Household electrical problem

Swerd

Swerd

Audioholic Warlord
Might be best to have a nice new amp on hand for when the old one comes out
I'm too cheap to do that just yet. However, if I absolutely must get another amp, I have this in mind. Less expensive alternatives would be a similarly sized ATI amp, or something from the used world.

For now, I moved the cables for the left & right front speakers from the cold amp (I am unwilling to call it anything else for the present) to the AVR. That works for now. The B&K AVR 507 is rated at 150 wpc (measured at 1 kHz), with an 8 ohm load, at 0.09% THD, delivering 28 amps current (peak-to-peak). The external stereo amp is rated at 200 wpc (measured at 1 kHz), with an 8 ohm load, 350 wpc at 4 ohms, at 0.09% THD, delivering 75 amps current (peak-to-peak).

Now that I have the manual open, that amp's maximum power consumption is 650 watts max, 6.9 Amps maximum current draw, 70 watts with no input. Replacement fuses: Line 12A Slow Blow; Rails 6A Slow Blow. I'll go find a Radio Shack and get some of each.
... f^%& sakes, get yourself an hdmi rec'r while you're at it
I'm too cheap to do that yet (see above).
... and maybe have a sparky run you 3 dedicated 20 ampere lines for the new amplifier and future subwoofer locations.
See above for max current draw of 6.9 Amps. Besides, if I got a dedicated 20 amp line, I'd have to hand in my Audio Skeptic Membership Card.
If you have to knock out any walls you know you can count on me for spackling tips.
:eek: :eek: :eek: No Comment!
 
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Johnny2Bad

Johnny2Bad

Audioholic Chief
@Swerd

You are 100% certain that there is not some similar switch for 1/2 of your HT outlet? Possibly hiding behind a shelf or door? Or (less likely) in some other room?

A good idea is to simply place a piece of tape over the switches that you do not want to get "accidentally" switched to the off position. It won't stop a person determined to flip the switch, but it does serve as a good reminder, "don't turn this switch off".

I would likely try to plug in my amp to a different outlet as the next step for troubleshooting. If you can't easily get to the wall outlet, would it be easier to pull the amp out a foot or so, disconnect the IEC (assuming it has one) connection at the rear of the amp, and plugging in a new cable there just for testing? Or, pull the IEC from a different piece of gear in the rack and temporarily use it on the amp? Otherwise, you may try to run an extension cord to another outlet to troubleshoot only.
I use a half clamp over the switch (for example I have a heat tape on my main water line, and it's on a switched outlet, but only run it in winter. But you don't want someone accidentally turning it off during cold months) ... you have to get your finger in from the side to use the switch. You could also just use a piece of metal or plastic bent to cover the switch. You secure it with the two screws already holding the cover to the outlet. But the clamp looks neater, like it was supposed to be there.
 
KEW

KEW

Audioholic Overlord
...The external stereo amp is rated at 200 wpc (measured at 1 kHz), with an 8 ohm load, 350 wpc at 4 ohms, at 0.09% THD, delivering 75 amps current (peak-to-peak).

Now that I have the manual open, that amp's maximum power consumption is 650 watts max, 6.9 Amps max current draw, 70 watts with no input.
Those specs seem questionable!
Max consumption of 650 watts seems low to be able to produce 400 Watts (200WPC X 2) at 8 or 700 Watts at 4 Ohms. I don't think Class A or A/B can be that efficient.

Maybe not RMS watts? Some sort of peak power? Are you sure it is Watts per channel as opposed to both channels? I looked at the manual and it does not say per channel.

My Niles SI-275 (which seems very well designed) has 600 Watts labeled at the IEC plug (I'd assume max. input power) and produces 75 WPC RMS @ 8 Ohms and 120 WPC RMS @ 4 Ohms. Unless your amp is Class D or something, the same ratios for 650W input work out for 81.5 WPC RMS @ 8 Ohms and 130 WPC RMS @ 4 Ohms.

Do you think your new speakers may have loaded the amp beyond its design (with a dose of old age thrown in)?
 
Swerd

Swerd

Audioholic Warlord
Those specs seem questionable!
Max consumption of 650 watts seems low to be able to produce 400 Watts (200WPC X 2) at 8 or 700 Watts at 4 Ohms. I don't think Class A or A/B can be that efficient.

