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Old 19th January 2005, 10:36 PM   #61
Luke is offline Luke  New Zealand
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if capacitance is so important, maybe a capacitence multiplier or voltage regulator would work well. Any one tried this?
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Old 19th January 2005, 11:04 PM   #62
GregD is offline GregD  United States
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Quote:
Originally posted by ericpeters
You can sell me your Diva's, there is no better room than mine to put Diva's I can pick them up myself. I have to be in Southern California anyway next week. The calipers will fit everywhere. ALtough I'm not sure if the airline will accept diva's as hand luggage.

The zero distortion link is the one I meanth (Designing your own power supply). I followed their calculation regarding the leak-resistor sizing and estimated 10watt would be OK, but I found only these at my local supliier.

I've had discussions with LC-audio regarding the required size of Caps and transformer as well, but listening proved them wrong (or maybe lesser standards)
In my experience size of transformer (= low output impedance of the PS) is most important. And the quality of the of Capacitors.
My theory is that the high efficiency of the modules is the main reason for this: the current they draw from the ps will fluctuate almost linear with the music levels, this will result in an unstable spply voltage if your transformer has not got enough guts. (anyway it is just a theory)
Yes, I think Divas would have to be checked in. Of course the excess baggage charges at about 200 pounds each might be costly.

Even a 2 watt version of your leakdown resistors should be enough since they should only need to dissipate about .44 watts. Not that the bigger resistors will hurt anything, but you could save some space and maybe some money in the future. From the zero distortion site:
Quote:
You can work out the values yourself, remembering that current equals voltage divided by resistance, and power equals this current times the supply rail voltage. Make sure the power rating of the resistor is at least four times what you will need, because it will tend to heat up quite considerably in the period it takes to discharge the capacitors. I would prefer to see twice that; so, if you have a 2W resistor, work out its value so that current times voltage comes out as no more than 0.4-0.5 watts.
I basically agree with your theory, but I plan to do the experimentation to prove or disprove it. At lease in my system.
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Old 19th January 2005, 11:21 PM   #63
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I only used a plain star point. Ericpeters amp is the one with the copper bus bars. Personally, I think either approach should be fine as long as you connect everything to one grounding point on the bus bars. I did the wires primarily so that it would be easier to swap different capacitors in and out. For a final version, I think I'd probably go to bus bars for ease of assembly and looks.
[/B]
OOps, sorry, good point though. Yeh the bus bars are a handsome approach, heard some bad about them, but you're probably right, apply it properly and all.

Quote:
The case has actually worked out great for putting the amp together: easy to modify, adequate space, no apparent performance compromise, and easy access for getting to and working on all of the parts. For a final version of the amp, I'd like something that looks nicer, but for experimentation, and for anyone who doesn't care too much about the looks, I'd highly recommend it. Besides, it's funny to have what looks like a couple of computers on the floor functioning as amplifiers.

The tower of power! [/B]
Yep, cheap too. Dime a dozen. I put off an amp due to cost and I was factoring in the case with that, it's a big chunk which really can wait. I didn't think of this though. I'm waiting on the day I see someone put an amp in one of those newer modded cases with the see through sides and the lights. It might look sharp and still alot cheaper than a ~500$ designer aluminum job.

Quote:
Originally posted by GregD


One additional note, I wouldn't say that the power seemed to be dropping off, unless it was just at certain frequencies. The bass in all cases was very impressive, and some music played loud sounded great. It's kind of hard to describe what I was hearing, having never heard anything quite like it before. Also, the lack of airiness, or space, to the sound bothered me at least as much.
I can see that happening, XL is inverse of XC right(with frequency that is)? Maybe ~5Khz is the point at which one swamps the other and your power factor goes right out of wack. I hope someone with more of a clue will step in eventually and correct me..... I'm no expert and as you may have seen it is difficult finding this information for a non switching power supply, but I know it exists, Bruno uses power factor as the reason for not going over 20 000uF. His word is good enough for me, but I would like to know more about it as well. I'm sure there is more to it!


Quote:
Originally posted by serengetiplains
Amplifiers can draw very high peak currents which can swamp a transformer's capacity, causing distortion. Any such distortion, of course, is augmented by DC on the AC line. Suffice it to say I see many benefits, including lower DCR, to using so-called over-spec'd transformers.

Personally I disagree with the OEM 70% of calculated transformer sizing. I would think 100% of calculated would be just fine, and statistically speaking you're already 30% over-rated. Anything more is wasted unless it gets you tighter regulation.
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Old 20th January 2005, 06:44 AM   #64
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In my zappulse i use a 2*50 volt 1000VA transformer (and it`s huge physically 5 Kg) and a Predator power supply with 15000uf 80V Chemicon capacitors one for each channel.The thing is when i play rather loud but still so you can listen the modules shortcircuts starts blinking and shut down the amplifier.Unfortunally something happened with the right cannel and it`s still blinking very heavily when you start up the amplifier (sent in return to LC audio waiting for a new module) it also killed the woofer in in mine SL:3:s.As i see it the modules did`nt get enough power could it be the softstart,designed for max 1000VA causing this problem or do i need more capacitors.I don`t think the modules should clip so early with this amount of power supply.Anyone have any suggestion to this problem? I don`t want to kill more Woofers and modules.
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Old 20th January 2005, 08:55 AM   #65
Luke is offline Luke  New Zealand
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Has anyone used regulated supply rails?
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Old 20th January 2005, 03:14 PM   #66
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Hi Ericpeters,
In post 58 (page 6) you mentioned that you have a B&O Ice module.
Have you done a comparison between the Ice and the Zap?
If you have which amp sounds better?
I am trying to decide whether I should build a zap 2.3se or buy the stero Ice amp from Acoustic Reality.


Thanks
Lawrence
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Old 20th January 2005, 07:38 PM   #67
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I just posted this question on the UCD400 thread. I'm wondering how these DIY class D amps compare to commercial offerings, including digital-only varieties like Tact? Anyone?
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Old 20th January 2005, 07:50 PM   #68
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Quote:
Originally posted by lawbadman
Hi Ericpeters,
In post 58 (page 6) you mentioned that you have a B&O Ice module.
Have you done a comparison between the Ice and the Zap?
If you have which amp sounds better?
I am trying to decide whether I should build a zap 2.3se or buy the stero Ice amp from Acoustic Reality.


Thanks
Lawrence

Hard to say, because I am not able to do a fair comparison.
Im the current setup the Zap sounds a lot better than the Ice variant i got. But the Zap has a lot bigger power supply. Also the ICE I got costs me about 1/5th of the zap (including everything). On the other hand the first variant I had of the zap amplifier was a lot worse than the current Ice amp I got.

If you spend enough on good and big enough compenents the zap amp is quite easy to get to really good levels. The average beginning DIY-er will not manage to get there with the Ice modules. But a proffesional amp builder like Acoustic reality or the manufacturers of the H2O amp should be able to do that.

From a module point of view in my opinion the zap builders used better components and put more effort in to qualtiy where B&O is much more focussed on a compromise between manufacturing costs and quality.
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