transformers is *really* helpful. I'm trying to clean up a stubborn power problem at my house (people keep bench-testing my stuff and telling me there's nothing wrong with it), and have replaced the service panel, but wanted to cover the possibilities of DC-offset and common mode interference, both. So, no transformers except for the CDP, and no felix on the CDP, and felix on the preamp but no transformer on the preamp, right? And the amp straight into my dedicated AC line?

"Standoffs" is apparently the noun I meant to use when I said "mounting bosses," so let me re-ask the question about them: Can I add standoffs to a project enclosure that doesn't come with them already installed, and if so, how do I attach them to the enclosure?

I didn't mean for the earlier post to sound scratchy -- I just think that it's worth the benefit-of-the-doubt when someone says they're planning to learn about the stuff ahead of time, and respect the danger, and maybe come out of it with a lot more knowledge and skill, if not necessarily a better project. (Though I'll admit to being more optimistic about the end result of the project than you are. Ha.) At all events, I'm not gonna blindly solder six parts together and plug it to my wall and grab ahold of it to see what happens, and got a bit ticked-off when someone made it sound like they thought I might.

In the meantime, what is solder flux? Do I need some of that? Can I get "helping hands" at rat shack? What about static -- are there products I need to buy (tools?) to keep my mui-expensive X2-rated caps from being destroyed the first time I try to pick them up?

THANKS for being a little more patient with me!!!!

 

I hadn't thought of that. (Eeek.), posted on July 29, 2009 at 07:18:46
author@escapeclause.net
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 Thanks -- that was something I wouldn't have thought of, which for sure could've been ugly. ;-)

 

Indeed, poor advice can kill, posted on July 29, 2009 at 07:40:01
pmkap
Manufacturer

Posts: 552
Joined: March 21, 2001
 Zanash,

Please try to understand what the posted circuit's functionality prior to 'fixing' it. It is a dc blocker, not a rectification module. There are NO snubbers. The circuit, as posted, has been used by Brystron as a dc blocker for years.

Author - I'll post in that other place by tomorrow

 

Those are NOT snubbers!, posted on July 29, 2009 at 07:47:30
clifff
Audiophile

Posts: 1741
Location: English Riviera
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 Nor is the bridge "rectifying".

Read the OP, 'tis a DC blocker abd the back-to-back caps are passing AC.

 

Thank you!!! (NT), posted on July 29, 2009 at 08:15:55
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 .

 

well....., posted on July 29, 2009 at 09:17:03
Oface
Audiophile

Posts: 1497
Location: columbia, south carolina
Joined: May 3, 2003
 I have an issue with your post(s).....

There is nothing wrong in wanting to learn how to do something... along as you take the proper precautions in doing it....

You have this "attitude" of some of the kids I trained in the navy. They were so used to doing things "their way", and you could not tell them nothing, till after they got hurt and had to go to med call. That kind've thinking gets one killed or worst, others killed. All be cause you think you're cocky enough to do it all......with out following others advice.....


Here you are asking about how to hook up bridge rectifiers and all, and you do not know what is solder flux?? C'mon....


You need to read up some things first. I would try google, and also check out the navy NEETS modules...... There are a few other books out there that will tell you how to do things properly.....


good luck in your project....You need to learn the basics first, (safety) especially with electronics.

-chris

 

"Just trying to help," may we presume? :-) :-) :-) :-), posted on July 29, 2009 at 09:55:04
author@escapeclause.net
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 So the guy who started this thread with seven open-ended questions is JUST LIKE those KIDS in the Navy who got hurt because they never asked questions, have I got that right?

Maybe all those kids you tried to help in the Navy trained themselves not to ask you anything because they couldn't bear the sweeping pomposity that came joined at the hip with the compartmentalized answer to the compartmentalized question they needed to ask.

Now I know what you're going to say. You're going to say, "Look. I was just trying to help." So after agonizing about how to walk this line I've settled on a multiple choice question. Which of the following people is *JUST* trying to help:

a) "There are a series of modules on this subject put together by the Navy that you might find interesting."

or

b) "You're just like the arrogant *KIDS* I used to train in the Navy, who wouldn't be told anything and had to hurt themsleves, and by the way there are a series of modules on this subject put together by the Navy that you might find interesting."

In psychology circles this is called "stealing power," and it happens in these pages *a* *lot*.

A guy on a street-corner asks you the best route to the seafood restaurant, and you stub out your cigarette and tell him that the mercury in seafood is bad for him, and the environment is being damaged by overfishing. He didn't ask you that. He's already bought the parts from Newark and Mouser. He's making his project.

I know the sorts of replies this is going to get, but tough. If you want to help, suggest the NEETS modules. If you want to compare the guy whose asking the questions in the first place to a bunch of kids in the Navy who hurt themselves by refusing to ask questions, buggar-off.

 

sniff, sniff,,,,, posted on July 29, 2009 at 13:23:17
Oface
Audiophile

Posts: 1497
Location: columbia, south carolina
Joined: May 3, 2003
 guess i need to wipe the shit off of my shoulders then.....

