Answered Two brand new Marantz Amplifiers faulty?

Heavenlysounds

Standard Member
I bought a brand new Marantz PM 6006 Amplifier in January of this year. We had it for about three months before it stopped working When I sent it in for repair they said it was a blown resistor or transistor (can't remember which).

When we got it back, we had it for a few days before smoke started coming out of it, so I sent it back and they gave me a brand new one. We had the second one for about two weeks before it developed the exact same fault as the first one!

Basically what happens (on both amplifiers) is there is a burning smell and the amplifier switches off (mid song) and the light goes red. This seems to be some circuit protection feature.

I also think whatever the issue is causes problems with volume because the volume was very loud when we first got them, but the person who last used it had it up to three quarters (which is quite loud) and I am guessing there is a loss of volume as the problem develops?

The question is whether I just have really bad luck with amplifiers lately (and they both just happen to be lemons) or whether the problem is a power issue (we are having the plugs checked by an electrician soon) or whether its a mismatch between the speakers and the amp or if its a speaker wiring issue? The speakers have been there for many years! They look very old.

The amplifier is Marantz PM 6006 and the speakers are the following:
Two Mordaunt Short Avant 902i
Two B&W DM601 S2

Thank you
 

Jamie

Distinguished Member
Powering 2 pairs of speakers at high volumes could easily explain the situation.

Amps with speaker A + B switching will connect them in parallel. 2 pairs of 8Ohm speakers would give a combined impedance of 4 Ohms.

You B&W speakers are 8 Ohm but the MS speakers are rated at 4-8 Ohms which takes the combined.piad under 4 Ohms and places extra load on the amp.
 

Heavenlysounds

Standard Member
Thank you for such a quick response.

I am not sure if the volume is high because they like it too loud or if the volume is high because the sound is not as loud as it should be! The amplifier is being used in a school Hall. I have put in the Marantz MP6005 amps in a couple of other schools with no issues although obviously the school had different speakers.

Unless I am misunderstanding how the connections work, I have connected all four speakers to the A connections (not the B connections). The four connections at the bottom are A and the four above are B. We only use the A speakers button as well. Is this relevant.

Yes I noticed that about the MS speakers being 4 ohms, but I am not sure that I understand why this is a problem. The amp is rated to support 4 ohms as well as 8 ohms. Am I wiring it incorrectly or should I be using four speakers with the same ohm rating - bearing in mind that the original amplifier which died last year had no issues driving these speakers for many years!

We are looking at replacing all four speakers as we don't know how old the speakers are and it's either the speakers or the power that is the problem. But I would like to understand what I am doing wrong.

Thank you
 

Joe Fernand

Distinguished Member
AVForums Sponsor
'The amplifier is being used in a school Hall' - that will be your problem, it is not designed for that job.

How large is the hall, how many folk in the hall and what is the system being used for?

You should have one pair of speakers connected to A and the other to B not all four to A or B - why would you do that when there are two sets of binding posts?

'We are looking at replacing all four speakers as we don't know how old the speakers are and it's either the speakers or the power that is the problem'- no it is the system design which is the problem not the kit. Specify and purchase kit which is designed for the job.

Joe
 

Heavenlysounds

Standard Member
Sorry I should have been more clear. I am talking about primary schools here. The size of the hall is not that big! While it's obviously bigger than even a large lounge - it would not be by much. And it's not like they have the volume pumped up to the max as it were. Don't be misled by the hall reference. I only mention it because the amplifier seems to be loud when we get it, but obviously is not working properly towards the end volume wise! The volume itself it not the issue but whatever is causing the amp to be faulty seems to affect the volume down the line!

They only use it to play music at school assemblies and after school club like P.E. I very much doubt volume is an issue particularly as I have put several Marantz PM6005 (the earlier model) in at several other schools and no complaints about volume and the amps worked flawlessly.

The reason I connected them all to A is because I assumed that there would be no difference between putting them all on A or half/half on A/B. Either the amp can power the speakers or they can't. The old amplifier which I think was a Cambridge only had four speaker inputs (A only i.e). I also was under the impression that the point of the A/B feature is like to play A speakers in your lounge or B speakers in your kitchen?

I think the issue may be as Jamie says more to do with the ohms differences between the 2 sets of speakers.

