ewildgoose said:
As I see it you have 2 possibilities; mechanical or electrical. The Mechanical you have already discussed with doing some kind of isolation or damping. If this is the case I would find other transformers. As for electrical, there are several forms it can take but mostly due to core saturation causing very high peak currents. This can be checked out by current limiting. Try a 2-3 ohm 5-10 watt res. in series and see what happens. Better to bring it up with a variac if you have one but should not be a problem without one. The other thing is how is the transformer mounted? Do you have a connection on top and on the bottom as well? If you do this can be a shorted turn and cause a lot of current draw. It will probably heat up the chassis as well. Don’t ask how I know this!
Check your line voltage aginst the transformer spec. If you are more than 10% over you will need a new correct transformer. Does the transformer get hot? If it does you need to find out where the power is going. Like disconnect the secondaries, does it still get hot and buzz? Then it has a shorted turn and will need to be replaced.
If the series res. Stops the buzzing, check the voltage drop across it to determine current flow. If it seems reasonable there should be no reason for the buzzing other than a defective or under voltage transformer that is saturating under normal conditions. If the res. Burns out, try it again with the secondaries disconnected and trouble shoot from there.
If all this don’t answer the question make a simple low pass filter with 100 kohm res. and .22uf cap. Use this to filter the AC and measure the DC component. This was suggested earlier and is a good idea as it allows much better reading of the small DC voltage. If you do have a significant amount like anything over 100MV the other blocking methods can be tried.
Roger
lne937s said:
I wouldnt' even be tempted to add any form of damping material in the case. We'll call it insulation, what we require in the case is cooling/air flow. I think if you start trying to do things like that the next thing you'll be doing right after is digging your modules out of it to replace them.
Air is often the best insulator as well, and I'd be worried about possible fire hazards from anything in contact with the internal electronics other than air.
You can submerge electronic devices /circuit boards in non conductive liquids. Liquid hydrogen has been used to cool certain parts allowing them to be pushed well beyond normal operating specs, that's of course the most extreem you could go. Less fun, I've seen people submerge their motherboards in mineral oil inside of a cooler, and sit an air conditioning unit on top of it, the guy left it on all day and when he came home it had a solide block of ice built up on it.
It's possible only choice parts of the output stage could handle something like hydrogen cooling as the low powered portion just won't suffer enough loss to generate enough heat that would require it, and of course the components are rated over a certain range wich is likely much higher than they'd be cooled to. Still I wonder what kind of an effect a liquide hydrogen cooled output inductor ...superconductor core.... would have on the THD at 1000W+. Now if you liquide cooled the low powered portion of it seperatly it could have the advantage of excellent temperature sharing amongst components.. Who's going to try it first? Might be neat to do it in a leap frog way so you could drive a thousand amps into a dead short with it continuously with ultra low distortion.
At least if you're going to consider liquid cooling have a real goal in mind other than trying to muffle a bit of hum.
If these were more like class A amps I'd consider liquid cooling just to get some real power out of it but.... I chose class d instead.
Regards,
Chris
I've heard of liquid nitrogen being used by some crazy overclockers. Liquid hydrogen is a new one to me, especially since the stuff is highly flammable - it'd be like cooling with liquid methane - and many materials react poorly to LH2 temperatures (steel becomes brittle as glass, for example). Are you sure about that?
trafo humming
ewildgoose
Try mounting the transformers with nylon bolts.
the steel bolts you are using will be magnetised by the field inside the tranny.
Never use steel bolts to mount a toroid transformer.
If you want to use a metal bolt use a non-magnetic one and make sure they are electricaly insulated from the case.
This solved my humming problem.
btw the capacitor size in the DC filter is dependend on the maximum current drawn by the primairy windings.(larger trafo = bigger capacitor)
They only supply current from 0V to the point the doides start to conduct.
If you want more DC protection(higher voltages)you can put diodes in series.
ewildgoose
Try mounting the transformers with nylon bolts.
the steel bolts you are using will be magnetised by the field inside the tranny.
Never use steel bolts to mount a toroid transformer.
If you want to use a metal bolt use a non-magnetic one and make sure they are electricaly insulated from the case.
This solved my humming problem.
btw the capacitor size in the DC filter is dependend on the maximum current drawn by the primairy windings.(larger trafo = bigger capacitor)
They only supply current from 0V to the point the doides start to conduct.
If you want more DC protection(higher voltages)you can put diodes in series.
humming
richieboy
The fact that the bolt is insulated at one end only stops a current from being induced in the bolt.(not a closed cirquit)
If you place a iron core in a alternating machnetic field the core will vibrate.