Now, if you would get off of your throne and understand things like normal people would , then you wouldn't get offended by the advice that i laid out to you..

Better yet ,, if I was you or anyone around , I would recommend you shouldn't even pick up a Phillips head screwdriver....

Look , you are dealing with some serious shit here, bud... If you take it lightly , it will bite you on the ass.. less the attitude elsewhere...

Trust me the people I trained , as far as I know , never had to rteport to medical...


have a nice day !!....


remember the one hand rule....


-chris

 

Last one was too long, sorry, posted on July 29, 2009 at 13:27:08
author@escapeclause.net
Audiophile

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 I don't think we're as far apart (or at least *were* as far apart) as you've presumed all along by presuming that I was going to start attacking my AC-mains before I knew what flux is, so instead of another long-winded reply let's keep it here:

a) "There are a series of modules on this subject put together by the Navy that you might find interesting."

or

b) "You're just like the arrogant *KIDS* I used to train in the Navy, who wouldn't be told anything and had to hurt themsleves, and by the way there are a series of modules on this subject put together by the Navy that you might find interesting."

It is, it remains, my assertion that *one* of these guys was just trying to help, and would've been forgiven for feeling sh*t all over from my throne for bothering.

...One of them, that is.

 

Some answers..., posted on July 29, 2009 at 16:08:18
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 Solder flux is a chemical that cleans the solder joint while the solder is being applied. Many wire solders have a flux core, and, if the parts you are joining are already 'tinned' (coated with solder), this flux will be adequate to give you a good joint. Only use resin flux for electronics. There are acid fluxes for plumbers, etc., but the residual acid can destroy electronic components.

Try to avoid breathing the fumes from the heated flux. A small fan that blows the smoke away is useful. Too much exposure to the fumes can cause lung disease.

I find it helpful to use the liquid flux (GC Electronics, 10-4202) on all joints. It is essential with bare copper, and helps get a better solder joint appearance with tinned items. It is better to remove the solid residue (toasted resin) by scraping and brushing.

I don't know if Radio Shack still carries this kind of thing. You may have to order on line or find a more serious electronics parts store in your area.

None of the parts in your DC-blocker project are sensitive to esd. They are too large and self-protecting to be bothered by the small energies you could accumulate. Don't be concerned because Mouser sent them in esd-protective packages: they do that with everything. If you ever do get to working on sensitive parts (integrated circuits, field-effect transistors, voltage regulators, etc.), you will need a conductive mat for your work bench and a wrist strap that connects you to it. These are available from Mouser or a series electronics parts store.

Standoffs are metal or plastic. They typically come with tapped holes so all you need is a matching machine screw and a hole in the box. If you are working with line voltages, I would use Nylon standoffs. Just avoid over-tightening the screws, as the threads will strip easily.

As long as the caps are big enough, your DC blocker should work with your power amp. Try it and see if it helps or hurts the performance.

 

RE: A helpful and proportionate answer -- PERFECT!-The problem?????, posted on July 29, 2009 at 16:33:47
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 So what do you "think" is wrong with your gear (that nobody can find a problem with) that you think this "fix" is going to solve?

Are you saying that there is DC on the AC line and that is causing your problems? If so-how do you think that DC is getting through the power transformers in your gear?

Maybe I am missing something.

 

RE: Naive questions re d-i-y, posted on July 29, 2009 at 17:10:53
John Swenson
Audiophile

Posts: 2422
Location: No. California
Joined: October 13, 2002
 Given the rest of the posts I'll leave off the "this is dangerous" stuff and try and answer your questions and and ask you some more.

The bridge rectifier has a hole in the middle for mounting, just use a screw to mount it to the board. There are four "lugs" coming out one side, one marked - and one marked + and two marked ~ . The ones marked - and + match the - and + in the schematic. The other two corners which are unlabled in the schematic are the ~ lugs. (it doesn't matter which is which). You solder a wire between the + and - lugs as shown in the schematic.

The caps usually used with these circuits are called "snap" types. They have weird bent stubby pins coming out one end. These are designed to "snap" into holes on the board, this holds the cap in place on the board, no other mechanical connection is usually required. You may have to enlarge the holes on the perf board to get the pins to fit. But don't make them too big otherwise the "snap" won't work.

The caps will have a broad white stripe going up one side. The pin closest to this stripe is the - pin. The other pin is the + pin.

The overall connection to the felix is as follows:

The neutral wire from the source hooks up just like a regular felix. It does NOT connect to the DC blocker. If it does you will get explosions, smoke etc.

The hot wire from the source goes to one side of a fuse.

The other side of the fuse connects to the DC blocker. Its the wire coming in from the left in the schematic. it connects to one of the ~ pins on the bridge, and to one side of the caps.

A wire gets soldered between the + and - pins of the bridge.

The other ~ pin of the bridge gets connected to the other side of the caps. This connection also goes to the hot connection of the felix.

The caps get wired in parallel with the - of one soldered to the + of the other.