Thank you
 

dannnielll

Well-known Member
Thank you for such a quick response.

I am not sure if the volume is high because they like it too loud or if the volume is high because the sound is not as loud as it should be! The amplifier is being used in a school Hall. I have put in the Marantz MP6005 amps in a couple of other schools with no issues although obviously the school had different speakers.

Unless I am misunderstanding how the connections work, I have connected all four speakers to the A connections (not the B connections). The four connections at the bottom are A and the four above are B. We only use the A speakers button as well. Is this relevant.

Yes I noticed that about the MS speakers being 4 ohms, but I am not sure that I understand why this is a problem. The amp is rated to support 4 ohms as well as 8 ohms. Am I wiring it incorrectly or should I be using four speakers with the same ohm rating - bearing in mind that the original amplifier which died last year had no issues driving these speakers for many years!

We are looking at replacing all four speakers as we don't know how old the speakers are and it's either the speakers or the power that is the problem. But I would like to understand what I am doing wrong.

Thank you
You have come to the correct place for good advice.. But you are not going to like the response. The amplifier is intended 8 Ohms and you are running parallel loudspeakers. If those were indeed 8ohm speakers, then the combined load of two in parallel would be 4 ohms, and will be stressing the current capacity of the amplifier.. But you are now saying that one of the speaker pairs is a 4 ohm speaker, so your load is now a maximum of 3 ohms, maybe less. .. That is totally outside the design specifications for those amplifiers. That is why they are continuing to fail. Indeed I would suggest that the supplier was repairing/ replacing them under false pretences
 

Joe Fernand

Distinguished Member
AVForums Sponsor
You are using an Amp designed for use in a Residential setting in a Commercial setting - most Retailers would not offer you a Warranty for your usage, have you told the supplier you are using them in a Commercial setting?

As others are pointing out the Amp is not faulty - the system is faulty.

There are lots of options for kit designed for Commercial use that will not kill your budget.

Joe
 

Heavenlysounds

Standard Member
Interesting. I will have to ask the supplier what these amps are rated at. According to this picture I have attached, using A or B is 4-16ohms and using A + B is 8-16 ohms. Now I remember why I never used the A+B because I knew one of the speakers was 4ohms, therefore according to the diagram A + B would not work. whereas A or B would work. Unless I am misunderstanding this very badly!

It's not a question of liking or not liking the answer. It's more that I don't know enough about matching amplifiers to speakers to understandwhat is happening. I have over the years bought a few amplifiers for various schools and to date have never had any problems (volume or otherwise).

I think the problem this time is because two speakers are 8ohm and two are 4-8ohm (why are they not 4 or 8 but rather a range - most speakers are either 4 or 8). In addition, if I have understood what you guys are saying correctly when you put two 8 ohm speakers in, the amp is using 8 ohms, but when you attach 4 8ohm speakers yu are actually driving at 4ohms not 8 ohms. Is that correct.

Audio Solutions Marantz PM6006 Integrated Amplifier
 
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Heavenlysounds

Standard Member
@joe, I will have to contact the company that I bought the product from and get them to advise based on the information that I have received here.They are aware that the amp is being used in a school because I mentioned it when we were concerned about possibility of fire because of the first amp smoking.

My first preference would be to replace the speakers based on the fact that we don't know how old they are, second because I don't like speakers with different ohm ratings as it causes this sort of issue we are seeing and it would make sense to buy speakers that they sell that will match whatever amplifier we end up getting.

I also feel that the main issue is the ohm rating and using speakers in parallel so this is what I will focus on addressing. Matching speakers to amp I mean.

I don't know what amp to look at because it's not like they label them as home user or commercial. But I will ask the guys at the shop what they recommend as the Marantz PM 8006 is more expensive than the school can justify considering the use it is put to as it probably gets less use than a home amplifier does!
 

Ugg10

Distinguished Member

Joe Fernand

Distinguished Member
AVForums Sponsor
'the guys at the shop what they recommend' - ensure they supply Commercial and not Residential systems.

Schools always come up with a reason to not 'justify' a realistic outlay - and then expect trouble free performance for the next 100 years :)

Plenty of affordable, Commercial Amp/Speaker combinations you could consider.

Joe
 

Ugg10

Distinguished Member
We do use systems like that in the schools. Not that brand, but something similar. However the reviews on this particular device don't look good!