Just connect a toroid to the mains and connect a load.Take a bolt or a piece of iron and hold it in the center.You can feel it vibrate without it being connected to anything but youre fingers.
richieboy
The fact that the bolt is insulated at one end only stops a current from being induced in the bolt.(not a closed cirquit)
If you place a iron core in a alternating machnetic field the core will vibrate.
Just connect a toroid to the mains and connect a load.Take a bolt or a piece of iron and hold it in the center.You can feel it vibrate without it being connected to anything but youre fingers.
classd4sure said:No, the heat already got to me by the time I had my coffee today
Nitrogen is what I meant to say, my mistake.
Regards,
Chris
I know the feeling. I just adopted a new cat and she's NOT getting along with cat 1.0, who feels put out at having to share her space. Imagine hissy-fits at 0-dark-hundred and you get the idea.
Anyway, hydrogen's been in the news a lot recently, so it's a natural mistake. The heat conductivity *is* pretty good..... Hmmmmmm....
*slap myself* NO! Bad engineer! BAD!
Francois.
Having looked into it a little, there were a few things that made me think liquid silicone would be the way to go...
The first was that it was stated to be the prefered electrical cooling fluid for industrial applications, as opposed to cheaper mineral oil- which was listed above.
It conducts heat well and does not corrode metals or dissolve plastic or electrical insulators.
It is a great electrical insulator.
It thermally degrades at about the same temperature that many types of electrical insulation and solder melt and has a flash point even higher- so fire really isn't an issue.
Silicone dampens vibration very well and is often used as a dampening fluid- would be useful dampening not just the transformer but vibrations caused by speakers/subs, etc. as well.
It would allow an essentially sealed design without any holes- basically using the silicone and the entire case as a giant heat sink. If there is no oxygen, water vapor, dust, etc., there would also be no corrosion/chance for fire.
Since it wouldn't be cooling the components below room temp, there wouldn't be any condensation associated.
Anyway, it was just a thought...
The first was that it was stated to be the prefered electrical cooling fluid for industrial applications, as opposed to cheaper mineral oil- which was listed above.
It conducts heat well and does not corrode metals or dissolve plastic or electrical insulators.
It is a great electrical insulator.
It thermally degrades at about the same temperature that many types of electrical insulation and solder melt and has a flash point even higher- so fire really isn't an issue.
Silicone dampens vibration very well and is often used as a dampening fluid- would be useful dampening not just the transformer but vibrations caused by speakers/subs, etc. as well.
It would allow an essentially sealed design without any holes- basically using the silicone and the entire case as a giant heat sink. If there is no oxygen, water vapor, dust, etc., there would also be no corrosion/chance for fire.
Since it wouldn't be cooling the components below room temp, there wouldn't be any condensation associated.
Anyway, it was just a thought...
Hmm, just tried removing the load on the secondaries and leaving them totally unattached and the wretched transformers still buzz gently. I guess this means that they are just rubbish then?
I did try with just the DC filter, but the startup load keeps blowing the fuses.
The problem is now where to get some alternatives in the UK. Also since I have limited room I really need them to fit into the same space as the old ones. The last ones were the standard Farnell 500Va ones. I notice that RS do some from apparently a different firm, but the dimensions are EXACTLY the same and so I have a hunch it's the same thing? Anywhere else in the UK to try?
Thanks
EDIT: My mistake. Looking closer at the specs from RS they seem to be different transformers, and looking closer at the specs from Farnell they don't claim "low noise"... I will order some of the RS ones and see how they compare
I did try with just the DC filter, but the startup load keeps blowing the fuses.
The problem is now where to get some alternatives in the UK. Also since I have limited room I really need them to fit into the same space as the old ones. The last ones were the standard Farnell 500Va ones. I notice that RS do some from apparently a different firm, but the dimensions are EXACTLY the same and so I have a hunch it's the same thing? Anywhere else in the UK to try?
Thanks
EDIT: My mistake. Looking closer at the specs from RS they seem to be different transformers, and looking closer at the specs from Farnell they don't claim "low noise"... I will order some of the RS ones and see how they compare
Hi,
Francois, I do appreciate such a mistake corrected, I make them often enough, nice to know someone is paying attention
lne937s, I'm sure you're correct about the silicone but what a mess, I also understand it's rather expensive.
If it were a class A amp sure. I wonder if the silicon would dampen better than air, being a liquid it must have the potential to transmit pressure rather effectively? I dont' think you'd end up with a "water hammer" inside but all the same, with a few humming transformers in the soup your electrolytics may disagree.
