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final report on switching trans vs halo trans for filament supply

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Posted on January 3, 2017 at 06:34:16
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 Looks like it is going to be the halo trans for me folks. I just like the sound of AC on the 813 filaments better. Clean & pure. The small size of them is a big plus also. I was able to run two 813's off of one of the 30 amp switching trans, but they are larger than the 15 amp units so it is not much help. The fans on the 30 amp units could be problematic as well if the amp is to close to the listening position. They cycle in and out once they warm up, and are a bit noisy. Now all I have to do is try and get one of the 60 watt halo units down to 1.5 volts ac and give that a try on the 26's. The fun never stops ......

 

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RE: try the 220v input supplies, posted on January 3, 2017 at 15:34:00
deafbykhorns
Audiophile

Posts: 1067
Location: Florida
Joined: October 17, 2003
 They have more primary windings and will run off 120volt, you can remove enough secondary windings to get around 3 volts or less.
I may try to add some primary windings which should lower the voltage some more. The stock are about 12.5:1
You could always buy the ferrite core from digikey and wind your own

 

RE: try the 220v input supplies, posted on January 3, 2017 at 19:06:00
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 That turns ratio makes sense. The 120V units are about 5.5:1. The cores are available from multiple sellers on eBay, and they're extremely cheap (see link below).

Question: How do you reconcile the increase in primary current when you use the 240V unit on 120V? Have you compared the primary wire gauge used on the two versions?






 

RE: try the 220v input supplies, posted on January 3, 2017 at 15:40:00
vinnie2
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Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 Thanks deaf, I will keep that in mind if I can't get the 120 volt units low enough.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 11:46:59
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 Forgot to mention if anyone wants a couple of 30A units for a 12 volt bench supply let me know. I will let them go for 1/3 less than what I paid for them plus shipping.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 11:45:23
megasat16
Audiophile

Posts: 207
Location: SoCal
Joined: April 15, 2015
 I once had a 30Amp SMPS with fan pulling a filament duty for the combined L and R. The fan noise could be loud and annoying at times so I modded the fan with extremely low noise (9dB) outboard fan and I can barely hear the fan noise with my ears next to the SMPS.

I have yet to experiment with Halo transformers so I don't know yet. May be I'll find them good for filament duty too. Well, I am going to order a bunch and try them out in the coming Spring.






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.Thou shall not stand where I type for I carry a bottle of Certified Audiophile Air and a Pure Silver Whip.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 11:50:27
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 I think I will just sell mine and keep the 15A units since I am going with the halos for the amp. I think you will like the halos; they sound good and take up very little room. The required mods are real easy to do as well.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 11:56:24
used-hifi
Audiophile

Posts: 1100
Location: Surprise AZ
Joined: March 18, 2003
 please post some pictures of these units

I am using raw linear power supply with colman regulators and its very good

but am always looking for less expense if it works right


Lawrence

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 12:32:47
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013






Here they are next to a 15A switching supply (dc) and a close up of one as well.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 12:42:33
megasat16
Audiophile

Posts: 207
Location: SoCal
Joined: April 15, 2015
 Vinnie,

What's the big cap for? Is it at the output stage from the halo transformer or somewhere in the circuit?

I need schematics if someone has it.
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.Thou shall not stand where I type for I carry a bottle of Certified Audiophile Air and a Pure Silver Whip.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 13:07:32
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 I've posted a complete schematic for this unit. You'll find it if you read through the threads on this topic over the last two weeks.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 13:23:41
megasat16
Audiophile

Posts: 207
Location: SoCal
Joined: April 15, 2015
 I do find a lot of your posts on the halo transformers but not the one with schematics in it. I recall you posted a schematic somewhere but I can't backtrack hundreds of posts so leave it be if you don't have one handy.

Do you have a filter cap like Vinnie and where's it wired at?
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.Thou shall not stand where I type for I carry a bottle of Certified Audiophile Air and a Pure Silver Whip.

 

Halo Transformer Schematic, posted on January 3, 2017 at 17:53:35
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 Here's the schematic. This was drawn from the original 60W units that were common until about a year ago. The new units are slightly different. A diode is connected from the top of the Diac to the junction of the two transistors, and capacitors C3 and C4 are 0.47u.

It's necessary to add a filter capacitor (shown with dotted lines in the schematic). A value of 47u will yield a waveform like the one below. This level of 120Hz ripple will be inaudible if a hum pot is used.













