Low power UcD?

dwk123 · 22nd January 2007, 02:50 AM

This is probably covered somewhere in the current threads, but searching didn't really turn much up.

I have efficient speakers (97dB/W) and so don't need a whole lot of power. I'm currently using a TI Equibit system (Panny XR25) modified to run off a 12V battery supply, which sounds pretty good, but since I need either 4 or 6 channels depending on my ultimate configuration, it's not enough by itself. I also have a couple of the Teac AL-700P units that I could mod into higher-performing units. However, the buzz around the UcD modules makes me curious to at least explore the options.

I know the datasheets for the UcD indicate that a minimum supply voltage of +-30 is needed, but it's not clear whether the unit will cease to function at lower voltage levels, or whether it will work but wont' meet spec. In a perfect world, a UcD 180 running off +-12V for ~10-15W into 4 ohms would be possible, but I'm not that optimistic.

If I 'know' I'll never draw more than maybe 20W peak out of any individual channel, what is the minimal UcD setup that I could consider? Would a single HG supply and 4 -180 modules work OK with this low power draw? What minimal xformer spec would be needed? Is DC even in the picture as a practical option?

classd_fromru · 22nd January 2007, 12:32 PM

Hi dwk123

I think it that is necessary for you

http://www.classd.fromru.com/circuits/ucd3.html

Use on-line translator (google) for translate russian to english.

rogs · 22nd January 2007, 07:54 PM

Iv'e run my UcD 180's from +/- 20V with no problems -- If I get the chance I'll try them on a lower supply, and see what happens.

I would guess one of the main considerations would be just how much of a voltage drop is needed across the input op amp supply regulators, to allow them to continue to function correctly.

Reducing the supply voltage would also reduce the switch driver tail current, which in turn might increase the dead time, and perhaps increase the THD to an unacceptable level.
I guess you'd have to make your own mind up just how much of a spec. drop you'd accept - I would think that the minimum values Hypex recommend have been selected to retain a decent spec level.

BWRX · 22nd January 2007, 09:33 PM

There's nothing wrong with a lot of headroom, it's just that it usually costs more.

Portlandmike · 7th April 2007, 09:08 PM

If you don't need the power, there is absolutely no penalty for running the UCD's at higher voltage. In fact there are advantages in distortion, as the switching frequency will vary less.
You can use fairly wimpy transformers too if you don't need much power.

Portland Mike

22nd January 2007, 02:50 AM	#1
dwk123 diyAudio Member Join Date: Feb 2002	Low power UcD? This is probably covered somewhere in the current threads, but searching didn't really turn much up. I have efficient speakers (97dB/W) and so don't need a whole lot of power. I'm currently using a TI Equibit system (Panny XR25) modified to run off a 12V battery supply, which sounds pretty good, but since I need either 4 or 6 channels depending on my ultimate configuration, it's not enough by itself. I also have a couple of the Teac AL-700P units that I could mod into higher-performing units. However, the buzz around the UcD modules makes me curious to at least explore the options. I know the datasheets for the UcD indicate that a minimum supply voltage of +-30 is needed, but it's not clear whether the unit will cease to function at lower voltage levels, or whether it will work but wont' meet spec. In a perfect world, a UcD 180 running off +-12V for ~10-15W into 4 ohms would be possible, but I'm not that optimistic. If I 'know' I'll never draw more than maybe 20W peak out of any individual channel, what is the minimal UcD setup that I could consider? Would a single HG supply and 4 -180 modules work OK with this low power draw? What minimal xformer spec would be needed? Is DC even in the picture as a practical option?

22nd January 2007, 09:33 PM	#4
BWRX diyAudio Moderator Emeritus Join Date: Jan 2005 Location: Pennsylvania	There's nothing wrong with a lot of headroom, it's just that it usually costs more. __________________ Brian

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22nd January 2007, 12:32 PM	#2
classd_fromru diyAudio Member Join Date: Nov 2006	Hi dwk123 I think it that is necessary for you http://www.classd.fromru.com/circuits/ucd3.html Use on-line translator (google) for translate russian to english.

22nd January 2007, 07:54 PM	#3
rogs diyAudio Member Join Date: Jul 2006	Iv'e run my UcD 180's from +/- 20V with no problems -- If I get the chance I'll try them on a lower supply, and see what happens. I would guess one of the main considerations would be just how much of a voltage drop is needed across the input op amp supply regulators, to allow them to continue to function correctly. Reducing the supply voltage would also reduce the switch driver tail current, which in turn might increase the dead time, and perhaps increase the THD to an unacceptable level. I guess you'd have to make your own mind up just how much of a spec. drop you'd accept - I would think that the minimum values Hypex recommend have been selected to retain a decent spec level.

7th April 2007, 09:08 PM	#5
Portlandmike diyAudio Member Join Date: Feb 2006 Location: Portland, OR	If you don't need the power, there is absolutely no penalty for running the UCD's at higher voltage. In fact there are advantages in distortion, as the switching frequency will vary less. You can use fairly wimpy transformers too if you don't need much power. Portland Mike

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