Maybe not RMS watts? Some sort of peak power? Are you sure it is Watts per channel as opposed to both channels? I looked at the manual and it does not say per channel.
The amp is definitely rated as 200 watts per channel at 8 ohms and at 1 KHz, 350 wpc at 4 ohms.

The manual does not specify RMS or FTC watts which would involve rating at 20-20,000 Hz, so I can't rule out EIA watts, considering the 1 KHz measurement. I've wondered about that before. I didn't worry because the amp is certainly not puny.

The amp operates with a class A predriver and class AB MOSFET output stages – not class D.

How did you find a manual for a B&K EX4420 amp? B&K stopped making it in 1998. When I bought the amp, I emailed them and they sent a pdf manual scanned from a paper copy they had.
Do you think your new speakers may have loaded the amp beyond its design (with a dose of old age thrown in)?
I can't rule that out, but according to Dennis, the Veracity STs are only "somewhat" less sensitive than SongTowers.
 
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Swerd

Swerd

Audioholic Warlord
I just looked up prices for some new "big iron" amps:

AVA Synergy 450 $1999 plus shipping
225 wpc, 20 Hz to 20 KHz, into 8 ohms, at <0.01% THD, class A/AB, 8 double-die MOSFET output transistors, stable at 2 ohms and up

AVA Synergy 300 $1499 plus shipping
150 wpc, 20 Hz to 20 KHz, into 8 ohms, at <0.01% THD, class A/AB, 8 MOSFET output transistors, stable at 4 ohms and up

ATI AT1802 B stock at Classic Audio Parts, $1121 plus shipping
180 WRMS/channel into 8 Ohms (300 WRMS at 4 ohms), 20 Hz to 20 KHz, <0.03% THD & IM distortion.

ATI AT4002 at Classic Audio Parts, $2995 plus shipping
200 WRMS/channel into 8 Ohms (300 WRMS at 4 ohms), 20Hz to 20KHz, <0.03% THD & IM distortion.

I can't seem to find an ATI AT2002 which, if I remember, cost less than the new AT4002.

I guess I'm getting ahead of myself.
 
Swerd

Swerd

Audioholic Warlord
I have had an offer from my brother to help move audio gear & furniture. That would do the trick, as soon as we work out some timing.
 
KEW

KEW

Audioholic Overlord
The amp is definitely rated as 200 watts per channel at 8 ohms and at 1 KHz, 350 wpc at 4 ohms.

The manual does not specify RMS or FTC watts which would involve rating at 20-20,000 Hz, so I can't rule out EIA watts, considering the 1 KHz measurement. I've wondered about that before. I didn't worry because the amp is certainly not puny.

The amp operates with a class A predriver and class AB MOSFET output stages – not class D.

How did you find a manual for a B&K EX4420 amp? B&K stopped making it in 1998. When I bought the amp, I emailed them and they sent a pdf manual scanned from a paper copy they had.
I can't rule that out, but according to Dennis, the Veracity STs are only "somewhat" less sensitive than SongTowers.
https://www.manualslib.com/manual/14276/BAndk-Two-Channel-Amplifier-Ex4420.html

I agree that it looks like a good solid amp, but there is a contradiction somewhere between the Input Watts and Output Watts specification.

@PENG any ideas?
 
KEW

KEW

Audioholic Overlord
I just looked up prices for some new "big iron" amps:

AVA Synergy 450 $1999 plus shipping
225 wpc, 20 Hz to 20 KHz, into 8 ohms, at <0.01% THD, class A/AB, 8 double-die MOSFET output transistors, stable at 2 ohms and up

AVA Synergy 300 $1499 plus shipping
150 wpc, 20 Hz to 20 KHz, into 8 ohms, at <0.01% THD, class A/AB, 8 MOSFET output transistors, stable at 4 ohms and up

ATI AT1802 B stock at Classic Audio Parts, $1121 plus shipping
180 WRMS/channel into 8 Ohms (300 WRMS at 4 ohms), 20 Hz to 20 KHz, <0.03% THD & IM distortion.

ATI AT4002 at Classic Audio Parts, $2995 plus shipping
200 WRMS/channel into 8 Ohms (300 WRMS at 4 ohms), 20Hz to 20KHz, <0.03% THD & IM distortion.

I can't seem to find an ATI AT2002 which, if I remember, cost less than the new AT4002.

I guess I'm getting ahead of myself.
Hopefully it is just a fuse!

