Bottlehead Forum
General Category => General Discussion => Topic started by: caffeinator on October 24, 2012, 06:34:03 AM
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Hello, All~
I've long been interested in using a balanced power supply (essentially wiring a transformer to split power from 120V relative to ground to +60 / -60 relative to ground), due to the touted noise reduction benefits.
This results in there being a +/-60 on the normal 'hot' side and a -/+60 on the normal 'neutral' side. I note that most of the Bottlehead kits I've built appear to tie the neutral and ground together (taking both to chassis ground after the IEC socket input).
This may seem like a dumb question, but to try the balanced power, wouldn't it be necessary to sever the neutral/ground tie? Also, anyone have experience with balanced power? Is it worth the trouble?
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To be safe you really need a DPST power switch, and you'll want to switch both hot and neutral separately, and then connect the earth ground on the IEC inlet to the chassis ground.
As to the effectiveness of balanced power, it all really depends on how noisey your local electric grid (or household wiring is) but it can often make things a bit quieter, but often at the expense of best dynamic response. Which may or may not be audible or important to you.
Also, both hot and neutral should be fused, which can be a problem in terms of finding room on some of the BH chassis.
HTH,
Jim
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Thanks, Jim - I hadn't even thought about the switching - that's a great point. While it's not too hard to find info on the internet about balanced power, and DIY balanced power supplies, few, if any, devote any ink to what happens on the device side of the supply.
I can't perceive a lot of power-line noise in my current residence, apart from transients (clothes dryer switches off, other big draw goes on), which are really not a problem.
Would a 1:1 isolation transformer give any benefits?
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I don't really know about the 1:1 isolation transformer -- to my mind they are mostly used for eliminating severe ground loop or DC offset problems. I've never found one of these that negatively effects the sound so none have ever stayed that long in any of my systems. Of course many people perceive no difference whatsoever, so whose to say one way or another without trying it.
-- Jim
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I can't find any Bottlehead equipment that ties neutral to ground. That is properly done at your service panel. But, you are right, if there was such a tie there would be a problem.
So I see no problem using balanced power with the Eros, Seduction, Paramour (all), Paramount, SEX or any version of the Foreplay. Those are the ones I looked at.
My PS Audio P300 has a balanced (60V/60V) output and it feeds my Eros/FP 2/Paramours. All are fine.
I can't tell you if it was the balanced nature of the output or the cleaner regenerated power that made it sound so good when I put the P300 into my system. I had thought my power was fine and then I got the P300. I was wrong! It was a big step up.
Jim,
Great point on the switching and fusing. I'll look into that for my pieces. Mostly I just turn the system off at the P300.
Should the fuses be sized 1/2?
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... I note that most of the Bottlehead kits I've built appear to tie the neutral and ground together (taking both to chassis ground after the IEC socket input)....
None of the kits tie neutral to ground or chassis. That would be dangerous!
We do switch the hot lead, not the neutral lead, in accordance with normal US practice. I agree, it would be preferable to switch both if you have balanced power.
As for the advantages, it is like most noise sources - the effect of using balanced power depends on which of the many noise mechanisms is a problem in your environment. In my humble opinion, the only practical way to tell is to try it - there are too many possible problems and too few ways to test for them.
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If I have read correctly, balanced power is like balanced interconnects. Both are good for eliminating, not just suppressing, "common mode" noise.
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Hi Grainger,
Thanks for the clarification! When I was pondering this the other day, I know I referred to an image somewhere (thought it was a CD manual, but can't find it now) that depicted the connected neutral/ground, but can't find it now. A quick look at my SEX amp shows them separated from the IEC inlet to the PT inputs. I'll visually check everything prior to connecting if I decide to try balanced power.
I have the pieces to put together a DIY balanced power box (trafo, powerline noise filter, MOV's, caps). If I get around to it, I'll try to post pix and results.
I can't recall if it was on this forum or somewhere else, but back when I was originally looking into this, another poster offered his suggestion for balanced power - some small, chassis mountable sized transformers wired to convert from regular AC to balanced inside the chassis. Seems like there was some combo IEC inlet combo that provided for this, but I may be misremembering.
