Bass worse after 3 hours

alfa100

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Aug 29, 2014
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I could be wrong. Appears that bass gets more prominent after 3 hours with Pass Xa 100.8. First hour bass is a light. Then up to 3 hours sounds in good proportion to rest of frequencies. Thereafter bass becomes over prominent up to 100 hz. Does anybody have similar experience.
 

alfa100

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Aug 29, 2014
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South Africa
The amplifier is always on standby. This occurs approx 4 hours after listening. Any idea why this occurs? Pass Labs dealer who also sells Wilson speakers says the Xa 100.8 has enough power for the Sasha.
 
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alfa100

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Aug 29, 2014
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I have a friend with Sasha‘s and he has the XA160.5 ‘s. I had Magico mini II and the XA 100.5 and they were under powered so I moved to the 160.5.

I don’t see why the problem you are describing would only occur after four hours of being fully turned on.
I guess so. What of the class AB models from Pass Labs in terms of bass control?
 

PeterA

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Dec 6, 2011
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I guess so. What of the class AB models from Pass Labs in terms of bass control?

I have not heard the X series, but people really loved the 350.5 and 600.5. You should be able to find the former for $8K or so. I think one recently went for under 6K. That would really be worth considering, IMO.

I now have the Magico Q3 with Pass XA160.5. The needle moving indicates leaving Class A. It never moves but today I blasted the Sheffield Drum track to see what a friend's cartridge could do and the needle did move very slightly, about 1/16th inch when we hit high 90s dB. My amps are 320 watts of Class A into the 4 ohm load, and more of AB.

I'd call Mark at Reno or Pass and ask about your observation. It seems very strange to hear worse sound after 4 hours.
 
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Duke LeJeune

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@alfa100, it might not be your amplifiers, but I need a bit more information before hazarding a guess.

Does it occur after three or four hours regardless of the volume level, or is it most noticeable after you've been pushing the system pretty hard for that length of time?

If you stop playing music for an hour or so, when you come back, is the bass back to normal?
 
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BlueFox

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How does it sound after being on 12-24 hours? When I listen to my stereo I turn the amps on the night before, and the preamp is on 24/7.
 

MasterChief

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Jun 26, 2012
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I could be wrong. Appears that bass gets more prominent after 3 hours with Pass Xa 100.8. First hour bass is a light. Then up to 3 hours sounds in good proportion to rest of frequencies. Thereafter bass becomes over prominent up to 100 hz. Does anybody have similar experience.

Just another perspective that may not be relevant for you. For me, listening for hours give me listening fatique and the things I hear do sound different. For many years this what not the case but as I grow older it suddenly appeared. Before I was familiar with this phenomenon I actually thought my speakers got "tired" in some way with a more prominent bass and muddier tremble. Shorter sessions and a lower volume is the way to go for me.

 
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wil

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Jul 22, 2015
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Just another perspective that may not be relevant for you. For me, listening for hours give me listening fatique and the things I hear do sound different. For many years this what not the case but as I grow older it suddenly appeared. Before I was familiar with this phenomenon I actually thought my speakers got "tired" in some way with a more prominent bass and muddier tremble. Shorter sessions and a lower volume is the way to go for me.

Exactly my thought. It seems very possible it's your ears/brain not the amp?
 

Duke LeJeune

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Haven't heard back from alfa100 so this is just a guess:

IF the bass prominence issue arises after you've been playing the system pretty loud for 3-4 hours, but NOT if you play at low level for the same amount of time; and

IF it goes away after you've turned the system off for a while (maybe an hour, maybe a half-hour, I'm not really sure),

THEN....

It may not be your amps.

It may be your speakers.

Those symptoms would be consistent with the woofers' motors slowly heating up enough for the magnets to temporarily lose strength. Weaker motor = boomier bass. Then given a chance to cool down, the magnets return to normal strength.

