Which DACs bypass digital filtering?

[vvcv]

On 5/27/2017 at 5:09 PM, rikhav said:

Sorry for being off topic but I always assumed that if one sends a stream of max bit rate a dac supports, it automatically avoids digital filtering by a dac

 

For example I have a burson conductor which supports maximum bit rate of 192 khz, so if send a stream of 176 or 192 khz from my PC the filtering of dac is automatically bypassed

 

Someone please let me know if this right or I am completely wrong

 

Hello Rikhav,

 

After some discussion today on a thread I started, I too was under this same impression. However, I remembered a time when it was suggested I change some jumpers on my Benchmark HGC2 DAC. Before I did, and just today, i remembered reading quickly about something regarding the DACs filter and how it takes in and lets go of a signal. Anyway, after this discussion started to confuse me a bit this afternoon, I called Benchmark and spoke with the lead sales rep. A great guy who has always helped me with every tech problem I've had, and solved them. So, when I gave him a basic idea of how HQP uses filters, including the ability to upsample to DSD64. This is the highest DSD the DAC will upsample to, and Kent (the Benchmark contact) was close to 100% certainty that the Benchmark HGC2, and HGC3 for that matter, would indeed take HQPs signal and resample it yet again so the DAC would know it is releasing the parameters and sound quality it should be outputting. Now, he assured me he is not the engineer, but also assured me that no one at Benchmark, that he knows of, uses HQP, and suggested I go straight to the developer to ask this specific question -so I would know for sure. I hope this helps, though I'm sure you've figured it out.

 

I'll post the thread from today, but I'm sure you know most if not all information we discussed.

 

[vvcv]

10 hours ago, semente said:

The Benchmark DAC1 up- or down-samples everything to 110kHz:

https://benchmarkmedia.com/blogs/application_notes/13127453-asynchronous-upsampling-to-110-khz?

 

The Benchmark DAC2 and DAC3 up- or down-sample everything to 211kHz:

https://benchmarkmedia.com/blogs/application_notes/inside-the-dac2-part-2-digital-processing

 

Frequency Shifting the Transition Band

Benchmark has selected the ES9018 filters which provide the lowest pass-band ripple. We then frequency-shift the filter transition band upward so that it is centered at 110.5 kHz. We do this by operating the ES9018 at an input sample rate of 211 kHz. This means that the entire transition band of the ES9018 filter is always above the highest audio frequency contained in the incoming audio. At a 192 kHz incoming sample rate, the highest incoming frequency is 96 kHz. This is completely below the lower limit of the transition band that is centered at 110.5 kHz. Benchmark's system effectively eliminates the filters in the ES9018 by frequency shifting the filters out of the audio band. It also completely eliminates all traces of image fold-back. The Nyquist frequency of the D/A converter exceeds the Nyquist frequency of the incoming digital audio.

We used this same frequency-shifting technique in our DAC1 converters. When the DAC1 was designed, the available technology limited us to a D/A input sample rate of 110 kHz. In the DAC1, the D/A filters were out of band for sample rates up to 96 kHz. The DAC2 extends this unique technology to all sample rates up to 192 kHz. The goal for all Benchmark converters has always been to make the digital filters as transparent as possible. The accuracy and precision of the filters is a function of the oversampling ratio used in the filters. Benchmark moves the low-pass filter out of the D/A converter so that it can be executed at a much higher oversampling ratio.

 

 Thanks a lot for this. Great info. for a buddy that wants to buy my Benchmark -or if i sell it.