I assume you are aware, but just in case, this is an ATI amplifier and will save you a lot of money:
https://www.monoprice.com/Product?p_id=15595&gclid=CjwKEAjw3pTJBRChgZ3e7s_YhAkSJAASG9Vra69nAiV6UWBTYjwV9FdBdow_shgkuPSLVNaGop6keRoCU4vw_wcB
 
Swerd

Swerd

Audioholic Warlord
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Swerd

Swerd

Audioholic Warlord
Not at all. This is moving in the right direction at a good pace.

I bet your speakers sound thin running off the avr. :D
There must be a special place in hell for those who wish that others buy expensive big iron amps :mad:.

I'm still holding out for 1) a failed AC outlet, 2) a disconnected or mouse bitten power cord, or 3) a blown fuse.

Jim Salk says the speakers are 88 dB, 4 ohm minimum/6 ohm average impedance, and recommends 100 watts to drive them, same as for the SongTowers.

I may just keep using the AVR :p.
 
Johnny2Bad

Johnny2Bad

Audioholic Chief
https://www.manualslib.com/manual/14276/BAndk-Two-Channel-Amplifier-Ex4420.html

I agree that it looks like a good solid amp, but there is a contradiction somewhere between the Input Watts and Output Watts specification.

@PENG any ideas?
Input watts (drawn from the AC line) and output watts (measured at the loudspeaker output terminals) are not the same thing. Although there is a relationship, output watts should always be higher than the power drawn from the AC line in watts. The exact amount depends on the power supply and amplifier's overall efficiency, so there is limited value in comparing the two.

There was a time when the FTC rule applied to every power amplifier, but in the last few decades the requirements have been either watered down or ignored altogether. First was the FTC modifying the pre-conditioning requirement from ⅓ power for 1 hour to 1/6th power for 1 hour. Next was the advent of multichannel amps, which considered themselves exempt as the original FTC rule of 1973 specified mono or stereo amplifiers only.

"Portable" devices have always been exempt, so car stereos and battery-powered blasters never have been compliant. Merely placing a handle on any device also made it "portable" and allowed ignoring the FTC rule.

Also the FTC rule only applies to discreet audio components, so "Home Theatre in a Box" systems or stereo systems that include amplifiers and speakers do not need to comply.

After years of ignoring the FTC rule on multichannel (more than two channels) amps on the basis that the FTC rule did not apply to amps of more than two channels, when the FTC revisited the idea of making them comply with the general requirements of the 1973 rule, the manufacturers successfully argued that those who had bought gear under their previous practice would feel "cheated" if the true nature of the power ability was revealed, and that yesterday's 500 watt multichannel amp would appear to consumers to be much cheaper than tomorrow's 500 watt amp, hampering sales.

So the FTC backed off. Currently there is no real requirement for multichannel amps to comply with the specification rules. All consideration of revising the FTC rule to reflect multichannel amps is currently in a permanent abeyance.

Perhaps worse, there is no current enforcement of the FTC rule for mono or stereo amplifier manufacturers. It's essentially unregulated today.

Some manufacturers (eg Anthem) do rate their multichannel amps as if the FTC rule was applicable, and this practice is worth noting when found.

In a nutshell, the FTC Rule required:
An FTC-compliant power specification must be the most prominent spec listed in all advertising in a font size that is equal or larger than non-compliant specifications.

Amplifier must be specified with all channels driven, and only after a 1 hour pre-conditioning at one third / (now one sixth) power, into a specified impedance that does not result in protection circuit tripping or other aberrations (eg blown fuse), from either 20 to 20,000 Hz at a specified distortion percentage, or at a defined frequency response for high or low-pass filtered amplifiers (such as sub amps).

Also, if the amplifier cannot sustain power into a given impedance after pre-conditioning without aberrations, you cannot specify any power rating into that impedance anywhere on the spec sheet.

Finally, if an amplifier doesn't mention specs in advertising, or is not advertised in a US-based print or video media, the FTC rule can be ignored. So spec sheets that are downloadable PDFs do not necessarily need to be compliant.
 
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Johnny2Bad

Johnny2Bad

Audioholic Chief
Swerd, please let us know the eventual outcome of the issue described in your OP.
 
Alex2507

Alex2507

Audioholic Slumlord
There must be a special place in hell for those who wish that others buy expensive big iron amps :mad:.

I'm still holding out for 1) a failed AC outlet, 2) a disconnected or mouse bitten power cord, or 3) a blown fuse.

