Marantz pearl lite amp trouble

[vonchief]

In need of some more advice yet again.

I have had my amp for a little over a year now (2year guarantee)

I am really pleased with it, but occasonally I have been aware that the sound from the right hand speaker seemed a little quieter. I usually listen in direct mode.

Thought this may have been the recording or a speaker placement issue, or me going a bit deaf in my right ear.

Some days all would be fine so thougth no more of it.

Anyway, Turned my amp on a few days ago and the stereo image was again towards the left, I switched out the direct mode and moved the balance control which confirmed the right side was quieter.

After trying the obvious, checking leads and connections plus switching speakers round with no change I thought I would try using the speakers 'B' output on the amp. Straight away the sound was central with voices clearly between the speakers.

Switched back to using speaker 'A' outputs to compare but now all was OK.

Switching from A to B seems to fix the fault. If I turn the amp off for a few hours it still seems to work fine.

If the amp is left off overnight, when switced on the right speaker is quieter again. This has not happened every time so I am a litle worried about taking it back incase the fault does not show.

There is a charge if they can't reproduce the issue.

Any ideas what it could be ? or what to do ?

 

[Mooly]

First thing is to check all connections for being secure. That's both ends of speaker leads and all source component cables. Remove and reinsert them to clean them.

When the problem occurs does it happen on ANY source, eg CD, Tuner etc ?

Does the problem appear/disappear if you give the amp a little tap or jolt while it's on ?

I'm not familiar with the exact circuitry of the Pearl Lite amp... so this is a generalisation.

When you power up from cold is there a delay and then a definite click from within the amp as a speaker relay connects the speakers to the amp ? It's not unheard of for relays like that to give trouble... but on a newish amp it's unlikely. If (if !) it were something like that then it's nothing more than a tarnished contact and the effect is worse at low volume. Turn the volume up and the higher current flow "cleans" the contact by breaking through the microscopic insulating layer on the contacts.

I would look elsewhere first though.

 

[vonchief]

Cheers for the reply.

All connections have been double checked and are fine.

I only have a CD player and have not tried any other inputs, tapping the amp makes no difference either.

There is a delay when switching the amp on as you describe.

I only listen at low volumes so this may be causing the problem.

One thing I should have mentioned is I have some attenuators fitted at the amp end, I took these off last night as an experiment and when I tried the amp this morning all was fine.This was using speaker'A' output which was previously showing the fault.

I am now wondering if the attenuaters were lowering the input too much and causing this inballance ?

I had previously swapped them around incase one was faulty but they were both working fine.

When the amp is working as it should, the attenuaters do their job and allow finer adjustment of the volume which is quite handy. I have been using these since the amp was new with only a few times noticing something wasn't quite right.

Just leaving it off overnight with the attenuaters plugged in seems to cause the right side to be quieter occasionally.

Does any of this make sense ?

 

[Mooly]

The attenuators shouldn't cause an issue at all. They are just resistive and barring a physical problem with them there's nothing to go wrong.

If the problem persists I would try and narrow it down a bit more. You could swap left and right phono leads over (including the attenuators) at the CD player output and the amp input. That would preserve correct channel ID but just swap L and R cable. If the problem moved to the other channel then that would point to a lead/atenuator problem.

Also try using a different input on the amp such Aux or Tuner by feeding your CD player into that for a while to eliminate a problem with the input/source selection on the amp. You can use any input EXCEPT one for a record deck.

Before any of that though I would just try and reproduce the fault again with it all connected up as normal. Make a note of the CD playing and track location/time and if the problem occurs turn the amp up quite loud for a minute or two and then back to the original level and replay the same track section again and see if the problem has dissappeared.

Another thought altogether... just to cover all bases. If the effect is quite subtle it can actually be down to listening position/room acoustics/type of music (frequency content makes a difference) as the sound is reflected around the room. There will be points in the room where there is either cancellation or accentuation of various frequencies. If you feel the image isn't centered then move slightly toward or away from the speakers and see if the image shifts. Sometimes just a few centimeters can make a big difference.

 

[altruistic.lemon]

Don't use the attenuators for a spell. If there's no problem, then you know what's at fault.

 

[vonchief]

Just tried the amp again, speakers 'B' and no attenuaters.

Listened to the first three tracks or so and left side was again slightly quieter, I mainly notice vocals are not central.I continued listening and the next few tracks were sounding OK.

When I went back to track 1 to check , it sounded equal so it seems like the amp needs warming up to sound correct.

Ive switched it off now and will try in a few hours to see if it's quiet on the left side once powered up again.

Thanks for all the sugestions.

 

[Mooly]

When I went back to track 1 to check , it sounded equal so it seems like the amp needs warming up to sound correct.

On solid state circuitry the gain doesn't (shouldn't) change one iota with temperature or leaving on. It's determined 100% by a few passive components in the design (the feedback networks of the amplifier).

If it really is changing then something isn't right somewhere, not necessarily an amp problem either. That has to be proved by simple tests.

