Poll for Topping PA5 owners only please.

[pma]

Hope that the designer(s) ever heard about

ZNR surge absorber

ZNR® (Zinc oxide Non-linear Resistor) products are also known as varistors or MOVs.

industry.panasonic.eu

and other kind of both surge voltage and surge current protection. Isn't the arguing here a bit childish?

 

[Deleted member 46664]

Obviously it is the transient voltage and current switching response of both the power supply and the amplifier that gives rise to the argument of whether or not power supply design specifications are adequate.

Good comment, thanks for posting it.

In most of these mini-amps the amplifier's internal bulk capacitor is between 3300 uf and 4700 uf and it is generally connected directly to the power input connector. When these caps are drained (which takes about 20 seconds in standby with no AC power) there is a huge rush of current from the external brick into the amplifier to charge those capacitors.

We've likely all seen the mini-amp spark when we connect the power supply to the amp... yeah, there's some current there!

The smps brick itself is designed to get itself up and running then provide it's rated current. However, when those bulk caps are fully discharged and the AC is turned on, the supply has first the problem of getting itself going and then immediately the problem of charging huge capacitors. Many just aren't up to doing that repeatedly on a day in and day out basis. They will provide their rated voltage and current... but that first several milliseconds is a killer that can burn out the input diodes in it's own internal rectifier.

Yes a soft start circuit is a good idea here... Why it's not in these amps is simple enough to figure out... price. It's extra parts and they all add to the cost.

Now to be fair... these little bricks will take that kind of abuse a few times before they die. But it does shorten their lifetime as the main diodes suffer minor damage on each repetition, until they finally give up. Hence my suggestion to just plug the whole thing in and leave it on, but in standby between uses.

 

[pjug]

Good comment, thanks for posting it.

In most of these mini-amps the amplifier's internal bulk capacitor is between 3300 uf and 4700 uf and it is generally connected directly to the power input connector. When these caps are drained (which takes about 20 seconds in standby with no AC power) there is a huge rush of current from the external brick into the amplifier to charge those capacitors.

We've likely all seen the mini-amp spark when we connect the power supply to the amp... yeah, there's some current there!

The smps brick itself is designed to get itself up and running then provide it's rated current. However, when those bulk caps are fully discharged and the AC is turned on, the supply has first the problem of getting itself going and then immediately the problem of charging huge capacitors. Many just aren't up to doing that repeatedly on a day in and day out basis. They will provide their rated voltage and current... but that first several milliseconds is a killer that can burn out the input diodes in it's own internal rectifier.

Yes a soft start circuit is a good idea here... Why it's not in these amps is simple enough to figure out... price. It's extra parts and they all add to the cost.

Now to be fair... these little bricks will take that kind of abuse a few times before they die. But it does shorten their lifetime as the main diodes suffer minor damage on each repetition, until they finally give up. Hence my suggestion to just plug the whole thing in and leave it on, but in standby between uses.

I have no idea if these particular power supplies are well designed or not, but does the reported problem seem to have anything to do with power supply? I haven't seen reports of power supply failures. Isn't this thread about collecting evidence to get some idea of what is causing the particular problem, which has happened both with continuous power and with repeated power cycling?

 

[Deleted member 46664]

I have no idea if these particular power supplies are well designed or not, but does the reported problem seem to have anything to do with power supply? I haven't seen reports of power supply failures. Isn't this thread about collecting evidence to get some idea of what is causing the particular problem, which has happened both with continuous power and with repeated power cycling?

Oh no that's not specifically the reason ... I'm just as concerned that they're running a 36 volt chip on 38 volts.
As I keep saying ... we don't actually know what the problem is at this point.

 

[pjug]

Oh no that's not specifically the reason ... I'm just as concerned that they're running a 36 volt chip on 38 volts.
As I keep saying ... we don't actually know what the problem is at this point.

I did notice that there seem to be some remnants in the TI literature that seem to indicate that at some point they did consider 36V to be the max operating voltage. For example, see Figure 25 here

https://www.ti.com/lit/ug/slau751/slau751.pdf?ts=1650849944748&ref_url=https%253A%252F%252Fwww.google.com%252F

and even in the current data sheet they say 12V-36V in the "Features" whereas they say 12V-38V in the "Recommended Operating Conditions". So TI has done a poor job with specifying this. I would hope that Topping noticed this and got the go-ahead from TI to use 38V. My guess is that they did so.

 

[Deleted member 46664]

I did notice that there seem to be some remnants in the TI literature that seem to indicate that at some point they did consider 36V to be the max operating voltage. For example, see Figure 25 here

https://www.ti.com/lit/ug/slau751/slau751.pdf?ts=1650849944748&ref_url=https%253A%252F%252Fwww.google.com%252F

and even in the current data sheet they say 12V-36V in the "Features" whereas they say 12V-38V in the "Recommended Operating Conditions". So TI has done a poor job with specifying this. I would hope that Topping noticed this and got the go-ahead from TI to use 38V. My guess is that they did so.

I doubt Topping needed permission.

Yes 38 volts is the maximum recommended voltage ... but the "typical" spec. which most engineers would follow is 36. At 38 volts even minor errors in supply voltage could become problematic. Wanna guess how many 12v supplies I've had in there that actually output 13 volts?

Once again let me stress that any and all concerns are valid until we know what is actually going on.

