if i were to make a high voltage psu, i will wind three 300v windings and rectify, then the resulting dc is then series connected.....my unsolicited advise...
lower voltage secondary's are easier to make than 900 volt ones imho...
lower voltage secondary's are easier to make than 900 volt ones imho...
You are on the good path but still missing data.
More than secondary "volts" or even bare turns ratio, what matters is flux density
Classic safe is 10000 Gauss; going higher is possible but only after actually measuring steel performance.
Same here, but you are a PRO and buy at transformer supply shops, not exactly everywhere 🙂 , and probably at least 4 liter cans; now a DIYer has easy access to his friendly nearby hardware or (home type) paint shop.
Famous brands are expensive but "Special of the week" tends to be cheap 🙂
today I have been met with the transformer factory, well the problem is that for general purpose the make the transformer over 1,3 Tesla include the mine, for audio purpose need 0,8 tesla if want silent and cold, with my cores need 2 turn per volt.
when I say mechanical noise is when the noise comes for bobbin wire, my prefer transformer factory close after pandemic and now the new need to calibrate the new factory 🙂 . I have two transformer that will be sent to the rubbish too hot for my target.😢
I have potted many transformer before with epoxy mix with silica powder to help to dissipate heat, but with this wrong transformers that work over 80º C 176º F if I potted them to reduce the noise the bobbing up near 100ºC give problem in early future .
when you have a good transformer do not need to be worry about the filter diodes etc, this experience is one step more to increment the quality, my last 10 year only be worry about the sound, now I think a ultrasilent amplifier is import too
when I say mechanical noise is when the noise comes for bobbin wire, my prefer transformer factory close after pandemic and now the new need to calibrate the new factory 🙂 . I have two transformer that will be sent to the rubbish too hot for my target.😢
I have potted many transformer before with epoxy mix with silica powder to help to dissipate heat, but with this wrong transformers that work over 80º C 176º F if I potted them to reduce the noise the bobbing up near 100ºC give problem in early future .
when you have a good transformer do not need to be worry about the filter diodes etc, this experience is one step more to increment the quality, my last 10 year only be worry about the sound, now I think a ultrasilent amplifier is import too
With capacitor input you will excite the coil windings mechanically from the high pulses of current, I suspect this to be the primary reason. To prove otherwise, try loading the secondary with a resistance only (no capacitor input filter) and verify.
Thamks 50AE, but have been different wrong things.
The most important is the rule 50/cross section core, to work under 1 Tesla that give 2 turn per volt in my case EI126 60x42 bobbin. Is important also the type of filter after diode bridge, but I have made many amp without problem as Diode C L C, but after this discussion I have check that Diode R C L C or diode L C L C help a lot. Where 0.9 Tesla transformer with a filter R C L C work totally quiet transformer, 50AE you make a very good transformer, are you agree with 0.9 Tesla I would like to know your opinion
The most important is the rule 50/cross section core, to work under 1 Tesla that give 2 turn per volt in my case EI126 60x42 bobbin. Is important also the type of filter after diode bridge, but I have made many amp without problem as Diode C L C, but after this discussion I have check that Diode R C L C or diode L C L C help a lot. Where 0.9 Tesla transformer with a filter R C L C work totally quiet transformer, 50AE you make a very good transformer, are you agree with 0.9 Tesla I would like to know your opinion
Core magnetizing noise is one part of the noise. There you need to pay attention to the core. Ideally, you want a monolithic core assembly, where each lamination is rock hard glued to the next.
Winding noise is a secondary subject. You might have a well built core, but still winding noise problem. It is especially a problem with capacitor input filters, but less problematic on choke input or simply resistive loads.
You can address the following by using the two ways, ideally combined.
-Vacuum impregnating the windings - transformer lacquer, epoxy, wax, etc. Make the winding assembly monolithic too.
-Potting the transformer into an enclosure. The potting compound will couple the transformer coil to the rest of the assembly, increasing coupling mass, surface area and lowering resonant frequency.
Winding noise is a secondary subject. You might have a well built core, but still winding noise problem. It is especially a problem with capacitor input filters, but less problematic on choke input or simply resistive loads.
You can address the following by using the two ways, ideally combined.
-Vacuum impregnating the windings - transformer lacquer, epoxy, wax, etc. Make the winding assembly monolithic too.
-Potting the transformer into an enclosure. The potting compound will couple the transformer coil to the rest of the assembly, increasing coupling mass, surface area and lowering resonant frequency.
You are describing a real phenomenon but which applies to 99% of power supplies out there ... yet they usually don´t buzz uncontrollably.
I guess here we have a combination of poor or lack of proper impregnation, plus somewhat wild design choices by transformer makers.
