Minimalist DAC: is this possible?

beppe61

Member
2005-02-08 11:00 am
torino
Dear Sirs,

I read that a DSD does not need necessarily a DAC to be amplified.:eek:
What is needed is just a low-pass filter (that can be analog of course).:rolleyes:
So, my question is: is it possible to build a minimalist DAC based only on a PCM to DSD sample rate converter followed by an analog low-pass filter?:confused:
It could be very interesting.;)

Thank you very much indeed.

Kind regards,:D

beppe61
ITALY
 

beppe61

Member
2005-02-08 11:00 am
torino
gmarsh said:
You've just described a 1-bit DAC.


Dear Sir,

thank you very much for your kind and valuable reply.
Then, what is your opinion?
Here in Italy there is a modder that performs this on the Sony SCD1 and he states that the sound is fenomenal.
The building of a minimalist DAC like this ( a Purcell on very cheap) would be very interesting.

Thank you very much indeed for your helpful reply.

Kind regards,

beppe61
 

Bricolo

Member
2002-11-11 6:52 am
I think it's one of the reasons why the designers made the DSD format this way.

PDM and PWM digital modulations have the ability of giving an analog signal, proportionnal to the pulse density/width, if you low pass it.

So, you can build a simple minimalist DAC. Even better, amplify your DSD signal, and low pass it just before the loudspeaker, you've just made a basic digital amplifier
 

beppe61

Member
2005-02-08 11:00 am
torino
Bricolo said:
I think it's one of the reasons why the designers made the DSD format this way.

PDM and PWM digital modulations have the ability of giving an analog signal, proportionnal to the pulse density/width, if you low pass it.

So, you can build a simple minimalist DAC. Even better, amplify your DSD signal, and low pass it just before the loudspeaker, you've just made a basic digital amplifier

Dear Sir,

Thank you very much for your kind explanation.
Then why this kind of DACs is very uncommon?
I mean, I know that dCS makes a very expensive PCM to DSD upsampler (Purcell) to be linked to another DAC unit.
Are you aware of any cheaper product that upsamples PCM to DSD ?
I have also read that it is easier to convert a DSD stream to analog, but I really don't understand why.

Anyway thank you very much indeed for your valuable help.

Kind regards,

beppe61
 

beppe61

Member
2005-02-08 11:00 am
torino
phase_accurate said:
Those DACs are by no means uncommon. Almost any delta-sigma 1 bit DAC works that way (although not all of them use the DSD bit-rate) and there are many players and soundcards using them.

Regards

Charles

Dear Sir,

Thank you very much for your kind and very valuable reply.
I must explain you one thing.
Here in Italy there is a digital sources modder that modifies a SONY SCD1 (a really great machine per se) taking the DSD signal directly to the output with just a low-pass analog filter in between with (this is his opinion) great results.
Then my idea: why don't build a extremely basic DAC with a PCM to DSD sample rate converter followed by just an analog low-pass filter?
Is this a dumb idea?
The cost would be very low and may be the result quite good.

I would appreciate very much to know your position on this topic.

Kind regards,

beppe61
 

Bricolo

Member
2002-11-11 6:52 am
PCM to DSD isn't as easy as DSD to analog.


DSD to analog is easy, but not often used like you explained, because a simple "low order" filter will let some unwanted HF go to the amp. this can be considered as acceptable in DIY, but for commercial products I think that designers aren't ok with that

here's a self explaining picture, the square is the DSD, the sine is the same signal after a low pass

[IMGDEAD]http://www.bolton.ac.uk/mind/paderborn/motors/induction/PWM.gif[/IMGDEAD]
 

beppe61

Member
2005-02-08 11:00 am
torino
Bricolo said:


PCM to DSD isn't as easy as DSD to analog.
DSD to analog is easy, but not often used like you explained, because a simple "low order" filter will let some unwanted HF go to the amp. this can be considered as acceptable in DIY, but for commercial products I think that designers aren't ok with that
here's a self explaining picture, the square is the DSD, the sine is the same signal after a low pass

[IMGDEAD]http://www.bolton.ac.uk/mind/paderborn/motors/induction/PWM.gif[/IMGDEAD]

Dear Sir,

Thank you very much for your kind and extremely competent reply.
Anyway I noticed that some manufacturers offer DSD upsampling on their newer cd player, like the MUSICAL FIDELITY A5.
It could be that DSD upsampling can give some positive traits to the resulting sound also for CDs.

Thank you very much again.

Kind regards,

beppe61
 
Bricolo said:
positive traits, maybe
cheaper, or consummer appealing, certainly

if you want to understand design choices, you must think like a designer ;)

Dear Sir,

thank you very much for your kind and very valuable reply.
I must confess that my skills are too limited to understand design choices.
But I have a further question for you.
One of the top brands on digital equipment, dCS, offers a product the PURCELL that performs only the upsampling of PCM to DSD, and at a very high price.
So my question is: if dCS offers this kind of product there must be something of good in the upsampling process?
dCS products are rated at the very top of the available digital equipment.
I would like very much to know your opinion.

Kind regards,

beppe61