This sort of thing can happen to musicians on a gig. Towards the end of a loud set, the amp seems to run out of gas - it's not as loud and sounds mushy. So they crank the volume which heats the magnets even more with little increase in loudness, which just makes it worse - it's a vicious cycle. They vow to bring a bigger amp next time. But by the beginning of the next set, the magnets have cooled off enough that the dynamics and impact are good again. Anyway what they really need is not more amp but more speaker, and unfortunately that's not obvious to them.

Something like that may be going in here.
 

MAXPWR

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Dec 1, 2019
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Iowa, High-End, Fly-Over Country
I could be wrong. Appears that bass gets more prominent after 3 hours with Pass Xa 100.8. First hour bass is a light. Then up to 3 hours sounds in good proportion to rest of frequencies. Thereafter bass becomes over prominent up to 100 hz. Does anybody have similar experience.
Hi alfa100,
I have a XA160.5 driving Wilson Sasha speakers and have experience a similar effect and have a possible solution. Here is some information to set up my findings. Your XA100.8 like my XA160.5 are both class A amplifiers that for all practical listening levels will always draw the same amount of current from the power line. Let’s call this MAX current draw, since it is likely not going to be higher for any practical listening levels.

The Pass Labs amplifiers are designed to run at around 53 degrees C on their heatsinks. The reason for this is that the MOSFET output devices sound their best at that temperature. This is why the amplifiers take about 3 hours to start sounding their best coming from standby. It takes that long for the mass of the amplifiers and heatsinks to get to a stable temperature equilibrium with the ambient temperature of the room. During this time the power system powering the amplifier is also gradually heating up given the amplifier is drawing MAX current all the time. The power cords, outlets and any downstream conditioning equipment (in my case a 5 KW isolation transformer) are also heating up gradually.

In my system I observed significant sound quality (SQ) improvement during the 3 hours during amplifier temperature stabilization, then slower SQ improvement to the fourth hour, but then in the fifth to sixth hour the system started losing SQ and sounded less detailed. It had a warner overall balance that was not as neutral sounding and loss of bass definition. Your XA100.8 having very different feedback may manifest the bass difference differently your power system difference I found in my system that was the culprit.

I was using Porter Port AC outlet for the power amplifiers. I believe it was warming up over time and the grip on the AC plugs was relaxing. To use my ISO transformer in a balanced power configuration it forces me to have only one output; thus, one outlet for both amps. The MAX current draw of both amps on that single outlet causes a lot of heating compared to if I only had one amp plugged into it. Since heating is a current squared times resistance relationship if I had two separate outlets the heating effect would be 4 time less.

So what was my solution? I replaced the Porter Port with an Oyaide R1 outlet. I’m not going get into the fact that the Oyaide R1 outlet sound different than other outlets and took a significant amount of time to break in. I’m going to make the point that the Oyaide R1 has a better grip than most outlets and that the degradation of SQ that I heard in the fifth to sixth hours of operation with my XA160.5 has gone away in my system with everything else being the same. I seldom have the amps on for more than 10 or 12 hours at a time, so I cannot speak to running times longer than that. I do not notice SQ changes anymore for the longer periods I have the amps turned on has been my experience.

My next move is to implement a different ISO transformer that has 3 separate 20 Amp balanced outputs, which I will be able to have a separate 20 Amp outlet for each mono amplifier.

Hope this helps if you might be experincing the same issue....
 

Gregadd

WBF Founding Member
Apr 20, 2010
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Congrats on having a system you can l listen to for three hours.
IME intermittent problems are usually the result of a malfunction.
I assume you went through the normal procedure for assuring which component is the problem. Switching it out and seeing if the problem persists. Are you sure it is not source dependent?
Have you considered having it professionally evaluated? It is unusual because it usually happens in reverse. It starts out bad and then improves.
 
