Bass leaves after amp warms up?


I don't understand-after my Musical Fidelity M6i amp warms up for about an hour I notice the deep bass & kick drum aren't the same.
They sound less musical with loss of weight/depth.The notes are there but the moving of air have left.Sound is has much less impact and boreing.
I had the same problem with Bryston amp so there is no defect with amps nor with the rest of my equipment/
PSB Synchrony one speakers,AQ cables,Bryston CD Player.
My question has anyone heard similar & is there a plausable reason?
fishing716
I have an observation:
When I use Marantz Learning remote to press mute on the amp.Many instances that's when I notice the sound changed for the worse.
Is that "remotely" possible?
It's possible that you're still young enough that your hearing extends up this high and you're bothered by the spike

I'm 53 years old
So you use the learning remote to mute the system, and then what? Does the sound change for the worse when you unmute it?
I didn't read all 250 posts. Did you try different speakers? Hopefully a different brand and one that has a warmer tonal balance. I still believe your system is going through its normal cycle, but where most people would say the sound improves your is going too far to the lean side. It doesn't take much in the way of warmth to make the bass sound dried out and make the music uninteresting.
It seems switching between sources or mute using the remote
causes a break in the circut.
When I release mute The fuller sound has been comprimised.
Sounds less like an audiophile system
I noticed sometimes while turning a record & putting needle down the same "distruption".
This dosen't happen all the time but enough to make me aware of it.
I always loose the good sound at some point
After using remote for the amp odd concidence that's when the sound may change
I haven't tried other speakers since I like PSB sound & look..But my second choice would be Joseph audio
I prefer not to advertise,box up & sell synchrony one's unless necessary.
It seems that you have spent a considerable amount of time trying to regain the good sound after it is lost but have you spent anytime trying to lose the good sound. IOW have you done the mute/unmute or switching inputs etc repeatedly before you have lost the good sound to try and create the problem?

If you have some success on causing the problem on purpose it would give us another clue.
I think ignore comments about learning remote distrupting the sound..too far fecthed

Atmasphere:
For second day in a row after losing the better sound
I shut amp off,came back 1 hr.later & the sound returned to optimal/
If it happens next time I'll consider this a breakthrough of some sort>
NO listener fatigue here
The optimal sound rarely lasts past one CD/LP
The sound goes flat after being dynamic..sometimes before a song ends.
This has been happening for a year w/multiple components,cables & speakers.
But I did stay with Audioquest & PSB not knowing for sure if they were a problem for me.
For the record I have a steady girlfriend that hears when the music changes..
Just the other day said "what happened" like the air out of a balloon.
It's been a while since I used stock power chords but will give it a shot.
Did you ever try a different power cord on the amp?
Lets get back to the electrician visit....

When the electrician visited, did he monitor the power before, during and after you had these issues? If it included during your problems (what would be the point otherwise?), did he not hear the issues too?
Has anybody yet suggested cold solder joints somewhere in the speaker or DC saturated inductors.
When the electrician visited, did he monitor the power before, during and after you had these issues
NO
"did he not hear the issues too"?
No,I had deep bass while he was here
A few minutes after he left the bass changed
I called him back and he returned but was unable to hear the difference
The depth behind the bass notes was clearly diminished to my ears but not to him
So I guess draw what conclusion you seem appropriate..
Ralph after the bass diminished today I turned off the amp for one hr.
When I returned the bass was full & satisfying again

I believe this is the third time in a row that this procedure has worked.
I thought turning off my amp and fiddling with cables was the trick
Apparently turning of the amp was making the difference

I made it through an entire CD this evening before retiring.
And had satisfying bass most of the day
Clearly we're making progress

But something in the amp must be overheating for changes in the dynamics when warmed up.
That shouldn't be
Why don't you pick up a couple of very quiet "whisper" fans to keep the amp cool to see if it is truly a warm up thing.
"Clearly we're making progress"

What progress have you made? I'm not seeing it. If you have an audio dealer close by I suggest trying a different speaker. Maybe your favorite stereo store will loan you a demo speaker. I have a feeling this problem will go away with another speaker.