Jim Salk says the speakers are 88 dB, 4 ohm minimum/6 ohm average impedance, and recommends 100 watts to drive them, same as for the SongTowers.

I may just keep using the AVR :p.
I'm the one who should just be using an AVR but "it's a disease". Actually, I think I might have found the cure with some monoblocks for the living room and that multi channel job from Kurt for ManTown. If I thought you'd miss the money, I wouldn't wish for you to spend it. The whole point of audio forums is to encourage excess but even at that, the stuff you guys are linking seems steep. A grand for 200 watt/ch amp? I enter my zip code for Audiogon searches. A 100 mile radius has everything I ever needed and then some.

So when's Dan coming over? This seems like a family emergency to me. I'm just relieved to know that it's not radio silence there.
 
TLS Guy

TLS Guy

Seriously, I have no life.
There must be a special place in hell for those who wish that others buy expensive big iron amps :mad:.

I'm still holding out for 1) a failed AC outlet, 2) a disconnected or mouse bitten power cord, or 3) a blown fuse.

Jim Salk says the speakers are 88 dB, 4 ohm minimum/6 ohm average impedance, and recommends 100 watts to drive them, same as for the SongTowers.

I may just keep using the AVR :p.
I would snap up this amp. They don't come up very often on eBay anymore.

Beautiful class A sound and they run cool. The power specs of your current amp are obviously embellished. You can not get more power out than you put in. That is impossible.

The Quad 909 is a reliable beautiful sounding amp. Class A performance and they run cool.

By the way, your installation needs revision. Not even being able to get to the power socket is not close to a safe convenient installation.
 
Swerd

Swerd

Audioholic Warlord
I would snap up this amp. They don't come up very often on eBay anymore.

Beautiful class A sound and they run cool. The power specs of your current amp are obviously embellished. You can not get more power out than you put in. That is impossible.

The Quad 909 is a reliable beautiful sounding amp. Class A performance and they run cool.
Duly noted. I see the Quad 909 is considered a class A amp at low power and then class B – in effect a class A/B amp.

I also note the Monolith is said to be a class AB amp, unlike the other ATI class A/AB amps. My old B&K amp is also a class A/AB amp. It also runs (ran?) quite cool.

Is there anyone who can comment intelligently on audible differences among these different amp classes?

Swerd, please let us know the eventual outcome of the issue described in your OP.
Will do.

Once I pull out the old B&K amp, I'll get the line fuse out and go out this afternoon to find a suitable replacement. Amazon lists 12A slow blow ceramic fuses in two sizes, 5×20 mm and 6×30. I'll also examine the power cord, and reach back to the outlet in question with an outlet tester.

By the way, this is a frequent poster here on AH who used to work at the Federal Trade Commission. He is now retired. If I recall, he was involved in the FTC's 2008 re-examination of power amplifier ratings. In a nutshell, he said the FTC decided to maintain the rating regulations from the 1970s for one or two channel amps and receivers with the additional requirement that multichannel home theater amps and receivers state power when two channels are driven. It didn't satisfy those who wanted ratings when all channels were driven, but it did provide a way for prospective buyers to compare various products while similarly rated. Apparently, the FTC decided there was enough competition in the market such that further regulation was not needed. Also the FTC had much more serious problems to deal with, such as online banking and credit card fraud, and that power ratings home audio products were not among them.

Maybe Dennis Murphy can chime in with corrections or further info. @Dennis Murphy
 
Irvrobinson

Irvrobinson

Audioholic Spartan
Duly noted. I see the Quad 909 is considered a class A amp at low power and then class B – in effect a class A/B amp.
Not true. The Quad uses a completely different strategy that employs a Class A amplifier of limited current capability to control through feed-forward a much higher capability secondary amplifier stage, so the high-current stage's native distortion is not important. I'm sure TLSGuy is busy keying in a complete treatise on these current-dumping designs, but the resulting amp is measurably indistinguishable from a Class A amp of similar power. The gotcha is that these circuits are quite complex (Nelson Pass did some derivative work in this area for Threshold and Nakamichi), and even Quad struggled to make them reliable early on.
 
TLS Guy

TLS Guy

Seriously, I have no life.
Duly noted. I see the Quad 909 is considered a class A amp at low power and then class B – in effect a class A/B amp.

I also note the Monolith is said to be a class AB amp, unlike the other ATI class A/AB amps. My old B&K amp is also a class A/AB amp. It also runs (ran?) quite cool.