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MAXPWR

Well-Known Member
Dec 1, 2019
34
44
105
Iowa, High-End, Fly-Over Country
I could be wrong. Appears that bass gets more prominent after 3 hours with Pass Xa 100.8. First hour bass is a light. Then up to 3 hours sounds in good proportion to rest of frequencies. Thereafter bass becomes over prominent up to 100 hz. Does anybody have similar experience.
alfa100,

If the prominent bass effect remains constant after many hours, and this has been the attribute of the amplifiers since new, it may just be the characteristic of the amplifier after it warms up. Other people have related the strong bass of the Point 8 series over the Point 5 series amplifiers. As I mentioned in my previous post, Nelson Pass changed the way he implements feedback on the Point 8 series vs the Point 5 series amplifiers and this has changed the amplifiers bass characteriscs. The Point 8 series amps are DC coupled. The Point 5 series amplifiers are not DC coupled, which also changes the very low end presentation.
 

alfa100

Well-Known Member
Aug 29, 2014
262
49
258
South Africa
Congrats on having a system you can l listen to for three hours.
IME intermittent problems are usually the result of a malfunction.
I assume you went through the normal procedure for assuring which component is the problem. Switching it out and seeing if the problem persists. Are you sure it is not source dependent?
Have you considered having it professionally evaluated? It is unusual because it usually happens in reverse. It starts out bad and then improves.
I’ll have it checked. Thank you
 

alfa100

Well-Known Member
Aug 29, 2014
262
49
258
South Africa
Hi alfa100,
I have a XA160.5 driving Wilson Sasha speakers and have experience a similar effect and have a possible solution. Here is some information to set up my findings. Your XA100.8 like my XA160.5 are both class A amplifiers that for all practical listening levels will always draw the same amount of current from the power line. Let’s call this MAX current draw, since it is likely not going to be higher for any practical listening levels.

The Pass Labs amplifiers are designed to run at around 53 degrees C on their heatsinks. The reason for this is that the MOSFET output devices sound their best at that temperature. This is why the amplifiers take about 3 hours to start sounding their best coming from standby. It takes that long for the mass of the amplifiers and heatsinks to get to a stable temperature equilibrium with the ambient temperature of the room. During this time the power system powering the amplifier is also gradually heating up given the amplifier is drawing MAX current all the time. The power cords, outlets and any downstream conditioning equipment (in my case a 5 KW isolation transformer) are also heating up gradually.

In my system I observed significant sound quality (SQ) improvement during the 3 hours during amplifier temperature stabilization, then slower SQ improvement to the fourth hour, but then in the fifth to sixth hour the system started losing SQ and sounded less detailed. It had a warner overall balance that was not as neutral sounding and loss of bass definition. Your XA100.8 having very different feedback may manifest the bass difference differently your power system difference I found in my system that was the culprit.

I was using Porter Port AC outlet for the power amplifiers. I believe it was warming up over time and the grip on the AC plugs was relaxing. To use my ISO transformer in a balanced power configuration it forces me to have only one output; thus, one outlet for both amps. The MAX current draw of both amps on that single outlet causes a lot of heating compared to if I only had one amp plugged into it. Since heating is a current squared times resistance relationship if I had two separate outlets the heating effect would be 4 time less.

So what was my solution? I replaced the Porter Port with an Oyaide R1 outlet. I’m not going get into the fact that the Oyaide R1 outlet sound different than other outlets and took a significant amount of time to break in. I’m going to make the point that the Oyaide R1 has a better grip than most outlets and that the degradation of SQ that I heard in the fifth to sixth hours of operation with my XA160.5 has gone away in my system with everything else being the same. I seldom have the amps on for more than 10 or 12 hours at a time, so I cannot speak to running times longer than that. I do not notice SQ changes anymore for the longer periods I have the amps turned on has been my experience.

My next move is to implement a different ISO transformer that has 3 separate 20 Amp balanced outputs, which I will be able to have a separate 20 Amp outlet for each mono amplifier.

Hope this helps if you might be experincing the same issue....
This is very helpful. I uograded to dedicated lines for my amps and use Furutech NCF GTX R outlets. Your explanation makes sense. I will email Pass Labs . Their after sales support is super
 
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