Since large currents are flowing through these circuit you want to use at least 16 gauge wire. I would recommend THHN solid core wire, you can get this at pretty much any hardware store. Many people prefer 14 or even 12 gauge wire, but its much harder to work with. I would stay away from stranded wire. Its easier to work with, but you have a much higher probability of a stray thin little strand of wire escaping a joint and touching something it should NOT be touching. Often times these thin little strands are very hard to see, you usually only spot then when they burst into flames etc. When working with AC line voltages and currents this is a risk I think is best to avoid.

On the box issues, there are two schools of thought, some prefer grounded metal, other prefer the "double insullated" strategy. Since it sounds like you have chosen the double insullated approach you have to make SURE that nothing metalic goes from inside to outside, NOTHING. Its difficult to meet the double insullated standards, but it can be done. If you are using standard duplex outlets you've violated the goals since the sockets for the mounting screws are connected to the backstrap on the inside. There are special "insullated ground" outlets which fix this problem.

As for mounting boards etc you can use nylon spacers and nylon screws, these make sure that nothing metalic pierces the "outer barrier"

If you are using an IEC inlet, again make sure you use a type that does not use some form of metalic fastener.

If you use a fuse holder that sticks through the case again make sure that no metalic part goes through the case. (it might be easier to just have the fuse holder completely inside the box)

Are you using one of the felix PC boards or are you putting it together on perfboard?

A link to the box you have (or at least a part number) would help, I'm not getting a good mental picture of how this box works from your description.

Finally a couple tips:

when working on any AC circuit like this, never do the work when you are tired. If you've been working on stuff for several hours and its getting late, stop and go to bed, don't try and push it through to completion.

Always try and make a mechanical connection with the wires rather than just laying one next to the other and soldering. If you didn't make a perfect solder joint the currents flowing through such a circuit can cause the joint to get hot which has a very good chance of causing the joint to fail, and then the wire could spring over and touch something else. If you've crimped the wire around a pin (or other wire) if the joint does fail the wire has a much lower probability of going anywhere else.

John S.

 

THANK YOU! (NT), posted on July 29, 2009 at 17:54:48
author@escapeclause.net
Audiophile

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Location: Gainesville, FL
Joined: May 28, 2006
 .

 

A great question but a soap-opera answer, posted on July 29, 2009 at 18:05:25
author@escapeclause.net
Audiophile

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Location: Gainesville, FL
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 I've had a lot of trouble figuring out how to keep this brief, and I'm not brief generally. If I leave too much out, let me know (obviously).

I've had a series of problems with the home audio gear, both the electronics and the speakers -- though usually the electronics seem to fail first and then, if I convince myself there's nothing wrong, I eat another pair of speakers. From a staticky whooshing sound in one channel of a Parasound pre-power combo in 2006, through intermittent input-selector lockup and overmodulated midrange on a Naim Nait5i in 2007, to a loud bang when a McCormack MAP-1 is disconnected from power in 2008, to an audible hum and very hot running temps for an Arcam FMJ-CD23 in 2008-09, to an Integra DTR that ran for less than a week before it totally died, in 2009, I've had more "bad luck" with more products, from more different vendors, than is scientifically plausible even with pre-owned stuff.

Moreoever, the stuff that still functioned at all when it was sent for service (Parasound, Naim, McCormack, Arcam) always checks out perfectly on the bench. The service folk at the other end call me in, oh, four to seven days, and say, "Well we're shipping you your amp; there's nothing wrong with it." And this happens whether it's factory techs or after-market specialists. The only exceptions are when things are mechanically, fatally damaged somehow, in which case the answer so far has been to throw whatever it is, in the garbage.

*NOBODY* seems to be able to actually help. Ever. I've asked the local service people (and the local utility) and both of them roll their eyes and say "there's no such thing as DC-offset on your AC mains."

I've installed a dedicated, safety-grounded AC line (all the other lines in the house are two-pin), replaced and upgraded the entire power entry using an electrician (the shared neutrals from the old box are replaced with a brand-new, gleaming, humongous ground bar that has like fifty extra holes), and the only things left other than a high resistance to ground is DC-offset or common mode interference.

Thoughts?

 

Wow, thanks!, posted on July 29, 2009 at 18:17:56
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 I'm watching "how-to-solder" type videos on Youtube and getting a much better feel from those of what I've been doing wrong up to now and how to do it right -- at the very least it looks like some practice on nonsense parts from rat-shack would be a terrific idea. Indeed so terrific that a fellow would be an idiot not to spend a weekend doing this over and over until he got it right. (That and buying more tools, of course!)

I don't have felix PC boards (are they even still available?) so my plan was to prototype one using a perfboard and then, if everything worked, there's a guy in town who will etch (is that the right term?) some permanent boards. Obviously if there were felix boards kicking around that would save me both time and money.

The reason the box part of my story is tough to visualize is because I didn't actually have any idea what I was talking about. I bought an all-aluminum box from Newark and another box also from Newark that was all-plastic and a little bigger, except that it wasn't bigger *enough*, in fact the dimensions listed on the outer box aren't nearly correct and they're both exactly the same width. The double-insulated thing sounds from the way you're describing it like it's going to add several degrees-of-difficulty to the overall project; is it your counsel that I bag that part of the scheme and return the inner box?

