Transformer hum

[bullpup]

I recently bought a 3 amp AC transformer from Maplin to power my Pinkie modified X-Cans v1 and while I know a transformer of this size is total overkill, it seemed the most cost effective solution at the time.
The amp is singing beautifully, however the transformer is humming appallingly. I have tried stick on foam feet and even a large foam sponge but I can still hear it. Is there a way to cure it or should I take it back to Maplin and start again?

[Deleted]

Bullpup
Usually not a great deal you can do about lamination hum.Toroial transformers are a better choice. Just make sure they are well below a steel top cover.

SandyK

[bullpup]

Sandyk

Thanks for that.

I think I might just take it back and swap it perhaps for a wall wart. It was just chosen because it was the same price as the Rapidonline one Mike recommends by the time shipping is factored in.

[Sol]

You can (according to Mike IIRC) dip the transformer in varnish and bake or paint the sirface with araldite.

I've got both my X-PSU V3 humming and my Wellborne labs PSU transformer humming. The latter due to a bad batch and he's redesigned his board to accomodate a different transformer.

Eventually I'll remember to try the araladite approach on the wellborne labs one, and I really should look for my MF warrantly for the X-PSU V3.

[sometrolls2]

I have a spare DIYed PSU for V1, I have one in an ugly white box( was on a white shelf in front of a white wall so it blended) and one in a nice Hammond with switch, 2 outputs and external fuse. PM if interested in helping to pay for my Solo.

[bullpup]

sol said:

You can (according to Mike IIRC) dip the transformer in varnish and bake or paint the sirface with araldite.

I've got both my X-PSU V3 humming and my Wellborne labs PSU transformer humming. The latter due to a bad batch and he's redesigned his board to accomodate a different transformer.

Eventually I'll remember to try the araladite approach on the wellborne labs one, and I really should look for my MF warrantly for the X-PSU V3.

Interesting - could I just fill the casing with hot melt glue - If so which one works? I have a loctite kit I think?

[PinkFloyd]

could I just fill the casing with hot melt glue

Nooooooooo! you want something that's going to set hard, remember that the transformer will give off heat and may well melt the hot melt glue.

You haven't mentioned what type of transformer it is? Do you have a Maplin part number I'll have a look at it.

[bullpup]

Thanks Mike

Part no. is L54BR

[xerxes]

I think it comes down to quality with transformers. I have some 200VA EI type mains isolation transformers in my mains filter and they hum and I'm sure they are louder than when I first got them so it seems they are getting worse with use.

In my power amps there are some 800VA toroidal transformers which are fully encapsulated and they are completely silent. At some point I'm going to replace the mains isolation transformers with something better, preferably some fully encapsulated toroids.

[PinkFloyd]

bullpup said:

Thanks Mike

Part no. is L54BR

A wallwart. and not a classy wallwart either. Dump it. Sorry, I thought you had bought a dedicated transformer. The 1amp Rapid job is better built than the 3 amp Maplin and you deffo won't get any buzz from it.

Phone Maplin up and tell them it's shite in service, they will tell you it's not worth returning to them "bin it" and give you a refund.... nice try but you get what you pay for. If you want the best try www.rock-grotto.co.uk/pinkiev2.htm if you want the next best try www.musicalfidelity.com/ if you want the cheapest best bang for the buck then visit www.rapidonline.com and go for part number 85-2923... these little puppies deliver the goods

BTW my Little Pinkies come with IEC inlets these days..... I must update that link.

[aurum]

Transformer hum is often due to DC contaminating the AC line. :-*I run all my components through a power conditioner otherwise nearly all my components hum. Once filtered everything is quiet.
My filteration unit consists of a couple of caps (sorry don't remember the values) & a transformer set in epoxy. The tranny steps the power down by only 10 volts, but works well to shut things up. This is all encased in a sheilded box.

You could try a few things like installing thick sorbothane under the tranny & maybe build a mains parallel filter like the one Triode Systems has :
www.triode-systems.com/modules/wfchannel/
Pre-made filter units can be found from most electronic suppliers, but you don't want to listen to a compressed soundstage, so if you make your own then its easy to fiddle with it until you have the recipe for your setup.

I would also consider running a strip of copper tape around the core & to earth to improve RF rejection, & paint high temperature violin varnish on the laminations (takes ages to cure but smells heavenly)

[Deleted]

Sometimes you can reduce the buzz by tightening up the bolts a little. If starting from scratch, toroidal transformers are the way to go.
Regarding mains filters, many homes now have earth leakage breakers, and the capacitors to earth inside many of these filters may cause intermittent operation of the ELB. Usually at the most inconvenient time ! Not much fun when you are doing something complex on your PC, and earlier operating systems aren't so resilient to these small power outages either .Some routers can be a pain in the rear end to get going properly after a power failure too.
Note that I am not against Aurum's and Xerxes solutions to remove residual DC etc. from the mains supply, but they are expensive alternatives, and not suitable for our less technical members.
SandyK

[xerxes]

Note that I am not against Aurum's and Xerxes solutions

I didn't actually know anything about residual DC causing hum, but it's nice to be creditted all the same.

