Pure Digital amplifier modules?

I have begun reading up on the subject Class D amplifiers. I have seen links to various Amplifier moduls which seem rather excellent in their own right. I wonder if there are any Pure Digital amplifier modules out there, which completely skip the D-to-A converter and are fed through a digital input?
 
The D2 modules are aim squarely at the consumer audio market – despite the big play about THX ultra approval – this means nothing. The D2 modules have some very impressive front end control software – allows you to implement your own cross-over etc. If I where in the business of manufacturing higher-end “all in one” home cinema systems I would be taking a VERY series look at D2.

D2 modules are a good fit for the China market where true R&D skills are very rare, and time to market is critical. I just don’t understand the crazy politics that meant D2 modules are manufactured in India – the markets in China and so is the best and lowest price manufacturing.

D2 do what YOU know you should do – manufacture your modules in China!

The DAX 1 is designed for a completely different market – the best sound no matter what the component cost.

The ECL logic used for the reference PWM nodes cost almost 7 times the cost of a complete 100W + 100W D2 module alone.

If you’ve ever heard the difference that changing audio interconnects and coupling capacitors can make (and there compromises) – then you will understand the greatest advantage a pure digital amplifier has – the “simplest” and most direct replay path.

John
 
JohnW said:
The D2 modules are aim squarely at the consumer audio market – despite the big play about THX ultra approval – this means nothing. The D2 modules have some very impressive front end control software – allows you to implement your own cross-over etc. If I where in the business of manufacturing higher-end “all in one” home cinema systems I would be taking a VERY series look at D2.

D2 modules are a good fit for the China market where true R&D skills are very rare, and time to market is critical. I just don’t understand the crazy politics that meant D2 modules are manufactured in India – the markets in China and so is the best and lowest price manufacturing.

D2 do what YOU know you should do – manufacture your modules in China!

The DAX 1 is designed for a completely different market – the best sound no matter what the component cost.

The ECL logic used for the reference PWM nodes cost almost 7 times the cost of a complete 100W + 100W D2 module alone.

If you’ve ever heard the difference that changing audio interconnects and coupling capacitors can make (and there compromises) – then you will understand the greatest advantage a pure digital amplifier has – the “simplest” and most direct replay path.

John

Hi John,
I'm intrigued! So a Stereo amp would cost around USD 899 when this project is finished? If the amplifier is as good as you say it is, it seems to be very good value.
If I were to use a digital crossover in an active design in conjunction with your amp and would have something rather special right?
 
The D2 modules are VERY cheap...but currently only available as either a dev kit or in OEM quantities. I keep pinging one of their sales guys and he keeps telling me they want to sell to the boutique market or even possibly one-off quantities...but no word yet on firm plans to do so.

The DS125 is attractive because it could implement a complete 3 or 4 way speaker complete with crossovers. A pair of modules comes in under the cost of a DCX2496 alone!
 
tiroth said:
The D2 modules are VERY cheap...but currently only available as either a dev kit or in OEM quantities. I keep pinging one of their sales guys and he keeps telling me they want to sell to the boutique market or even possibly one-off quantities...but no word yet on firm plans to do so.

The DS125 is attractive because it could implement a complete 3 or 4 way speaker complete with crossovers. A pair of modules comes in under the cost of a DCX2496 alone!

Even more appealing is the adaptive digital input, no upsampling to 96kHz when using a normal Cd-Player.
 
tiroth said:
The D2 modules are VERY cheap...but currently only available as either a dev kit or in OEM quantities. I keep pinging one of their sales guys and he keeps telling me they want to sell to the boutique market or even possibly one-off quantities...but no word yet on firm plans to do so.

The DS125 is attractive because it could implement a complete 3 or 4 way speaker complete with crossovers. A pair of modules comes in under the cost of a DCX2496 alone!

Ok, maybe a silly question. With digital inputs into each speaker, how do you split the digital signal from the Cd-Player, as the S/PDIF is just one connector?
 
tiroth said:
There are a bunch of options...you could add a second transmitter to the CDP or you could daisy-chain one speaker to the next.

The XS125 include a built-in mixer so that you can simply pan the appropriate channel to the proper amps.

Using a daisy chain seems like a rather untidy option, are there any special products you have in mind for the second transmitter?

I would also like to use some analog sources such as a vinyl player and an FM radio. Preferably I would be able to use a volume control as well. And to be a real pain Digital room correction wouldn't be too bad either. A product such as the Behringer DEQ2496 would allow me to get all these things (not too sure about the volume though). I can use the SPDIF output on the Behringer and connect directly to the speakers.
Are there any products out there I should checkout?

