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Discussion Starter · #1 ·
I recently added a couple of Parasound monoblock amps to feed my main speakers off my Yamaha RX-V3300. I have had then running a few days now and they sound great but I ususally turn on the receiver before the amps and I have found that when I go to flip on the amps the receiver shuts off. What might be happening here?



I should add that it does not happen every time... after everything is warmed up it does not happen so easily.
 

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It could be that the amps have such a high inrush current that the voltage is sagging momentarily. Is your equipment plugged into a power strip, via an extension cord, and a long, 15-amp circuit?


In other words, the higher the total circuit impedance (resistance), the more a current increase causes a voltage drop. Try a different receptacle, cord, circuit, etc. as a temporary test.


Another clue is the fact that, when "warmed up", the power supply capacitors may not have fully discharged, which means a lower initial current demand.
 

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Discussion Starter · #3 ·
Is your equipment plugged into a power strip, via an extension cord, and a long, 15-amp circuit?

>>>>>>>>>>>>>>>>>>>>>>>>>>

Why yes. :)...How did you guess?



I will try separating the power source of the amps and receiver and get back to you.
 

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Not a guess; expertise and experience.
 

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Discussion Starter · #5 ·
I was kind of hoping for a more detailed answer. :)




I still have not tried another power source because there is not a convienent one.



But now the thought of this power source not being compentent is bothering me. I live in a house built in the 1930s, most of the house groundless electric jacks , the laundry room is the only place with a regular 3 pronged grounded jack. I believe its a 15amp outlet.

Anyways I am using a 50' high quality extension cord that is running into my HT room, its 12awg so I figured it was plenty. An basic 8 outlet surge protector is connected to the extension cord and it feeds all of my HT gear.


2 Parasound high current monoblocks

A Yamaha RX-V3300

a Directivo

a few DVD players

an Infocus X1 projector

a lamp



Although it only takes turning on the receiver and one of the monoblocks when they are cold to repeat the receiver shut-down problem.

I would think that a 50' 12awg cable is plenty to provide a steady 15 amps, after all its made for power hungry construction tools.


How much power could a single mono block possibly consume for a spit second , enough to cause a voltage drop?

Also wouldn't the receiver allow a certain voltage drop without shutting down?

I am an auto mechanic by day so I will bring home my Fluke multimeter and watch the voltage. I am not sure if its fast enough to catch a spit second voltage drop but I can at least try.
 

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Discussion Starter · #6 ·
BTW the amps only put out 150wpc @ 8ohms with 20,000uF capacitance, the PSU is rated @ 1.5kVA.


I have never had something else in the chain shut down as a result of flipping on my previous 250WPC JBL subwoofer that was connected to the same surge protector a short time ago nor have I had anything shut down as a result of flipping on the receiver which is on the stout side of receivers , 50lbs , big PSU and 27,000UF ...although I have noticed that the lights dim a tad when any of these units are powered on.
 

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Quote:
...although I have noticed that the lights dim a tad when any of these units are powered on.
then you've seen the effect of the inrush current.


A discharged capacitor is effectively a short circuit. the inrush current can be very high, resulting in huge IIR losses.
 

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also spend some money on a electrician and scrap the extention cord-
 

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forget that, do it yourself....most houses that use circuit breakers have extra spare slots you can add to make new circuits.....it does not take a rocket scientist to figure out how to wire a plug........
 

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forget that, do it yourself
I usually agree with that sentiment but the house was built in the 30s. Unless you know exactly what you're doing, it would be worth calling in a pro, at least for a consultation. A lot of those old houses are a fire waiting to happen and the dimming lights bit is enough to make me suspect this may be one of them.


I recently remodelled one built in the early 40s and what I found when I tore into the walls was truly frightening - single wires with the insulation crumbling off and lots of bare copper showing, running right through old wadded-up newspapers stuffed in the walls as insulation. I ended up replacing every wire, outlet and fixture, all the way back to where the service came into the house.