THANK YOU FOR ALL YOUR TIME AND INPUT. Try not to worry too much; I'm going to go slower and far more inquisitively about all of this than I probably made it sound in my OP.

Dave.

 

RE: A great question but a soap-opera answer-Guessing, posted on July 29, 2009 at 19:07:23
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 I don't think you have a DC offset that is causing a problem. Again I ask-how do you think DC is getting through the transformers in your equipment?

A transformer CANNOT pass DC-no matter how much you think it can.

But you can do whatever you want-as long as you don't kill yourself, but unless you can somehow prove you have DC on the line-which is real easy using a oscope-you are just guessing.

Regarding all your problems-some people are just prone to electronic problems. I am a bench tech and honestly believe this.

My daughter is one of those. Everything she touches that is electronic fails very early. Myself-my stuff lasts a long time. Maybe that is your problem.

But hey it is your gear and your money-so do what you want.

But the FIRST rule of treating ANY problem is defining the REAL problem-not an imagined one.

BTW where did you get the idea that "DC" is affecting all your gear?

 

RE: A great question but a soap-opera answer, posted on July 29, 2009 at 19:08:44
Uncle Mike
 "and the only things left other than a high resistance to ground is DC-offset or common mode interference."
First if your reading any more than a few meg ohms resistance to ground you need to work on a better ground scheme. That itself can cause a world of problems.
Next: How are you measuring this DC offset? Or more to the point what convinces you it is there?

 

RE: Naive questions re d-i-y-Hate to tell you, posted on July 29, 2009 at 19:17:48
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 I hate to tell you-but the only thing that circuit can do is to drop the AC voltage by 1.6V-the voltage drop across 2 diodes in series.

If there was any DC on the line, on e pair of diodes will be forward biased, no matter whether the DC is + or - on the particular leg this "circuit" is installed on. Of course it would be dropped by 1.2V-again the drop across the pair of diodes that would be forward biased.

If you have a better idea on how this works-please enlighten me.

Yes the caps will block DC-but the diodes allow a path "around" the caps for the DC-if it actually exists.

 

No technical data, just symptoms, posted on July 29, 2009 at 21:15:58
author@escapeclause.net
Audiophile

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Location: Gainesville, FL
Joined: May 28, 2006
 I've been hearing a lot about DC-offset causing transformer saturation and rattle. If so, this would explain why my CDP gets hot and hums loudly in my rig, but not on the bench. Since the parts are cheap, I didn't think it was worth an exhaustive inquiry to verify.

The electrician didn't test the new ground stake that he established beneath the new service because he didn't think it was necessary. "Try everything now and see what you think," he said, "and if you've still got problems we'll come back and test that too." I think he thinks that all those shared neutrals in the ground bar inside the old service were a much bigger problem.

Over to you....

 

Symptoms only, posted on July 29, 2009 at 21:19:18
author@escapeclause.net
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 From what I've read, the presence of a DC-offset can lead to saturation and rattling of the transformer, not passage through the transformer to the rest of the piece of equipment. If true, this would explain why my CDP hums loudly and runs extremely hot when it's in my system, but not on someone else's bench.

I've been wondering if it's in my fingertips, somehow, but I've been afraid to ask this question out of fear that it would sound completely crazy. Could there really be a technical explanation -- a scientific explanation -- that had something to do with me, physically? I've had terrible trouble with car electrics my whole life, but the home audio stuff only started after I moved into this house.

 

Couldn't disprove it by me by a *longshot*, posted on July 29, 2009 at 21:21:35
author@escapeclause.net
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 All I know about this circuit is (a) that it's used by Bryston inside their amplifiers -- in the capacity of blockage of DC -- and (b) that it is embraced by the tweakers in audiocircle dot com, for that same purpose. If it doesn't work, that'd be news to them -- but that doesn't have to mean that what you're saying is incorrect.

 

RE: Naive questions re d-i-y-Hate to tell you, posted on July 29, 2009 at 22:54:31
John Swenson
Audiophile

Posts: 2422
Location: No. California
Joined: October 13, 2002
 The circuit is designed to block small DC voltages. In normal operations the caps do the blocking, the diodes are there simply as a protection device to prevent the DC across the caps from getting too high. (too high being 1.2V in this case) The caps used are very high value low voltage electrolytics. The value of the caps is high enough that the impedance is quite low at 60Hz so the voltage drop across the caps is significantly less than 1V even at ten amps of AC through the caps.

The measured DC from many peoples houses is usually less than 400mV so a 1.2 protection voltage is perfectly sufficient in most cases.

John S.

