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Old 22nd January 2013, 07:04 PM   #31
tomchr is offline tomchr  United States
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Quote:
Originally Posted by Magz View Post
Just wondering...have any of you switch-o-philes considered using a HV SMPS for the B+?
Have a look at Post #9.

On a satellite project years ago, I developed a 2500 V flyback switchmode supply. Worked pretty well... It wasn't designed for high current so it wouldn't be as useful for a B+ regulator, but I would think it would be possible to build a B+ regulator that way.

It'd be quite a project, though. Switchers contain a lot of little trap doors and pitfalls -- especially the ones that handle high energy. Be careful.

~Tom
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Old 22nd January 2013, 07:12 PM   #32
Magz is offline Magz  United States
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I wouldn't be building it, I'd be buying it. I see lots of companies that OEM these things for scientific instrument and medical scanners. Most have plenty of voltage but are a little short of current. I'd need 2300V and 160mA per monoblock, so that's ~370W. Most of the ones I see on the web are 200 - 250W. Now I suppose two could be paralleled to get enough wattage, but the question is - how would these things sound?? Have they solved the RF issues or would I be swamping my lovely tubes with all sorts of HF noise?

Just exploring the options at this point and trying to think outside the box.
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Old 22nd January 2013, 09:15 PM   #33
tomchr is offline tomchr  United States
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You will have some amount of ripple at the switching frequency. That's simple physics. But if the switching frequency is above the audio band and the ripple voltage is low, does it impact circuit performance? My suspicion is that you won't hear the ripple as it's well outside the audio band (my filament regulators run at 500 kHz - most mains level regulators run well above 20 kHz). And the ripple is tiny compared to the normal 120 Hz ripple you have on a linear supply - unless you design a linear voltage regulator. Switchers - or any series regulator - will have a very low output impedance. In my experience (from my 21st Century Maida Regulator), that really tightens up the sound. If you want a low noise floor, low hum, lots of sound stage go with a regulated supply. That's my subjective experience anyway.

In my case, I'm using switchers for the filament power. In that case, any switching noise would actually be amplified by the tube. I have not seen any adverse effects of using switchers on the filament supplies. The amp measures well and sounds good.

Buying a switcher for the B+ application sounds like a good idea. It's a bit safer that way. 2300 V, 160 mA. Damn. That's a lot of power.

~Tom
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Last edited by tomchr; 22nd January 2013 at 09:20 PM.
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Old 23rd January 2013, 11:38 AM   #34
bekim is offline bekim  Albania
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Originally Posted by tomchr View Post
I am using switchmode supplies for the filaments in my 300B amp. They work really well. I am selling assembled modules as well as bare boards for DIY use on my website (Neurochrome.com : : Audio : Universal Filament Regulator). These modules have been extensively tested, both in the lab and in my stereo in the living room.

Unless you are using several 300B tubes in parallel, you will need one regulator per 300B tube. For parallel tubes, you can run two tubes off of one of my filament regulators.

The (-) output of the filament regulator should be connected to the lowest potential of the 300B filament. This is generally the end where the cathode resistor is connected. If one end of the 300B filament is connected to ground, connect the (-) terminal of the filament regulator there. The (+) terminal then connects to the other end of the filament. I hope this makes sense...

I should draw up some figures of this at some point...

~Tom
Tom, thank you for the reply.
It makes sense connecting filaments as you suggested.

On my 300B amp project I'm collecting parts to build, will be only one tube on output stage, and 8 ohm speaker per channel.
I know this thread is for smps and tube heaters, but you are experienced on tube amps, and other question will be, what output transformer I should consider to purchase in terms of primary resistance? I can see 2.5K, 3.5K, 4.2 and 5K primary and this confuses me.. Regardless the design, does the output transformer resistance makes a big difference and why, what will be your decision, and if you have any suggestion or brand just let me know.

I like your modules which you are offering on your website, they could make my life easier..

thanks

bekim

Last edited by bekim; 23rd January 2013 at 11:43 AM. Reason: typo
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Old 23rd January 2013, 04:22 PM   #35
tomchr is offline tomchr  United States
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Quote:
Originally Posted by bekim View Post
Tom, thank you for the reply.
It makes sense connecting filaments as you suggested.
Cool!

Quote:
Originally Posted by bekim View Post
I know this thread is for smps and tube heaters, but you are experienced on tube amps, and other question will be, what output transformer I should consider to purchase in terms of primary resistance?
I think a better thread for this question is my 300B Amp build thread:
DeathTrap400 : : A Pretty Damn Good 300B Amp

I'll answer it there.

Quote:
Originally Posted by bekim View Post
I like your modules which you are offering on your website, they could make my life easier..
Yep. That's why I started doing modules. That takes the stress of SMD soldering out of the equation for you.

~Tom
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Old 23rd January 2013, 05:21 PM   #36
Magz is offline Magz  United States
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These units from Ultravolt (link) are oh so close, with the 2C units capable of 2000V and 125mA. Just shy of what I need. Output impedance is ~2ohms according to the applications engineer I talked to! Talk about a responsive power supply!

Too bad they cost $1300 each or I'd parallel two per monoblock and be done with it. I guess that's cheap compared to a WAVAC 833 amp ($350K!), but not according to my wife.


http://www.ultravolt.com/uv_docs/HPCDS.pdf
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