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    Building, troubleshooting and testing of these amplifiers should only be
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Transformer core for tube amplifier

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Hi guys,

I want to make a power and 2 output transformers using the toroidal cores for my tube amplifier project. But I do not know which kind of core(iron powder, silicon steel and so on) is the best and how to make it. Can someone give me some advice?


Hi, welcome. From my experience with cores you have a problem because there are so many types and factors to consider. For example, do you try to concentrate on providing more magnetic material for low-end, but causing more hysteresis, or less to try to get less distortion. It would be nice to be able to make one with air coupling, but it would have to be huge. I look forward to other thoughts in this area.
Hi Joe,

Thanks for your reply. I used to work at sonic frontiers internation.The company is using some EI type transformers from Hammond, some toroidal transformers from Plitron( for line series preamp) and Craftman( for Athem AMP2). I know the transformer core is a very important factor for the tranformer. So I plan to order some good cores from China(cheaper there) to make some quieter,lower hysteresis to reach the Hi END level. The first thing is to chose the proper magnetic core, but I do not know which material is the best for the hi end( sound best and deadly quiet).

Hi Suoliang

What about ferrite? It provides more permability than the iron powder ones I have seen, so it may be able to concentrate more magnetic flux. That would provide you with more low end with a smaller transformer. The problem with transformers wound on a magnetic core is that they saturate. That limits the power they are able to transfer and could blow your tubes. If you can get a hold of lots and lots of wire, you may want to experiment with winding some large air core transformers.

Saturation of a ferrous core depends on the frequency and the power proportionally. If you can get 20 watts out at 100htz, you can get only 10 watts out at 50htz before saturation.
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depend the taste of music U liker it. If U like volin & human voice, pls choice permalloy core. But al least over 42%.
lower than 40% is not good. permalloy core had more moisture & higher density sound.
More detail choice amphorous core but lack of powerful punch.
Hi-B is cheap buy the sound is not natural, very mechanical.
I don't like it.

Other is choose the EI or C-core. EI more power ounch but c-core is high density.


pls see the file I take from japan output trans factory.

Max. flux density Very high (¡Ö18000gauss), easy to maintain high inductance> good bass

Permallory comparative high(¡Ö15000gauss), depends on Nickel % content, middle between 3 materials

Amorphous low to high (¡Ö10000-15000gauss), need more winding to maintain high inductance>> higher low freq loss or weak bass

High freq. Iron loss (>10kHz) High Low Very low, good high freq. response
Distortion high low low
General Application Industrial power transformer High freq filtering choke (>20kHz) in switch-mode power supply, Moving coil step up transformer
High freq. filtering choke, distribution power transformer, high freq. pulse transformer

pls study.



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