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Class D Switching Power Amplifiers and Power D/A conversion

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Old 21st July 2010, 02:49 AM   #481
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Quote:
Originally Posted by bambadoo View Post
Just a couple of techical questions.
1. Since this board already has a bridge rectifier and if we want to use a different psu - is it possible to solder the rectified voltage Vdc from (for instance) batteries directly to the legs on cap C48? - if so - what is the limit of Vdc here? ( I assume it is approx 31Vdc ?)
If we connect Vdc to the terminals would it not be rectified 2 times? I am not sure how that works..

2. Is the input caps really necessary?. Lets say we have output caps on the dac with value 3.3uf and relative short signal cables.
Is it then possible to solder the input signal directly to R4 and R1? (Assuming to use the board as a power amp) ?
You can connect DC directly to the 4700uf cap. Voltage limits will be 1V less.

I connected my dac directly to the amp without any caps first, and it worked fine, but later I connected two 1uf POI caps. And the sound is still amazing, didnt experiment too much going back and forth with cap/no cap there, it is still so much better with the cap then through the dac's output stage.
If you removed the vol pot on the board, you could maybe do with only one set of caps, but Hifimediy said something about that two voltages could sometimes cancel out each other...

Quote:
theoretically you can also measure the vibrations in the air which also lead in heat. This is usually notified in dB (you said it yet also). But current measurements are easier to handle than different sonic waves out from the speakers. For example you supply the speaker with 5 W amp power. If your speaker produces 4 W heat that means to me 1 W is converted in sonic or air movement, vibrations - call it as you like. That´s also heat/energy.

So I could also say that an amp produces current and not watt...
Could I go out in the street and measure Watt from surroundings?
I don't quite follow your thoughts about the speakers heat generation. Normally speakers loudness output is measured in dB produced for 1 Watt, for example 90dB/1W. (althought this measurment can be misleading because it is not defined the other surrounding parameters like room size ..)

Every speaker produce heat, some have complicated crossovers which will use lots of the signal before it gets to the speaker, and some speakers don't have a crossover.
i guess you could calculate or measure how many Watts are wasted in the crossover. But in the speaker ? If you had a "perfect" speaker which didn't produce any heat, how many dB would you get from 1W?
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Old 21st July 2010, 02:56 AM   #482
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Quote:
Originally Posted by Don Jerry View Post
What about the uH value on both the boards?
I assume coils are 10uH but I ask you.
And what changes in audio listening using a lower (or higher) uH value?
How to adeguate the output cap values if using other coils (lower or higher uH)?
Thanks!!
We use 11uH on V1 and V2 boards now. Please refer to the attach file to calculate the values. Co=0.47uF on V2, and 0.33uF on V1.
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Old 21st July 2010, 03:06 AM   #483
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I have to remind that the relay will draw some current too.
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Old 21st July 2010, 03:46 AM   #484
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I have just measured the current on v2 board and read 0.15 (150ma) on idle.
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Old 21st July 2010, 05:41 AM   #485
teamacc is offline teamacc  Netherlands
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Schematics in manual are incorrect: C1 and C2 are not onboard. There is room for them, but they are not installed.

Without C1 and 2, you can desolder the pot and directly connect dac out without caps from the dac side, or without caps on the amp side.

you will need to have caps once in the line though..

about the canceling out of the bias: it might be that some dacs have 2.5v bias on the output, but if the tc2000 bias is higher/lower, problems might occur (even from 10mV differences). Would not advise anyone to try that.
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Old 21st July 2010, 07:45 AM   #486
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Quote:
Originally Posted by Nisbeth View Post
According to the datasheet the "supply current" (by which I think they mean Idle current) is 60 mA, so the figure sounds about right to me with two channels running.
/U.
With 110mA @ 30V you're at only 3W... raising up the volume the current consumption have necessarily to increase.
Also from idle to the max voulme the current consumption can't be always the same.
My 2 cents...
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Old 21st July 2010, 07:57 AM   #487
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I didn't raise the volume that much, maybe only 2*0,5W outputlevel..

But there has to be someone on this forum that can confirm if I have done it the right way from my description?
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Old 21st July 2010, 08:24 AM   #488
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Yes you did it right.
You've to connect the multimeter in series to "read" the current.
You could also connect it to the negative rail instead of the positive rail, it's the same.
Bye!
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Old 21st July 2010, 08:27 AM   #489
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Thanks!
I'll try connecting my 87dB/W speakers later so I can raise the volume a bit more to see how much it draws then.
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Old 21st July 2010, 09:31 AM   #490
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Quote:
Originally Posted by teamacc View Post
Schematics in manual are incorrect: C1 and C2 are not onboard. There is room for them, but they are not installed.

Without C1 and 2, you can desolder the pot and directly connect dac out without caps from the dac side, or without caps on the amp side.

you will need to have caps once in the line though..

about the canceling out of the bias: it might be that some dacs have 2.5v bias on the output, but if the tc2000 bias is higher/lower, problems might occur (even from 10mV differences). Would not advise anyone to try that.
These two caps are 100pF normally. As I test, they are used to prevent noise when plug-in(or plug-out) the input cable duiring amp working. But it's ok to unuse them if there is a pot. Unsolder these caps are better for sound quality.
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