Torroid for UCD180 Module

nlRenderman · 10th March 2007, 03:08 PM

I found some 100Va 28Vac Torroids that i would like to use with the UcD180 Modules. According to the information by Hypex 100Va per UcD180 module should be sufficient.

My question is about the ground. I see in the PDF by Hypex http://hypex.nl/docs/UcD180_manual.pdf They connect the ground to the center of the secondary coil of the torroid.
Can this be done with this torroid aswell and is it necessary?

sek · 10th March 2007, 08:05 PM

Hi,

this transformer doesn't really look appropriate. It's not specifying to be capable of supplying 100VA out of the 28V line! The 100VA total also include the 15V line!

You would need one of those transformers in order to form a single supply rail. As the UCD modules require a dual voltage supply, two transformers are required for both supply rails. The best way would be to make a PSU like with a dual secondary transformer (which yours aren't) and connect the two transformer 28V coils in series, just like the secondaries of one transformer.

But remember that those trafos could likely be too weak to deliver stable voltage to a UCD180.

Cheers,
Sebastian.

nlRenderman · 10th March 2007, 08:40 PM

Thank you for your explanation Sebastian, i understand now 2 secondary coils are neccecary for the UcD modules. And it is possible to link 2 of these transformers together in series. I have done some investigation on the transformers and it seems they are capable of handling 100Va on the 28V coils. Since the 15V Rail can only handle about 1Va this is not taken into account by the manufacturer.

I think i will go ahead and make a power supply using these torroids, since the first UcD amp i'll make will be only or testing. Partly because i am new to making amp's and partly because i would like to know what they sound like. If i am able to make a decent sounding (and working!) amp i want to try to make a 5.1 amp using UcD180 modules. Offcourse i will buy some nice dual secondary torroids for that amplifier.

iwf · 11th March 2007, 10:55 PM

Actually you don't need dual voltages out of the trans.

i've just built a 180 based amp with only a single 30v voltage. you only need the second voltage if your doing things with the aux part of the amp.

28v seems a bit low though

nlRenderman · 12th March 2007, 07:36 PM

What do you mean by aux part? I really would like to use these torroids. Could you send me a schematic of how you connected it?

iwf · 12th March 2007, 11:01 PM

sorry i wasn't being very specific. I'm a newbie and don't really understand much

I built my 180 based amp using the HG power supply.

the torroid I bought had only 30v secondaries, a bit like yours.

the guys on the UcD questions thread answered my question here

basically you only need the lower voltage secondaries if you make amendments to the PS. Hypex confirmed this and mine works fine with a 500VA and 30v secondaries.

nlRenderman · 14th March 2007, 04:33 PM

Dear iwf. I appreciate your help but i think we arent talking about the same thing. I dont mean a lower voltage secondary (~12v). My torroid only has 1 28V secondary coil, i think your shas 2 31V coils but nu ~12V coil. I know i dont need the lower voltage 1. I just would like to know if it is possible to use this torroid that has only 1 secondary 28V coil instead of 2 (i have 4 of these torroids in total) would it be at all possible to use this with the UcD180?

nlRenderman · 14th March 2007, 05:17 PM

I have drawn a circuit of how i think it might work for the module with only 1 secondasy coil. Could anyone tell me if this is basically correct and will work? If not, any help correcting it would be appreciated.

sek · 14th March 2007, 08:23 PM

Hi,

this is possible, but dangerous.

The center potential between the caps, which becomes the ground for the amplifier, has no DC path to the rails, it's noisy and unstable as a reference. With any deviation of the charge between the caps, the ground reference would float around, affecting stability, sound and safety.

Additional resistors (to form a voltage divider) would be better, but they would constantly conduct current and thus waste power.

After all, there's a reason why everybody uses (and recommends) dual or split-secondary transformers (or two single secondary ones like yours)!

Cheers,
Sebastian.

nlRenderman · 17th March 2007, 05:05 PM

Thank you for your reply (and concern) Sek

I made a new circuit diagram for the power supply using 2 seperate torroids (i have 6 of these so cost is no object) Would this be a usable design? And if so, wich sides of the secondarys would i have to connect to the top of the rectifiers?

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10th March 2007, 08:05 PM	#2
sek diyAudio Member Join Date: May 2003 Location: Berlin	Hi, this transformer doesn't really look appropriate. It's not specifying to be capable of supplying 100VA out of the 28V line! The 100VA total also include the 15V line! You would need one of those transformers in order to form a single supply rail. As the UCD modules require a dual voltage supply, two transformers are required for both supply rails. The best way would be to make a PSU like with a dual secondary transformer (which yours aren't) and connect the two transformer 28V coils in series, just like the secondaries of one transformer. But remember that those trafos could likely be too weak to deliver stable voltage to a UCD180. Cheers, Sebastian.

10th March 2007, 08:40 PM	#3
nlRenderman diyAudio Member Join Date: Jan 2007 Location: Holland	Thank you for your explanation Sebastian, i understand now 2 secondary coils are neccecary for the UcD modules. And it is possible to link 2 of these transformers together in series. I have done some investigation on the transformers and it seems they are capable of handling 100Va on the 28V coils. Since the 15V Rail can only handle about 1Va this is not taken into account by the manufacturer. I think i will go ahead and make a power supply using these torroids, since the first UcD amp i'll make will be only or testing. Partly because i am new to making amp's and partly because i would like to know what they sound like. If i am able to make a decent sounding (and working!) amp i want to try to make a 5.1 amp using UcD180 modules. Offcourse i will buy some nice dual secondary torroids for that amplifier.

11th March 2007, 10:55 PM	#4
iwf diyAudio Member Join Date: Feb 2007 Location: London	Actually you don't need dual voltages out of the trans. i've just built a 180 based amp with only a single 30v voltage. you only need the second voltage if your doing things with the aux part of the amp. 28v seems a bit low though

12th March 2007, 07:36 PM	#5
nlRenderman diyAudio Member Join Date: Jan 2007 Location: Holland	What do you mean by aux part? I really would like to use these torroids. Could you send me a schematic of how you connected it?

12th March 2007, 11:01 PM	#6
iwf diyAudio Member Join Date: Feb 2007 Location: London	sorry i wasn't being very specific. I'm a newbie and don't really understand much I built my 180 based amp using the HG power supply. the torroid I bought had only 30v secondaries, a bit like yours. the guys on the UcD questions thread answered my question here basically you only need the lower voltage secondaries if you make amendments to the PS. Hypex confirmed this and mine works fine with a 500VA and 30v secondaries.

14th March 2007, 04:33 PM	#7
nlRenderman diyAudio Member Join Date: Jan 2007 Location: Holland	Dear iwf. I appreciate your help but i think we arent talking about the same thing. I dont mean a lower voltage secondary (~12v). My torroid only has 1 28V secondary coil, i think your shas 2 31V coils but nu ~12V coil. I know i dont need the lower voltage 1. I just would like to know if it is possible to use this torroid that has only 1 secondary 28V coil instead of 2 (i have 4 of these torroids in total) would it be at all possible to use this with the UcD180?

14th March 2007, 08:23 PM	#9
sek diyAudio Member Join Date: May 2003 Location: Berlin	Hi, this is possible, but dangerous. The center potential between the caps, which becomes the ground for the amplifier, has no DC path to the rails, it's noisy and unstable as a reference. With any deviation of the charge between the caps, the ground reference would float around, affecting stability, sound and safety. Additional resistors (to form a voltage divider) would be better, but they would constantly conduct current and thus waste power. After all, there's a reason why everybody uses (and recommends) dual or split-secondary transformers (or two single secondary ones like yours)! Cheers, Sebastian.

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