Is there anyone who can comment intelligently on audible differences among these different amp classes?

Will do.

Once I pull out the old B&K amp, I'll get the line fuse out and go out this afternoon to find a suitable replacement. Amazon lists 12A slow blow ceramic fuses in two sizes, 5×20 mm and 6×30. I'll also examine the power cord, and reach back to the outlet in question with an outlet tester.

By the way, this is a frequent poster here on AH who used to work at the Federal Trade Commission. He is now retired. If I recall, he was involved in the FTC's 2008 re-examination of power amplifier ratings. In a nutshell, he said the FTC decided to maintain the rating regulations from the 1970s for one or two channel amps and receivers with the additional requirement that multichannel home theater amps and receivers state power when two channels are driven. It didn't satisfy those who wanted ratings when all channels were driven, but it did provide a way for prospective buyers to compare various products while similarly rated. Apparently, the FTC decided there was enough competition in the market such that further regulation was not needed. Also the FTC had much more serious problems to deal with, such as online banking and credit card fraud, and that power ratings home audio products were not among them.

Maybe Dennis Murphy can chime in with corrections or further info. @Dennis Murphy
No, the Quad current dumping amps do not fit the usual A/B description. The output transistors are A/B but heavily biased to B, so they run cool. These are the dumpers. There is a very high quality but lower power class A amp. This feeds a feed forward error signal to correct the dumpers. Peter Walker proved mathematically that the performance is dependent entirely on the high performance class A amp. Measurements bear this out.

It is a stroke of genius. The part count of the amp is very low. It looks like a total sleight of hand, which it is. It is just elegant. Better still all components can wander by at least 30% without affecting measured performance. So there are absolutely no internal adjustments. There are none of those pesky surface mounted pots that pepper all other designs. This makes these amps long lasting and reliable. The output stage is large triple transistors, so six per channel. They are all operating well inside their safe point. Peter like me was obsessed with reliability. Anything blowing up is just a bad day and costly.

Here is the schematic. I would only state that it is deceptively simple. It does take some thought to realize how it does work. Yes, Nelson Pass did infringe the patent I think and over complicated it to cover his traces.

 
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Dan

Dan

Audioholic Chief
So when's Dan coming over? This seems like a family emergency to me. I'm just relieved to know that it's not radio silence there.
So crack of dawn Saturday I'm dragging him to http://katiescarsandcoffee.com/ to check out the exotic wheels there. Then back to the Swerd lair for furniture moving, amp hoisting, general trial and error to figure this out. Perhaps we should start a poll as to what the mysterious trouble is. I'm in for a bizarre wiring setup when the house was built and a single failure in the power to those two outlet halves but we shall see...
 
Swerd

Swerd

Audioholic Warlord
@Johnny2Bad, @Alex2507, @KEW, @TLS Guy, @Irvrobinson, @Dan and all others still interested.

I pulled out the amp this afternoon.
  • It was not plugged into an AC outlet behind the cabinet, but an accessible outlet off to the side. I'm smarter than I give myself credit for or can remember. Both outlets of the duplex (tested by both items shown below) were good.


  • The amp's removable AC power cord appears to be working. When it was plugged into the outlet, I used the non-contact voltage test pen, it beeped and showed red, indicating voltage at the amp end of the cord. I inspected behind the cabinet with a flashlight, and I saw no sign of dead mouse (mice).
  • So, that leaves the fuse and the amp. The initial symptom, after switching the amp on, was no sound came from the speakers, and the red LED above the amp's power switch did not come on. That suggests the amp's power supply is the problem.
  • I'll get some fuses next, but if the fuse had failed, it suggests an internal problem. The fuse 12A Slow Blow, 250 V, ceramic not glass, is 30 mm long. It appears to be polarized with a red stripe around one end and a black stripe at the other. Of course, I pulled it out without noticing which color was at what end. Does anyone know if this matters?
  • For what it's worth, the tag on the back of the amp says 900 W and 64U (anyone know what 64U means?). The manual said 650 W. I'm inclined to believe the bigger number is correct.
  • This amp is 19 to 24 years old. I bought it used in 2008, for $400 plus shipping. Unfortunately B&K is out of business. I wonder what it might cost for local repair?
Irv – thanks for your comments on the Quad 909 design. A recommendation from both you and TLS Guy is worth something. Any suggestion of a good price to bid?
 
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