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After years of using ALL kinds of power filters, etc, I couldn't be a bigger fan of balanced power. Even though I hold the PS Audio products in high regard, I personally chose a product from BPT. Not only does have the advantage of balanced power, but the transformer has five separate secondary wings with Faraday shields between each, and other forms of isolation as well. This amounts to dedicated power for every outlet. No doubt you can take this on yourself and save money, but I went the quicker route and bout the item used. I wouldn't dream of going back.
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Thanks to all for the replies. I think my curiosity is peaked enough to try it and see.
My sincere apologies for the mistaken description of typical Bottlehead practice re: neutral and ground. Thanks to everyone for correcting that, too.
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I've used a step down transformer to get balanced power to my older Bottlehead equipment for years with no problems. I agree that the wiring should be handled as hot/hot/grd with a DPDT switch.
I don't have any filtering, but believe I get a benefit of isolation from other AC noise. Lots of noise sources on house lines...computer, TV, LED lights, programmable appliances, chargers...
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After years of using ALL kinds of power filters, etc, I couldn't be a bigger fan of balanced power. Even though I hold the PS Audio products in high regard, I personally chose a product from BPT. Not only does have the advantage of balanced power, but the transformer has five separate secondary wings with Faraday shields between each, and other forms of isolation as well. This amounts to dedicated power for every outlet. No doubt you can take this on yourself and save money, but I went the quicker route and bout the item used. I wouldn't dream of going back.
Plitron makes (or used to) the transformer for the BPT unit. It is a gorgeous piece of work. Plitron used to sell it to the public, but the last time I checked they had discontinued that practice. BPT used to have some good pics on their site of the innards of their unit (can't get their site to load at the moment to see if they still do). It appeared they followed practice typical of what one sees on DIY sites - the transformer, of course, a powerline filter (they used one whereas I've seen other approaches placing one on each output), MOV's, capacitors...one notable difference was what appeared to be a huge ferrite tube - like an elongated or more like extruded - ferrite toroid around the incoming power line.
Here's a link to one diy approach: http://home.comcast.net/~thomasw_2/CheapskateBP1.html
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Yes, they have many options for their products. The ferrite sleeve that you noted may not be essential, but considering the amount of RF now days, I would opt for it. Piltron seems to be in high esteem with a lot of the power guru's. I especially liked the one I bought from BPT, because as I mentioned before, it has separate windings for each outlet, and each winding has a Faraday shield further isolating each winding. Mine weighs about 60 pounds. Now here is the trick to my product. The primary winding is rated at 10 amps RMS, and each secondary winding is rated at 10 amps RMS ass well. You cannot exceed 10 amps RMS for total load from your system. Looking more closely at each component, you will note that they do not draw as much as you might think except for turn on surge. If you turn on the more beefy components after the smaller ones, you will likely avoid any trouble. As it is, my system does not have that much draw to concern myself with in the first place.
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Greg,
This seems to be an exception to the transformer rule that the volt-ampere product of the primary being equal to the volt-ampere product of the secondary. But this rule can not be violated. So something is amiss.
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I thought to be strange as well, but the owner of BPT and I discussed it and he was sure to say that the total amperage of the primary is the actual rated amperage for the whole device.
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It doesn't sound like there's a conflict between BPT's statements and what Grainger is saying. BPT says the rated current capability of the is 10A and that each secondary winding is also rated at 10A. That's not the same, though, as rating the VA capacity of the primary and secondary (or secondaries), is it? Those do have to be the same.
With respect to VA, I'm pondering this myself. The transformer I have for my balanced power project is rated at 1,500 VA. It has two secondaries, though each will be used to form half the outbound balanced power. 1,500 VA in; 1,500 VA out, right? So, at a 120VAC nom. output, I could have up to about 12A continuous, though that seems highly unlikely - unless I wanted really low powerline noise for a space heater or something.
But, what kind of power consumption, or current consumption, and turn-on surge does one figure for, say, a Paramount (or a Pair o' 'mounts), a FPIII, a seduction, etc. ?
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Greg,
That seems to be different to your post above. In the post where you say the primary is rated at 10A (probably at 120V) that gives a VA rating of 1200VA. The secondary having more than one winding rated at 10A (again, probably at 120V) gives a VA rating of each secondary winding of 1200VA. So the VA product of the primary, 1200VA, is not equal to the total of multiple secondary windings all rated at 1200 VA.
