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Class D Amps


rodacademy
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[quote name='Mr. Foxen' timestamp='1378332082' post='2198914']
The bit that makes class D not digital is the lack of an analogue to digital conversion step.
[/quote]

Analogue comes in and is converted to a 2 state (On/Off) signal at the output transistors, albeit PWM. Filtering/smoothing and frequency response of the speaker then converts this PWM signal to an approximation of the original analogue signal.

The output of the amplifier as whole is analogue (I've never argued otherwise ). The output devices are working digitally.

I guess it comes down to whether you call PWM digital because its on/off, or analogue because ?????.

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[quote name='ead' timestamp='1378330502' post='2198877']
OK I think I understand where you are confusing analogue and digital. The control aspect of class D amps are often driven my MOSFETs which act like switches (or indeed by digital controllers), however these components are controlling an analogue waveform and you have to consider the difference between analogue and digital in terms of how they are quantised. The amps are not digital in the sense that they do not deal with discrete voltage levels (steps).
[/quote]

I refer the honourable gentleman to my previous answer. Except to add that they do deal with discrete voltage levels. Off and on!!!

Typed on my trusty analogue computer.

:)[size=4] [/size] :) :lol:[size=4] [/size] :lol: :P :P

Lot of smilies because it's really not that important.

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[quote name='Mr. Foxen' timestamp='1378334370' post='2198969']
Its analogue because the pulses can be any width. And a filter isn't a digital to analogue converter.
[/quote]

Any width that's a multiple of the controlling DSP clock (might be thinking more in terms of servo amplifiers here), and the filter takes a digital signal (all right, one bit resolution) and generates a true analogue value. Sound like an D to A process to me, if not in the conventional sense.

So is a bit in my PC memory, that can be set to 0 or 1 for any length of time, an analogue device?
According some definitions here the only thing that's digital on my computer is the sound card, because it has A/D and D/A converters.!

Please don't think I'm taking this too seriously by the way. It's just a bit of banter you know.

Irrespective of what we call them here's a link to an interesting, not too technical, article on how they work, including some of their short-comings.

[url="http://www.eetimes.com/document.asp?doc_id=1274757"]http://www.eetimes.com/document.asp?doc_id=1274757[/url]

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Still loving my SHTL9 - had it since 2009 and it's still my favourite sounding amp I've ever owned, I've recently acquired a TC BH250 which is great for a back up/practice/small gig thing - but the Genz ST9 is so warm by comparison - as it has a tube in it as well. Sounds awesome with all of my basses... light as hell and wonderful for gigging...

Edited by urb
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[quote name='Count Bassy' timestamp='1378376177' post='2199253']
Any width that's a multiple of the controlling DSP clock (might be thinking more in terms of servo amplifiers here), and the filter takes a digital signal (all right, one bit resolution) and generates a true analogue value. Sound like an D to A process to me, if not in the conventional sense.

So is a bit in my PC memory, that can be set to 0 or 1 for any length of time, an analogue device?
According some definitions here the only thing that's digital on my computer is the sound card, because it has A/D and D/A converters.!
[/quote]

All devices are analogue, because digital functions only really happen in theory, as a data process, thus need the conversion step, its numbers not a real thing. Analogue device, digital function. A wind up clock moves a set distance each tick, still analogue, there is no digital data processing, I could rig up a mechanical device with a digital output, in the sense it could have the 88:88 style display, just working of moving parts, it would be analogue, but that time output would be digital to read out, half past four in the afternoon would be 16:30, you see those digits, a digital output, and convert it to half past four, that is the conversion step.

There is no digital signal, so the filter is a filter not a converter. At no point is the signal been rendered into digital data form. DSP is a separate thing.

Edited by Mr. Foxen
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[quote name='Badass' timestamp='1378380666' post='2199343']
Cheers Jack, checking out Dawsons now.

.....After checking I see no Genz Benz there. Anyone know who stocks them in the UK?
[/quote]

Check out bassdirect, Mark is a top guy too:

http://www.bassdirect.co.uk/bass_guitar_specialists/Home.html

Cheers

Thebassman

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