Need a little advice on some AR Mono Block Amplifiers...and Speaker wires

-Jim-

-Jim-

Full Audioholic
Gents,

A good friend of mine has a stereo system with a pair of Wilson Maxx Speakers, AR Mono Block Amplifiers, and MIT Cables (amongst other high end gear). He's into vinyl and frankly never left it. (He's in his early 70s now and never thought CDs sounded as good as vinyl. He doses have a Mark Levinson CD/DVD player).

The problem, since new, one or the other of his AR Mono Block Amplifiers has blown up 14 times. He used to send them back through the dealer for repair until he retired and closed his doors. He then sent them to the AR Factory in the USA (Minnesota?) a couple of times. Even though he spent considerable $$ no one ever could find out what causes the failures. He dutifully warms up these Tube Amps before pushing anything through them.

I read an old Stereophile article here http://www.stereophile.com/floorloudspeakers/324/#6XcAuwTOquVAgVOx.97

which said:

Wilson claims a somewhat lower sensitivity, 92dB/W, than the X-1's 95dB. In amplifierspeak, that means a doubling of the necessary amplifier power to achieve the same effective loudness. While the X-1 offers a reasonable 8 ohm load, the new MAXX admits to a more demanding minimum of 3 ohms, which might prove too much for some tube amplifiers, even high-power ones, to bear.
Read more at http://www.stereophile.com/content/wilson-audio-specialties-maxx-loudspeaker-page-2#Xi5lywYkr7hLqjVC.99

I'm wondering if his issue may be related to this. What do you think?

I'd also like your opinion on expensive MIT Speaker Cables. Years ago he told me they cost him $10,000 Canadian (about $7,500 USD). I wonder if they could be the culprit instead.
 
lovinthehd

lovinthehd

Audioholic Jedi
Not familiar with the amp brand; no interest in tubes whatsoever nor Wilson speakers for that matter.

Is it the MIT cables with the little boxes in line with mystery electronics inside? Check out these pics of what's inside LOL. Audiophoolery at its finest IMHO (along with Audioquest, Wireworld, etc). Pretty much all high end cable is a scam in terms of audio qualities....but it wouldn't surprise me if these goofy boxes could create issues. Real speaker wire is good copper wire of the right gauge; if you want fancy aesthetics that's about all the high end wire/cable is good for.

Here's some threads here at AH on the subject. Search AVSforum or Reddit, too.

If a cable brand is in this list I'd avoid it....
 
G

Got Hi-Fi?

Audioholic Intern
Not that all high end cables are bad (this forum seems to be plagued with cable haters) .. but I would certainly look into that particular cable as possibly being the culprit, especially if no one could ever find any problems with the amp. Those little boxes on the cable are just stuffed with useless electronics that could go bad and cause problems with the amps.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Not that all high end cables are bad (this forum seems to be plagued with cable haters) .. but I would certainly look into that particular cable as possibly being the culprit, especially if no one could ever find any problems with the amp. Those little boxes on the cable are just stuffed with useless electronics that could go bad and cause problems with the amps.
Your friend needs deep therapy. He has obviously been fleeced for years by a high end "Audiophool" dealer. Its a good thing he has now closed his doors.

Having amps repaired 14 times is insanity, as repeatedly doing the same thing and expecting a different result is diagnostic.

What is causing the problem is difficult as this system is awash with culprits.

Lets begin with the tube amp. Acoustic Research of Annapolis Lane Plymouth Minnesota was founded by William Z Johnson in 1970. They specialize in massive vacuum tube amps among other tube products. They are now part of the McIntosh Group.

If you must have a tube amp these are among the best of them and they are an ethical company even if selling monstrously expensive tube amps, which are arguably inferior to good solid state amps. This is especially true driving difficult speaker loads as they have output transformers which don't perform well with varying impedance loads and negative phase angles between voltage and current. So if you do insist on a tube amp you have to choose your speakers with great care.