 

RE: A helpful and proportionate answer -- PERFECT!-The problem?????, posted on July 29, 2009 at 23:06:46
John Swenson
Audiophile

Posts: 2422
Location: No. California
Joined: October 13, 2002
 The DC comes from non-resistive loads on the AC line such as light dimmers, switch mode power supplies etc. These add harmonics which distort the AC waveform. It doesn't take much of a non symmetric distortion to produce an overall DC offset. Its not much, a couple hundred millivolts or so, but thats enough to cause transformer saturation in some devices. Many modern transformers run the specs right to the hairy edge in order to save money and even a little DC can push them over said edge.

John S.

 

RE: Couldn't disprove it by me by a *longshot*, posted on July 30, 2009 at 03:37:52
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 Inside your amp is one thing-outside on the AC mains is quite another.

But go ahead and satisfy yourself.

 

RE: Naive questions re d-i-y-Hate to tell you-.4V????, posted on July 30, 2009 at 03:42:48
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 Ok so let's say that somehow there is a 0.4V offset in the AC line. Agreed that it won't pass across the diodes because there is not enough forward bias.

Do you think that small a voltage is going to cause all of his gear to start failing and rattling and so forth?

I think not.

 

RE: Symptoms only, posted on July 30, 2009 at 08:37:53
Uncle Mike
 "the home audio stuff only started after I moved into this house."
Poltergeists? Ya think? Just funnin'

 

RE: Naive questions re d-i-y-Hate to tell you-.4V????, posted on July 30, 2009 at 10:58:08
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 Maybe not all of it -- but could it explain why the CD player was emitting mechanical transformer hum (and maybe explain why it was getting hot) in my rig, but not on the bench?

 

The calls are coming from inside the house!!!! (nt), posted on July 30, 2009 at 11:05:53
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 .

 

RE: Naive questions re d-i-y-Hate to tell you-.4V????, posted on July 30, 2009 at 12:59:56
Solder n Listen
Audiophile

Posts: 132
Location: Thermionia
Joined: December 15, 2007
 DC voltage applied to a power transformer will cause saturation of the
core (unless there is a gap, which is unlikely in a power transformer)
and can also cause heating and buzzing in many cases.

As far as " failing and rattling and so forth" I really don't know.

 

"DC" on the AC comes from asymmetrical loads., posted on July 30, 2009 at 15:47:01
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 Some hair dryers, for example, have a half-power switch that uses a diode to pass only one side of the sine wave into the heater. The I*R drops on the wiring apply a one-sided offset to all other loads on the same leg of the utility transformer.

This "DC" is a low voltage but has a low source impedance. It easily saturates some toroidal power transformers in audio gear.

My neighbor is a school teacher. Every school day morning my power amp transformers hum loudly for a minute or so shortly before I see her leave for work.

 

I think so., posted on July 30, 2009 at 15:57:22
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 See my reply to another one of your posts below.

 

That teacher must be smoking, posted on July 30, 2009 at 16:34:10
dhrab
Audiophile

Posts: 302
Location: new england
Joined: January 22, 2003
 >>"My neighbor is a school teacher. Every school day morning my power amp transformers hum loudly for a minute or so shortly before I see her leave for work."<<

I hear ya on that one ... My Phase Linear D500 with a 960Kva Iron core tranny HUMS out of control everytime the UPS deliver person shows up

Scroll for picture of UPS delivery person
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RE: Naive questions re d-i-y-Hate to tell you-.4V????-A little math, posted on July 30, 2009 at 16:49:54
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 OK let's look at something practical. Let's say you have 1VDC on the line-more than twice the suggested .4V.

If the input resistance (not impedance as impedance is only for AC circuits) is 1 ohm. I just measured a bunch of typical transformers used in various audio gear. For a 400 watt power transformer I got 1 ohm on the primary windings. For a signal type device (such as a CD player) I got 40 ohms. Others were in between that-and some higher.

So lets assume your CD player has a LARGE heavy transformer and you have a 1 ohm load on the AC line. By the way-how much power is your CD player rated to draw?

So with a higher than stated DC voltage on the line the wattage the transformer would be dissapating would be 1 watt. Do you really think that 1 watt is heating up your device?

If we use the more realistic numbers of say 500mV and a 40 ohm load we have 0.006 watts. Do you really think that huge amount of power is causing much heat and even worse damage?

I don't. But you can believe what you want.

I also wonder how DC (especially the small amounts discussed here) can cause vibration in a transformer? That takes AC or maybe a HUGE amount of DC-not the little amounts discussed here. There is no freq with DC. Vibration is by nature an AC event. If it wasn't "moving" it would be DC.

Maybe it is not secured properly?

I hope you find your solution-but I doubt it is DC on the line.

Good luck. Sorry to confuse myths with facts.

 

Ivan, posted on July 30, 2009 at 17:32:50
Solder n Listen
Audiophile

Posts: 132
Location: Thermionia
Joined: December 15, 2007
 Ivan -
There are plenty of places on the web to study up on transformers.
They have been around for more than a century, and their operation
is well understood. You might want to zero in on how DC affects an
ungapped core. It is well known science, not myth.

 

Well I'm happy to have inspired this post (nt), posted on July 30, 2009 at 18:20:07
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 .

