Wall warts!....the fewer the better it seems

[Nitrous]

I thought I would share yesterday's experience. I swapped out my squeezebox classic (with wall wart) and CA Dacmagic (with wall wart), for a CA NP 30 (very good price new and no wall wart). In the process my vinyl front end with CA 640p (only wall wart left on the 6 six gang extension now) is now singing like never before...........just shows yeh! The NP 30 sounds ok too!

Nick

[system7]

There IS a scientific basis for your observation, Nick. Computer switched mode power supplies and wall warts have in common that they produce a positive 5 or 12V rail relative to neutral. This results in the 50Hz AC mains supply gaining an unwanted (-ve) DC offset.

A DC offset on an amplifier balanced power supply produces a buzzing from the toroidal transformer. It's not good.

Usually your phase is shared with 3 or 4 neighbouring houses, before three sets of them are combined into the usual 3 phase mains at the local substation. It's a complex problem, but mains works most cleanly into resistive loads like electric fires. Fluorescent lighting also is messy and noisy, though an attempt is made to balance the load with a coil.

Bottom line is your mains is cleanest at night when most of the dodgy loads are switched off IIRC. :mental:

[Nitrous]

Thanks for reply System7, I've heard and read some of things you out lined in different places, and I always try and follow some basic setup and cables dressing etc., which I didn't think was that bad to begin with. But the surprise here was that although I was playing around with the digital side of things without touching the vinyl side it improved noticeably.

I gues what we all need is a detached house with its own sub-station:D

[Stubies]

Steve

You should have been part of the 'mains filter/conditioner' discussion' it was a thread in need of more technical input!

starts around here in the thread:
http://theartofsound.net/forum/showthread.php?27029-Upgrade-Fever-%96-Doctor-Needed/page4


There IS a scientific basis for your observation, Nick. Computer switched mode power supplies and wall warts have in common that they produce a positive 5 or 12V rail relative to neutral. This results in the 50Hz AC mains supply gaining an unwanted (-ve) DC offset.

A DC offset on an amplifier balanced power supply produces a buzzing from the toroidal transformer. It's not good.

Usually your phase is shared with 3 or 4 neighbouring houses, before three sets of them are combined into the usual 3 phase mains at the local substation. It's a complex problem, but mains works most cleanly into resistive loads like electric fires. Fluorescent lighting also is messy and noisy, though an attempt is made to balance the load with a coil.

Bottom line is your mains is cleanest at night when most of the dodgy loads are switched off IIRC. :mental:

[AlexM]

There IS a scientific basis for your observation, Nick. Computer switched mode power supplies and wall warts have in common that they produce a positive 5 or 12V rail relative to neutral. This results in the 50Hz AC mains supply gaining an unwanted (-ve) DC offset.

A DC offset on an amplifier balanced power supply produces a buzzing from the toroidal transformer. It's not good.

Usually your phase is shared with 3 or 4 neighbouring houses, before three sets of them are combined into the usual 3 phase mains at the local substation. It's a complex problem, but mains works most cleanly into resistive loads like electric fires. Fluorescent lighting also is messy and noisy, though an attempt is made to balance the load with a coil.

Bottom line is your mains is cleanest at night when most of the dodgy loads are switched off IIRC. :mental:

Uh oh... I've got at least 10 t4 cabinet lights in my kitchen, which use high speed switching balasts. Bugger. Maybe need an isolation transformer in my kitchen lighting supply feed!. Given they are all made in China I doubt much effort has been made to make them electrically quiet either...

Cheers,
Alex

[Arkless Electronics]

There is nothing specifically wrong with wall warts as such. They are just a transformer, rectifier and smoothing cap in a plug top encapsulation. Often these days of course they are also just as likely to be a fairly crude switch mode PSU (smpsu), which has its own problems due to switching noise (at supersonic frequency usually).
However, as I went into greater length in the earlier thread, they are not necessarily a limitation on the SQ attainable. It all depends on how they are used and what filtration and regulation is used after them. If all this is taken care of optimally then there will be no further improvement in SQ from swapping out a wall wart for something better..... no matter how much better or how expensive!

Obviously things are often not taken care of optimally though and in these cases then yes an improvement can be obtained from a good after market linear supply.

In the case of the 640P mentioned earlier (and which, as many will be aware, I offer a modification service for) the wall wart is an AC supply and so there is really nothing you can do to improve matters anyway. The 640P takes the input 12V AC and by using dual mirror image voltage doublers it manages to give both + & - DC supplies to the internal regulators which then provide + & - 18V DC to the rest of the circuitry. There is also R-C filtration between the V doublers and the regulators and again after the regulators. All you can do is fit a larger 12V AC supply and that will make no difference as the standard one is more than large enough.. It may in fact cause it to malfunction as it relies on the poor regulation of the small transformer to give more like 17V AC rather than the rated 12V! A much larger transformer would have better regulation and would provide closer to 12V which could leave it short of voltage internally and not working as it should.... ;)

[Barry]

My concern with "wall warts" (apart from the hash produced by SMPS) is the lack of fusing. I have been told that many do have an internal fuse, however this is not replaceable, as most wall warts are assembled with either single-use barbed plastic 'click together' fixings, or use screw fixings that cannot be unscrewed (so called tamper-proof fixings)!

[Arkless Electronics]

My concern with "wall warts" (apart from the hash produced by SMPS) is the lack of fusing. I have been told that many do have an internal fuse, however this is not replaceable, as most wall warts are assembled with either single-use barbed plastic 'click together' fixings, or use screw fixings that cannot be unscrewed (so called tamper-proof fixings)!