Agreed, this was just an example. Others on my next post from gear4music are probably better.
 

Heavenlysounds

Standard Member
'the guys at the shop what they recommend' - ensure they supply Commercial and not Residential systems.

Schools always come up with a reason to not 'justify' a realistic outlay - and then expect trouble free performance for the next 100 years :)

Plenty of affordable, Commercial Amp/Speaker combinations you could consider.

Joe

There is some truth to that statement, but I generally buy good quality stuff and my schools are used to expecting to have to pay a bit more because I have taught them that you get what you pay for - although my field is IT Support, so any laptops, computers, wireless systems etc that I sell are not cheap and cheerful. They are always fit for purpose.

With IT, I know my stuff very well, but amplifiers are something that I am not that knowledgeable about, but was lucky enough to never have issues before.

So when I started looking to supply amplifiers I went with Marantz as I know that they are a very good product and I particularly like them for their warm sound. Some amps sound very cold. I had assumed that Marantz was up to the job. But I will look and see what would be better for future clients as perhaps one that can supply 70 watts is more suited than one that can supply 45 watts.

So I do get what you are saying, but commercial is not as relevant in the case of a school amplifier where they probably use it for less than a few hours a week - I suspect less than an hour a day and they probably are not playing quite as loud as we would at home (if you are anything like me that likes to immerse myself in the sound :)). In other words I would expect the requirements for an amp to be higher at home than at any of my primary schools based on usage. It does not get a lot of usage!

I hadn't realised however (because it's never happened before) that the ohms changed based on the number of speakers. Not sure why I did not have problems with the other schools where I put in the Marantz PM6005 model all of them over three years old and still going strong! One of the schools I know has four speakers, but I am not sure what ohms their speakers are!

I think what is more relevant - the ohm factor than the fact the amp is intended for residential use. Anyway, i will speak to the company I bought the amp from and see what they have to say. Thank you
 

Jamie

Distinguished Member
Electrically connecting both sets of speakers to the A terminals is exactly the same as using the A and B terminals.

In both cases the speakers are connected in parallel which gives an approximate combined impedance of 2.66 recurring. The amp is rated for a combined load of 4 to 16 ohms. Connecting those speakers in series might have been a better option.
 

Heavenlysounds

Standard Member
Electrically connecting both sets of speakers to the A terminals is exactly the same as using the A and B terminals.

In both cases the speakers are connected in parallel which gives an approximate combined impedance of 2.66 recurring. The amp is rated for a combined load of 4 to 16 ohms. Connecting those speakers in series might have been a better option.

I see that I will have to brush up on my knowledge of series versus parallel wiring as this is something that I had long since forgotten about as knowledge never used like bi-wiring and bi-amping etc!

Thank you.
 

BlueWizard

Distinguished Member
Sorry I should have been more clear. I am talking about primary schools here. The size of the hall is not that big! While it's obviously bigger than even a large lounge - it would not be by much.

If the Volume Control has Stops at both end, that is you can not turn it beyond a give physical points, usually 8 o'clock on the low end and 4 o'clock on the high end, then tell us the position of the volume control when you are using the amp?

11 o'clock? 12 o'clock? 1 o'clock? Higher? Lower?

If the volume does not have stops, but turns continuously, indicating a Digital Volume Control, the volume will be displayed on a Read-Out, what is the range of the read-out, and what is the number displaced with the Amp is in use?

Next, do I understand right that even though you have FOUR Speaker Terminals, you are still wiring the speakers to TWO? Are you using Banana Plugs? Are you simply putting bare wire into the terminals? Are you ABSOLUTELY SURE that there are not stray stands of wire shorting the output terminals?

Are you 100% irrefutably sure that all the speakers are wired correctly? That in every case the Red+ on the Amp goes to the Red+ on the speakers and of course Black to Black?


The reason I connected them all to A is because I assumed that there would be no difference between putting them all on A or half/half on A/B. Either the amp can power the speakers or they can't. ...

True technically there is no different between both on Speaker-A, and one pair of Speaker-A and one pair on Speaker-B. But practically, the security of the connection is perhaps not as good when cramming two speaker wires into one set of terminals.

I would very much like to see a Photo of that wiring. I suspect it is not all that secure, especially if it is being moved around, and more so if it is being move around by students.

