oon_the_kid said:
You've just described the Zetex DDFA...
http://www.zetex.com/audio/audio06.asp
Their latest measured results show around 120dB dynamic range at the speaker outputs, which rivals the best standalone DACs (which then have added noise and distortion from power amplifier stages etc)
http://www.zetex.com/audio/audio06_4.asp
Unfortunately the chips (and any design support) are only available to OEMs as far as I'm aware :-(
http://www.zetex.com/audio/audio06_2.asp
Ian
P.S. Disclosure -- I don't work for Zetex, but I did design the ZXCZM800 clock and PWM modulator output stages which would limit the dynamic range if they had jitter of more than a few picoseconds
Workhorse said:I think yes, but i found T-amps attract many guys except me.
And many of those guys don't have your knowledge or experience in regards to class-d; including myself. Anything more than a class-d "chipamp" is beyond my reach. Does that mean I have no right to post here and discuss what little I do understand (or at least try to), even if the subject of the discussion happens to be a non-UcD design?
No one is stopping you or anyone else from discussing other designs, and you are free to skip any lame Tripath threads or posts.
Maybe the class-d elites here should start their own forum where they are free to heckle and ban people with less knowledge.
theAnonymous1 said:
And many of those guys don't have your knowledge or experience in regards to class-d; including myself. Anything more than a class-d "chipamp" is beyond my reach. Does that mean I have no right to post here and discuss what little I do understand (or at least try to), even if the subject of the discussion happens to be a non-UcD design?
No one is stopping you or anyone else from discussing other designs, and you are free to skip any lame Tripath threads or posts.
Maybe the class-d elites here should start their own forum where they are free to heckle and ban people with less knowledge.
Dude, dont hype the statement, i never said that T-amp lovers should be banned or not allowed to post, i was just saying that this forum is comprised more of T-amp Diyers, thats all........
I still regard myself as a learner in Class-D field, not an elite..........but i love to take part in discussions involving non-T-amps & non-UCD amps...
bwaslo said:
Class D is analogue if you start with an analogue signal and then make a PWM via triangle+comparator or by hysteresis selfresonance or by UCD. Because in all this constellations you start with analogue and code the information in a PWM which allows any duty cycle values - without quantization steps. The information remains 100% analogue.
If you go through a signal processor and generate a digitalized PWM with quantization steps for your power switches, then I would tend to call it digital - even if there is usually something like a passive power DAC in the end of the chain, formed by the output filter and the speaker.
What is better? Good question.
But I would also guess that digital-analogue-digital-analogue is not straight forward and might cause more damage to the signal than a chain with less conversions.
If we compare:
Digital-analogue and staying analogue with traditional class D designs.
Versus
Digital-into a digital class D and convert to analogue in the passive end stage....
Then I would guess it will end up in the question of how good the chosen digital coding & filtering + D-A conversion of each system and output filter are fitting together. I am sure you can mess up both ways.
In fact most of our music, which we hear, is already digitzied with quantization steps and quite poor sampling rate.... And with respect to the catastrophic appearing CD standard, I am again and again wondering how well our ears do accept it.
Yup, this is precisely what I am looking for. Unfortunately, only available to OEM, I guess. I saw the ad for inclusion in a NAD. Maybe we might see it in a NAD soon. I think the true genius of tripath, is the usage of a digital processor to achieve the accurate switching, which means it probably a very high speed PID, this tends to reduce the overshoot and instabilities etc normally associated with analogue.
Well Ian, if you find out which other products uses it, maybe we can get hold of one and modify it....
Well the Apogee DDX chips look interesting.
The power chips can even be driven by Tripath controllers, if you want analog input. Otherwise the Apogee DDX control chips sure have a ton of features.
It's all going to end up as variable duty square wave that gets low pass filtered on its way to the loudspeaker - but how you get to that square wave is the interesting part. The digital path up to that point "should" have some advantages.
But of course you have to deal wit the volume control, for better of for worse.
The power chips can even be driven by Tripath controllers, if you want analog input. Otherwise the Apogee DDX control chips sure have a ton of features.
It's all going to end up as variable duty square wave that gets low pass filtered on its way to the loudspeaker - but how you get to that square wave is the interesting part. The digital path up to that point "should" have some advantages.
But of course you have to deal wit the volume control, for better of for worse.
oon_the_kid said:
The digital PWM modulation processor is clocked at over 100MHz in the DDFA, including the error digitiser in the feedback path -- this is how Zetex get very fast and accurate correction of errors (distortion) because the total delay round the digital correction loop is small (<20ns), so the feedback loop can have very wide bandwidth and high gain without any (analogue) stability issues.
NAD are presumably a flagship DDFA user to gain market acceptance of DDFA as a high-quality class-D amplifier, though I guess they're not exactly small volume. I believe Zetex are primarily targeting the high-volume Far East audio manufacturers in markets like home cinema, because this is where the big production volumes are and Zetex want to sell lots of chips (which would make us happy too since we manufacture them
So I guess whatever product NAD come out with is likely to be the best candidate for class D/audiophile modding -- unless you want to try and reverse engineer a multichannel Chinese-sourced home cinema box...
Ian
The nice part about tripath to diy is the simplicity of usage. One can easily buy a kit and modify from there. There are no programing needed, no support chips and just a normal analogue input.
The unfortunate thing, I believeabout fully digital system is, quite frequently they require you to have some sort of support chips to generate the volume control, remember the last setting of the volume control
, booting up the system etc. There must be a reason for them to have so many legs.... So I would not probably do it unless there is a full kit or modify a preexisting set., since i know nuts about digital....Oon
oon_the_kid said:
The nice part about tripath to diy is the simplicity of usage. One can easily buy a kit and modify from there. There are no programing needed, no support chips and just a normal analogue input.
The unfortunate thing, I believeabout fully digital system is, quite frequently they require you to have some sort of support chips to generate the volume control, remember the last setting of the volume control
Oon
Well the reason I bring this up is that I thought the question was about fully digital amps and as far as i understand this can't be said for the tripath technology.
I have been using a TacT/Lyngdorf Millennium with great pleasure for quite a few years. I also realise that this of course not a kit amp but I remember very explicit data sheets and application notes from TI with designs for systems.
There seems to an awful lot of possibilities in the TAS5000 series, but perhaps it is more aimed at high volume OEMs.
Yup, I agree the Tripath is not fully digital, and I think the texas chip would probably be good. The only thing is, how are we going to DIY it. Afterall . This is the DIY forum, not so much the audio OEM designer forum, so it is natural that we tend to talk about things related to what we can build wth our hands...
But I wish somebody would sell a kit or a built board, so we can modify it from there...
Oon
. This is the DIY forum, not so much the audio OEM designer forum, so it is natural that we tend to talk about things related to what we can build wth our hands...But I wish somebody would sell a kit or a built board, so we can modify it from there...
Oon
Steven said:
There certainly seem to be similarities between the D2Audio and Zetex approaches, though the detailed circuits are undoubtedly different.
However it's possible that I can get information about the Zetex chips (which might mean there's some chance of DIYers getting hold of them at some point) because I know the Zetex guys; I doubt that anyone will do this for the D2Audio chips...
Ian
P.S. No promises, but at least more than zero chance
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