Of course, that assumes you own the house and are allowed to upgrade the electrical system. People renting old houses are in a tough spot. Best to get renters insurance to cover that expensive gear. ;)
 

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Discussion Starter · #11 ·
Larry, I was able to capture a small voltage drop using the min/max feature on my muti-meter. My line is around 119V and the lowest drop I recorded was about 3.5 volts and this is what it takes to shut down the receiver, the amps have to be ice cold for this to happen....is it reasonable that the receiver would shut down with shut a short drop?
 

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Quote:
Originally posted by catapult
I usually agree with that sentiment but the house was built in the 30s. Unless you know exactly what you're doing, it would be worth calling in a pro, at least for a consultation. A lot of those old houses are a fire waiting to happen and the dimming lights bit is enough to make me suspect this may be one of them.


I recently remodelled one built in the early 40s and what I found when I tore into the walls was truly frightening - single wires with the insulation crumbling off and lots of bare copper showing, running right through old wadded-up newspapers stuffed in the walls as insulation. I ended up replacing every wire, outlet and fixture, all the way back to where the service came into the house.


Of course, that assumes you own the house and are allowed to upgrade the electrical system. People renting old houses are in a tough spot. Best to get renters insurance to cover that expensive gear. ;)
I hate to think of it. When I was in college, I rented out a 4 bedroom house with three other guys that was built in 1900, we moved out in '99, so it was 99 years old. I'm sure there was no major rewiring done in the last 50 years in that house, probably only rewiring occured when they first go power. You could see where there was a little brick paved path out the back door to where there used to be an outhouse. Back then, I never really considered the wiring or anything like that. I just thought "4 bedrooms, all large, huge living room and great room, excellent party house..." I think I'll end that story on that note :rolleyes:
 

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Discussion Starter · #13 ·
I have more confidence in my old wiring than some of today's cheap wiring jobs.. aluminum etc. :)


Actually the wiring in my old home is considerably better than the apartment I used to live in back in the early 90s that was brand new. ...god what a piece of crap!...I remember having to keep dozens of light bulbs on hand because that place ate them like they were nothing!

Furthermore one circuit on the the apartment blew breakers so often that I quit using it all together.



Also I have never lived in a home where the lights did not dim momentarily to some degree when I flipped on a power hungry piece of electronics...currently I get maybe a .2 fluctuation in voltage at most when I flip on my amps..big deal...besides .you guys are naive if you thing your homes wiring is always the weakest link in the chain.


My old house has excellent wiring for its age, overall its very stable ..one proof of this is that I never have to replace light bulbs.
 

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Quote:
Originally posted by James W. Johnson
I have more confidence in my old wiring than some of today's cheap wiring jobs.. aluminum etc. :)


Actually the wiring in my old home is considerably better than the apartment I used to live in back in the early 90s that was brand new. ...god what a piece of crap!...I remember having to keep dozens of light bulbs on hand because that place ate them like they were nothing!

Furthermore one circuit on the the apartment blew breakers so often that I quit using it all together.



Also I have never lived in a home where the lights did not dim momentarily to some degree when I flipped on a power hungry piece of electronics...currently I get maybe a .2 fluctuation in voltage at most when I flip on my amps..big deal...besides .you guys are naive if you thing your homes wiring is always the weakest link in the chain.


