[hybride]

Get one and try it out - they are dirt cheap.

This one i used. One of the cheapest and best i know.

http://cgi.ebay.nl/DIY-2x25W-Class-T-Amp-TRIPATHS-TA2021B-KIT-BAUSATZ-/230509579789?cmd=ViewItem&pt=LH_DefaultDomain_77&hash=item35ab710e0d#ht_3560wt_1139

http://www.art0.de/

[Dracule1]

BTW, the poster of the link I provided is none other than Thorsten of AMR:

http://www.amr-audio.co.uk/html/cd_individual.html

I like his CDP using the TDA1451.

[bhobba]

This one i used. One of the cheapest and best i know.
http://cgi.ebay.nl/DIY-2x25W-Class-T-Amp-TRIPATHS-TA2021B-KIT-BAUSATZ-/230509579789?cmd=ViewItem&pt=LH_DefaultDomain_77&hash=item35ab710e0d#ht_3560wt_1139
http://www.art0.de/

Thats actually a bit more powerful than the one I used.  Yea they really are cheap and it is a real hoot to see them compete against much more expensive amps.  Those amps are better but the Tripath is not shamed and in the area of detail retrieval and acceleration they are up their with the best at any price.

Thanks
Bill

[bhobba]

BTW, the poster of the link I provided is none other than Thorsten of AMR:

http://www.amr-audio.co.uk/html/cd_individual.html

I like his CDP using the TDA1451.

Thanks for that.  Just one technical thing I will mention.  It is well known noise shaping easily gives 16 bit resolution to one bit DAC's eg:
http://web.mit.edu/jonas/www/6.341/paper.pdf

Now the exact detail of these latest 32 bit DAC's is not generally known but that is understandable because its propriety.  I do not believe it is unreasonable to take the engineers word and while it is only 6 bit resolution believe it has an effective resolution of 32 bit using more modern techniques than what was done with the older one bit DAC's.

Thanks
Bill

[hybride]

Not to promote ECD, but what i appreciate is that he discusses all his knowledge on the forums. He even published the full schematic off his latest 1541DAC. A part of the joy testing DAC's is imho also to learn why it is like it is.         

[bhobba]

Hi Guys

Just returned form Mikes and the DAC shootout is still all go.  The only thing, due to the extra work required if a lot turn up, is it may not be blind.

Thanks
Bill

[jdbrian]

Hi

  You should really try to maintain the blind testing as it looks like the designers of 2 of the DAC's will be present.

Brian

[Jon L]

Hi

  You should really try to maintain the blind testing as it looks like the designers of 2 of the DAC's will be present.

Brian

Strongly agreed.  It usually works out better if one person is designated to do all the switching and kept out of the official listening panel.

One thing often forgotten is how the "unused" DAC's need to be powered up all the time while one DAC is being played.  They cannot be unplugged while waiting.  However, having DAC's plugged to the wall will contaminate the power line, so the best thing to do is get a power conditioner that isolates the components from wall.  A simple isolation transformer will do, and I strongly recommend all the unused DAC's be plugged into the isolator in another room while in wait..

[jdbrian]

   A fair comparison is not as easy as it seems. The power issue is something I hadn,t thought of.
  There are a lot of pre conceived notions on what certain chips and implementations sound like. NOS does this well and OS dose that well etc. It will be interesting to see if these notions hold up in the face of these very serious implementations both on the NOS and OS sides.
  My instincts tell me that at this level these DAC's will sound more alike than different and that as a group they will be much better than lesser efforts of either type. It will be interesting to see the outcome. Hopefully you can keep the blind testing in the mix.

Brian

[hybride]

Yesterday spend all day in John Brows lab to update my 1541DAC with his the latest tweaks. We talked about dac technics and there main differences in sound perception. He just posted a short explanation in another forum. But it might be interesting for readers here:

"NOS vs OS

Unfiltered NOS offers highest accuracy in the time domain and poorest in the frequency domain.

Filtered NOS offers reasonable accuracy in both time and frequency domain.

OS offers highest accuracy in the frequency domain and poorest in the time domain.

Linear interpolation (multiple DAC chips in parallel fed by delayed I2S signals) works excellent at lower frequencies, but distorts higher frequencies causing early trebles roll-off among other things. It can work very well in combination with a digital brickwall filter like used by Cambridge Audio in their 4 x TDA1541A CD player.

