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Old 2nd July 2005, 08:32 AM   #31
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Join Date: Feb 2005
Location: Antwerp
I always read here that 45 secondaries are too high for UcD400, or was the cleared in the new versions?

I'm going to use the HQ power supply by Hypex to run 2 of them. The caps on that PS are 63V, so that's also a worry at 45V.

If I have a 10% overshoot on the mains voltage (which is not impossible in Belgium) I hit 69V on the rails, wouldn't that trigger the over voltage?

Thanks for your opinion!
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Old 2nd July 2005, 08:44 AM   #32
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Join Date: Feb 2005
Location: Antwerp

You could also use our 500VA transformer. Ok, 500VA is less as 800VA. Small suggestion go to two 500VA for two true mono block?


Thanks for the suggestion. 2x500VA and 2 HQ PS are simply too expensive for my budget.

The reason I'm looking at 800VA is partly psychological, I must admit.... I will be using the amps nowhere near their max output in normal life (stereo channels of a surround setup, about 70% stereo, 30% surround) so i'm not worried there, even when my speakers are known to be very current hungry ("old" B&W nautilus 804)

However sometimes we do have a "fuif" (party) sometimes, and I want to use my amp there as well. Usually we connect 4 speakers so we hit 4 ohms (and probably lower) pretty often at high volumes. I'm not sure if 500VA + 1 HQ PS will handle your typical heavily compressed techno music at sustained high volume? I'd love to have a software tool to check out what the average percentage of maximum output power for a giving recording is.

Would it however, be possible to connect 2 of your 500VA's to a single power supply or is this totally not recommended/impossible?

All suggestions are welcome. I want to get rid of my "test setup" that's been running for way too long. It looks like sh..
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Old 2nd July 2005, 09:24 PM   #33
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Join Date: Apr 2004
Location: BE/NL/RW/ZA
You can play a party with 2 UcD400's on one 500VA transformer and one supply with absolutely no problems. This is really no problem. The last time I measured average power in heavily compressed music, it was still below 10% of constant sinewave of equal amplitude.

Only if you are making amplifiers for export to South America, using a larger transformer can be worthwhile because it is a known fact that parties are played in full clip there, and last for days (only half joking there).
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Old 29th July 2005, 09:43 AM   #34
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Join Date: Jun 2005
Location: near Delft
Originally posted by Bruno Putzeys
Apologies. I don't always look at the main page of diyaudio. One should contact me directly if one needs a certain reply.

160VA, 30 or 35V is OK. Use "slit foil" caps (available only as 10000uF so that answers that question). Soft-recovery rectifiers with 47nF caps across them. If your transformer has 2 separate secondaries, consider using 2 separate bridge rectifiers, so you get two single 45VDC supplies that you then place in series. If you want, this allows you to use schottky diodes for the rectifiers (half the voltage). In that case, substitute 1nF+10R for the 47nF caps.

Short the infamous input coupling electrolytics on the modules. If you expect a DC problem, use better caps that you place at the inputs of the modules (higher impedance than where the standard coupling caps are).

Let me know when you've gotten this far.
Sorry for a maybe stupid question, but why would you not be able to use schottky diodes anyhow, with a single bridge rectifier?
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