SMPS for tube amp?

kubeek · 1st May 2006, 05:00 PM

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?

cerrem · 1st May 2006, 06:05 PM

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

kubeek · 1st May 2006, 06:14 PM

could you post some schematic? I don´t 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..

Stocker · 1st May 2006, 07:22 PM

It is dangerous. This is the sort of project to undertake only after very much study.

Geek · 1st May 2006, 08:09 PM

Try searching the forums too. We beat this horse a few times

kubeek · 2nd May 2006, 04:38 PM

Well, I changed my mind, I don´t 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?

Geek · 2nd May 2006, 04:43 PM

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

kubeek · 2nd May 2006, 04:51 PM

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?

Geek · 2nd May 2006, 05:49 PM

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

Stocker · 2nd May 2006, 06:55 PM

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.

1st May 2006, 05:00 PM	#1
kubeek diyAudio Member Join Date: Dec 2005 Location: Prague, Czech Rep	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?

1st May 2006, 07:22 PM	#4
Stocker diyAudio Member Join Date: Dec 2003 Location: Austin	It is dangerous. This is the sort of project to undertake only after very much study. __________________ Jesus loves you.

2nd May 2006, 06:55 PM	#10
Stocker diyAudio Member Join Date: Dec 2003 Location: Austin	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. __________________ Jesus loves you.

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1st May 2006, 06:05 PM	#2
cerrem diyAudio Member Join Date: Jun 2005 Location: San Diego, CA	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

1st May 2006, 06:14 PM	#3
kubeek diyAudio Member Join Date: Dec 2005 Location: Prague, Czech Rep	could you post some schematic? I don´t 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..

1st May 2006, 08:09 PM	#5
Geek diyAudio Member Join Date: Sep 2004	Try searching the forums too. We beat this horse a few times

2nd May 2006, 04:38 PM	#6
kubeek diyAudio Member Join Date: Dec 2005 Location: Prague, Czech Rep	Well, I changed my mind, I don´t 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?

2nd May 2006, 04:51 PM	#8
kubeek diyAudio Member Join Date: Dec 2005 Location: Prague, Czech Rep	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?

2nd May 2006, 05:49 PM	#9
Geek diyAudio Member Join Date: Sep 2004	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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