What am I missing here?
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Heh heh, let me try again. Normally, you would expect that the total secondary draw would equal the capability of the primary winding rating. At least, that would be my presumtion. The owner of the company(just can't remember his name now) and I were discussing this, and felt that since he likes build products as robust as possible, he made a special order in which EACH secondary winding was capable of full load(there are five secondary windings), and that the primary winding was capable of only ONE of the secondary windings rating. However, he carefully rated the entire product by the capability of the PRIMARY winding, so as not to imply that the customer could hook up equipment in excess of the primary winding in the first place. Perhaps the secondaries are overbuilt only to allow a little inductive reserve. Somewhat over my head, but that is what I know about it. Hope I didn't somehow contradict myself again.
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After years of using ALL kinds of power filters, etc, I couldn't be a bigger fan of balanced power. Even though I hold the PS Audio products in high regard, I personally chose a product from BPT. Not only does have the advantage of balanced power, but the transformer has five separate secondary wings with Faraday shields between each, and other forms of isolation as well. This amounts to dedicated power for every outlet. No doubt you can take this on yourself and save money, but I went the quicker route and bout the item used. I wouldn't dream of going back.
Hey Greg - any comparisons between the BPT and PS Audio stuff? I have been curious about this topic for some time. What BPT do you have/recommend?
thanks - Eric
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But, what kind of power consumption, or current consumption, and turn-on surge does one figure for, say, a Paramount (or a Pair o' 'mounts), a FPIII, a seduction, etc. ?
Don't worry about turn on surge and your transformer. The current ratings exist considering several factors, and a brief turn on surge is not going to build up much heat. This also presumes that you turn everything on at exactly the same time, which is unlikely.
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Eric,
I am divided on this issue. PS Audio products have versatility that I like. For example, the PS regenerators(older ones anyway) can give several different wave forms for the AC output. This can be really cool, depending on how your equipment responds to it. On the plus side, many times equipment responds very favorably with lower noise floor and greater detail, for example. I really like that. But some of my equipment transformers would hum given one or two of the choices that I selected. One Krell cd player actually failed, new, right out of the box! Never did know why. It was replaced with an exact model(and NOT used with the PS Audio P300, and did well). Hmmm. Now, for some reason, there was trouble with my PS Audio premier model here. I do actually blame some kind of radio transmission signaling device nearby, but the unit would turn on for no reason. After sending it back to the factory for a complete checkup, it was returned, and the same problem persisted. I do not think that was the fault of the unit. Having said that, I decided to go another way. That's when I tried other quality conditioners with various results, and just to be done with it. I saw BPT, and decided to take my business there. You see, the balanced power devices offer almost as much in lower noise floor just by design(cancellation due to out of phase or common mode rejection). In addition, they don't the many delicate circuits of the PS Audio units. Since the BPT units added additional passive circuitry, I gave them a try. All in all, there has been improvement and they are immune to airborne troubles from the PS units. As to what model you should choose, it does depend on the needs of your system. Take a look at the site, and then confer with the owner if you need to. He is quite willing to help.
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wow - thanks Greg - lots of good info. ;D
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Greg,
That seems to be different to your post above. In the post where you say the primary is rated at 10A (probably at 120V) that gives a VA rating of 1200VA. The secondary having more than one winding rated at 10A (again, probably at 120V) gives a VA rating of each secondary winding of 1200VA. So the VA product of the primary, 1200VA, is not equal to the total of multiple secondary windings all rated at 1200 VA.
What am I missing here?
I assume it's so you can connect the biggest draw (probably your big Krell class A monster, right?) to whichever secondary is convenient. The others just loaf along.
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Actually, the Krell was a cd player, and I have moved on since to an SACD player made by Yamaha. That was a step in the right direction. I must say however, that after reading your post Paul, it reminded me of a time when I used a PS Audio unit to supply voltage to a Mark Levinson Amp! I'm not kidding. I would first fire up the amp with regular(household current from another household socket), and then when the capacitors were charged, I used the PS300. You may admire my bravery, but dam my judgement. It worked, and it was fun to experiment, but ultimately, the ML did quite fine with 'regular'. Anyway, you are correct in assuming that the secondaries can loaf for the most , allowing maybe one of them to pull the weight by running some bigger draw.