The way to prove it absolutely conclusively is to play a test track (a low amplitude sine wave test tone) and measure and record the voltage across the speakers. This should be equal for left and right channels.

 

[vonchief]

Well I have just tried it again and it is working perfect.

The way of testing it seems a bit technical for me so I will just keep my eye on it and take it back if the problem persists.

I still have just under a year's guarantee left so no need to rush back to the shop at this stage.

Cheers.

 

[007L2Thrill]

Best thing is to swap the speaker cables around to the opposite channels, but you say in your first post that it had no effect, if this is true, then to me it sounds like one of your speakers is the problem and not the amp as if one channel is louder say the left and you change the speaker cables around to the opposite channels and there is no difference and the left channel is still louder, then I would swap the speakers around and test again.

I had an arcam amp that had a similar problem, but when I swapped the speaker cables around the channel that was louder swapped too, proving it was the amp.

 

[vonchief]

I have now had more time and re-cheched all connections and found this..

When set up correctly the right speaker seems quieter.

If i switch the interconnects round so left output on CD goes to right input on amp., the left speaker goes quieter.

I have also tried swapping the interconnects completly round so the normal cable for the right is used on the left and vise versa.

This makes no difference and the right speaker is quieter both ways round.

I think This means the interconnect cable is fine and so is the amp, possibly the CD player has an intermittent balance fault ?

I will listen a bit more as Im certain it sounds fine sometimes, some tracks seem to highlight the problem but when I listen again it seems to correct itself.

Most strange.

 

[vonchief]

Just tried my DVD player connected to my amp and the same problem persists, quieter on the right hand side.

I guess this proves nothing is wrong with the CD player.

007L2Thrill,after you suggestion of swaping the speaker cable round again I have found that doing this does makes the left hand quieter.

Does this mean the amp is at fault ? Im getting totaly confused now with all this cable swapping.

 

[Mooly]

You say with it set up correctly RH speaker is quieter.
You swap L and R interconnects and the left now goes quieter... if that is so then that points to a source issue rather than amp and speaker problem. If it were amp/speaker related the problem would stay on the right channel.

Swapping cables over completely has no effect on fault... the right is always quieter. That seems to eliminate the interconnect.

You say some tracks seem to highlight the problem. That to me suggests this may be more of an acoustic peculiarity with your room/listening position set up. It can be quite a pronounced effect and seem very real.

Trying the DVD player and the right is still quieter... this is where it gets contradictory because when you can swap L and R on the CD player and reverse the faulty (quieter channel), then that appears to be a definite effect you could reproduce.

Swapping speaker cables... not sure exactly what you mean there. If you removed both cables completely from amp and speaker and then wired them up with what used to be the left cable now feeding the right speaker then it is just the cables you have swapped. Everything else stayed the same ? Or was it just swapping "cables" at the amp and driving left speaker with right hand channel.

I know it is confusing swapping stuff around

I think the only way you will nail this for sure is to do a proper test. You are always going to be wondering on this.

If you own a digital multimeter that can measure AC voltage then this is dead easy to do by just measuring the voltage across the speaker terminals while playing a known test signal. It's 100% conclusive and takes seconds to do. It eliminates all doubt.

 

[vonchief]

Trying the DVD player and the right is still quieter... this is where it gets contradictory

because when you can swap L and R on the CD player and reverse the faulty (quieter channel), then that appears to be a definite effect you could reproduce.

When wired up correctly both CD and DVD player sound quieter on the right. When I swap L and R at the amp input , the left side then goes quieter.This is the same when using the CD player or DVD.

Swapping speaker cables... not sure exactly what you mean there. If you removed both cables completely from amp and speaker and then wired them up with what used to be the left cable now feeding the right speaker then it is just the cables you have swapped. Everything else stayed the same ? Or was it just swapping "cables" at the amp and driving left speaker with right hand channel.

This was just swapping cables at the amp end and driving left speaker with right hand channel.

This makes the left hand side go quieter.

You say some tracks seem to highlight the problem. That to me suggests this may be more of an acoustic peculiarity with your room/listening position set up. It can be quite a pronounced effect and seem very real.

This could well be the case, it could be that on many tracks the vocals should be slightly off centre ?

If you own a digital multimeter that can measure AC voltage then this is dead easy to do by just measuring the voltage across the speaker terminals while playing a known test signal. It's 100% conclusive and takes seconds to do. It eliminates all doubt.

This seems the way to get this sorted.

When you say a known test signal, is this something I could download and get onto a CD to try ?

 

[cse]

What do you run the Pearl Lite amp with?(ie source and speakers). I have the Pearl Lite SACD player and was considering buying the matching amp. Could describe its characteristics.

 

[vonchief]

Hi cse,

I have a marantz CD17 KI and Leema xone speakers.

Bass is backed up with a Rel B1 set at a low crossover so not really adding bass,just taking it lower.