 

[pjug]

I doubt Topping needed permission.

Yes 38 volts is the maximum recommended voltage ... but the "typical" spec. which most engineers would follow is 36. At 38 volts even minor errors in supply voltage could become problematic. Wanna guess how many 12v supplies I've had in there that actually output 13 volts?

Once again let me stress that any and all concerns are valid until we know what is actually going on.

You crack me up. I didn't say they would ask for permission. I said they would consult with TI if they were unsure about 38V, to be sure TI was confident that the amp would have very good reliability at that voltage. Haven't you ever done similar consulting when you have this kind of question?

 

[Deleted member 46664]

You crack me up. I didn't say they would ask for permission. I said they would consult with TI if they were unsure about 38V, to be sure TI was confident that the amp would have very good reliability at that voltage. Haven't you ever done similar consulting when you have this kind of question?

Well gosh, it might have been this: "I would hope that Topping noticed this and got the go-ahead from TI to use 38V. "

 

[Solveit]

Useless poll.
How do we know that all voters own the amp?
Or competing companys vote it broken?

 

[pma]

Useless poll.
How do we know that all voters own the amp?
Or competing companys vote it broken?

Conspiracy theory?
With this kind of reasoning anything on the web might be considered useless. And you may reverse the suspicion and say that those who love the amp vote positive .
Do not go this way. Experience from real operation shared on the web is important. The noise issue is definitely not a fake news.

 

[Deleted member 46664]

Conspiracy theory?

A valid but unlikely concern ... there have only been 42 votes. If there was tampering going on the count would be much higher.

With this kind of reasoning anything on the web might be considered useless. And you may reverse the suspicion and say that those who love the amp vote positive .

LOL... it pretty much is. I don't have numbers but if you set aside cat videos and streaming entertainment... I'd bet the internet --especially facebook-- is about 50% BS.

Do not go this way. Experience from real operation shared on the web is important. The noise issue is definitely not a fake news.

Yep ... it's a problem. I wish I could get a production sample over here and tear it right down to find out what's going on. (It's called "testing to destruction") But that's not likely to happen any time soon.

 

[Solveit]

Conspiracy theory?
With this kind of reasoning anything on the web might be considered useless. And you may reverse the suspicion and say that those who love the amp vote positive .
Do not go this way. Experience from real operation shared on the web is important. The noise issue is definitely not a fake news.

Same people who always downvote everything from Topping?

 

[Fleuch]

The statistical distribution of component tolerances provides a range of maximum operating conditions. In any product headroom is required between the design operating conditions and the specified maximum value to account for any variation in individual component tolerances. Where the individual sample parameter values are close to, or even below the specification value, implies operating close to or above the individual actual maximum will increase the possibility of failure.

Where amplifiers are failing or developing audible anomalies, the operating conditions at the point of failure are essential background information.

For example, thermal stress is a contributing factor to failure as well as electrical stress. Accepting that failure should not occur, the environmental and operating conditions at the point of failure are indicators to the cause. Design operating conditions close to maximum tolerances may be one approach to investigating the root of known failures.

 

[Solveit]

The statistical distribution of component tolerances provides a range of maximum operating conditions. In any product headroom is required between the design operating conditions and the specified maximum value to account for any variation in individual component tolerances. Where the individual sample parameter values are close to, or even below the specification value, implies operating close to or above the individual actual maximum will increase the possibility of failure.

Where amplifiers are failing or developing audible anomalies, the operating conditions at the point of failure are essential background information.

For example, thermal stress is a contributing factor to failure as well as electrical stress. Accepting that failure should not occur, the environmental and operating conditions at the point of failure are indicators to the cause. Design operating conditions close to maximum tolerances may be one approach to investigating the root of known failures.

And what have this to do with THIS poll?

 

[Fleuch]

So far there are 94 previous posts regarding PA5 amplifier failure, when a poll should simply be a poll, period - no comments. However there has been an ongoing discussion on possible causes of failure, so what contribution can you offer to THIS discussion?

 

[raest]

changed my vote. just now started hearing crackling in my left channel

i don't think i'm buying a Topping product ever again. pointless SINAD chasing while compromising build quality does not a good product make

 

[REK2575]

changed my vote. just now started hearing crackling in my left channel

i don't think i'm buying a Topping product ever again. pointless SINAD chasing while compromising build quality does not a good product make

@raest -- sorry to hear it. that's really disappointing. Would you be willing to tell us the first 4 digits of your PA5's serial #? Wondering if there's any pattern with some of the other serial #s folks are posting here for units that have failed.

 

[raest]

the first 4 digits are 2201

 

[Eggs Ackley]

Just for the record my serial number begins with 2110 it has been continually powered with the stock power supply since Dec 17 2021. It also is connected to a Topping E50 DAC using proper balanced cables and to a pair of Klipsch Forte speakers ( 8 ohm, 98dB SPL one watt one meter). There is around 100 hours of listening time on it. I have no noise in either channel or any other issues.

 

[REK2575]

the first 4 digits are 2201

Thanks -- I appreciate it. I have a 2201 as well, and I'm going to send it back while I still can, sad to say.

All this awe and amazement over the new Topping LA90 review.... yeah, SINAD is great... will the thing last more than a few weeks? Apparently, lots of folks do not seem to care if it does, based on the poll...