 

Finishing one's sentences, posted on July 31, 2009 at 04:03:10
dhrab
Audiophile

Posts: 302
Location: new england
Joined: January 22, 2003
 If you are a student of Al S. like I am ... then you would know Al didn't finish his last sentence completely in the post about the school teacher
The rest of the sentence goes on to tell how it was ... "the school teacher's hair dryer that was injecting the asym. waves back on line and the resultant DC offset causes Al's amps to hum in the morning, when teacher is drying her hair, just before she leaves for work.

As for my Phase Linear tranny's humming when the UPS gal shows up ... well it isn't DC offset ... and who cares

Now let me finish another sentence ... most agree that ... "DC offset is real and can cause certain tranny's to rattle and go into saturation ... (now to finish the sentence)

... This asym. wave (DC offset) will decrease the effected transformers efficiency, limiting it's headroom, and reducing it's dynamic range

Another interesting point ... while most of the focus was on the diode's roll in the circuit and their questionable effectiveness .... not one word was mentioned of the nifty little filter that Bryston places on the 3rd wire safety/ground wire that keeps counter currents caused by high soil resistivity, RF, and ringing due to impedance mismatches of the termination out

Love the way you handled the tough room with aplumb ... You da man

Bryston circuit Ck out 3rd wire filter




 

Now I wanna build 3rd wire filters too! :-), posted on July 31, 2009 at 06:28:45
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 I'm still a little confused about how the dc-blocker gets soldered together but I think part of that confusion is that I haven't gotten the parts out of the box and actually looked at them yet. (It does appear as though my parts list for the DC-blocker has the wrong value of caps, though -- I bought 35v 3,300uf and it looks as though I needed 6v 33,000uf, instead, which presumably is a pretty big friggin' difference.

Presumably a filtration scheme for the third wire could be added at a single point, inside the felix, too -- right?

...Hey, we're all havin' fun after all. And nobody has blown himself up. Win-win.

-Dave.

 

How do I test resistence to ground?, posted on July 31, 2009 at 06:56:44
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 I have a nice digital multimeter and a brand-new service entrance on the outside of the house, complete with new ground stake. How do I test how much resistance there is to my home's ground? Presumably I put the multimeter on 200 ohms, put the red lead on the top of the ground stake, and then the black lead -- where, exactly? Preferably someplace where I'm not going to close a main-AC circuit using my index finger?

 

What about static discharge?, posted on July 31, 2009 at 07:10:54
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 One possibility that Ivan hinted around the edges of with his reference to his daughter, was the possibility that something having to do with *me*, personally, was causing all of the trouble. Could that something be an unusual accumulation of static? I have adult-ADHD (surprise, surprise) and probably scuttle around on my rugs a lot more than most people, flitting from the first third of the dishes to the second fifth of the laundry to the third seventh of the eighth chapter of the book I still haven't finished writing -- am I damaging my own stuff by walking over to the rig and touching it?

The Parasound problem, in particular, seemed like static: A cloudy whooshing sound, almost like water in your ear, that would go away with a 'pop' if you broke the IC-connections.

Is there a safe way to discharge static each time I approach my rig?

 

This is easier and safer, posted on July 31, 2009 at 08:24:12
dhrab
Audiophile

Posts: 302
Location: new england
Joined: January 22, 2003
 I know you're a very intelligent guy so I will pay you the complement of being very blunt ... Don't Screw with the safety ... beyond DIY skills you need EE skills

Here is a link to a product that is designed to deal with the grounding problem ...

http://www.ep2000.com/Templates/ep2750.html

... also Audio Magic makes a ground interrupt ... both can be expensive in the $600 range

Here's another way you can work around ... it is an IEC which offers both common mode (X caps) and diff. mode (Y caps) attenuation and also has a ground filter.

The nice thing is the X and Y Caps should be line rated and the ground interrupt has to be properly implemented or they couldn't sell them

No DIY confusion ... just pop the IEC in and add your DC off circuit

http://www.schaffner.com/components/en/_pdf/Datasheet%20FN9244E%20e%20104.pdf

There are also many other power related issues that need to be addressed ... most of your equipment feeds back high frequency noise due to the components normal operation ... switching power supplies, click it T clack clocks and dacs and any chip that turns on and off will put noise back into the system ... must back filter or bi-directionally filter

Also you have the Dark Side to deal with ... this is the magnetic side of the wave ... the EM portion ...the Force that makes the whole show happen

Like Denise Richards says ... "it's complicated"

 

Looks good, on first blush, posted on July 31, 2009 at 09:00:33
author@escapeclause.net
Audiophile

Posts: 779
Location: Gainesville, FL
Joined: May 28, 2006
 ...but I'd still either need to wire an outlet to the other side of that Schaffner IEC, or wire the IEC inside each of my components -- so am I really gaining that much, especially since I already have the parts? Non-rhetorical question.

How much does the Schaffner IEC cost?

 

You are embarrassing yourself., posted on July 31, 2009 at 09:35:12
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 Time to learn a little about transformers.

