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Old 8th October 2004, 05:25 AM   #21
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Join Date: Oct 2004
Location: Sydney
Quote:
Originally posted by classd4sure
Hi,

I've been pricing some power transformers, 40V rms secondaries at 650, 750 and 1000 VA. I think for two modules off one transformer I'd want at least 650VA.

So my question is this:

I've found "low noise" transformers offered, they don't even say what is different about them, such as any screens, magnetic shielding, or otherwise.

What is different is they're triple the cost of a regular one.

What's the consensus on having such a "low noise" transformer. Is it a must have? Is it a joke? Is it worth the extra cost? Would you notice any difference at all?

Now what I found was just marketing hype, no specifications offered or anything, so I'll also ask, how important is any screen /shielding as well, and we'll consider that to be low noise for the purpose of this part of the discussion.

Thanks

I just ordered two 500VA transformers. I got a low flux density design, which results in less hum noise. As a result the transformer is a couple of millimeters bigger. I also got electrostatic shield and a magnetic shield. It also comes with the centre potted.

The only reason I got all the bells and whistles is because it didn't cost me much more. For a standard off the self it would of cost me around $120 (Australian), I paid $150.

The only reason I got the low noise design is a friend of mine tells me he can hear his transformer humming during quiet passages. You don't buy transformers every day.
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Old 8th October 2004, 06:47 AM   #22
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Hello,

nickywicky;
Steel is a very BAD thermal conductor, please use a piece of aluminium. A size of 150 x 150 mm is already enough.

Peranders;
http://www.hypex.nl/classd/UcD400.pdf

DSP_Geek ;
The modulator PCB of the Ucd180 and UcD400 is EXACTLY the same

The higher the VA rating of the transformer, the better load regulation. So you will get the most power out of the UcD400.

Regards,

Jan-Peter

www.hypex.nl
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Old 8th October 2004, 02:54 PM   #23
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Default What are the maximum current ratings

Jan Peter,
I read the specs on your web-site for both the UcD180 and UcD400.
Could you provide information of both modules on:
- frequency response
- speed (rise time, settling time and slew rate)
- the output (peak) current ,
-
Thankx
Henk
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Old 8th October 2004, 07:23 PM   #24
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Location: Santa Cruz, California
Quote:
Originally posted by Jan-Peter
Hello,

DSP_Geek ;
The modulator PCB of the Ucd180 and UcD400 is EXACTLY the same

www.hypex.nl

Sweet. I just got my UcD180s, by the way. Beautiful work.

So which part of the circuit is it which has the 1.8kohm input impedance? Is it easily modifyable to the 100kohm if the UcD400? At that point, one can use polypro caps for AC coupling and not have the capacitors dwarf the board.

Thanks,
Francois.
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Old 8th October 2004, 07:55 PM   #25
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Calimero,
Outputpeakcurrent of the UcD400 15A.

A copy of a part of a documentation written by Bruno;
Given the fact that the frequency response is a second order filter cutting off at around 50kHz (the exact function is a sensible compromise between Butterworth and Thomson), the impulse response is accordingly. Frequency and impulse responses always go hand in hand. You may recognise the problem of trading frequency response with impulse response is a recurrent theme in audio converter design as well. A perfectly damped response corresponds with significant droop in the frequency response, and a maximally flat frequency response necessarily has some (though not in the case of a 2nd order filter) overshoot. Filter characteristics cutting the middle ground between Butterworth (maximally flat frequency response) and Thomson (constant delay) are mostly chosen.

Power response (slew rate) is limited only by the steepness of the impulse response of the output filter, which cuts off at 35kHz.
Keeping the discrepancy between power bandwidth and small signal bandwidth small is essential in preventing slew-rate induced distortion. During the course of the development of UcD, some had been made that were flat (>-1dB) up to over 100kHz, but they misbehaved quite terribly when confronted with wide-bandwidth input signals.


Francois,

The 1,8K inputimpedance is in the modulator, the small 90o potted PCB. When you like to use no coupling cap, you must use an other opamp as the NE5532, please go for an OPA2134. And you have to be VERY shure you source is DC free.

Succes!

Regards,

Jan-Peter

www.hypex.nl
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Old 9th October 2004, 09:00 AM   #26
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Hi,

Just trying to come up with a bit of a plan here.

Luckily for me there's a good transformer manufacturer close enough to home to make buying from them a total none issue, as I'd imagine they can be costly to ship.