 

Interesting! , posted on January 4, 2017 at 12:19:33
megasat16
Audiophile

Posts: 207
Location: SoCal
Joined: April 15, 2015
 Thanks for the schematic. Adding the filter cap makes the Output looks more SET friendly. It looks much like a DC with high ripple on both sides due to the Diac firing on both direction.

I don't see any square wave like in that scope trace so the ripple is all that is making that of the AC heated DHT?

Whatever the case, that output looks much more amp friendly than the square waves I have seen before.

I think you can reduce the ripple by a considerable amount if you put a larger uF cap behind the rectifiers.
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.Thou shall not stand where I type for I carry a bottle of Certified Audiophile Air and a Pure Silver Whip.

 

RE: Interesting! , posted on January 4, 2017 at 13:33:47
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 It's a 66kHz (approximate) square wave modulated with 120Hz ripple. The square waves aren't visible in the trace above because the sweep speed is set to show the ripple. As for being SET friendly, most of the harmonic energy in the square wave is third and above. That puts it at 180kHz.





 

RE: Interesting! , posted on January 5, 2017 at 16:16:51
megasat16
Audiophile

Posts: 207
Location: SoCal
Joined: April 15, 2015
 I also had a thought that the time domain wasn't stretched enough to show that square wave. But that waveform looks very clean to even suggest there is such underlying square wave. Anyhow, my worry with the square wave is the fundamental 66KHz. F3 wouldn't be a concern. There are plenty of other harmonics besides F3 with considerably amplitude but they are at much higher frequency so they may not be audible.

Without the additional filter cap, I guess the halogen transformer works fine without the additional 120Hz ripple.

What's the amplitude of the 120Hz ripple? And you said the hum pot eliminates that ripple hum?
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.Thou shall not stand where I type for I carry a bottle of Certified Audiophile Air and a Pure Silver Whip.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 09:27:43
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 Glad to hear it's working for you.

"Now all I have to do is try and get one of the 60 watt halo units down to 1.5 volts ac and give that a try on the 26's."

After more work on this, I don't think these high step-down ratios will be feasible with the half-bridge circuit. It might be better to gut the oscillator components (except the two switching transistors) and add a daughter board. The added board could use a high speed, differential output device to drive the two transistors. With this approach, frequency could be set using RC components, and the duty-cycle could be adjusted to exactly 50% for ease in setting the RMS voltage. This might also have some benefit in generating the higher filament voltages needed for 211/845/GM70 tubes. I'll post any progress I make with this.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 09:52:01
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 Now you are WAY over my head. No chance of me doing something like that without step by step instructions. I have two of the 60 watt units on the way, and when they get here I will try peeling off some windings and see what happens. Did you actually measure the lowest voltage you got? If so, how many windings were left?

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 11:26:32
used-hifi
Audiophile

Posts: 1100
Location: Surprise AZ
Joined: March 18, 2003
 I am interested too for other project

anyways you could count the number of turns divide into the voltage then you will have a good idea how many turns= how much voltage then just unwind until you get what you need i hope this makes sense



Lawrence

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 10:31:52
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 Vinnie, it's not as complicated as it probably sounds. I think the minimum voltage possible was 5-6V rms (10-12V pk-pk). Probably four or five turns on the secondary.





 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 11:35:32
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 So what happens if you only leave one or two turns on the secondary?

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 13:04:48
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 "So what happens if you only leave one or two turns on the secondary?"

It won't oscillate.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 13:50:46
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 And what does that do to the operation?

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 17:40:04
Triode_Kingdom
Audiophile

Posts: 10044
Location: Central Texas
Joined: September 24, 2006
 If it doesn't oscillate, there's no output.

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 18:23:06
vinnie2
Audiophile

Posts: 4481
Location: North Carolina
Joined: September 28, 2013
 That can't be good! : )

 

RE: final report on switching trans vs halo trans for filament supply, posted on January 3, 2017 at 11:47:44
used-hifi
Audiophile

Posts: 1100
Location: Surprise AZ
Joined: March 18, 2003
 well first count how many turns are wound on the core then divide into the specified voltage that they are rated for

so once you have the turns/voltgage/ratio you should be able to understand



you maybe only able to take off some of the winding and make it work correct I have no time with these...suck it and see!

 

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