Again, make absolutely sure that there are not stray lose strands of wire sticking out, check this on both the amp and the speakers, and make absolutely sure Red+ goes to Red+.

In case you are not aware virtually all speaker wire is marked for polarity. One of the wires in the wire pair will have a Ridge molded in, or it will have embossed printing, or it will have actual printing, or it will have a colored strip or mark of some kind. Make sure you use the wire consistently. I usually let the marked wire be Red+ and the unmarked wire be Black-, but it doesn't matter make a choice - marked = + or marked = - and them be consistent.

Can you give us the dimension of the room 25ft x 25ft (7.5m x 7.5m) ...bigger? ... smaller?

I'm inclined to agree, you probably need commercial equipment. For one, commercial equipment will very likely use Plugs on both ends, so less chance of there being a problem with the wiring.

Though specifically how far you need to take it is unclear. Also, how far you take it will be limited by your budget.

While the Marantz is certainly a nice amp, it is really a very modest 45w/ch. OK for a home, but for a large room a bit weak.

Curious, what is the source of the sound? CD? Turntable? Computer? MP3 Player? Network Player? Other?

At a reasonable price, I think something like the Behringer EPS500MP3 PA system with 500w and 8" Speakers is more like what you need. This is perhaps not as Hi-Fi as what you have, but certainly more powerful with a lot more secure connections, and you can probably mount the speaker on Stands to get them up in the air a bit.

https://www.amazon.co.uk/Behringer-EPS500MP3-Portable-PA-System/dp/B00E87OLBU/

BEHRINGER - EPS500MP3 | Behringer | PA System

https://media63.music-group.com/media/sys_master/h1e/he9/8849459707934.pdf

https://media63.music-group.com/media/sys_master/h23/h43/8849963024414.pdf




This system would not only accept common Line Sources, but will also accept Microphones an can be used a a PA system which I suspect most schools could use. And because it has multiple channels (8 inputs) it can be used for music and PA at the same time.

Studiospares Pro PA Speaker Stands and Bag

The Stands linked below are adjustable from 1300mm up to 2015mm (4.2ft to 6.6ft). Though I would recommend you use the lower height rather than the highest, especially around children. Again, this is just one example, there are dozens of the Speaker Stand to choose from.

Obviously stands like this, around kids, would have to be secured to keep them from falling over. Also, I'm not specifically recommending these speaker stands, though they are rated up to 60kg, I'm simply using them to illustrate the point.

I think even that specific PA is not necessarily being recommended, though it certainly would be good, but simply illustrating an alternative approach.

Steve/bluewizard
 
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Merv71

Novice Member
"Interesting. I will have to ask the supplier what these amps are rated at. According to this picture I have attached, using A or B is 4-16ohms and using A + B is 8-16 ohms. Now I remember why I never used the A+B because I knew one of the speakers was 4ohms, therefore according to the diagram A + B would not work. whereas A or B would work. Unless I am misunderstanding this very badly!"

You are indeed "... misunderstanding this very badly!", Jamie is indeed correct. See pages 18 and 19 of https://www.marantz.co.uk/DocumentMaster/UK/PM6006U_ENG_CD-ROM_UG_v00.pdf. This explains better than the few words printed on the back of the amp. As already suggested, you could try connecting the speakers in serial as opposed to parallel (i.e. one of each different speaker on the left and right, NOT the same two on the left and the other same two on the right), however the resultant sound may be not as loud as running one pair of speakers.
 

BlueWizard

Distinguished Member
Interesting. I will have to ask the supplier what these amps are rated at. According to this picture I have attached, using A or B is 4-16ohms and using A + B is 8-16 ohms. Now I remember why I never used the A+B because I knew one of the speakers was 4ohms, therefore according to the diagram A + B would not work. whereas A or B would work. Unless I am misunderstanding this very badly!

...

Indeed poorly understood. When it say A or B, and A+B what it is saying is One Pair vs TWO Pair of speakers. It doesn't matter which terminal the speakers are connected to. If two pair are connected than the result is HALF.

