Poll for Topping PA5 owners only please.

[Deleted member 46664]

Just wondering: there has been some discussion on this forum about the downside of using single-ended input on the PA5. Is there any chance that using a mono-6,5mm to RCA adapter to connect a single-ended device could cause this noise? For now, I have disconnected my (single-ended) phono pre-amp from the PA5, until this issue has been thoroughly investigated.

It is possible. There is some reason (from another user's investigation) to believe the inputs are not wired for the TS/single ended cable trick.

There are both transformer and active adapters available that will convert single ended to true balanced signals. They're not terribly expensive. Give Amazon a search...

 

[antcollinet]

Open up any brick type supply ... you're going to find 1 or 2 amp diodes in the input rectifier.
You're asking them to handle an inrush current that can reach 6 or 8 amp peaks.
They're only going to do that a limited number of times before they go pop.

the 1 or 2 amp rating is continuous. Normally they'll have a higher pulse rating.

Unless you've done the design calcs on a range of devices (or find a study that has), it suggests you are speculating. If you open up one device and find a deficiency, then you can only state it applies to that device. Extrapolating it to all "these things" is invalid.

Here is an example of only the first device that came up from a google search. 1.5 amp rating. 40A non repetitive surge rating. It's almost as if rectifier manufactures have thought of inrush

 

[Deleted member 46664]

the 1 or 2 amp rating is continuous. Normally they'll have a higher pulse rating.

Unless you've done the design calcs on a range of devices (or find a study that has), it suggests you are speculating. If you open up one device and find a deficiency, then you can only state it applies to that device. Extrapolating it to all "these things" is invalid.

I'm guessing you missed this part of my first reply...

"This issue came to the fore with people shutting down their PCs and then turning off the "babysitter switch" on the back of the case. We had a large rash of failed power supplies because the current inrush was popping the rectifiers inside. We ended up replacing quite a few under warranty and advising that the power switch be left on all the time. After that, very few supply failures."

Here is an example of only the first device that came up from a google search. 1.5 amp rating. 40A non repetitive surge rating.

Keyphrase ... Non-Repetative Surge ... as in, it can do this ONCE.

If the intent was that the supply should be turned off and on repeatedly, why is there no switch on the power brick and why is the switch in the amplifier merely a "standby" switch? Really ... think about it.

It's almost as if rectifier manufactures have thought of inrush

It's almost like you are looking for a way to launch some long complicated contradiction to very simple advice offered to someone else.
How does that do anything to address their concern ... other than confuse the hell out of them?

 

[antcollinet]

I'm guessing you missed this part of my first reply...

You've just extrapoloated a particular problem from a completely different class of device to (apparently) "all power supplies"

Keyphrase ... Non-Repetative Surge ... as in, it can do this ONCE.

No, it means it can't do it at 50/60Hz.

It will be able to repeat that at an infrequent (but unspecified) rate. It is specifically intended for inrush. If it meant just once, it would not be a rating.

Most likely it can be repeated at a rate at which any impacts from the previous pulse have dissipated.

It's almost like you are looking for a way to launch some long complicated contradiction to very simple advice offered to someone else.
How does that do anything to address their concern ... other than confuse the hell out of them?

Many people don't like to keep devices permanently connected to mains for safety and/or power consumption reasons (or, indeed so they can power them from a remote). Telling them they must based on speculation extrapololated from unrelated data doesn't help them.

 

[Deleted member 46664]

You've just extrapoloated a particular problem from a completely different class of device to (apparently) "all power supplies"

Fine... ignore the obvious evidence of proper use (cords, switches, modes, etc) and ignore information about previous rectifier failures in SMPS devices that are far more sophisticated than these little bricks and ignore my 40 years in the industry .... advise this person to go ahead and blow up another amp.... Be my guest!

 

[antcollinet]

I think we'll just have to agree to disagree.

 

[Deleted member 46664]

I think we'll just have to agree to disagree.

Think about the advice I gave ... "use it as it's intended"... Worst case nothing gets worse ... best case the problem is solved.
Now think about the advice you would give... Seriously... think about it.

 

[pma]

Normally designed and produced electrical equipment cannot have failures when switched on/off several times a day. I cannot recall a single failure of any of my audio components in such conditions over decades. If it has issues, there must be a serious design flaw. I am speaking about normal components, excluding toys like A07.

 

[Deleted member 46664]

Normally designed and produced electrical equipment cannot have failures when switched on/off several times a day. I cannot recall a single failure of any of my audio components in such conditions over decades. If it has issues, there must be a serious design flaw.

Not really ... these new setups are actually designed to be plugged in and left powered up all the time.

As I said ... why do you think there's no switch on the power supply and the switch on the amp is just for standby mode. It's to keep those big bulk capacitors charged without giant inrushes of current.

Yes it's cheap design but I have a whole bunch of these (edit: TPA3116 amps mostly) out to friends and clients that run exactly as I describe and they've been spot on reliable for up to 6 years (i.e. as long as I've been using them).

