Got myself a pair of Noratel 160w 30 volt for one of my amps and they humm way to much! Both are the same though so can't say one is off spec so to say. They got a bit better once I tightened the screw holding them down but its still more than is ok.
Reading up on it here I understand all of them do humm more or less but these are very noisy compared to my other amps/power transformers.
Question, is there a consensus on here which make of Toroid transformers that are better/best in this respect?
Alternatively is there anything I can do to minimise this (other than baking them)?
All the other amps sit on the same powerline and are "mostly quiet".
Reading up on it here I understand all of them do humm more or less but these are very noisy compared to my other amps/power transformers.
Question, is there a consensus on here which make of Toroid transformers that are better/best in this respect?
Alternatively is there anything I can do to minimise this (other than baking them)?
All the other amps sit on the same powerline and are "mostly quiet".
Noratel are very good. Are these modern ones or older 220V types? The older ones hum when used on todays 230V. I assume they are not overloaded? You did measure the current flowing? Did you pay attention to phase of both connected transformers?
Most toroids, regardless of brand and quality, will hum when fed a slight DC component when the mains voltage is distorted. You could add a suitable DC blocker in that case. I think you can find those yourself. These are mains connected devices so be careful.
I see Nigel was again faster than his own shadow 🙂
Most toroids, regardless of brand and quality, will hum when fed a slight DC component when the mains voltage is distorted. You could add a suitable DC blocker in that case. I think you can find those yourself. These are mains connected devices so be careful.
I see Nigel was again faster than his own shadow 🙂
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I considered that but since the other amps sit on the same mains feed it seems unlikely to be the issue.
Please reply to the questions for adequate assistance.
1. Are these modern ones or older 220V types? The older ones hum when used on todays 230V.
2. I assume they are not overloaded?
3. You did measure the current flowing?
4. Did you pay attention to phase of both connected transformers?
5. Are they mounted with enough distance from each other?
1. Are these modern ones or older 220V types? The older ones hum when used on todays 230V.
2. I assume they are not overloaded?
3. You did measure the current flowing?
4. Did you pay attention to phase of both connected transformers?
5. Are they mounted with enough distance from each other?
I got them new a few weeks ago and I think they were rated 230v. As I mentioned the other amps sit on the same mains supply and as far as I know they do not have a DC blocker but are still quiet.
I'll run off and measure DC on the mains feed.
We need all info so do the other amps also have toroids? if not then this is a non item. You think they are 230V but I suggest to read the label on them and to check if they actually are 230V.
I hope you are knowing what you are doing by measuring the DC component on mains voltage. If not please don't.
I hope you are knowing what you are doing by measuring the DC component on mains voltage. If not please don't.
1. New ones.
2. No.
3. Yes, 0.3ah per rail in idle.
4. Yes, connected them the same.
5. Yes, on each side of the amp
OK, then you likely need DC blockers for them as suggested. These don't have negative side effects when there is no DC component on mains voltage.
If it is DC you will experience the toroids to be more quiet or even completely quiet at times.
If it is DC you will experience the toroids to be more quiet or even completely quiet at times.
Two of my other amps have toriods and the new amp was just installed in the rack so I will need to check next time I open it up but the secondary voltage is on spec so very unlikely to be 220v types, I've typically got 228-230v on the mains.
I used a std voltmeter to measure DC which gave DC readings between 0.01 and 0.05 volts.
Exaggerated for understanding. A toroid does not need much DC component to hum. Since loads are more and more complex compared to ohmic loads in the old days (light bulbs etc) a perfect sinus mains voltage is rare.
As usual Rodd nails it! He probably won't get rich of audio but his knowledge is rich and respected.
Mains DC and Transformers
As usual Rodd nails it! He probably won't get rich of audio but his knowledge is rich and respected.
Mains DC and Transformers
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Reading up on this further it seems and as usual with audio a lot of parameters that play into this. There are apparently "audio grade" versions with various design parameters to keep them quiet.
I did not even consider this ordering the ones I have but it seems they are simply not good enough.
It may be that a DC blocker will improve this somewhat but I don't have any space left for this and again as all the other amps are quite I don't think DC is a big problem.
Generally though the humm does not seem to give any additional noise/distortion on the rails.
I did not even consider this ordering the ones I have but it seems they are simply not good enough.
It may be that a DC blocker will improve this somewhat but I don't have any space left for this and again as all the other amps are quite I don't think DC is a big problem.
Generally though the humm does not seem to give any additional noise/distortion on the rails.
Assumptions....."may be", "think"..... let's keep to facts please.
Whether for audio (and with audio prices) or industrial: both toroids will possibly hum with a slight DC component depending on the time of the day. It is a widely known issue. If you want hum free and lower strayfield then R-cores are the answer. Toroids are cheap, easily available, easy to manufacture etc. but they're not the best of transformers. Toroids are the types most sensitive to the DC component which can be solved by DC blockers. Do not assume, build one to test if the Noratels are then quiet. Or buy audio grade 🙂D) toroids to discover they may also hum. Indeed the voltage secondary is OK but that is no surprise. The hum takes away much joy in using equipment. Wherever I can I use R-cores and never had one mechanically humming but I am sure there will exist cheaply made bad ones too.
The system choice you made by choosing toroids is mainly the cause. When using toroids DC blockers meanwhile are a must. It may be that toroid A is worse than toroid B but feed them any DC contaminated AC and they 'll both hum. The ones that are molded in epoxy are way more silent BTW. You could consider molding them in slow curing transformer epoxy but derate power then as heat is then an no no.