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It seems like its more common for todays big amps have soft start circuits (my Emotiva). In the old days it was a matter of pride to flick your power amp on and have the lights dim!
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Greg,
So are you saying that the secondaries are wound with wire that can deliver 10A on each winding? But you can't produce more than 10A on the total secondary. It is energy, it can't be multiplied. So if one secondary is drawing 10A, the others can't be used without the primary drawing more than 10A from the wall.
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Grainger, What I am saying is that the secondaries are RATED for 10amps RMS, each. That doesn't mean that you can draw more than a TOTAL of 10 amps, FROM ALL 5 secondaries at once. This is because the primary winding is limited to 10amps RMS as well. It is an unusual design, but I really like the overbuilt design. Because of the cost of this transformer, Chris Hoff, owner of BPT, doesn't offer this model any longer....DAM!TT Well, keep an eye out for one used. It is the model 10.5 ULTRA
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So are you saying that the secondaries are wound with wire that can deliver 10A on each winding?
I think it's just a transformer where all the windings are identical, so in practice you could apply your 120V line voltage to one winding and draw 10 amps through one of the other windings on its own.
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exactly
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[quote author=4krow link=topic=3443.msg30386#msg30386 date=1351471887 . . . That doesn't mean that you can draw more than a TOTAL of 10 amps, FROM ALL 5 secondaries at once. This is because the primary winding is limited to 10amps RMS as well. . . . [/quote]
That is what I was trying to say in my last post.
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Soooo....moving on to phasing, if I may. The transformer I want to use to try this out is a Hammond 182T60. It has two primaries and two secondaries. I know what to do on the primary side. My question is with respect to the secondaries - do I tie them together in or out of phase, or, more to the point, do I connect dotted terminals together, or not together?
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The secondaries should be connected in series. Done the wrong way they subtract. So, blue and gray tied together, the output voltage off of red and yellow. That is undoted of one winding tied to the doted of the other winding. That is additive.
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There is a diagram in the data sheet:
http://www.hammondmfg.com/pdf/182%20Insert.pdf
Note that this transformer will slightly increase the voltage; at full rated current it adds 3 volts (117v primary, 120vCT secondary) while at lower current draw it will add more. The regulation is not specified, but it's probably no more than another 3v. Still, you may want to check your power line voltage to be sure it's not already high.
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I am presently using a dedicated 240 VAC outlet with two stepdown transfomers to give 120 VAC for my system.
I have done this for a number of years in two locations and like the results. When I build things I use the DPST
switch as mentioned, and also fuse both hot leads. I'm more comfortable with protection on both sides. It seems
to me that your common mode rejection should be more complete (though hardly perfect) pulling at least
semi-balanced power from your panel.
Skip Pack
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Then, I am to understand that you are stepping down each leg of the 220V(110V, each leg) to 60V? That seems to be balanced power to me.
I used to run each leg of 220V to a mono block amp. For whatever reason, it sounded better.
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> Then, I am to understand that you are stepping down each leg of the 220V(110V, each leg) to 60V?
Yes, that's correct. My voltages here (80 miles south of San Francisco) tend to run around 250/125 at the
outlet. They sure seem to have crept up over the years.
Skip
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Line voltage is increased because it lowers the current. Increasing the voltage doesn't cause transmission lines to heat up, but increased current surely does.
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I had the same problem when I lived 30 miles out of Flagstaff. About 127V, and that was within one volt of 'good enough'. It screwed with everything, and so I bought two transformers with multiple taps that were activated by the voltage being sensed as too low or high. Tripplite makes them, but they are not perfect, and got a pretty good workout where I lived.
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There are things called "constant voltage transformers." They include a lot of reactance in the form of capacitors. They will put out 120V from 90V to 150V input. They are not cheap, they are an industrial device.
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I've seen the multi-tap ones as well. The 5v steps can make havoc with some equipment.
I've also seen a very cool General Radio servo motor driven variac. Fun to watch it hunting for the right voltage ...
Grainger, those reactive ones put out a nasty waveform. And IIRC lots of magnetic-field noise as well.
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We used them to power Modicon and A-B PLCs. Both were very sensitive to voltage problems.