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Old 1st May 2006, 05:00 PM   #1
kubeek is offline kubeek  Czech Republic
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Default SMPS for tube amp?

I am planning to change the power supply for an old tube amp (4xEL34), becuse it is way too heavy. The core of the transformere is for about 650W, so I would like to change it for something smaller.

I was thnking about step-up converter, but am not sure if it is the right way, becuase then there would be 500V non-isolated from Ground.
Is there any simple SMPS design without a transformer, which I would just build and leave, without any testing or setting?

And just by the way, will the SMPS bring much more noise to the circuit than the transformer?
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Old 1st May 2006, 06:05 PM   #2
cerrem is offline cerrem  United States
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You would still need to use a transformer for isolation....but it would be relativley tiny compared to what you were using...
SMPS for audio is easy and very do-able...
There are plenty of folks against SMPS for audio applications mostly due to ignorance...they still think in terms of 1970's -1980's switching technologies...This is because most of the books out there on SMPS, were written back then...as with the Unitrode stuff....
The big argument is mostlly over EMI issue... This can be simply avoided by using a quasi-resonant converter...
For your application your best bet is a Push-Pull converter in current mode...Quasi-Resonant... Switching no less than 500kHz..with a cross over frequency around 80kHz to 100kHz...

Chris
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Old 1st May 2006, 06:14 PM   #3
kubeek is offline kubeek  Czech Republic
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could you post some schematic? I donīt know how a quasi-resonant smps looks like.
I know I need an output transformer for tube amp, but do I need a supply with transformer? I thought I could use an off-line converter only with inductance, but as I think about it it sound kinda dangerous..
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Old 1st May 2006, 07:22 PM   #4
Stocker is offline Stocker  United States
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It is dangerous. This is the sort of project to undertake only after very much study.
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Old 1st May 2006, 08:09 PM   #5
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Try searching the forums too. We beat this horse a few times
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Old 2nd May 2006, 04:38 PM   #6
kubeek is offline kubeek  Czech Republic
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Well, I changed my mind, I donīt want to get electrocuted because of my own mistake.

Is it possible to create converter from 12 to around 500V, without a transformer?

Does anyone have some good link to a guide how to make a mains transformer or HF trafo for SMPS?
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Old 2nd May 2006, 04:43 PM   #7
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Quote:
Originally posted by kubeek
Is it possible to create converter from 12 to around 500V, without a transformer?

Does anyone have some good link to a guide how to make a mains transformer or HF trafo for SMPS?
Yup!

http://schmidt-walter.fbe.fh-darmsta..._e/smps_e.html
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Old 2nd May 2006, 04:51 PM   #8
kubeek is offline kubeek  Czech Republic
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That was fast, THX!

Do you think that simple boost converter is good enough for my start with tubes? I mean the noise and such like. It will be supplied from a PC supply, what about that?

BTW what is EMI?
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Old 2nd May 2006, 05:49 PM   #9
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EMI = Electo Magnetic Interference and is the plague of SMPS + hi-Z input devices, tubes or FET's.

I did a small (55W) one for auto use. The final schema and thread of R&D is here:
http://geek.scorpiorising.ca/GeeK_Zo...14416#msg14416

Shielding and feedthrough caps for the power leads are a must.

I didn't try a transformerless boost convertor yet. Plan to in the future when I want to be brave and try SS again
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Old 2nd May 2006, 06:55 PM   #10
Stocker is offline Stocker  United States
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I seem to recall so many cases of members unsuccessfully attempting SMPSs without a magnetic element that it has almost acquired an aura of impossibilty without a full-on research and design facility.
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