That brings me to Watt speakers. Watt are well up my list of lousy speakers to be avoided despite their high cost. I have never heard one of their speakers I like and I strongly suspect the speakers are incompetently designed.

In reference to the problem at hand, these speakers are the most likely cause of your friend's amp failures. So let us look at the impedance curve and phase angles.



There are two things that strike me.

The first is that the impedance actually drops to almost 2.0 ohms where there is a lot of power required at 250 Hz. Now I would be strongly suspicious that that reading is lower then the DC resistance of the drivers at that frequency. If that is so then the crossover is in resonance. That alone would explain your friend's difficulty.

But there is another serious problem.the phase angle is going off the bottom of the chart at 6 KHz. It is -90 degrees and still heading south. This means there is a huge gap between voltage and current phase. Now this is just the sort of thing well known to send tube amplifiers in to ultrasonic oscillation. The oscillation is well above the range of human hearing. This problem really blows up tube amps.

So we already now have two causes that could be responsible for these disasters. You absolutely have no business marketing a speaker with curves like that.

In fairness to Watt, this sort of thing is prevalent in the high end exotic speaker market. This was addressed by Dr Floyd Toole in these forums in the recent past. He specifically called them "incompetently designed speakers requiring arc welder amps!" This does not excuse Watt though.

Exotic powerful speakers are not well served by passive crossovers and are much better served by electronic crossovers with multiple power amps. I use three amps per speaker in my reference design.

Lastly the cable. This could also have a bearing on the issue. The marketing hype surrounding exotic cables is made up out of the back of the neck and or delusional. As Peter Walker of Quad used to say, "Bloody wire is just Bloody wire!" And he was and is still right. These cables costing thousands have no advantage over zip cord. Worse quite a few exotic cables have high capacitance. If his MIT cables do, then that would increase the potential for ultra sonic oscillation.

Now I'm particularly concerned about these cables. The designer used to do work for Monster Cable, one of the most unethical companies around.

This is what I'm particularly concerned about. "The termination housing features a three-position switch marked SD, HD, and SHD. Two six-position knobs on one end of the termination box are marked “Articulation,” one for the bass and one for the treble. looking next at the interconnect, its termination box is small in comparison (3.5" x 6"). It offers two adjustments, one to match the cable to the input impedance of the component it is driving, and the other a five-position knob marked “Articulation.”



This sets a new low or high in Audiophoolery whichever way you want to look at it.

In summary, you friend should definitely ditch those cables. However there is a high chance he will still have the problem. He does really have to decide whether he wants to get rid of those speakers and get ones more compatible with tube amplification, or get rid of the amps and find an "arc welder" category solid state amp that will drive those speakers.

This case I think is the worst we have seen of the damage wrought on people by the lunatic high end. This is not innocent marketing buyer beware but I believe a deliberate effort to defraud which is criminal.
 
killdozzer

killdozzer

Audioholic Samurai
Not that all high end cables are bad (this forum seems to be plagued with cable haters) .. but I would certainly look into that particular cable as possibly being the culprit, especially if no one could ever find any problems with the amp. Those little boxes on the cable are just stuffed with useless electronics that could go bad and cause problems with the amps.
You shouldn't be so 'trigger happy' on the 'plagued with haters' labels to label people with firm stands, which seems to be very popular these days. First off, you have Jim's friend who suffered some real injustice and damage that has been done to him. So, if it's anyone, it's that poor guy you should have compassion with and not the money hungry con-artists.

About that 'plagued' thing; so far I couldn't find one single member here claiming that "all high end cables are bad". Few of them claimed that all expensive, high end cables are a con, simply because you're giving a lot of money for nothing. Some of them are indeed good, BUT the point is those that are good are almost always just as good as the inexpensive ones.

