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Class D Switching Power Amplifiers and Power D/A conversion

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Old 20th July 2009, 03:37 PM   #21
Pano is offline Pano  United States
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I have a few evaluation boards with various DDX controller chips. I like them a lot.
Neil D probably knows these chips the best, in fact he has a couple of my eval boards that he is doing surgery on.

The nice thing about the these chips is that they take an I2S signal in and give you the PWM out. So you don't need no stinkin' DAC or preamp. Just digital. And that has some definite sonic advantages.

What I like about them:
  1. Very high S/N ratio. You just don't hear noise. They are clean, clean, clean. As there are no analog stages before the DDX chip, you don't have the buzzes, hums, hiss, etc. that analog stages can bring. What you will hear is a lot of noise IN the original recordings. Maybe a little too reviling!
  2. The amp can be set to shut off when it receives a string of zeros. So it auto-mutes between tracks or during pause/stop. Dead silence. That's nice.
  3. Detail is rather amazing. Going straight from the digital signal to the PWM signal seems to mean a lot less error. Detail goes way up. As good as a very expensive, well built analog signal chain for a lot less money and fewer parts.
  4. The quiet and detail really bring out a lot of the music you didn't know whas there.

What I don't like about them
  1. I2S is the standard input so you need a receiver chip to go from spdif or toslink. But so do most DAC chips.
  2. If the receiver chip is not well implemented it will pass the jitter along to the DDX. This sounds awful. If you don't think interconnects make a difference, just try a few different ones with these eval boards. Yikes! Getting the right cable is a must. Reclocking would be even better.
  3. My eval boards sound a bit "thin". Don't know if that's the chip, or just the way the board is laid out and the components used. I did mod a few and got better results, but no quite as full sounding as I'd like. Need to dig into that more.

I do think this type of digital to PWM amp is the wave of the future. Done right, the results can be quite surprising. And as Neil says, there is the possibility of DSP EQ and crossovers right there in the amp. Pretty cool.
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Old 20th July 2009, 03:53 PM   #22
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Quote:
Originally posted by Havoc08
Nice... thank you panda.
Since I don't want a pc turned on to control the amp and don't have the skills to program something standalone like the spherex set. I'll have to pass on this one.

The Tripath amps have better specs, are easier to input select, volume control etc. as they are analogue, but unfortunately doesn't feature those nice advanced settings like xover, pwm timing etc.

I'd better stick to the T-amps

Havoc08,


I also think that it is too complicated. My next plan is TA-2022.
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Old 20th July 2009, 08:34 PM   #23
Havoc08 is offline Havoc08  Denmark
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@panda
Yup...
When skillz are lacking, easier projects must be found to dampen the hifi diy cravings. I made quite a few amp32, amp9, amp9b and amp 10 from 41hz and they sound fantastic
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Old 20th July 2009, 11:51 PM   #24
hoka is offline hoka  Netherlands
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I'm still in for one of these but I need help getting one!

I got a message from cac liu but when I mail him back all I get is chinese again

Panda do you want to sell me yours?
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Old 21st July 2009, 12:32 AM   #25
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Quote:
Originally posted by panomaniac
And as Neil says, there is the possibility of DSP EQ and crossovers right there in the amp. Pretty cool.
The amp has some built-in "auto" modes that provide a 5-band Equalizer and some preset EQ settings. The interface that I've got will let you play with them. But if you have a way of calculating the biquad coefficients yourself, the amp becomes very interesting. There is a briefing that I gave at DCDIY this past weekend that describes some of the capabilities:

DIY Digital Crossovers

Michael--the second amp is almost done, and I'll get it to you shortly. I had to build another controller board, but that's done and working, and I actually fired it up last night. I just have some final wiring and assembly to do. I'll need to add a little more code since yours uses two rotary encoders instead of one, but that won't take long. The picture shows the first one I made. Yours isn't as pretty.

Click the image to open in full size.
Click the image to open in full size.
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Old 21st July 2009, 02:47 AM   #26
Pano is offline Pano  United States
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Cool. Looking forward to it!
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Old 24th July 2009, 06:41 PM   #27
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Quote:
Originally posted by hoka
I'm still in for one of these but I need help getting one!

I got a message from cac liu but when I mail him back all I get is chinese again

Panda do you want to sell me yours?

Good news, Hlly will lauch full Digital amp end of this year. See below.

http://www.diyaudio.com/forums/showt...76#post1887476
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Old 27th July 2009, 11:50 AM   #28
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Dear wwenze,

Isn't it obvious.... Malaysian PR...

We ought to get together one of these days...

Oon
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Old 27th July 2009, 12:23 PM   #29
wwenze is offline wwenze  Singapore
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It would be interesting to see how a DDX fares against a Tripath + a good DAC for the same price.
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Old 27th July 2009, 09:07 PM   #30
goodjun is offline goodjun  China
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it is good
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