I had a similar problem with a pair of Ruark Talisman speaker. I was driving them with a pair of Dynaco MKIII monos. After the system warmed up the sound became too lean. I replaced the Ruarks with Living Voice Auditorium speakers and the problem never revealed itself again.
Fishing716. What I believe is happening is that when the amp is cold the bias is naturaly low, this does not tax the power supply as much as when the amp has warmed up, and the bias is at it's max adjusted setting.
However if the power supply is not up to the task it will sag on bass transients more when the amp is warmed up than when it's cold. As the bias is asking for more current when it's warm than when it's cold.

Cheers George
Quiescent current is higher when the amp is cold and decreases as it heats up whether the outputs are mosfets or bi-polar. But more so with mosfets than with bi-polar outputs.
You're right I haven't made any progress
The problem persists

I didn't expect to have a problem with such high end equipment.
Apparently what you say about the amp seems to be happening:

"if the power supply is not up to the task it will sag on bass transients more when the amp is warmed up than when it's cold. As the bias is asking for more current when it's warm than when it's cold".

I should either change speakers or amp right?
"I didn't expect to have a problem with such high end equipment."

Now that's funny.

It is my understanding you have tried more than one amplifier. So, you think the power supply is sagging on all of the amplifiers you tried with identical results?
I'm betting the SPL test when it happens will be inconclusive.

Fishing, do you have a CD with frequency-specific tones you can use, like one of the old Stereophile Test CDs? One-third octave warble tones would probably be good and you want individually measure enough of them to cover the range from deep bass up through the midrange.
04-19-13: Fishing716
I have a portable cd recorder & plan to record when the bass is there & not-maybe hear the difference from the cd I make.
The following was written before seeing Drubin's post just above, with which I agree:

What would really be ideal, if you can arrange it, would be to mount a good quality microphone on a stand at the listening position, and record its output when the problem is and is not present (using a suitable microphone amplifier together with the CD recorder, if the recorder doesn't provide a mic input).

You could then upload the two files to a web hosting or file sharing service, and we could analyze them with audio editing software some of us have (including me).

One reason that may be more meaningful than an SPL measurement is that unless you use a CD or other recording that provides test tones, in conjunction with the SPL meter, the SPL measurements may not be able to distinguish between a reduction of bass frequencies, and a reduction of volume that may be perceived as a reduction of bass as a result of the Fletcher-Munson Effect.

Regards,
-- Al
do you have a CD with frequency-specific tones you can use,like one of the old Stereophile Test CDs? One-third

Yes I have Stereophile test cd #3
I will get a SPL soon as possible

Also I can record from my listeing positin when the
Problem is and is not present

I will upload on my computer & be able to send a copy by email
Are you using the "plugs" on the bottom woofer ports? If not you should try them. You may find that with the plugs the bass is lean at first but fills out after the amp is fully warmed up.
OK I recorded a Song "Respect yourself" Staple Singers w/The bass the way it sounds right to me and with the bass not the same to me
I can send in email and will open in your real player
Anyone would like to hear the two versions please mention your email addresss
Thanks
AP
Anyone would like to hear the two versions please mention your email addresss
I don't think that A'gon allows posting or communication of email addresses, and the onsite messaging system can't accommodate attachments. Can you upload it to a web hosting or file sharing service and provide a link?

Regards,
-- Al
Fishing, When you run your tests with the SPL meter, set up as Al suggested and using your test disc, be sure to chart your results on a graph. This will allow you to have visual evidence of the changes you experience and will serve as an easy reference if you try moving your listening chair or speakers which you should also note on your graph. This will serve you well on your current problem, but it will also serve as a base in the future should your start to move your stuff about. It's a bit tedious, but considering all of your efforts so far it's worth while to solve or rule out possible issues.

Also, room temps can affect sound levels at some frequencies somewhat so I would note the room temp when the tests are made so you can compare them to later tests at different temps.