The problem with the Behringer is that it uses upsampling on the Cd signal.
Tact RCS 2.0 might also be an alternative (it also upsamples the signal).
 
JohnW said:
If you’ve ever heard the difference that changing audio interconnects and coupling capacitors can make (and there compromises) – then you will understand the greatest advantage a pure digital amplifier has – the “simplest” and most direct replay path.

I still fail to see the point in claiming a "pure digital amplifier" while it is perfectly obvious that the PWM reference node constitutes a DAC and that the subsequent power stage has an analogue control loop around it to follow the analogue content of the PWM reference node albeit in superficial synchronicity with the DAC.

Precisely given the excellent work you did in the analogue design of this amplifier (knowing full well that actual "fully digital amplifiers" are pretty hopeless), it would seem better to capitalise on this.
 
Hi Bruno,

I can see by reading your old post you are very sensitive about the term “Digital Amplifier”. Now everybody’s still entitled to there own opinions, despite the direction this world seems to be heading these days.

In my post I was referring to a non Error correction output stage – however I personally don’t consider that the addition of an error correction scheme in a “Digital Amplifier” makes it analogue – again it very much depends on your own personal interpretation.

I consider my amplifiers “digital” because the digital PWM signal from the modulator is fed directly to the output stage – this output stage incorporates error correction, 1 & 0 In, 1 & 0 Out….. my own interpretation makes that’s plainly “Digital”.

Using the words of Bob Carver who was renowned for developing some very far-out terms for “His” technologies “I developed it, so I can call it what I want…..”

Your correct in saying that the PWM reference node is a “DAC” – but don’t mislead – the output of this “DAC” is PWM - digital 1 & 0’s, only with an incredibly accurate “energy” content. The addition of a LPF at this Node allows recovery of the analogue audio data – the addition of an output stage to this PWM Reference Node with or without Error Correction allows extra voltage and current gain.

At the end of the day – the only factor that is important is the Audio quality – to be able to control and optimize the “entire” replay chain apart from the speakers, offers some very important benefits – despite my digital amplifier being complex – it has a short & simple audio path.

And finally using something along your very own words – “you would think that the low level signal path would be easy to get correct – however in reality this is where most of the distortion and noise is generated” – in reference to 99% of "Mass Market" audio designs.

Lets make music :)

John
 

bcarso

diyAudio Member RIP
2005-05-03 4:09 am
Canoga Park, California
John, does your error correction technique have any effect on what is typically the highish output Z of "pure digital" amplifiers, due to the absence of global feedback?

Comment on an earlier portion of this thread: Harman/Kardon has been shipping some A/V receivers with D2 Audio modules inside. There have been mixed reviews of the sonics. It is interesting that fully 3/4 of the internal volume of the receiver is taken up by the D2 module and a very elaborate and costly power supply.
 
D2 Modules

I am designing a product using the D2 XS100 8 channel module. I have also been to D2's offices in Austin, Texas and even had dinner with several of the top executives. The D2 modules are as pure digital as you are ever going to see. Other than feeding the input of the A/D converters, there is no analog circitry in them.

They offer S/PDIF input as well as I2S to feed from your own A/D converters in case you don't like theirs. The output stage of digital PWM in that the circuitry convcerts the digital input stream directly to a PWM output signal. There are NO analog comparitors the way there are in ICE and Hypex modules. Because there is no feedback loopon the output stage, the power supply rejection ratio is low, only what you get from having an H-Bridge output. Hence we operate the module with a fully regulater switchmode power supply. We buy a PFC corrected, Taiwan made, 325W 48V supply from a company called Skynet.

No matter what some may say, the D2 modules meet the definition of a pully digital amplifier while the ICE Power and many others are actually Analog PWM amplifiers.

Actually, the ICE Power people get a bit bent out of shape when you call their amplifiers "digital" as I found out once at their demo room in the Las Vegas Hilton a couple years ago at the CES.

The sound quality of the D2Modules was originally a little below my acceptable limites when I first saw them three years ago but last year, they came up to quite acceptable high fidelity standards. The sound is somewhat different than an analog PWM amp or a class AB amp. Different. Not inferior. Some will like the crisp pure digital sound and some won't.

However, the team at D2 are dedicated to providing the finest sound quality they can produce with pure digital technology. They have designed their own DSP chips dedicated to this purpose. The only thing I cannot speak about is the availability to the DIY market. If there are people interested, I could ask.