Actually in this case -

Rt = (R1 x R2) / (R1 + R2)

If both are 8 ohms then ... 64/16 = 4 ohms

If one of the speakers is 4 ohms then ... 32/12 = 2.67 ohms

Likely the speakers rated at 4-8 ohms meaning 4 to 8 ohms, are mostly 8 ohms but at one or two frequencies the impedance dips down in the 4 ohm range. This typically happens at lower frequencies.

In your case while the combination is mostly 8 ohms (or 4 ohms total) are certain frequencies it can drop down to 2.7 ohms combine impedance.

Speaker-A and Speaker-B are in parallel, so it doesn't matter if you wire everything to Speaker-A, or if you use Speaker-A and Speaker-B, the result is the same.

Steve/bluewizard
 

Heavenlysounds

Standard Member
@BlueWizard I will have to have a look at the wiring and double check the wiring. The amp is not being moved around. It is stationery. When I put the amplifier in, I tested it at loud volume and it was under half, so about 11-12 o clock. However the teacher when it was last used had it 3 quarters of the way she said - I didn't see it, but I would imagine that would be around 1 o clock. However I did not need it this loud when I put it in.

But we have obviously established that impedance is the issue here. What I need to do is match the amp to speakers.

Next, do I understand right that even though you have FOUR Speaker Terminals, you are still wiring the speakers to TWO? Are you using Banana Plugs? Are you simply putting bare wire into the terminals? Are you ABSOLUTELY SURE that there are not stray stands of wire shorting the output terminals?

I really need to have a look at the wiring again, because I know see what you mean. There are only 4 wires which now that you mention it doesn't make sense if there are four speakers - there should be 8 wires! I didn't notice that until you mentioned it. When I installed the thing, I just plugged the wires in, and didn't actually click that I am four wires short!

I am wondering if the speakers are connected in Series after all!

Mainly we are using a laptop, but sometimes an ipod or a cd player.

I will be going out to the school today to investigate.
 
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dannnielll

Well-known Member
Please read what has been posted. ..and what the manual for the amplifier says. It can handle 1 speaker per set of terminals, and that should be an 8 ohm nominal impedance. If your speakers were 16 ohm speakers, you could connect another set to the B set of terminals and run the amplifier in A+B mode..
May I say with a little surprise,that as someone who claims to be very familiar with IT equipment, you are exhibiting a very poor knowledge of OHMs Law.
If you continue to run both sets of speakers through the amplifier,then a number of things happen.
1. The current demanded by the low impedance load, Doubles.
2. The votltage available to any speaker Drops ..and is less audio power generated
3. The heating effect inside the Amplifier increases 4 yes FOUR times ,
4. Heat kills electronic components

Some amplifiers have a special switch on the back called 8 ohm or 4 ohm, what this does is reduce the voltage in the power supply when feeding low impedance loads,so as to reduce the internal heating.
 
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gibbsy

Moderator
Basically your putting a Ford Focus engine into a ten ton truck and excepting the truck to have the same acceleration and top speed as the Focus. Wrong tool for the job, plain and simple. You've had excellent advice and reasoning, the fault doesn't lie with the Marantz it lies in you and the application you've given the amp.
 

Heavenlysounds

Standard Member
Basically your putting a Ford Focus engine into a ten ton truck and excepting the truck to have the same acceleration and top speed as the Focus. Wrong tool for the job, plain and simple. You've had excellent advice and reasoning, the fault doesn't lie with the Marantz it lies in you and the application you've given the amp.

There is no need to be rude especially if you are a moderator. I find your reply very unhelpful given that I have already said I don't know a lot about amplifiers and I have already said that I am going to address the amplifier speaker mismatch by replacing the speakers and presumably the amplifier, so what more do you want?

I have acknowledged that the speakers and the amplifier won't work together because of the ohm impedance issue. I didn't know why the amp was blowing which is why I came here and asked and I have now got an answer as to what the problem is and I can start with a resolution process!

So I will sort it by matching amps to speakers taking into account size of room obviously. I just ask a lot of questions because it's not an area that I understand very well as I don't normally deal with worrying about voltages, ohms etc in my line of work, but I do have an interest in hi fi equipment, so i am just wanting to understand how it all works that's all!

Anyway I will go to the supplier and explain the situation and he can advise the best solution for our situation, my preference would be to replace speakers and amp together to ensure that we get a match! Thank you for you help as you made it clear replace the amplifier! I will mention that to them.
 

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