Another thing you can do is to disconnect one speaker. Then set up your mic/SPL meter about 3ft from the center of the connected speaker. Then run your test and chart it. Then disconnect that speaker, connect the other speaker and run the same test. This will help you rule out problems with the cross over in either of the speakers because they won't measure the same. (I once had a new pair of speakers with a bass problem in one speaker created by the manufacturer's mis-wiring a cross over. One speaker was flat to 32hz, the other rolled off starting at 100hz.)

Hope that helps a bit.
Fishing- you can try to message someone like Al like this;
to give him your email, spread the words out...
joeshmow at so and so dotkom
Anyone shoot me an email:
[email protected]

I will send 2 versions of recorded song with what I feel if different bass output

Thanks
IMO, It sounds like you have about the same bass energy in both good and bad recordings. It seems to be the character or quality of the bass that is changing. Tight and defined when amp cool, loser and woolier when warmed up. The Bryston amps I've used in the past had this quality to them. If you do not have the plugs installed in the lower vents I suggest you try them. The speaker will have an overly tight or lean bass until the amp gets warm upon which the bass should take on a more normal "Q".
It sounds like you have about the same bass energy in both good and bad recordings. It seems to be the character or quality of the bass that is changing
Exactly!
I do have one of the bass plugs installed
Have you tried the speakers without the plugs? If so and it is even worse than I'd say we are on the right track. When you add the plugs you are lowering the "Q" of the speaker. Some speaker companies included different lengths of plugs so that the owner could tailor the speaker for the "Q" that works best for his room/amp combination.

The only other possibility is using a whisper fan on the amp so that it never warms up.
No matter what I try the bass changes character about 20 minutes or so into listening.
This happens all day long so I really don't know what to.
The enjoyment of listening is comprimised because I'm waiting for the bass to go out.
Plugs have not solidifed the bass response after many attempts.
You may be dealing with the inherent shortcomings of the gear. Nothing is perfect. Hot running amps such as tubes or ss class A may satisfy you more. Or be brave and learn how to set your amp up yourself. I would second guess anyone's adjustments, factory or not. Even (respectfully), Ralph's. I can pretty well guarantee it will change just in transit, never mind during break in. And I wouldn't trust factory break in periods either, (respectfully). I have never received gear back from a tech or engineer or brand new for that matter that didn't need tweaking in regards to offset or bias, even in reference to factory spec. And the sonic differences can be dramatic.
You may be dealing with the inherent shortcomings of the gear

I took that into account that is why I've tried over the last 6 months
3 amps,2 pair speakers and a partridge in a pear tree
Have you tried any type of fan to keep the amp as cool as possible to rule out warm up issues?

You could try any fan you have laying around and if that works you could install a very quite fan later.
Okay, but the operative here is that 'nothing' is perfect. Ivor Tiefenbrun, the inventor of the famed Linn Sondek TT started his quest after buying a system way back when and taking it home only to discover it had no semblance to reality at all. Well, he took it back to the store complaining it was defective. They unapologetically informed him that no, this is exactly how it should sound. He then(thankfully) went on to correct some of the problems. You clearly need a partridge in a pear tree.
Okay. Not following your question. Atmasphere's first post is what I conceded to and my subsequent post is the position I hold. Simply my opinion FWIW.
You have spent too much time dealing with this. There's only one thing in common and thats PSB speakers, which doesn't mean the integrated amps you've chosen aren't the problem. It sounds like your dealer is no help at all. I would find a new one or call mine. You need someone that can start you off on the right foot. My dealer would be at my house right now if I wasn't happy. I'm serious. He would be sitting in my living room on a Sunday night.
I'll try the fan but it's hard to belive amp's too hot
There are no signs of heat
My Dealer is pretty good but I'm hopeing he lends the necessary amp or speakers I requested.
He knows something is causing the bass to change(he agrees after hearing the tape I made.
But has no logical reason,and is skeptical
Glad to hear that you will be able to try some other equipment. It will hopefully give us some new clues.

I'm not suggesting that your amp is running hot. I know it's a long shot but I am trying to deduce if the sound of the amp when it is "cold" has the good bass. There is a reason that most reviewers will go to great lengths to fully warm up the equipment before they listen because the sound will usually change some from dead cold to fully warm.