The most common arrangement in the non switch-mode variety is a thermal fuse embedded in the transformer winding. It is indeed rare to find any sort of user replaceable fuse but then again it's also pretty unlikely that the thermal fuse will go unless there is a genuine problem. They are at least cheap if they do have to be replaced.....

[Clive197]

Oh the joys or not of SMPS's

[Arkless Electronics]

Oh the joys or not of SMPS's

They have their uses.... Unfortunately we are increasingly finding them foisted upon us for reasons more to do with manufacturing cost and shipping weight rather than sound quality. The crap can be filtered out and a low drop out linear regulator used after that of course ;)

[Barry]

The most common arrangement in the non switch-mode variety is a thermal fuse embedded in the transformer winding. It is indeed rare to find any sort of user replaceable fuse but then again it's also pretty unlikely that the thermal fuse will go unless there is a genuine problem. They are at least cheap if they do have to be replaced.....

Thanks for that Jez.

I was puzzled as they all sport the "C E" mark (not that that means much)! The charger for my camera battery is so small (about 1.5 x the size of the battery itself), there doesn't seem room for a transformer?

On a completely different tack - what do you know about the safety of those air freshners that plug into the mains? It seems odd that the heater element is only protected by the 30A fuse or circuit breaker of the ring main.

[Arkless Electronics]

Your camera charger will be a smpsu.

I can't comment on the air fresheners as I have never seen one apart from the adverts for them!


Thanks for that Jez.

I was puzzled as they as sport the "C E" mark (not that that means much)! The charger for my camera battery is so small (about 1.5 x the size of the battery itself), there doesn't seem room for a transformer?

On a completely different tack - what do you know about the safety of those air freshners that plug into the mains? It seems odd that the heater element is only protected by the 30A fuse or circuit breaker of the ring main.

[bobbasrah]

Heater element cannot draw any high current and will blow itself like a fuse, much the same as a very low power light bulb blows a filament rather than the fuse. The bulb cannot blow the fuse, only a wiring short does that....

[Barry]

Heater element cannot draw any high current and will blow itself like a fuse, much the same as a very low power light bulb blows a filament rather than the fuse. The bulb cannot blow the fuse, only a wiring short does that....

I can assure you when an incandescent light bulb blows, it can often cause the circuit breaker to trip.

[Mark Grant]

There is nothing specifically wrong with wall warts as such. They are just a transformer, rectifier and smoothing cap in a plug top encapsulation. Often these days of course they are also just as likely to be a fairly crude switch mode PSU (smpsu), which has its own problems due to switching noise (at supersonic frequency usually).


I cant think of any new device that has a transformer in the wall wart, as far as I am aware everything is switch mode now, even 'high end' hi-fi brands include a switch mode wall wart.

Most likely to comply with the less than 1 watt standby requirements. ( as well as being lower cost and light weight to ship in quantity)

http://en.wikipedia.org/wiki/One_Watt_Initiative

[Arkless Electronics]

I cant think of any new device that has a transformer in the wall wart, as far as I am aware everything is switch mode now, even 'high end' hi-fi brands include a switch mode wall wart.

Most likely to comply with the less than 1 watt standby requirements. ( as well as being lower cost and light weight to ship in quantity)

http://en.wikipedia.org/wiki/One_Watt_Initiative

There's plenty ;) Switch modes are becoming more and more widely used though of course... A few weeks back I was trying to source an unusually high output wall wart which was definitely fairly easy to obtain five years ago and in this particular output it was now only available in switch mode.

[StanleyB]

Switch mode power supplies can be made to produce an acceptable level of audio quality performance without costing a lot. I had designed for me a relatively low noise 12V SMPS for use with my DACs. I use it in two DACs that don't have any muting relays to hide the noise that an SMPS can inject into the power rails. But you can't hear any SMPS noise coming from the RAC/PHONO sockets.

[Arkless Electronics]

Switch mode power supplies can be made to produce an acceptable level of audio quality performance without costing a lot. I had designed for me a relatively low noise 12V SMPS for use with my DACs. I use it in two DACs that don't have any muting relays to hide the noise that an SMPS can inject into the power rails. But you can't hear any SMPS noise coming from the RAC/PHONO sockets.

Indeed yes this is sometimes the case. The noise from smpsu's is generally at supersonic frequencies and so well beyond human hearing anyway.... The thing is that this can cause issues at lower frequencies for a whole range of reasons. In some cases it won't of course. It all depends on the design of the equipment being powered and the exact nature and level of the HF noise being generated by the SMPSU. Another problem that can occur is "mode switching" and instability in the control loop of SMPSU's which can in fact cause them to generate very audible noise! This is less of an issue these days though than it once was due to improved design and parts used in SMPSU's. It can limit the universality of the SMPSU though as it will often be triggered by things such as insufficient load on the SMPSU.... That issue aside though, as I mentioned earlier the noise can be filtered out and a linear regulator used after the filter = jobs a good 'un. This will increasingly have to be the way things are done in the future as conventional transformers become more expensive and hard to get.

As an aside, it is becoming more and more of a problem these days to obtain certain parts required in quality hifi which were common 10 years ago... the valves which were once predicted to become unobtainable are now readily available but some semiconductors which were designed for precision and low noise applications (in industry as well as hifi) are now very hard to find as they were never used in mass market gear anyway and most of the applications outside hifi have been replaced with digital or integrated options....