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Hi Russ and Brian,
I have some technical questions I am hoping you would help answer. :^)
OTTO
Q: The specs on the relay show that max voltage supply is 7.5V (150% of 5V). Should I expect issues if I share a 7 VDC supply (VD from a LCDPS) with a Buffalo/Opus? Should a voltage regulator be used or rather the analog VDC side of a LCDPS?
Q: Would it otherwise be possible to use the USB power to power and switch the OTTO, while also powering the USB board (i.e. plug in the USB and the OTTO will switch to that I2S input)?
OPUS/BUFFALO
Q: Could a Opus and Buffalo both be powered by one LCBPS and one LCDPS, each PS connected to its own 25VA transformer?
Q: If that could be done, should I expect negative effects on sound quality?
BUFFALO
I would like to use the digital volume control capabilities of the Sabre chip, but fear "clicks" and "cracks" could somehow go through at full volume. Since I use a balanced headphone amplifier (Beta 22) for which i can not easily change the gain (and only using 20% of the potentiometer travel at max!), I fear for my headphones and ears.
Q: Is, in your experience, any noise in the digital signal also attenuated by the Sabre chip digital volume control?
Q: Could digital and analog attenuation be combined without much quality loss by using a combination of quality resistors (a sort of single attenuator setting) to "limit" the output volume and digital attenuation (Sabre volume control) to vary the output volume?
Many thanks in advance!
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tuneable wrote:OTTO
Q: The specs on the relay show that max voltage supply is 7.5V (150% of 5V). Should I expect issues if I share a 7 VDC supply (VD from a LCDPS) with a Buffalo/Opus? Should a voltage regulator be used or rather the analog VDC side of a LCDPS? No need to really. I usually wire it to run off the digital supply side to avoid the possibility of clicks in the analog outputs, though I have never heard that happen either. Quote:Q: Would it otherwise be possible to use the USB power to power and switch the OTTO, while also powering the USB board (i.e. plug in the USB and the OTTO will switch to that I2S input)? You can use the VBUS terminal (5V) on the USB to power the OTTO. I did that in the Burning DAC (only enabled the USB inout when USB was connected and 5V present). tuneable wrote:
OPUS/BUFFALO
Q: Could a Opus and Buffalo both be powered by one LCBPS and one LCDPS, each PS connected to its own 25VA transformer?
Neither the Opus and Buffalo only require a bipolar supply, so you only need a LCDPS, and yes, one could power both. If you are referring to two output stages off of one LCBPS, then yes, that would work as well. Yes, separate trafos are required for each supply (15VA would be enough). Many people power two Opus DACs off the same LCDPS (dual-mono). Quote:Q: If that could be done, should I expect negative effects on sound quality? No, though some people will disagree with me. tuneable wrote:
BUFFALO
I would like to use the digital volume control capabilities of the Sabre chip, but fear "clicks" and "cracks" could somehow go through at full volume. Since I use a balanced headphone amplifier (Beta 22) for which i can not easily change the gain (and only using 20% of the potentiometer travel at max!), I fear for my headphones and ears.
Q: Is, in your experience, any noise in the digital signal also attenuated by the Sabre chip digital volume control?
The digital volume in both the Sabre8 and WM8741 (opus) are very good, no pops, click, or crackle. The volume of the Sabre8 is the best digital volume I have heard. Don;t mistake the volume control of either of these chips with that of a digital potentiometer of digital controlled analog volume like the PGS23xx chips. The volume is done completely in the digital domain so there is no zero-crossing click possibility. Quote:Q: Could digital and analog attenuation be combined without much quality loss by using a combination of quality resistors (a sort of single attenuator setting) to "limit" the output volume and digital attenuation (Sabre volume control) to vary the output volume? I suppose you could do this. I think it would be best to set your max gain at the amplifier side. You could also limit max output of the Sabre8 in software, but it would be less desirable. Many thanks in advance!
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Thanks for the fast response! OTTO Great! I'll probably power the OTTO by digital side of the LCBCP and trigger it by the USB VBUS. BUFFALO I will have a closer look at the amp-side gain reduction in details. I'll take you word for the Sabbre volume control and try it out. Occasional I do hear clicks and crackles with the USB board and Opus combination, but they relate to the source. In my setup, a media PC source produces audible crackles if its CPU is on high load. I will test if these crackles end up attenuated digitally by the Sabre chip (which I hope) or not. Edited by user Saturday, September 27, 2008 7:53:49 AM(UTC)
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If the crackles are coming from your source, they will definitely be in the output. Nothing you can do about that except eliminate them at the source.
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Brian Donegan wrote:If the crackles are coming from your source, they will definitely be in the output. Nothing you can do about that except eliminate them at the source. I agree, this is true and makes sense if the crackles already are part of the audio stream that reaches the USB receiver. These crackles will simply be attenuated by the DAC, but not removed. To rephrase my main the question: how reliable is the digital attenuation of the Sabre chip if the digital audio stream is bad. Analog attenuation will attenuate everything (also crackles), but will the digital attenuation do the same? What if buffering problems in e.g. the USB communication is the cause? Can the DAC digitally attenuate nicely whatever noise the USB receiver uses to fill gaps, or does that data come out at 100% volume instead?
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This is a digital stream. If there are crackles in the digital data, the DAC will attenuate them as if they were part of the music. It would be as if the crackles were in the original recording.
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Brian Donegan wrote:This is a digital stream. If there are crackles in the digital data, the DAC will attenuate them as if they were part of the music. It would be as if the crackles were in the original recording. Thanks for the info and answers! :^)
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