It's actually the four isolation transformers in my mains filter itself that do all the humming. They are 200VA control panel type transformers: www.clairtronic.com/controlpanel.htm. I think they were only about £17.00 each and are probably fine for industrial aplications in places that are noisy anyway, but not so great for domestic use. You can't hear them over the music, but I'm sure they are noisier than when I first got them, so they will likely get worse.

[Deleted]

Xerxes
Perthaps you didn't realise it when you installed those buzzing monstosities in the shed, but that is one of the benefits you may have obtained for the gear inside.
SandyK

[Sol]

aurum said:

Transformer hum is often due to DC contaminating the AC line.

Interesting .... so is there any way of checking this? I have a multimeter if you have a suggestion! Is the DC contamination always from the mains? Or can something between the socket and the power supply (like a fourway block or somesuch) cause the issue?

[Deleted]

Sol
You would normally need something like a CRO (Cathode Ray Oscilloscope to) see it on the mains waveform. Don't try it though. You really need specialised gear to do that safely.
The DC contamination comes from some mains appliances,.speed controllers ,equipment power supplies due to rectifiers etc . Not necessarily from your place
SandyK

[aurum]

sandyk said:

Sol
The DC contamination comes from some mains appliances,.speed controllers ,equipment power supplies due to rectifiers etc . Not necessarily from your place
SandyK

Exactly, & that is why if you are going to all the trouble of setting up your gear, then some sort of power conditioning is essential. You cannot have a smooth sound or black background without some sort of power supply treatment. Even my Wadia hums if plugged straight into the raw AC line, & that has a power supply overkill for a CD player.

In my last home I had a couple of dedicated lines put in, & it didn't make half the difference of a decent line conditioner. You just gotta get one that doesn't choke up the juice.

[Deleted]

Aurum
You must have an unusually poor supply.Most people don't need to resort to power conditioners to get rid of hum from a premium product such as the Wadia. Even a good mains filter is usually not necessary, and they can't do anything about hum, unless it is caused by R.F. from something like a close proximity TV transmitter. Have you had the mains earth of the house checked ? I once lived in a rented house where the earth was high resistance due to corrosion.Also, are you running all the equipment using 3 pin mains plugs ,off the one powerboard ? You may have some kind of earth loop.
SandyK

[Sol]

sandyk said:

Aurum
You must have an unusually poor supply.Most people don't need to resort to power conditioners to get rid of hum from a premium product such as the Wadia. Even a good mains filter is usually not necessary, and they can't do anything about hum, unless it is caused by R.F. from something like a close proximity TV transmitter. Have you had the mains earth of the house checked ? I once lived in a rented house where the earth was high resistance due to corrosion.Also, are you running all the equipment using 3 pin mains plugs ,off the one powerboard ? You may have some kind of earth loop.
SandyK

I suspect it's an earth loop in my case .. but have no way of knowing, and the cost of power conditioner is way more than I'd want to pay .. even at eBay prices!

Are the ISOTEK products really worth the money?

[PinkFloyd]

Blimey, you guys must have some right dirty mains to get all this interference I just plug my equipment straight into the wall and, voila!, noise free listening. Hows about strapping some class x2 suppression caps all over the house? that should help.

[xerxes]

Are the ISOTEK products really worth the money?

That's a tough one. I found that my ISOL-8 Minisub, pretty much the same thing as an Isotek had a very positive effect on the sound, but in purely material/component terms, not great value. I reckon the £595.00 Minisub2 might cost around £100.00 to £150.00 to make, but then again a 5:1 markup is fairly typical for retail products.

Here's what's inside: www.tdsf.co.uk/Audio/Mains.shtml

Why not try a DIY version: www.triode-systems.com/modules/wfsection/viewarticles.php?category=1

[PinkFloyd]

I've found those schaffner filters can actually do more harm than good to the sonics and, in the worst case, can actually strangle the life out of it. I used to fit one regularly until some guy over at Head-Fi told me to "run, don't walk over to your nearest bin and throw that thing in it" Right enough, without it there was a lot more energy to the music as if it had been injected with liquid "boing!" deffo not as flat as it was with the Schaffner in circuit.

I may be talking bollocks but I always try to stick to raw mains.

[xerxes]

I've heard it suggested before that filters strangle dynamics, obviously some people like them, some don't.

It's not expensive to find out, buy a 16A filter, put it in a box, then connect a 4 or 6 way mains distribution block to it, something like this: www.triode-systems.com/modules/wfsection/article.php?articleid=4

[Deleted]

"It's not expensive to find out, buy a 16A filter, put it in a box, then connect a 4 or 6 way mains distribution block to it, something like this: www.triode-systems.com/modules/wfsection/article.php?articleid=4"

Xerxes
One of these might be good for TV/STB use, but connecting a whole pile of appliances to this is probably not a good idea. Individual filters using heavy wire gauge inductors ,as in the previous example would be a much better choice with impulse noise type distortion.
None of the types mentioned will address hum problems, unless it is "frame buzz" from a close proximity TV transmitter.In that case, if you are watching the TV station concerned at the time, you will notice the hum level varies with picture brightness.
SandyK