The question would be what's most important for realistic sound reproduction, highest precision in the time domain or highest precision in the frequency domain. Based on many years of experimenting and listening to equipment designed by other developers it seems that accuracy in the time domain is much more important for achieving most realistic sound reproduction than we realize.

This is the reason why I choose unfiltered NOS. Compromise I have to make is reduced accuracy in the frequency domain.

The problem is, we can't have both, using 44.1 / 16 format, it's either one, the other or a combination of both. It looks like we have to make our own choices based on our personal preferences as there is no perfect way to go.

We also have to realize that sound quality is determined by audio component matching. Connecting some random equipment together is very likely to cause mismatches and resulting sound quality degradation. It is also very important to understand specific audio component properties in order to achieve optimal matching.

Example, unfiltered NOS won't work optimally with class-D or comparable switch-mode power amps as frequency spectra of both DAC and amplifier will inter-modulate."

[bhobba]

The problem is, we can't have both, using 44.1 / 16 format, it's either one, the other or a combination of both. It looks like we have to make our own choices based on our personal preferences as there is no perfect way to go.

Interesting.  I wonder how up-sampling to 192/24 using programs like J River would change things - would you get the best of both worlds with a NOS then?

Thanks
Bill

[jdbrian]

Yesterday spend all day in John Brows lab to update my 1541DAC with his the latest tweaks. We talked about dac technics and there main differences in sound perception. He just posted a short explanation in another forum. But it might be interesting for readers here:

"NOS vs OS

Unfiltered NOS offers highest accuracy in the time domain and poorest in the frequency domain.

Filtered NOS offers reasonable accuracy in both time and frequency domain.

OS offers highest accuracy in the frequency domain and poorest in the time domain.

Linear interpolation (multiple DAC chips in parallel fed by delayed I2S signals) works excellent at lower frequencies, but distorts higher frequencies causing early trebles roll-off among other things. It can work very well in combination with a digital brickwall filter like used by Cambridge Audio in their 4 x TDA1541A CD player.

The question would be what's most important for realistic sound reproduction, highest precision in the time domain or highest precision in the frequency domain. Based on many years of experimenting and listening to equipment designed by other developers it seems that accuracy in the time domain is much more important for achieving most realistic sound reproduction than we realize.

This is the reason why I choose unfiltered NOS. Compromise I have to make is reduced accuracy in the frequency domain.

The problem is, we can't have both, using 44.1 / 16 format, it's either one, the other or a combination of both. It looks like we have to make our own choices based on our personal preferences as there is no perfect way to go.

We also have to realize that sound quality is determined by audio component matching. Connecting some random equipment together is very likely to cause mismatches and resulting sound quality degradation. It is also very important to understand specific audio component properties in order to achieve optimal matching.

Example, unfiltered NOS won't work optimally with class-D or comparable switch-mode power amps as frequency spectra of both DAC and amplifier will inter-modulate."

  There is a long discussion on his topic over on HeadFI.com forum titled NOS DAC -marketing bs where Dan Lavry goes into basic sampling theory that governs DAC and ADC operation. It is worth a read for anyone who has an interest in the technical side of the NOS/OS discussion. I can also recommend National Semiconductors Application Notes 236 and 237 as a basic primer.
  In the quote above there is  reference to time domain and frequency domain as separate charecteristics. When viewing the same signal these 2 domains give you the same information in the end.
  When viewing the output of an unfiltered NOS DAC you are not just seeing the audio signal but also the image energy which is related to the sampling frequency. This additional HF energy is what appears to give NOS a faster impulse response.
   Much like in the tube/solid state amplifier debates, the end result of listening and studying these issues will result in better DAC's in the future.

Brian

   

[hybride]

Interesting.  I wonder how up-sampling to 192/24 using programs like J River would change things - would you get the best of both worlds with a NOS then?

As far that i know there are no DAC chips who are capable to do 192/24 NOS DA converting.

[bhobba]

As far that i know there are no DAC chips who are capable to do 192/24 NOS DA converting.