Whether for audio (and with audio prices) or industrial: both toroids will possibly hum with a slight DC component depending on the time of the day. It is a widely known issue. If you want hum free and lower strayfield then R-cores are the answer. Toroids are cheap, easily available, easy to manufacture etc. but they're not the best of transformers. Toroids are the types most sensitive to the DC component which can be solved by DC blockers. Do not assume, build one to test if the Noratels are then quiet. Or buy audio grade 🙂D) toroids to discover they may also hum. Indeed the voltage secondary is OK but that is no surprise. The hum takes away much joy in using equipment. Wherever I can I use R-cores and never had one mechanically humming but I am sure there will exist cheaply made bad ones too.
The system choice you made by choosing toroids is mainly the cause. When using toroids DC blockers meanwhile are a must. It may be that toroid A is worse than toroid B but feed them any DC contaminated AC and they 'll both hum. The ones that are molded in epoxy are way more silent BTW. You could consider molding them in slow curing transformer epoxy but derate power then as heat is then an no no.
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Aside from vibrating windings, large mains toroids are usually designed to operate to the limits of the core. Unlike an EI type there is no gap in the core. So any modulation of the mains voltage by DC or subsonic harmonics, where buzzing comes and goes randomly, it is the peak of the waveform where the summation of AC and the noise drives it beyond the limit, encroaching on saturation. I had a large toroid "kit", it required that you wind your own secondaries. Initially it had these issues, but I added some extra primary turns to lower flux just a bit. Not a big deal since the secondary wasn't on yet, turns ratio was calculated accordingly. The buzzing went away. Although this does slightly derate the power output, it was a 1.4KVA transformer so no real problem there.🙂 DC and low subsonic noise can also be filtered with a "DC blocker" as stated above.
Toroid transformers is more sensitive to DC then IE transformers, but I can depend when you connect transformer, because industry using lots of power during day time can cause distortion on the network, maybe can try late in night when voltage supply is cleaner.
Transformers are clearly made different and it turns out I can get "audio grade" ones guaranteed to be quiet for the same money I paid for the Noratel's.
Delivery is a few weeks though but I will report back on my findings (the set up will be identical, just swapping the transformers)
Delivery is a few weeks though but I will report back on my findings (the set up will be identical, just swapping the transformers)
Toroids for audio are made on the same machines as the industrial ones but they get a different label 🙂 Medical ones are truly made according higher specifications. No toroid is safe for DC but ... it just came to my mind that I once had Amplimo toroids that were humming just too much. These turned out to have cracks in the ferrite core from rough transport.
The advice to use a DC blocker on any toroid still is a good advice. If it does not hum today it may hum tomorrow otherwise.
Last question: you did mount them as done standard did you? If these are mounted the way that the bolt is a shorted turn (i.e. between 2 metal sheets that are in contact) they may also protest sonically, even the best ones. And it would not cost much time to reverse L and N of one of the Noratel ones just to check if it makes a difference.
The advice to use a DC blocker on any toroid still is a good advice. If it does not hum today it may hum tomorrow otherwise.
Last question: you did mount them as done standard did you? If these are mounted the way that the bolt is a shorted turn (i.e. between 2 metal sheets that are in contact) they may also protest sonically, even the best ones. And it would not cost much time to reverse L and N of one of the Noratel ones just to check if it makes a difference.
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I don't question a DC filter will help with DC or that it is good advice or best practise but as I said, I have never had this issue with any of my other amps.
A DC filter in this amp mess up the install and if I can fix this by getting the right transformers and keeping it clean so to speak that is better for me.
They are mounted with metal on both sides connected by the screw that holds them. It's a bit tricky to reverse one but I can easily disconnect one channel to see if that makes a difference. Interestingly my other "2 toroid" amp have plastic caps holding them down 🙂
A DC filter in this amp mess up the install and if I can fix this by getting the right transformers and keeping it clean so to speak that is better for me.
They are mounted with metal on both sides connected by the screw that holds them. It's a bit tricky to reverse one but I can easily disconnect one channel to see if that makes a difference. Interestingly my other "2 toroid" amp have plastic caps holding them down 🙂
There you found the cause I think. You have a shorted winding when a toroid is mounted between metal sheets that are in contact with each other and now also make contact via the bolt and nut. Well another proof that the one helping must ask more questions (to a level the requester even becomes irritated/angry) to compensate for the lack of essential information of the requester.
The metal disk to mount toroids is not what is meant. It is the donut type of mounting in a (theoretical) U shaped sheet of metal. You could of course post a picture as that says more than 1000 words and takes less of your time then it costs me and others reading your issue to understand or maybe even solve your issue. In fact the requester should post as much information as possible as it is in his/her own interest to be helped adequately courtesy of the helpers and to make it a more efficient affair for everyone.
A "right" transformer can be mounted "wrong".
The metal disk to mount toroids is not what is meant. It is the donut type of mounting in a (theoretical) U shaped sheet of metal. You could of course post a picture as that says more than 1000 words and takes less of your time then it costs me and others reading your issue to understand or maybe even solve your issue. In fact the requester should post as much information as possible as it is in his/her own interest to be helped adequately courtesy of the helpers and to make it a more efficient affair for everyone.
A "right" transformer can be mounted "wrong".
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