BFD Convert to DC Power - Home Theater Forum and Systems - HomeTheaterShack.com

 
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post #1 of 10 Old 06-15-07, 12:42 PM Thread Starter
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BFD Convert to DC Power

SO I finally got my BFD hooked up last night, and have a descent graph now. In order to keep electrical consumption to a minimum, I am using the switched ports on the back of my receiver to fire off an ac relay that is hooked in to mains (Receiver is only allowed to do 1a switched) I then have this ac relay turn on the sub amp and the BFD. This saves me about $30 per year electrically in "standby" power. The BFD by itself uses about 2 watts accroding to my kill a watt, which equals about $5.00 alone.

Now when I fire it up, the BFD pops, and the amp does not kick in that fast, so I don't care about it, but when I turn off the system, the BFD pops, and the amp still has some power saved up inside somewhere. I was wondering if i yanked off the transformer inside the BFD, and soldered a dc connection after the rectifier, then wired that to a wall wart (that is circuit based, not transformer based. Think laptop power supply type) of the same voltage if this would remove the "pop" when I turn it off. It would also remove the transformer hum that many seem to get.

Has anyone tried this before?
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post #2 of 10 Old 06-15-07, 02:02 PM
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Re: BFD Convert to DC Power

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The BFD by itself uses about 2 watts accroding to my kill a watt, which equals about $5.00 alone.
Mmmm. The BFD consumes 2 watts. That's 48 watt hours a day - that's 17.5 kwatt hours a year. At the average cost of 7.5 cents a kwatt hour, that's $1.30 a year to run a BFD continuously..

I wonder if it's worth the trouble of turning it off. You'd probably be surprised at the amazing amount of standby 'leakage' all the electrical products in your house use. Everything with a remote has to be turned on all the time to ensure it responds. etc, etc.

My point is that the BFD is likely fairly low on the list of energy consumers in the home.

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post #3 of 10 Old 06-15-07, 02:18 PM Thread Starter
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Re: BFD Convert to DC Power

unfortunately, I live in southern California, home of high energy prices. Our bill is always in the 200-300% of baseline which is 29.4 c / kw hour. that = $5.25. Since I allready have these energy saving devices in place (relays), my entertainment center uses 34w continiously, and 32 of which is the DVR.

Unfortunately, im not suprised by "standby" leakage. I have measured all sorts of things, and through similar processes, and turning my computer off, I on average save $40 per month. So this is not a wasted effort.
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post #4 of 10 Old 06-15-07, 02:27 PM
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Re: BFD Convert to DC Power

Fair enough. Yeah, in my room where I have my two computers, I decided to check the 'turned off' standby power consumption (I have a device for it) and was surprised that my new 'green' computer monitor in 'off' drew only a few watts, but my older monitor was a ridiculous 75 watts when turned off. Can you imagine? sheesh....

I hooked up my power monitor and just kept plugging all my stuff in and it totalled quite high. Even devices that don't have on/off switched draw ~10 watts - routers, internet modems, etc, etc.....

Man, you guys pay a lot for electricity......

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post #5 of 10 Old 06-15-07, 02:33 PM
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Re: BFD Convert to DC Power

Anyway, back to your question. I would say it's not the transformer that determines how long it takes for the DC supply to deplete in the BFD, it's the power supply filter capacitor. It would be quite small, so would shut down the DC quickly on turn off and so create the pop. The sub amp would likely take much longer to shut down, so it's ready to make the pop. You need to sequence the BFD later than the amp on shutdown. They do sell power centers that have delays and sequencers built into them....

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post #6 of 10 Old 06-18-07, 06:51 PM Thread Starter
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Re: BFD Convert to DC Power

We pay lots for everythine here in SoCal...

Here is my plan. Im going to measure the voltage of the BFD after the filtercap/rectifier. I am assuming 12 or 5 volts cuz thats pretty normal for electronics. I have the older BFD DSP1100

After I have the voltage I will either Upgrade the filter capacitor or put on an external power source. If i switch the unit to an external power supply, it will have 2 benifits persons here will be interested in.

1. It will remove the ground loops, as AC power will not be fed into the sytem. I had bad ground loop problems. Most of which was caused by my TV, so no easy fix there. I just used a cheater plug, as I was allready thinking of this mod.

2. It will eliminate transformer hum, as there will be no ground, because a ground is not needed for low voltage dc operation.

The best part of this mod, is it is all from junk I have laying around the house, so its a "free" project. Thoes are always nice.
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post #7 of 10 Old 06-18-07, 08:24 PM
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Re: BFD Convert to DC Power

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After I have the voltage I will either Upgrade the filter capacitor or put on an external power source.
I doubt the filter capacitor replacment would have much effect - it seems suitable now. The hum from a BFD that people experience is either the mechanical hum (standard plate rattle), or they have a simple ground loop.

There is merit in replacing the supply with an external DC supply, but seems like a lot of work. It would allow you to easily control the on/off pop though.

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post #8 of 10 Old 06-21-07, 05:21 PM
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Re: BFD Convert to DC Power

isn't there a kind of external wiring to be done to remove this pop...I dunno where I read that.
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post #9 of 10 Old 06-21-07, 06:58 PM Thread Starter
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Re: BFD Convert to DC Power

I had a change to crack the BFD open today, and I found there were 2 AC voltages going into the unit. one aroun 6 or 7 volts, the other at like 18vac. Dual mode power suppies, and figuring out what happened here is above my electrical knowledge.

I think its simpler to make a relay just turn off 10 seconds aftter power is removed. This is a relatively simple circuit to power a dc relay, so it should work good.
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post #10 of 10 Old 06-22-07, 04:49 AM
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Re: BFD Convert to DC Power

The BFD pop is a pest. So I printed out a NASA-style launch list in very large bold type to show the order of switch on and off of my 9 boxes. Without the list my wife wouldn't touch the equipment after the BFD was installed. Nor could she be bothered to use a list if it meant her finding her reading glasses. So now I find her CDs in the player. It can be a bit of a shock having Limp Bizkit suddenly blaring out instead of Vierne or Widor.
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