The PCM1704 can and is in fact done in the Overdrive DAC:
http://www.empiricalaudio.com/products/overdrive-dac

Thanks
Bill

[bhobba]

There is a long discussion on his topic over on HeadFI.com forum titled NOS DAC -marketing bs where Dan Lavry goes into basic sampling theory that governs DAC and ADC operation. It is worth a read for anyone who has an interest in the technical side of the NOS/OS discussion. I can also recommend National Semiconductors Application Notes 236 and 237 as a basic primer.

Dan Lavry does have some interesting things to say.  Now I will lay my technical biases on the table.  I am with Chord when they say it is timing errors that are the important thing.  That is why higher frequency sampling rates sound better even though mikes simply don't, nor is there any reason for them to go that high.  That said the Tranquility DAC guys say there is much much more to this than the dac conversion technology used and they play as big if not bigger role. They optimized them and by doing that achieved excellent results with a simple 16 bit dac chip.

Thanks
Bill

[hybride]

The PCM1704 can and is in fact done in the Overdrive DAC:
http://www.empiricalaudio.com/products/overdrive-dac

Thanks
Bill

Look in the datasheet. Its maximum 48 khz/16 bit. It is a delta sigma DAC with oversampling digital filter. Not really a pure NOS approach i.m.h.o.
 

[bhobba]

Look in the datasheet. Its maximum 48 khz/16 bit. It is a delta sigma DAC with oversampling digital filter. Not really a pure NOS approach i.m.h.o.

I did - its a 24 bit R-2R ladder type DAC that can handle up to 768 khz - it does 192/24 NOS in a doodle:
http://focus.ti.com/lit/ds/symlink/pcm1704.pdf

Thanks
Bill

[hybride]

I did - its a 24 bit R-2R ladder type DAC that can handle up to 768 khz - it does 192/24 NOS in a doodle:
http://focus.ti.com/lit/ds/symlink/pcm1704.pdf

Thanks
Bill

The datasheet says:
FEATURES   
● SAMPLING FREQUENCY (fS): 16kHz to 96kHz   
● 8X OVERSAMPLING AT 96kHz

Further:
Digital data words are read into the PCM1704 at eight times the standard DVD audio sampling frequency of 96kHz (e.g., 8 x 96kHz = 768kHz) to create a sinewave output of 1100Hz.

Further:
The output of the I/V converter is then connected to a 40kHz, 3rd-order GIC low-pass filter. The filter output is then passed on to a programmable gain amplifier to provide gain for low-level test signals before being fed into an analog distortion analyzer.

Another approach then the TDA1541, which is filterless.
 

[bhobba]

The datasheet says:
FEATURES   
● SAMPLING FREQUENCY (fS): 16kHz to 96kHz   
● 8X OVERSAMPLING AT 96kHz

Further:
Digital data words are read into the PCM1704 at eight times the standard DVD audio sampling frequency of 96kHz (e.g., 8 x 96kHz = 768kHz) to create a sinewave output of 1100Hz.

Further:
The output of the I/V converter is then connected to a 40kHz, 3rd-order GIC low-pass filter. The filter output is then passed on to a programmable gain amplifier to provide gain for low-level test signals before being fed into an analog distortion analyzer.

The pcm1704 is designed to to be used with a separate oversampling filter that feeds 768khz to the DAC but you don't have to use it if you don't want and guys who use it as a NOS don't.  Audio GD for example use its own up-sampling rather than an over-sampling filter not to 768khz but to 192khz and if you feed 192/24 into an Audio GD dac that has the appropriate receiver then it is a nos DAC.  Steve Nugent with his overdrive DAC does no up-sampling or over-sampling at all.

I have zero idea why you are arguing about this.  Companies have been selling pcm1704 NOS DAC's for yonks and DIY designs aboud eg:
http://www.diyaudio.com/forums/digital-source/166290-192khz-24bit-dac-no-oversampling-no-digital-filter.html

Thanks
Bill

[hybride]

I have zero idea why you are arguing about this.  Companies have been selling pcm1704 NOS DAC's for yonks and DIY designs aboud.

It's not my intention arguing about the PCM1704. I only have some reservation about what is claimed by commercial companies. I agree that i would be interesting to hear high sampled recordings in NOS mode. upsampling a 44.1/16bit source to 192 won't bring much profit in a (NOS) DAC, because there is still the same information.