Are you really considering doing this or was it just some out of the box thinking (which is very cool)?
Ewildgoose,
Have you tried contacting Farnell and asking for a set of transformers in exchange that weren't built on a monday? Maybe they'll surprise you, surely they must stand behind their products?
It's little wonder you looked everywhere else first, low mechanical hum is supposed to be one of the reasons we use them in the first place, all the same I've learnt from your experience here.
I sure hope I dont' have the same kind of luck with my Plitron, they're just too expensive to start trying one after the other, but, if that's what you have to do....
I hit google with "toroid site:.uk" for you and the first link was..
http://www.toroid.co.uk/ (cool huh?) I dont' recall what VA you're using but they've got them up to 600VA with potted cores, 4% load regulation, same as Plitron rates them from 500VA and up.
Here's the direct link to their "non-enclosed" units:
http://www.toroid.se/docs/prod1.pdf
Here's your second choice:
http://www.ecmelectronics.co.uk/
Ooooooooh I found my prize choice there!
http://www.ecmelectronics.co.uk/pdf/toroidal_transformers_nexus.PDF That's in my next amp I swear!
Actually, they just may be a source for "Hypex" like transformers, check it out:
http://www.ecmelectronics.co.uk/pdf/toroidal_transformers_SRT.pdf
I'm sure you'll find more with the same google search too.
Happy hunting and better luck with the next ones.
Cheers,
Chris
Francois, I do appreciate such a mistake corrected, I make them often enough, nice to know someone is paying attention
lne937s, I'm sure you're correct about the silicone but what a mess, I also understand it's rather expensive.
If it were a class A amp sure. I wonder if the silicon would dampen better than air, being a liquid it must have the potential to transmit pressure rather effectively? I dont' think you'd end up with a "water hammer" inside but all the same, with a few humming transformers in the soup your electrolytics may disagree.
Are you really considering doing this or was it just some out of the box thinking (which is very cool)?
Ewildgoose,
Have you tried contacting Farnell and asking for a set of transformers in exchange that weren't built on a monday? Maybe they'll surprise you, surely they must stand behind their products?
It's little wonder you looked everywhere else first, low mechanical hum is supposed to be one of the reasons we use them in the first place, all the same I've learnt from your experience here.
I sure hope I dont' have the same kind of luck with my Plitron, they're just too expensive to start trying one after the other, but, if that's what you have to do....
I hit google with "toroid site:.uk" for you and the first link was..
http://www.toroid.co.uk/ (cool huh?) I dont' recall what VA you're using but they've got them up to 600VA with potted cores, 4% load regulation, same as Plitron rates them from 500VA and up.
Here's the direct link to their "non-enclosed" units:
http://www.toroid.se/docs/prod1.pdf
Here's your second choice:
http://www.ecmelectronics.co.uk/
Ooooooooh I found my prize choice there!
http://www.ecmelectronics.co.uk/pdf/toroidal_transformers_nexus.PDF That's in my next amp I swear!
Actually, they just may be a source for "Hypex" like transformers, check it out:
http://www.ecmelectronics.co.uk/pdf/toroidal_transformers_SRT.pdf
I'm sure you'll find more with the same google search too.
Happy hunting and better luck with the next ones.
Cheers,
Chris
>>I sure hope I dont' have the same kind of luck with my Plitron,<<
I have a 300VA Plitron feeding 4 UCD180 and its completelly silent and cool
However, if I had mecanical humm I would try dampening with a big wood base (I do in fact) or submerging in some natural resin if epoxi is too expensive.
I have a 300VA Plitron feeding 4 UCD180 and its completelly silent and cool
However, if I had mecanical humm I would try dampening with a big wood base (I do in fact) or submerging in some natural resin if epoxi is too expensive.
A question...
The UcD400 quality bit me in the a.. so hard that I'm thinking to combine the best of both worlds, stereo and surround.
I will be using my stereo UcD400 amp as L & R for my main channels, fed via unbalanced from my receiver.
Now, I'd like to add a "switch" so that I can either:
A) Take inputs "A" via cinch straight to the UcD modules (using input caps) - this would be for connecting the receiver.
B) Take inputs "B" via cinch to a passive volume control inside the amp's case, then to the UcD modules *bypassing* the input caps (as I'll be feeding it from a modified source) - connecting my CD player direct.
I realise that the caps on the UcD400 can be removed and make shorts on the PCB.
But as for switching the signal - How can I do this with good quality? What kind of switch should I look for? Should I use the signal through the switch or use relays?