So, no need to worry; there really are some overpriced, high-end cables that are as good as plain, inexpensive cables. Notice, however, that this holds true only until proven otherwise with at least one other thing than; 'well I felt better while listening to expensive cables'. People here would love to get their hands on a cable that truly improves acoustic properties of the overall system. But most of them simply say they didn't so far.
 
highfigh

highfigh

Audioholic Overlord
Gents,

A good friend of mine has a stereo system with a pair of Wilson Maxx Speakers, AR Mono Block Amplifiers, and MIT Cables (amongst other high end gear). He's into vinyl and frankly never left it. (He's in his early 70s now and never thought CDs sounded as good as vinyl. He doses have a Mark Levinson CD/DVD player).

The problem, since new, one or the other of his AR Mono Block Amplifiers has blown up 14 times. He used to send them back through the dealer for repair until he retired and closed his doors. He then sent them to the AR Factory in the USA (Minnesota?) a couple of times. Even though he spent considerable $$ no one ever could find out what causes the failures. He dutifully warms up these Tube Amps before pushing anything through them.

I read an old Stereophile article here http://www.stereophile.com/floorloudspeakers/324/#6XcAuwTOquVAgVOx.97

which said:

Wilson claims a somewhat lower sensitivity, 92dB/W, than the X-1's 95dB. In amplifierspeak, that means a doubling of the necessary amplifier power to achieve the same effective loudness. While the X-1 offers a reasonable 8 ohm load, the new MAXX admits to a more demanding minimum of 3 ohms, which might prove too much for some tube amplifiers, even high-power ones, to bear.
Read more at http://www.stereophile.com/content/wilson-audio-specialties-maxx-loudspeaker-page-2#Xi5lywYkr7hLqjVC.99

I'm wondering if his issue may be related to this. What do you think?

I'd also like your opinion on expensive MIT Speaker Cables. Years ago he told me they cost him $10,000 Canadian (about $7,500 USD). I wonder if they could be the culprit instead.
Tube amps can drive a low impedance, but the output transformer must be wound to handle this.

Ask him if he disconnects the speaker cables from either end when the amplifiers are powered- this is a big problem for tube amps and should NEVER be done.

Has he ever mentioned what fails in these amps?

I just posted my opinions of a system that probably cost high five figures, even with his discounts from being in the audio business for most of his adult life. My conclusion is that I'd rather use my own and I think he's having serious doubts about what he paid for. His cables are as thick as my thumb and are resting on some kind of blocks, possibly made of wood (like a witch). I have cable that was left over from an installation I did and they're laying on the floor among the other cables. I did cut them to the same length, but that was more for flexibility in future changes in equipment position but even that doesn't matter.

$10K for speaker cables? Holy hand grenades!
 
G

Got Hi-Fi?

Audioholic Intern
.

About that 'plagued' thing; so far I couldn't find one single member here claiming that "all high end cables are badt ". Few of them claimed that all expensive, high end cables are a con, simply because you're giving a lot of money for nothing. Some of them are indeed good, BUT the point is those that are good are almost always just as good as the inexpensive ones.
And you shouldn't be so quick to post before learning how to read someone else' post. Did I say anywhere in my post that members here said all high end cables are bad? Didn't think so. You might want to read what I did actually write again.
 
highfigh

highfigh

Audioholic Overlord
Now I'm particularly concerned about these cables. The designer used to do work for Monster Cable, one of the most unethical companies around.

This is what I'm particularly concerned about. "The termination housing features a three-position switch marked SD, HD, and SHD. Two six-position knobs on one end of the termination box are marked “Articulation,” one for the bass and one for the treble. looking next at the interconnect, its termination box is small in comparison (3.5" x 6"). It offers two adjustments, one to match the cable to the input impedance of the component it is driving, and the other a five-position knob marked “Articulation.”



This sets a new low or high in Audiophoolery whichever way you want to look at it.

In summary, you friend should definitely ditch those cables. However there is a high chance he will still have the problem. He does really have to decide whether he wants to get rid of those speakers and get ones more compatible with tube amplification, or get rid of the amps and find an "arc welder" category solid state amp that will drive those speakers.