13000 Gauss by design? .... as standard?
Wow!!!
Well after change the rectifier schematic as Diode R C L C buzz was reduced notably, but temp with full load up over 80ºC
my opinion is that the 13.000 Gaus is the problem, and with a 0.35A current without load.
Is not easy to find factories with experience in tube amp transformer
my opinion is that the 13.000 Gaus is the problem, and with a 0.35A current without load.
Is not easy to find factories with experience in tube amp transformer
I've seen many commercial transformers buzzing under the following conditions, especially EI cored ones. I'm also pretty certain that transformer buzz amount (in dB) is an individual preference, at least it was one of the precious lessons I learned when I began selling transformers. Some people tolerate more noise than others. I had a customer with tinnitus. On top of that, a transformer radiates its vibrations across the whole assembly and different ones can amplify or dampen the buzz. There are even cases where a high-leakage EI transformer can make a steel amplifier cover rattle. Within a few words I wanted to say that a power transformer can open many cans of worms.
Ones does not simply blame a parameter for the whole problem. 13k gauss alone of flux density doesn't mean it all, including the non-load current. To convert matters into dissipated heat, you need to take primary Rdc losses into account. 2R would result into 0.245W Pdiss. There's nothing wrong with 0.35A quiescent current if Rdc is within acceptable range.
It's a good exercise to calculate your overall windings Pdiss and be aware of the heat your power transformer dissipates. There are clever cooling tricks as well, one of them is to mount your transformer on a metal chassis and take advantage of its additional surface for heat dissipation. The second is to keep it away from heating tubes.
You can have overheating due to high magnetization current not from saturation, but low overall permeability due to core airgapping. Although this happened to me with garbage between cut core surfaces, it serves as an example not to isolate single parameters to blame.
As for coil noise from capacitor input rectifiers, I've experienced that higher leakage geometry transformers (eg split coil EIs) will buzz more. Noisest free strategy is tight magnetic coupling. I suspect toroidal transformer are a winner here.
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Reminds me of the quiet room that we experimented years before. Fully sound proof. You sit inside, will start to hear the ringing in the ears in the first minute. Then your breath and after 5-10 minutes you start to hear your heart beat. You will be called a champion if you could stay inside the quiet room for 45 minutes. Once the doors are opened, you will hear extremely loud noise of ordinary things for a few minutes and then all back to normal, Regards.
If the noise you mean is mechanical, then you probably bought the transformer from the companies who makes control transformers.
These are designed with slightly lower turns per volt to provide high short term output current. The no load magnetizing current is also larger.
They produce more hum if the application is for DC load. Or the core stampings are not good (not flat enough, have a small curved radius when punched ).
If the noise is electrical, you will need a screen winding between primary and secondary and ground it. This reduces the inter capacitance between primary and secondary by a fourth. Also connect snubbers rated to 3kv or more across each of the diodes.
Regards.
These are designed with slightly lower turns per volt to provide high short term output current. The no load magnetizing current is also larger.
They produce more hum if the application is for DC load. Or the core stampings are not good (not flat enough, have a small curved radius when punched ).
If the noise is electrical, you will need a screen winding between primary and secondary and ground it. This reduces the inter capacitance between primary and secondary by a fourth. Also connect snubbers rated to 3kv or more across each of the diodes.
Regards.
Is possible also that quality core, I am going to take a core to check the permeability, maybe the problem are more than one thing.
Transformer is good screw as monolith 🙂, has screen between P ans S, has two bath of varnish.
Noise is noise, when you listen at 3 meter the transformer and temp rise 80º C ( +25ºC that before transformer), has a problem.
this is the first time that has this type of problem, is very instructive.
Transformer is good screw as monolith 🙂, has screen between P ans S, has two bath of varnish.
Noise is noise, when you listen at 3 meter the transformer and temp rise 80º C ( +25ºC that before transformer), has a problem.
this is the first time that has this type of problem, is very instructive.
well after this time I have check Toroidal transformer with better result, 900V is not easy to do, when I potted in epoxy the temp reach the limit I have broke two under the work condition, to pot need to increase the size of all where begin others problem, vacuum varnish seem a good solution, but by the moment toroidal transformer work better.
Compare with 400v of 300b amp where these transformers are very silent and warm, but when you check both 300b transformer are too oversized compare with 211-845 transformer,
choke input is the best way to help the transformer or a big resistor, choke need space and resistor good cooling. Nothing is free
Compare with 400v of 300b amp where these transformers are very silent and warm, but when you check both 300b transformer are too oversized compare with 211-845 transformer,
choke input is the best way to help the transformer or a big resistor, choke need space and resistor good cooling. Nothing is free