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Old 6th March 2005, 08:14 PM   #11
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Quote:
Originally posted by Duck-Twacy
Hi Jan-Peter,

When is the UcD700 expected to surface

If used with a 45V AC toroid, how much power can I expect (at 8 ohm)?
The UcD400 will work perfectly fine with a 45V transformer and 8 ohms, and even 4 ohms. The UcD700 would offer no more if this is what you intend using for your power supply and you have 'normal' speakers. To take advantage of the next UcD level up from 400 you need to use a higher voltage, or use a silly load like 2 ohms.
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Old 6th March 2005, 08:30 PM   #12
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I thought that 45V AC was rather on the edge for the UcD400. AC from the wall outlet can easily be 10% higher than nominal 230V.

And I just happen to have 45V toroids.
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Old 6th March 2005, 09:24 PM   #13
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I guess it depends how tight your mains voltage is. I'm going to use 45V and twin 'block' bridge (so 2.2V drop per secondary) PSU, so will be seeing just under 67V worst case. Just inside the 68V limit on the UcD400 Could be a problem at light loading and high mains times, but will just have to see...
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Old 9th March 2005, 05:13 PM   #14
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Richie,

Am I reading this correct?

Using a single bridge rectifier block, the AC to DC gain is 1.41 - now you are talking a drop of 2.2V with 2 rectifiers?

Can you please explain this further?

Thanks!
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Old 9th March 2005, 11:05 PM   #15
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Each diode in a standard block rectifier has a voltage drop, the GBPC3502 I'm using has 1.1V per diode. This drop actually seems pretty typical of most block rectifiers. As I'm using a full block rectifier per secondary the current has to pass through two diodes on its travels.

At worst case the AC will be 10% higher.

DC = ((AC * tolerance) - Vdiode) * sqrt(2)

= ((45 * 1.1) - 2.2) * 1.414

= 66.88V

If you were to use just one bridge per whole transformer you would be over the limit for the UcD400 as only one diode is used per cycle:

= ((45 * 1.1) - 1.1) * 1.414

= 68.44V



I have overlooked the regulation of the transformer in these examples. If it is only lighly loaded then it is likely that these voltages will be exceeded. However, I believe that in Europe, former 220V countries actually have +7% tolerance on the 230V putting them in a better position to us Brits with 230V +10%. So in Europe you may be OK with 45V secondaries if you use a bridge per secondary.
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Old 9th March 2005, 11:32 PM   #16
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Hi,

Quote:
I have overlooked the regulation of the transformer in these examples. If it is only lighly loaded then it is likely that these voltages will be exceeded.
What do you plan on doing about that, turning it up, or just trusting that a 10% surge is a rare occurance? A TVS might be enough, would be cool to squeeze every last bit out of it.

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Old 10th March 2005, 03:36 AM   #17
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Quote:
Originally posted by classd4sure
Hi,



What do you plan on doing about that, turning it up, or just trusting that a 10% surge is a rare occurance? A TVS might be enough, would be cool to squeeze every last bit out of it.

Regards

Use a regulated power supply if you want to squeeze out the last few possible watts without going in protection all the time when the line voltage is a bit higher and when transformer regulation factor is an issue.

I plan to try a regulated switching power supply, not for the above reason however. I don`t care about those last few watts, I don`t think you can hear that 1 dB difference or so. Of course the power supply voltage should be as solid aspossible but I don`t think there is any need to make sure that you get the highest possible power supply voltage.

Gertjan
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Old 10th March 2005, 08:00 AM   #18
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Thanks for explaining, I have the GBPC3508 models, also 1.1V drop.
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Old 10th March 2005, 08:27 AM   #19
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Firstly, I will be using a 1000VA toroidal transformer, so regulation will already be quite tight. I am also relying on the fact that excursions to +10% will be a rare occurrence. As I mentioned earlier, I will be running either a pair of very power hungry subs or using the amp to pound out tunes in a pub back room or parties, so there will always be an amount of loading anyway.

I think a regulated PSU is a waste of time as it will not allow you to get the most out of your power supply and is something else to go wrong and create heat, EMI etc.

I just like to think that I can squeeze all that is possible out of the UcD400 This may not be the ideal for everybody.
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