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Class D Switching Power Amplifiers and Power D/A conversion

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Old 6th January 2007, 10:06 AM   #1
Avi28 is offline Avi28  Israel
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Default newbie,Where to start?

Hi all- New here ,

Well,After hearing some class d amp(CI Audio d-200)
I decided to go for it and buy but its quice expansive here so I understand that if i choose the right components and with care assemble(*) it ,I would be happy with results.
now for the *...
assemble- I think with the right instructions i can do good job,I dont know much about electronics but i have technical sense for thing,

I search for the site alot but can't find something to start with.

I heard the CI Audio d-200 mono blocks and i want to build something like that-It can be DualMono and assemble in one unit,that mean Hypex right?
UcD400*2?
what power sup is good?

Can anybody with lil patience pleasssssssse write what i need to order?

I need power( Sonus Faber ,86-87Db) and here in israel the electricity runs 220VAC.
can anybody make a list of things ,After I get allthe pasrts I believe its ain't that hard to assemble it all (At least that what Hypex saying).

thanx a lot .
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Old 6th January 2007, 03:55 PM   #2
Avi28 is offline Avi28  Israel
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Default anybody ?

Come on people.I read here msgs from the pro.
can anybody please refer my q?
Thanx a lot
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Old 6th January 2007, 11:16 PM   #3
RX5 is offline RX5  Philippines
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what are you searching for, an AMP or its power supply?
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Old 7th January 2007, 02:31 AM   #4
novec is offline novec  Norway
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I think he's asking for what we should have compiled a long time ago; a beginner's guide to DIY class D, from choosing an amp module to designing a fitting power supply. That'll be the day... But I'll give it a try, so bear with me (summary at the end):

A cheap, and therefore very popular way to go is Tripath, but considering you need some serious power, that's pretty much out of the question. Your best bets are the different flavours of UcD, L C Audio ZAPpulse (2.3SE or 700XE) or NewClassD by the same designer, Lars Claussen. The jury's still out on which are the best, and they both have their leagues of devoted fans, but they're all good amps.

Regardless of module, good class D sound is very dependent on a good power supply, because what the amp basically does is switching the power supply voltage on and off directly to the speakers, unfiltered. Both quality and quantity is important here - although class D is highly efficient, and a stereo amp may play nicely with a single 400 VA transformer, more enthusiastic builders have discarded their dual 500 VA trafos for dual 1000 VA and reported significant improvements. Go as big as you can afford, but don't blow your budget on it, there's more to come.

Dual transformers brings us to another point; unless you're cramped for money and/or space, go for a dual mono setup, meaning a completely separate power supply for each channel. It greatly improves channel separation and sound staging, and is well worth the investment.

There are two main ways of connecting a basic power supply: Center tap with one rectifier bridge, and separate windings with two bridges. The only reason to go for the former is to save a couple of bucks on the extra rectifier bridge, so for class D applications we'll discard it without further explanation. Your transformer most likely has six wires - one pair is the primary, going to your wall outlet, the other two pairs are for two identical secondary windings. Put one rectifier bridge on each of the secondary windings, connect the positive end of the first bridge to the negative end of the other, and voila!, you have positive and negative voltages with a stable ground in the middle.

Now comes the art: Filtering an buffering. First and foremost, that means connecting one or more massive capacitors on each voltage rail (across positive and ground, and across ground and negative), which have the tasks of filtering out much of the AC voltage still present after the rectifier diodes, and to act as a buffer for those demanding bass punches that are too quick for the transformer to keep up with. As a general guideline, use high quality capacitors with a voltage rating of at least 1.5 times your transformer voltage, and no less than 10 000 uF per rail - double or more is highly preferable. There are many makes and models, and choosing the right one does make a difference. Four pole capacitors, like the BNC T-Net caps found in Hypex' higher end power supplies, and the (in my opinion) even better Jensen 4-pole caps, have proven very beneficial for class D applications, but more affordable 2-pole solutions will also give you great sound. I'm not going to recommend any make or model in particular here, there are plenty of contradicting posts on that topic on these forums...

In addition to the main caps, I'll just briefly mention some other filtering tricks. One is to add a 22 nF MKP cap across each diode on the rectifier bridges. Another is to put a 100 nF directly across the secondary windings. Yet another is a 100 nF MKP and a 100 uF electrolytic across each voltage rail as close to the amp as possible (some modules have this incorporated). Then there's the snubber, which I won't even begin to explain here... The beauty of these tricks is that you can totally ignore them while you're a noob (which we all have been, so don't be ashamed!), and add them when you get a better understanding of things.