 

Only if the amp is seriously defective., posted on July 31, 2009 at 09:39:27
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 Yes, some poorly designed electronics can be damaged by the static charge a human could accumulate in a typical house, but the methods of avoiding this are well-known and it has not been a serious problem for years.

There is some notion that static charges accumulated by some audio components may influence the sound slightly. Removing this charge, typically with anti-static sprays, seems to help.

 

RE: Now I wanna build 3rd wire filters too! :-) Please, not that one!, posted on July 31, 2009 at 11:35:49
pmkap
Manufacturer

Posts: 552
Joined: March 21, 2001
 Please look at the whole shematic typical of the Brystron implementation-
http://bryston.com/pdfs/3B-SST-SCH-1C(Oct02).pdf
Please note that that ground 'standoff' is NOT in the Safety Ground, but rather is used as noise/ground loop minimizer for the power supply ground and/or the signal ground. Brystrons implementation does not intermediate the safety ground connection to the chassis, nor should you.

For a discussion of this technique, see the link at the bottom of this post. It can be used within your components, both not within an external powerconditioning units as that would compromise safety.

You cerainly could use safety ground conditioning in the form of wrapping a few turns of the safety ground wire around a type 26 or 52 material toroid, similar to the Shaefner filter described below.

As to using a Shaefner filter in lieu of a Felix, good luck with that.
FWIW, YMMV

 

RE: You are embarrassing yourself. Educate me please, posted on July 31, 2009 at 16:37:19
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 I am not arguing about what DC can do to a transformer and affect the operation-just about the very small amounts we are talking about.

IF it was such a problem-then why are there not all sorts of commercial products to prevent it-especially if it is causing all the damage that is claimed? According to the discussions here-it is a major problem that somebody could make a lot of money making plug in devices to stop the little bitty amounts of DC on the AC line.

You could even get the government to help out by having a device that will make other pieces of electrical last longer-therefore slowing the landfill rate and so forth.

Why is this not discussed on any regular forums and only on tweaker forums?

I can honestly say I have never seen damage to any device come across my repair bench-that would appear to have caused by anything like this.

Of course I only worked on pro and musical gear-so I guess the problem only bothers high end consumer gear. Does that make it better or worse?

To be honest, in my 35 years of working on electronics, I have never heard of this problem-untill I looked here.

I guess I have just been in the wrong circles-my bad. Maybe the industry is keeping this a secret?

If it were such a problem-why don't pieces of gear have this circuit on the primary side of the transformer to stop it from causing damage? I have never seen such a circuit before. Can you point me to devices that have this-with a schematic reference-not heresay?

Are there any articles in any professional magazines regarding this? Any AES articles? Anywhere besides Audiophile types? Why is this not discussed in any of the professional grounding classes or hum buzz seminars attended by industry professionals?

There are all sorts of equipment that has transformers in it-does this DC only bother audio equipment?

If this "DC" is getting on the AC line by such things as a series diodes on hair dryers (as has been suggested), then how is it getting rectified and filted into a DC voltage that is smooth enough to cause damage. A Chopped up signal on a AC line is still AC in nature-NOT DC.

Sorry for all the questions-but I am just looking for some education regarding this. This is just all new to me.

Some guidance towards real articles would be appreciated. I have Googled several different variations of this and cannot find any links-can you provide some-beside forums?

 

RE: Looks good, on first blush, posted on July 31, 2009 at 18:48:24
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 If your gear stops being damaged-then I would say that you are gaining-IF that is your problem.

On the other hand-you can just keep buying gear and do your part to stimulate the economy.

 

RE: You are embarrassing yourself. Educate me please, posted on July 31, 2009 at 19:19:32
budm
Audiophile

Posts: 556
Location: No.cal
Joined: August 7, 2003
 Check out Bryston and Plitron web site
http://bryston.com/BrystonSite05/BrystonDocs.html look at power amp such as sst series. Bryston and Crown have been using this circuits for a long time.

 

Here is another one, posted on July 31, 2009 at 19:23:21
budm
Audiophile

Posts: 556
Location: No.cal
Joined: August 7, 2003
 This is a great site.

 

Try a Google search on "DC on the AC" (with the quotes), posted on August 1, 2009 at 12:05:16
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 Here is one link to a Ben Duncan book from 1996:

http://books.google.com/books?id=-5UPyE6dcWgC&pg=PA234&lpg=PA234&dq="DC+on+the+AC"&source=bl&ots=wuGrooAGfX&sig=pce7VtBoNsIg9zI3wWVMCNXwTnA&hl=en&ei=_ZF0SpOABIegswPh0O3RCA&sa=X&oi=book_result&ct=result&resnum=8#v=onepage&q="DC%20on%20the%20AC"&f=false

 

RE: You are embarrassing yourself. Educate me please, posted on August 1, 2009 at 13:22:19
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 So only certain products are prone to effects? I guess that is why most products are immune to it and do not have filters built in. So maybe the products that are "bothered" by it, should have the filters already built in.

If that is the case-then why bother with external devices.