 

[pma]

See this ….

Adaptors, extension leads and avoiding electrical fires | Electrical and gas safety in HMOs | Oxford City Council

Gas and electrical safety requirements in HMOs

www.oxford.gov.uk

 

[Deleted member 46664]

See this ….

Adaptors, extension leads and avoiding electrical fires | Electrical and gas safety in HMOs | Oxford City Council

Gas and electrical safety requirements in HMOs

www.oxford.gov.uk

Yes... and? You think I don't know basic electrical safety?

 

[antcollinet]

Think about the advice I gave ... "use it as it's intended"... Worst case nothing gets worse ... best case the problem is solved.
Now think about the advice you would give... Seriously... think about it.

What? I need to think about it seriously? I never thought of that.

 

[iLoveCats]

Just wondering: there has been some discussion on this forum about the downside of using single-ended input on the PA5. Is there any chance that using a mono-6,5mm to RCA adapter to connect a single-ended device could cause this noise? For now, I have disconnected my (single-ended) phono pre-amp from the PA5, until this issue has been thoroughly investigated.

The people with failures need to say whether they are using it balanced or unbalanced.

 

[pkane]

The people with failures need to say whether they are using it balanced or unbalanced.

Totally agree. And also whether the amp was left on all the time, in standby, or turned completely off after each time. Mine has not had any issues so far (received early January), and is always fed balanced input, I keep it on most of the time, but do turn off the switch on the amp when I don't plan to use it for the remainder of the day.

 

[Deleted member 46664]

Totally agree. And also whether the amp was left on all the time, in standby, or turned completely off after each time. Mine has not had any issues so far (received early January), and is always fed balanced input, I keep it on most of the time, but do turn off the switch on the amp when I don't plan to use it for the remainder of the day.

As I explained above these things are not intended to work with the AC being turned off and on all the time. It can drastically shorten the lifetime of the power supply.

Also... the TPA3251 is only recommended for 36 volt operation and that is a 38 volt power supply. Any brief spikes during ACon or ACoff could place additional stress on the chip leading to the problems people have been encountering. ("Could"... not "Does"... because we don't know for sure what's happening yet).

Clearly the information requested (balanced, standby, AC...) does make sense ....

 

[pkane]

As I explained above these things are not intended to work with the AC being turned off and on all the time. It can drastically shorten the lifetime of the power supply.

Also... the TPA3251 is only recommended for 36 volt operation and that is a 38 volt power supply. Any brief spikes during ACon or ACoff could place additional stress on the chip leading to the problems people have been encountering. ("Could"... not "Does"... because we don't know for sure what's happening yet).

View attachment 201794

Clearly the information requested --balanced, standby, AC...) does make sense ....

Your explanation is a theory. What is important for owners of PA5 is to figure out if this or something else is the cause of actual problems being reported here. Unless you've reproduced the noise problem with PA5 by frequent disconnects from power, we have no evidence so far that this is the cause.

 

[Deleted member 46664]

Your explanation is a theory. What is important for owners of PA5 is to figure out if this or something else is the cause of actual problems being reported here. Unless you've reproduced the noise problem with PA5 by frequent disconnects from power, we have no evidence so far that this is the cause.

Power bricks dying prematurely when repeatedly plugged in and unplugged is not a theory. This is a known problem.

For the rest ... I take it you missed the part about "("Could"... not "Does"... because we don't know for sure what's happening yet)."

Actually unless multiple people have done power cycling we don't know for sure. We can't really ask anyone to put their amp at risk but we can get the information from those who have been power cycling.

 

[pkane]

I take it you missed the part about "("Could"... not "Does"... because we don't know for sure what's happening yet)."

Actually unless multiple people have done power cycling we don't know for sure. We can't really ask anyone to put their amp at risk but we can get the information from those who have been power cycling.

Right. And that's why we are asking those who have experienced the failure to report if those two potential causes were observed:

Was the amp power-cycled frequently, and was the input balanced or single-ended? Maybe this should be made into another poll.

 

[wlgreg]

Right. And that's why we are asking those who have experienced the failure to report if those two potential causes were observed:

Was the amp power-cycled frequently, and was the input balanced or single-ended? Maybe this should be made into another poll.

My defective units used balanced connections, and were always left on. First few weeks, no problems, then static problem started to manifest. I posted video in the “main” PA5 thread.

 

[pjug]

As I explained above these things are not intended to work with the AC being turned off and on all the time. It can drastically shorten the lifetime of the power supply.

Also... the TPA3251 is only recommended for 36 volt operation and that is a 38 volt power supply. Any brief spikes during ACon or ACoff could place additional stress on the chip leading to the problems people have been encountering. ("Could"... not "Does"... because we don't know for sure what's happening yet).

View attachment 201794

Clearly the information requested (balanced, standby, AC...) does make sense ....

I don't know why people keep saying the amp power supply voltage is out of the recommended range. It is right in the table you show that 38V is within the recommended range. All the graphs in the data sheet go up to 38V as well.