My old house has excellent wiring for its age, overall its very stable ..one proof of this is that I never have to replace light bulbs.
What I was referring to was his story how the wire insulation had basically dryrotted right off of his wiring so he had exposed wiring in walls with newspaper insulation. Even if it was a solid wiring job, with an older house, that definitely gives something to think about...not necessarily on the ability to do a good job providing power throughput, but the safety end...I was stupid in college and never had renters insurance (too cheap)...looking back, if I would have heard that story and thought about it while I was living in that house, I would have given blood a few more times to pay for it.:rolleyes:
 

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Quote:
Originally posted by James W. Johnson
I was kind of hoping for a more detailed answer. :)
Okay. I've been "into" electronics since before the first grade; I was doing audio and phone wiring by age 12; I did my first service change (alone) at 16; I seem to grasp electrical theory better than any electrician I ever worked under (as a helper) or with (as a journeyman). How's that?
Quote:
I would think that a 50' 12awg cable is plenty to provide a steady 15 amps, after all its made for power hungry construction tools.
"Steady" is the key word. Absolutely, a steady 15 amps is no problem for a 12 ga. cord, although there will indeed be a measurable voltage drop along that cord, as well as the circuit the cord is plugged into. If the cord doesnt have to be 50', it might be worth shortening it. (Get a plug and a socket, and turn it into two 25' cords.)
Quote:
How much power could a single mono block possibly consume for a spit second , enough to cause a voltage drop?
Ah! That's the $64K question. For a split second, that current demand peak could reach 100 amps or more.
Quote:
Also wouldn't the receiver allow a certain voltage drop without shutting down?
Here I would agree. It seems that the receiver is overly sensitive to momentary voltage sags. The only test is to change something, even if it means using a second cord (such as the second one made by my prior suggestion) for the receiver alone. The manufacturer would be the one to talk to.
Quote:
...the lowest drop I recorded was about 3.5 volts...
I can assure you that the meter isn't fast enough to capture the true extent of the momentary fluctuation. A special meter known as an 'event recorder' should have a much faster response, and be able to display it.


A temporary experiment with a second cord would be cheaper, and a new circuit would be the best permanent solution by far; maybe even a pair of circuits with a shared neutral, since the labor would be the same for a 12/2 or a 12/3 run.
 

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Discussion Starter · #16 ·
Well it looks like it was not a voltage drop problem after all...unplugging the receiver to amp pre-outs solved the problem.

After the amps sit abit and they are turned on, a spike of current is feeding back thru the amp inputs. Both amps do this!


I am not sure what kind of current it is or exactly how much but I know darn well nothing should be coming out of the amp inputs. :)



Any ideas Larry?
 

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Quote:
Originally posted by James W. Johnson
I have more confidence in my old wiring than some of today's cheap wiring jobs.. aluminum etc.
You won't find aluminum in use to much anymore, it's been basically outlawed in most places because of the problems with it. And anyplace that did have it, it's probably been replaced due to those problems.
 

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my house was built in the early 50's-had 3 -20watt fuses- no ground.

had a breaker system installed and 3 dedicated lines for audio.

well worth the $-also installed new line for fridge
 

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Quote:
Originally posted by Johnla
You won't find aluminum in use to much anymore, it's been basically outlawed in most places because of the problems with it. And anyplace that did have it, it's probably been replaced due to those problems.
Well, to be accurate, it's not in use in smaller sizes for branch circuits. You can still get it in size 8 and larger, especially in service cable types. In large-gauge uses, it hasn't had the problems it had in small-gauge use. Here's why:


When electricity travels through any conductor, it increases in temperature, whoich results in an increase in size. Aluminum warms up more for a given current, even in the larger size used, and also expands much more than copper for a given temperature increase.


An aluminum wire trapped under a screw-head, which is harder than the wire, has no where to go when it expands except sideways, so it flattens out slightly. When the current usage stops, it cools and contracts. Now we have a slightly looser-than-original connection.


Next time the current flows, the lightly-looser connection warms up more than before, due to the reduced metal-to-metal contact, and warms up more than before, which causes more expansion, more flattening, etc.


So, you see, it's the cycling of current that starts the snowball effect. If one re-tightens the connections after a few years of this cycling, the now-flatter wire actually has better metal-to-metal contact than originally.


Once tightened, these connections can actually stay a bit cooler for more years than when new, but the permanent fix is to remove all device connections, wirenut the wires, and use copper pigtails to the terminals.
 
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