When it comes to general layout, follow the logical route. Keep your toroids in the front of your case, followed by the rectifiers, main caps and finally your amps at the back. If you try to keep all these components close to the case walls, you can run the main AC cable through the middle without any interference. On the amplifier end, try to keep the signal input wire and loudspeaker output wires well separated.

Noob checklist
1. Get a good quality amp module, like ZAP 2.3SE/700XE, NewClassD or UcD.
2. Get two (for dual mono) toroidal transformers, with a VA rating of at least the wattage you're aming for. There is no such thing as overkill here, as long as your budget can hold it.
3. Get four bridge rectifiers (one for each voltage rail), preferably made up of separate fast recovery/soft recovery diodes of very generous amp ratings.
4. Be prepared to spend quite a bit of money on high quality main capacitors, be it 4-poles (BNC T-Net or Jensen) or regular 2-poles, with a voltage rating of at least 1.5 times your trafo voltage and totalling from 10000 to 50000 uF per rail.
5. Keep the wiring between your main caps and your amp short! Even with thick, high quality wires, there is an audible difference between 5-10 cm and 25cm. And it's a very easy step to do right.
6. Don't worry about the extra filtering on your first build, but leave a little room for improvement as you get wizer.
7. Use high-end internal cabling - given the short distances, it's not going to brake your budget, but it is going to make a serious difference.
8. Keep your signal cables and power cables as far apart as practically possible.

My final advice is to get going as soon as possible. Be sure to get high quality components, but don't spend weeks and months trying to read your way to the ultimate amplifier, when you can build a very good one and enjoy its sound within a week or two. DIY is all about improvement, and as long as you leave some room for it, your fully functional first attempt may evolve into something truly impressive as you get the hang of it.
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Old 7th January 2007, 03:00 AM   #5
Nanook is offline Nanook  Canada
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Default maybe where I did...

I started with a 41Hz amp 6 Basic. I added a 12V smps for a laptop computer, added some binding posts and some decent RCA inputs. Feeding it through a little passive preamp... it sounds quite good. I have Castle Durham 900s which are 6 ohm speakers, but not real efficient either and have never felt like I was pushing the amp or the speakers too hard. Find a suitable enclosure and you'r in business.

No fuss, no muss.

If you want more power 41 HZ and others (UCD etc) sell kits with more output, but subsequently will end up costing you more for dual mono construction---mainly the power supplies.

I have to believe that surplus 220V laptop power supplies would be available in Israel
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Old 7th January 2007, 04:43 AM   #6
RX5 is offline RX5  Philippines
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novec,

well said..

I guess the mods should MAKE a sticky thread as reference so others wont be RE-posting over and over the same questions...
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Old 7th January 2007, 11:50 AM   #7
Avi28 is offline Avi28  Israel
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Default Novec ...

I want to thanks for ur answer,I really appreciate it.
U wrote a lot of new info (New for me I guess..)
I have to print it and read it-lot of things to understand and consider.
My budget stand on something like 1300$ (excluding the case)
For what I read the UcD400 seem to be nice moudle for my needs.
About power sup and the other thing:
Can U(or anybody) write please what would be smart buy,consdering the priority of the importance of the componets ?
I guess a lot of newbies like me would set the budget around the 1000-1300$.
Thanx again !!!

P.Slease consider that the voltage here is 220VAC
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Old 7th January 2007, 01:01 PM   #8
RX5 is offline RX5  Philippines
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if you consider ucd, buy ps for ucd...like the one they sell in thier site...

or build your own ps..its not that hard...
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Old 7th January 2007, 07:26 PM   #9
Avi28 is offline Avi28  Israel
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Default :(

There is so much new companies and moudle that i cant find nothing right.
pleaseeeeeeeeeeee some1 just make my life easier and wrote good componets based on UcD400 with the 1000-1200 $ budget??????????
I know its much more deeper than that,But i think i would learn much more if the first will be perfectly guide by people like here,I see all msgs ended like "Its much more than write u a list of good things".I want class d amp and I choose as DIY cause ecnomic reason.
hopefully u understand me
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Old 8th January 2007, 12:35 AM   #10
RX5 is offline RX5  Philippines
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Avi28,

we all are HERE to learn... its best you google it 1st, and ask for questions later... novec has added his part, you should too...

A Forum is a place to learn(and have enemies ), does not work by "I need this-n-that" ..... but perhaps "I found this certain site/product interesting, any comments?"....

if you continue that, you WILL be ignored by some here... take your time... do SOME reading(on the threads)....or search info on the web..

Regards,
Raff
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