Finally, how are the input caps connected? In series with the signal?
Any idea for a good volume control is welcome as well. I was thinking Dact DC1 or DC2?
Thanks for your tips,
Yves
The UcD400 quality bit me in the a.. so hard that I'm thinking to combine the best of both worlds, stereo and surround.
I will be using my stereo UcD400 amp as L & R for my main channels, fed via unbalanced from my receiver.
Now, I'd like to add a "switch" so that I can either:
A) Take inputs "A" via cinch straight to the UcD modules (using input caps) - this would be for connecting the receiver.
B) Take inputs "B" via cinch to a passive volume control inside the amp's case, then to the UcD modules *bypassing* the input caps (as I'll be feeding it from a modified source) - connecting my CD player direct.
I realise that the caps on the UcD400 can be removed and make shorts on the PCB.
But as for switching the signal - How can I do this with good quality? What kind of switch should I look for? Should I use the signal through the switch or use relays?
Finally, how are the input caps connected? In series with the signal?
Any idea for a good volume control is welcome as well. I was thinking Dact DC1 or DC2?
Thanks for your tips,
Yves
Parts is parts!
Yves,
I use and recommend the DACT CT2 10k-2 control if you are using a solid state front end. 50k or 100k would be more appropriate with tube stuff driving it.
The Elma switch is the same basic design as DACT uses. I use a 4 pole 3 pos. 30deg sw. This is a non shorting type and if you switch the grounds as well you may have to connect them all together with something like 470 ohm resistors to eliminate switching pops. All inputs should be tied to ground with 100k res for the same reason.
Roger
http://www.elma.com/us/products/rotary_components/Switches & Encoders > Rotary Switches/6
http://www.dact.com/html/attenuator_datasheet.html
Yves,
I use and recommend the DACT CT2 10k-2 control if you are using a solid state front end. 50k or 100k would be more appropriate with tube stuff driving it.
The Elma switch is the same basic design as DACT uses. I use a 4 pole 3 pos. 30deg sw. This is a non shorting type and if you switch the grounds as well you may have to connect them all together with something like 470 ohm resistors to eliminate switching pops. All inputs should be tied to ground with 100k res for the same reason.
Roger
http://www.elma.com/us/products/rotary_components/Switches & Encoders > Rotary Switches/6
http://www.dact.com/html/attenuator_datasheet.html
what's the best Schottky rectifier to use for a PSU for an UCD400?
I know it must be somewhere on this site but the threads are just way too long. I want to use a halogen electronic PSU for this but a normal recifier will blow if you load it. Now these power units give a 50Hz sinewave out of a 40Kc carrier and this is the destructive part for a normal rectifier. Modified some 250VA units to do the job if possible. Anyone?
I know it must be somewhere on this site but the threads are just way too long. I want to use a halogen electronic PSU for this but a normal recifier will blow if you load it. Now these power units give a 50Hz sinewave out of a 40Kc carrier and this is the destructive part for a normal rectifier. Modified some 250VA units to do the job if possible. Anyone?
Roger,
What are quality resistors to use in the audio pathway (for the switch?)
Is it not harmful for the signal to put resistors between live signal and ground?
Sorry for the beginner questions, but I don't really know much about electronics' effects on audio. But I've learned a lot since I'm here...
What are quality resistors to use in the audio pathway (for the switch?)
Is it not harmful for the signal to put resistors between live signal and ground?
Sorry for the beginner questions, but I don't really know much about electronics' effects on audio. But I've learned a lot since I'm here...
A question of resistance
Yves,
I have used a large variety of resistors over the years and found that standard Dale 1% metal film, nonmagnetic are hard to beat for neutrality. They also don’t take weeks to break-in as some of the other far more expensive types do. When people tell you they like the sound of a part this generally means the part does have a sound and is not neutral. I really work at avoiding these kinds of parts and feel my designs have benefited greatly because of it.
The resistors I suggested you use are not harmful and will keep you from having problems with switching noise.
http://www.mouser.com/catalog/623/458.pdf
Roger
Yves,
I have used a large variety of resistors over the years and found that standard Dale 1% metal film, nonmagnetic are hard to beat for neutrality. They also don’t take weeks to break-in as some of the other far more expensive types do. When people tell you they like the sound of a part this generally means the part does have a sound and is not neutral. I really work at avoiding these kinds of parts and feel my designs have benefited greatly because of it.
The resistors I suggested you use are not harmful and will keep you from having problems with switching noise.
http://www.mouser.com/catalog/623/458.pdf
Roger