I would describe the sound as quite refined, I used previously Rotel 15 series pre and power amps but found them a little

too bright and harsh occasionaly for my tastes.

The Pearl lite has all the detail of the Rotel without the bright top end.

I like quite a smooth sound and found I had to use tone controls to lower the treble with Rotel to get a sound I liked.

The Marantz is used in direct mode and sounds fine to me like this. It may be a bit safe sounding to some but I listen for long periods without feeling the need to alter the sound in any way.

The problem I am curently having with channel inbalance may just be the amp revealing small differences in recordings, instruments are placed very precise in the sound stage and you can picture where the lead singer is perhaps all too easily.

I have checked with a sound meter now using a mono signal and both sides are the same level.

I don't have a test meter to hand so am unable to chek for voltage differences as was advised.

Overall I am really pleased with the amp and would reccomend an audition. It probably wont impress on a quick listen as nothing jumps out at you.To me it sounds very natural.

Hope this helps.

 

[Mooly]

So swapping L and R inputs to the amp seems to move the problem to the other channel. That would point to a source problem but both CD and DVD player... it can't be.

Swapping speaker leads at the amp moves the problem over to the other channel. That would tend to rule out speakers and speaker leads.

So what the measurement test involves is playing a test tone and setting the volume control so that you have say 1.00 volt across the left speaker. And then you just go and compare the voltage on right hand one which should be similar. We can work out any db differences from the readings and see how it all looks.

There are a couple of tracks you can download over here although you may have to register (free) to see attachements and photos etc.

http://www.diyaudio.com/

and they are on this thread,

http://www.diyaudio.com/forums/multi-way/204857-test-how-much-voltage-power-do-your-speakers-need.html

I spend far to much time over there

 

[Mooly]

Should just say that you need a meter that will resolve low voltages. Absolute accuracy is unimportant but you must be able to see say readings of say 1.1 or 1.6 for example and not just 1 and 2.

 

[vonchief]

Thanks mooly,

I did download a mono tone and played it through the CD player.

I don't have a multi meter but my dad has one so I will check the voltage as soon as he brings it to me.(should be Tomorrow)

I tried with my sound meter and found little or no difference with the speakers when playing the test tone so perhaps it's all in my head ?

I will post results with the multi meter once I have them. It would be nice to get back to just enjoying the music again.

 

[Mooly]

OK then.

When you do this it might be a lot louder than you expect. The test tones in my link are at a lower (-12db) amplitude level. If you used other tones at full 0db level then you would find you had to turn the volume only a tiny amount and it can be hard to control at low levels.

So start with the volume on minimum and turn up slowly. Remember that 2.83 volts AC is only 1 watt into 8 ohms... and I'm sure you'll be surprised how loud that is.

 

[Mooly]

You might find this interesting.

If you use the diyAudio test tracks and play the higher 220hz one at a low level and then move around your listening room you might find places where you can virtually make the sound disappear completely as you find points in the room where cancellation ocurs. Just moving a few centimeters or less can make the difference between virtually no audible sound and "normal" volume. This is caused by the sound waves reflecting off walls etc and there are points where this leads to cancellation. Equally there are points where it adds and the sound appears louder.

It's very room/frequency dependant of course but an effect you may notice.

 

[altruistic.lemon]

It's under warranty. Why not take it back to the dealer and get them to sort it out?

 

[vonchief]

If there is a problem with the amp then of course I will take it back.

I would just like to confirm there is actually a fault and not just a room issue or certain recordings causing this..

Taking time off work to take it back or the cost involved in posting it back only to find nothing is wrong would be annoying.

They charge if nothing can be found and I would be without the amp for quite a while.

I would also have to pay for return postage or make another trip back to the shop to collect it.

Seemed to make sense to have some idea of what the problem is, if indeed there is one before it goes back.

 

[altruistic.lemon]

You've found a problem, so take it back. Explain to them the exact conditions. As it stands this could be the start of a major fault which may not show until after the warranty is over. Then, you're ****ed, so better to be safe than sorry .

 

[vonchief]

Well I have now done the test with a mulitmeter.

Right speaker reads 1.0

Left speaker reads 1.1

Not sure how what this means though.

Would this be within tollerance or should the reading be exact ?

 

[Mooly]

In theory they should be the same but it sounds pretty close.

The difference equates to 0.8db. That's small.

Volume controls (assuming a normal resistive type) don't always track well channel to channel particularly at the lower end. That's a very very common issue.

Also your meter resolution may come into play. By that I mean is 1 volt actually 0.95 or maybe 1.05

So maybe try turning the level up a fraction. Perhaps aim for when the meter just changes from just less than 2 volts to exactly 2 volts. Then measure the other channel... should be 2 volts of course... but see if you can gauge how near to 2 it really is.

Depends on the meter for that. Some will resolve and display for example 2.01 volts and 2.02 volts.

Bit rushed all that... lunch time

See what you think. It all sounds reasonable up to now though.

I'll get back to you