I have yet to read anywhere that this DC is actually damamging equipment-as the OP was suggesting that was happening to his gear.

 

RE: You are embarrassing yourself. Educate me please, posted on August 1, 2009 at 15:38:31
Solder n Listen
Audiophile

Posts: 132
Location: Thermionia
Joined: December 15, 2007
 A quick word search on this thread shows that you are the only one who thinks damage is being done to audio equipment. DC can cause transformer failure, but typically it only degrades sound.

Try it yourself to discover the effects: put a diode in series with a battery, then bypass that with 2 large uf electrolytics wired in series.
Insert this in series with the AC line using suitable precautions.

Please offer the D battery a cigarette and a blindfold first.

You may well find that the sound is indeed affected.

 

RE: The reason for my statements, posted on August 1, 2009 at 15:53:03
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 It is not ME who thinks that the equipment is being damaged.

If you read this post

http://www.audioasylum.com/audio/tweaks/messages/16/164654.html

you will see that he is concerned that the DC on his line is damaging his equipment, so much that he is throwing it away.

And he wanted to stop that damage.

That is why I am making the statements regarding DC on the line. Others are agreeing that it is a problem and nobody has told the origional poster that putting this filter on his line will not stop his gear from being damaged, but might only affect the sonic quality.

THAT is the reason for my statements.

Maybe I am not reading his post properly. And since people are suggesting this as a fix-I assume they think that it is ALSO damaging his gear.

 

...seems to be to show us how clever you are., posted on August 2, 2009 at 12:52:34
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 They are not working.

The OP has one or more unusual problems with his audio setup, and a series of equipment failures. You seem to be more interested in humiliating him than in helping him.

He has offered one symptom: that his CD player buzzes in his setup but not on the service bench; that may point to DC on his AC. It may also point to excessive line voltage. None of us has the chance to examine his setup in person, so we discuss things that we know can cause his symptoms.

Enough DC offset can cause any line transformer to burn down. In fact, one global danger from solar storms is that a slowly-changing blast of ions could induce sufficient ground currents to saturate power system transformers and burn them up before automatic protection equipment can save them.

However, it is unlikely that the OP has enough DC offset on his AC to cause his rash of equipment failures. By eliminating DC as the cause of his CD player's buzz, we can help him make progress in finding the root cause of his problems.

 

RE: ...seems to be to show us how clever you are. Finding the problem FIRST, posted on August 2, 2009 at 14:26:16
Ivan Beaver
Manufacturer

Posts: 232
Location: Atlanta GA
Joined: September 1, 2007
 Of course a simple volt meter hooked across the AC line and monitored would be a FIRST step that I would take.

NOT learning how to solder-how to hook up components that he doesn't know what they are-AND applying this to an AC line voltage.

That just seems extreme to me.

Maybe a UPS that regenerates its own output voltage (rather than just a switch to battery backup when the line drops low) would be a much safer solution-or test anyway.

I am not trying to single him out, but rather that the notion of this rarely discussed issue (outside of tweakers forums) is his problem.

In ANY troubleshooting, the FIRST THING you do is to determine WHAT the problem is-not just jump as guessing possible solutions.

FIND THE PROBLEM FIRST-then propose a solution. How do you what the solution is-if you don't know what the problem is?

Maybe there is somthing physical about his CD player that is causing the problem-like a loose bolt for example-that had moved just enough during transport to tighten down the transformer.

What is vibrating in the CD player? Has he touched the case-put pressure on the outside? taken it apart to listen/feel/hear where the vibration is coming from? Those are all steps I would take first-long before I modified the AC line.

His AC voltage may be high or low-and that is causing the problem-we have no idea-but THAT is an easy check.

 

RF noise filters, posted on August 2, 2009 at 15:56:06
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 RF noise does affect sonic performance of some audio equipment, but it is not likely the source of your 'soap opera' difficulties.

Modifying equipment to accept a larger IEC inlet/filter device is not likely to be easy, and would almost certainly ruin any resale value. I would not assume that the performance would be improved by including the Schaffner device: the intentions are good but we don't know what specific capacitors and inductors were used, and what their sonic signatures may be. You could end up being less pleased with the equipment's performance.

 

You hire an electrician with the right equipment., posted on August 2, 2009 at 16:12:07
Al Sekela
Audiophile

Posts: 9169
Location: Northern California
Joined: February 18, 2002
 Your multimeter may or may not be confused by AC potential difference between something inside your house and the new ground stake. If you have any doubts about the grounding, it is better to hire another electrician.

Your audio equipment problems should not be caused by earthing resistance issues. Have you measured the line voltage (hot to neutral) at your system, and on a circuit connected to the opposite leg of the incoming 240 volts? Both voltages should be of the same magnitude, i.e. half of the total incoming voltage.

One way that it is possible to get an imbalance is if there is a heavy load on one leg and some resistance in the utility's neutral wire or connections. This causes some voltage drop in the neutral wire that adds to the voltage seen by the loads on the other leg. The heavy load could be in a neighbor's house with whom you share the utility transformer (any clandestine pot gardens around?).

 

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