The primaries are rated for 115V rms, I need 120. I trust it isn't a big deal for such a primary to operate at 120.

I took that as a 4.3% error, to which I added another 14% to account for a standard mains variation of 10% safety margin, and the load regulation provided by them.

I also took into account a 1.4 volt drop to account for the bridge rectifier.

So I'm after 35 Vrms secondaries, am I not?
Just want to make sure I'm on the right track here.

Also, I'm having a hard time finding a place for PSU caps. I don't want to have to sell my ferrari to buy BG's so I was thinking of ELNA Cerafine caps, or another alternative.

If anyone knows of a good place to get them from at a good price, please let me know.

Thanks
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Old 9th October 2004, 10:55 AM   #27
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Location: Sydney
Quote:
Originally posted by classd4sure
Hi,

I also took into account a 1.4 volt drop to account for the bridge rectifier.

So I'm after 35 Vrms secondaries, am I not?
Just want to make sure I'm on the right track here.

Thanks

35 Vrms secondaries? Are u buying the UcD400's? If so you should have 40VAC secondaries. That is 40*1.41= 56VDC. That is, with a 10% variance will take it to 62VDC (which is below 63V limit).

I'm going to add some 47VAC taps (if I'm not too late) as well just in case it's required. Based on Bruno's and Lars discussion on another thread. May be able to run the UcD400 at higher voltage with some modes.
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Old 9th October 2004, 11:42 AM   #28
Zodiac is offline Zodiac  United States
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Location: Kenfield, CA, USA
I have been lurking around this class D forum for a while, waiting for the time to pounce once the UCD400 was released.

I am planning on using one module to drive the bottom 2 open dipole woofers of the Linkwitz Orion, from 20hz to 120hz

This means the module would have to drive 4 ohms avg, lowest 2ohms at 100hz (two woofers paralleled)

In terms of power supply I was thinking 1*300VA, 40V secondaries per channel with one 6800uf cap per rail. Any comments or recommendations for changes?

Ta!
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Old 9th October 2004, 01:21 PM   #29
ghemink is offline ghemink  Netherlands
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Join Date: Jun 2004
Location: Japan
Quote:
Originally posted by Zodiac
I have been lurking around this class D forum for a while, waiting for the time to pounce once the UCD400 was released.

I am planning on using one module to drive the bottom 2 open dipole woofers of the Linkwitz Orion, from 20hz to 120hz

This means the module would have to drive 4 ohms avg, lowest 2ohms at 100hz (two woofers paralleled)

In terms of power supply I was thinking 1*300VA, 40V secondaries per channel with one 6800uf cap per rail. Any comments or recommendations for changes?

Ta!

If I were you, I would try the UcD modules also for mid and high. If you think UcD400 is overkill for mid and high, you could use the UcD180 for mid and high. I`m using UcD180 in an active dipole system, sounds great. UcD400 maybe better however since the coupling caps are gone, I`ll order some UcD400 modules later this year to try them out for mid and high as well. If those woofers are 4 Ohm each, you may want to spend one UcD module per woofer, you may not get maximum power at 2 Ohm because of output current limitations. And I guess those woofers need quite a bit of power, what do you use now to drive them?

Best regards

Gertjan
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Old 9th October 2004, 01:25 PM   #30
ghemink is offline ghemink  Netherlands
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Join Date: Jun 2004
Location: Japan
Quote:
Originally posted by classd4sure
Hi,

Just trying to come up with a bit of a plan here.

Luckily for me there's a good transformer manufacturer close enough to home to make buying from them a total none issue, as I'd imagine they can be costly to ship.

The primaries are rated for 115V rms, I need 120. I trust it isn't a big deal for such a primary to operate at 120.

I took that as a 4.3% error, to which I added another 14% to account for a standard mains variation of 10% safety margin, and the load regulation provided by them.

I also took into account a 1.4 volt drop to account for the bridge rectifier.

So I'm after 35 Vrms secondaries, am I not?
Just want to make sure I'm on the right track here.

Also, I'm having a hard time finding a place for PSU caps. I don't want to have to sell my ferrari to buy BG's so I was thinking of ELNA Cerafine caps, or another alternative.

If anyone knows of a good place to get them from at a good price, please let me know.

Thanks

I got my ELNA cerafines (10.000uf) from partsconnexion

http://www.partsconnexion.com/catalo...ctrolytic.html


gertjan
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