This case I think is the worst we have seen of the damage wrought on people by the lunatic high end. This is not innocent marketing buyer beware but I believe a deliberate effort to defraud which is criminal.
Looks like MIT stands for 'Morons In Training'.

An 'articulation' control, eh? Nice.
 
highfigh

highfigh

Audioholic Overlord
Not that all high end cables are bad (this forum seems to be plagued with cable haters) .. but I would certainly look into that particular cable as possibly being the culprit, especially if no one could ever find any problems with the amp. Those little boxes on the cable are just stuffed with useless electronics that could go bad and cause problems with the amps.
If Audioholics is plagued by anything, it's plagued with people who don't believe everything they're told and would rather have some way to verify the results of tests and the causes of anything that makes a change, good or bad.

If the system I mentioned is really worth the money, why does it sound so unimpressive, compared to mine? It's not because I wanted to come away with a bad impression- I really wanted it to sound amazing and I have heard it sound better but without doing an A:B test of the preamps or anything else that has changed since I was there before, it's hard to say but I think it has more to do with the speaker placement or the preamp than anything. At least, I hope it's that simple but with his cables being as heavy as they are and being on cable stands, I would hope they're able to transfer the energy from the amplifiers without loss or other effects.
 
G

Got Hi-Fi?

Audioholic Intern
If Audioholics is plagued by anything, it's plagued with people who don't believe everything they're told and would rather have some way to verify the results of tests and the causes of anything that makes a change, good or bad.

If the system I mentioned is really worth the money, why does it sound so unimpressive, compared to mine? It's not because I wanted to come away with a bad impression- I really wanted it to sound amazing and I have heard it sound better but without doing an A:B test of the preamps or anything else that has changed since I was there before, it's hard to say but I think it has more to do with the speaker placement or the preamp than anything. At least, I hope it's that simple but with his cables being as heavy as they are and being on cable stands, I would hope they're able to transfer the energy from the amplifiers without loss or other effects.
It could also be his room, has it been treated? Especially if he is comparing the sound of said system from being in the store, to being at his home. You are right, your system could very well sound better than his. Regardless of its cost, if it is put into a room that just doesn't work, or has no acoustic treatment, it is just not going to sound good. Room acoustics make a much bigger difference to sound than any cable will.
 
highfigh

highfigh

Audioholic Overlord
It could also be his room, has it been treated? Especially if he is comparing the sound of said system from being in the store, to being at his home. You are right, your system could very well sound better than his. Regardless of its cost, if it is put into a room that just doesn't work, or has no acoustic treatment, it is just not going to sound good. Room acoustics make a much bigger difference to sound than any cable will.
Not comparing it with anything in a store and his room is large enough that at low levels, the walls and windows (it's a Mid-Century Modern) aren't as much of a factor, but when I used one of the RTA apps in my phone, I saw a deep notch in the bass response. This notch wasn't where I was hearing the problems, though. He has a couple of panels of some kind and I didn't look at what they were made of, but they're not working for what the room needs. He said he's going to return the preamp (it has an annoying habit of muting every time he lifts the tonearm from a record) but I offered to bring my mic, USB interface, acoustic panels and laptop over so I can do some basic analysis and temporary treatment. I watched the difference in my room and it went from listening being an annoying experience to great enjoyment but I think a major factor in the sound quality for his system is in the speaker placement- he's going by what worked for the other speakers and I'm pretty sure the ones he's using now don't need to be so far from the walls.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Tube amps can drive a low impedance, but the output transformer must be wound to handle this.

Ask him if he disconnects the speaker cables from either end when the amplifiers are powered- this is a big problem for tube amps and should NEVER be done.

Has he ever mentioned what fails in these amps?

I just posted my opinions of a system that probably cost high five figures, even with his discounts from being in the audio business for most of his adult life. My conclusion is that I'd rather use my own and I think he's having serious doubts about what he paid for. His cables are as thick as my thumb and are resting on some kind of blocks, possibly made of wood (like a witch). I have cable that was left over from an installation I did and they're laying on the floor among the other cables. I did cut them to the same length, but that was more for flexibility in future changes in equipment position but even that doesn't matter.

