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Class D Switching Power Amplifiers and Power D/A conversion

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Old 10th September 2004, 04:34 PM   #21
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Thanks for the tip ! yes I do use icepower and like them a lot. maybe they can be improved ! very interesting !!! They would be surface mount i suppose ?

I know the class d preamp thing maybe is a stupid idee, but when I have a "perfect" power amplifier, why not "attck" the preamp.

But from Your answers I get the impression that there is not to much to gain here as the low level stages are already as good as can be. I settle for that for the time beeing.

I must check my ice modules to see if I can find the OP amps and identify them.

Thanks för all the answers !

Have a nice weekend all of You !

/


Quote:
Originally posted by Jan-Peter
TNT,

Didn't you use ICEpower?

As far as I know the ICEpowers run at +12VDC / -12VDC for the Opamps, perhaps you can upgrade the opamp in the inputsection of the ICEpower to an AD8620 or OPA2134.

Perhaps this will make the sound of your setup much better?

As thinking of a Class-D preamp...........

I would definatly go for a passive preamp and increase the input impedance of your amplifier, or a very nice discrete Class-A preamp.


Cheers,

Jan-Peter
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Old 10th September 2004, 04:44 PM   #22
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Quote:
Originally posted by TNT
I know the class d preamp thing maybe is a stupid idee, but when I have a "perfect" power amplifier, why not "attck" the preamp.
Stupid or not, first you have an analog signal, then you modulated it, filter it, then modualte it again and filter it again.

You make PWM conversion twice and each time you degrade the original signal.

If you want some "digital" in your preamp you keep the signal digital all the way from the CD or DVD, manipuilate it in the digital domain then lastly convert it in the power amp.

You can never gain quality when you convert from analog to digital. Anybody why disagress with me?
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Old 10th September 2004, 04:49 PM   #23
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It works for power amps, same number of conversions !

Your argument would also be valid for a class d power amp, still people like them !

(and, it's NOT "digital")

/


Quote:
Originally posted by peranders

Stupid or not, first you have an analog signal, then you modulated it, filter it, then modualte it again and filter it again.

You make PWM conversion twice and each time you degrade the original signal.

If you want some "digital" in your preamp you keep the signal digital all the way from the CD or DVD, manipuilate it in the digital domain then lastly convert it in the power amp.

You can never gain quality when you convert from analog to digital. Anybody why disagress with me?
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Old 10th September 2004, 05:01 PM   #24
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Quote:
It works for power amps, same number of conversions !

Your argument would also be valid for a class d power amp, still people like them !

(and, it's NOT "digital")

TNT,

This is not true!

All selfoscillating Class-D amplifiers like, ICEpower, Mueta, Zappulse, UcD. Are an analog amplifier but working with modulating a PWM signal and demodulating. This has NOTHING to do with D/A or A/D conversion.

Regards,

Jan-Peter

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Old 10th September 2004, 06:15 PM   #25
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Default How did I miss this one first time around........?

Yep, pretty silly idea. Howcum all the Class D amps like Hypex and ICEpower use op-amps in the input stage? Gee, must be a reason. Wonder what it could be????? I believe that the guy in Denmark who makes ICEpower amps also makes a small preamp. (He even posts here sometimes.)

It has 2 op-amps inside.....................

Good luck trying to shove a dual op-amp into the board space for a quad...................

Jocko
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Old 10th September 2004, 06:22 PM   #26
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Jocko,

I can only speak for the UcD.

The bare UcD amplifier stage has only a voltage gain of 4.5 times. When you preamp has an output of 5V rms, you don't need this extra gainstage......

Cheers,

Jan-Peter

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Old 10th September 2004, 11:26 PM   #27
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Ok per-Anders I see what You mean !

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Old 10th September 2004, 11:31 PM   #28
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Ok, OK - I admit it was not a good idee - please don't rub it in ;-)

For the record - I kniow there is no A/D or D/A going on in a class damp - that's what i tried to indicates saying "(and, it's NOT "digital")" !

however You agree, I hope, that some sort on conversion off the representation of the analog signal is going on ?

/




Quote:
Originally posted by Jan-Peter



TNT,

This is not true!

All selfoscillating Class-D amplifiers like, ICEpower, Mueta, Zappulse, UcD. Are an analog amplifier but working with modulating a PWM signal and demodulating. This has NOTHING to do with D/A or A/D conversion.

Regards,

Jan-Peter

www.hypex.nl
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Old 13th September 2004, 11:09 PM   #29
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Default Digital Pre-Amp

Well, with Class-D amplifiecatio already mis-named as digital in the forum name, I guess we could say that class-d or "digital" pre-amps are already on the market. They are called a DSP or digital signal processor. I have been working with the TAS3103 for quite a while and have another design with the AD21161 in the works.

However, it is quite possible to make a class D pre-amp as a class-D power amp like the ICE power or UcD180 are really just an op-amp that happens to have a really high output voltage swing and output current capacity.

On the other hand, the reasons for using class-d do not apply to a pre-amp. These are primarily high efficiency and low heat generation.

However, if someone wanted to do it for the sake of doing it, an analog PWM pre-amp is possible.
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Old 13th September 2004, 11:22 PM   #30
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Default ICE Power

The ICE Power amps usually use the MC33078 and MC33079 dual and quad op-amps. and indeed, they do require a separate ±12V power supply to function.
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