$10K for speaker cables? Holy hand grenades!
Yes, but what do you wind it for? That impedance curve is all over the map. I now notice something I had not noted before. I noted the phase angle heading south, at 6 K and disappearing. Now I note it reappears, and heads above +90 at 12 K and back down to -20 by 20 K. There is something really rogue with that speaker design in the last two top octaves. That is just the ticket for blowing up a lot of tube amps. As I think about it this is likely the cause of these repeated catastrophes.

This is a common problem with electrostatic speakers and tube amps. When Peter Walker produced the first ESL speaker back in the fifties, he had to design his Quad II tube amps to be unconditionally stable. I well remember that those speakers blew up his major amp competitors products, which at that time was Harold J. Leak. His amps went totally unstable.
 
highfigh

highfigh

Audioholic Overlord
Yes, but what do you wind it for? That impedance curve is all over the map. I now notice something I had not noted before. I noted the phase angle heading south, at 6 K and disappearing. Now I note it reappears, and heads above +90 at 12 K and back down to -20 by 20 K. There is something really rogue with that speaker design in the last two top octaves. That is just the ticket for blowing up a lot of tube amps. As I think about it this is likely the cause of these repeated catastrophes.

This is a common problem with electrostatic speakers and tube amps. When Peter Walker produced the first ESL speaker back in the fifties, he had to design his Quad II tube amps to be unconditionally stable. I well remember that those speakers blew up his major amp competitors products, which at that time was Harold J. Leak. His amps went totally unstable.

Ideally, it would be wound for the expected impedance range and then, choose speakers that don't operate outside of that parameter, which those clearly don't. But then, this isn't a musical instrument amplifier, it's a HiFi amp, which will undoubtedly be used for speakers that DO NOT match the amplifier.

If those speakers weren't difficult to drive, Wilson wouldn't be able to challenge anyone to make amplifiers that are up to the task, would they? Personally, I think that's a stupid way to operate. If they want their speakers to be driven by a welder, they should sell the speakers WITH one, as a matched system. That way, people won't be surprised when they go out of business.
 
mtrycrafts

mtrycrafts

Audioholic Slumlord
...(this forum seems to be plagued with cable haters) .. ....
Good start here at AH. :rolleyes:
Cable haters? Not hardly. We love cables. I have cables.
What we don't like are the peddlers of snake oil claims, got it?
 
TLS Guy

TLS Guy

Audioholic Slumlord
Ideally, it would be wound for the expected impedance range and then, choose speakers that don't operate outside of that parameter, which those clearly don't. But then, this isn't a musical instrument amplifier, it's a HiFi amp, which will undoubtedly be used for speakers that DO NOT match the amplifier.

If those speakers weren't difficult to drive, Wilson wouldn't be able to challenge anyone to make amplifiers that are up to the task, would they? Personally, I think that's a stupid way to operate. If they want their speakers to be driven by a welder, they should sell the speakers WITH one, as a matched system. That way, people won't be surprised when they go out of business.
It is not just being difficult to drive. That drive difficulty indicates a serious problem. Even if you drive them with an amp they don't blow up, they still won't be good speakers.
 
killdozzer

killdozzer

Audioholic Samurai
Good start here at AH. :rolleyes:
Cable haters? Not hardly. We love cables. I have cables.
What we don't like are the peddlers of snake oil claims, got it?
Aaahh, I see you made the same mistake I did. As he nicely and politely wrote and explained; he never said that. It was due to my lack of reading abilities and, I guess, subsequently yours.
 
mtrycrafts

mtrycrafts

Audioholic Slumlord
Aaahh, I see you made the same mistake I did. As he nicely and politely wrote and explained; he never said that. It was due to my lack of reading abilities and, I guess, subsequently yours.
Check again.
His words Not that all high end cables are bad (this forum seems to be plagued with cable haters) ..

But Then, I may be reading something else.
 

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