[Rob Watts]

I had listened to a USB cable that had ferrites installed - and no change. Again YMWV....

As to external RF, it only matters if there is a ground loop, so battery operation should mean no currents flowing into the DAC ground plane....

 

[SuperDuke]

Can Both the RCA and XLR outputs from DAVE be used at the same time w/o causing a problem?

 

[flyte3333]

I had listened to a USB cable that had ferrites installed - and no change. Again YMWV....

As to external RF, it only matters if there is a ground loop, so battery operation should mean no currents flowing into the DAC ground plane....

Brilliant, cheers Rob

 

[Rob Watts]

Can Both the RCA and XLR outputs from DAVE be used at the same time w/o causing a problem?

Sure

 

[Triode User]

I had listened to a USB cable that had ferrites installed - and no change. Again YMWV....

As to external RF, it only matters if there is a ground loop, so battery operation should mean no currents flowing into the DAC ground plane....

I on the other hand have noticed changes when trying ferrites on USB cables. This was on a USB cable between a streamer (with a mains power supply) and plugged into Dave USB input.

 

[Rob Watts]

I on the other hand have noticed changes when trying ferrites on USB cables. This was on a USB cable between a streamer (with a mains power supply) and plugged into Dave USB input.

Yes I was thinking of you when I posted that some had experienced benefits!
I guess it depends upon how noisy the source is - I get the very strong feeling that my MSI lap-top creates a lot less noise than my old Dell PC. And that would make sense, as it is newer, and much more power efficient, so less noisy to start off with.

 

[flyte3333]

As to external RF, it only matters if there is a ground loop, so battery operation should mean no currents flowing into the DAC ground plane....

Just on this Rob, for my learning purposes, so I understand the mechanisms behind what you’re saying.

If using a battery based USB, is airborne RF of zero concern , even if there’s no currents circulating through the ground plane?

Even if the mobile source is close to the DAC with it’s wifi, bluetooth and cellular radios active (assume all radios are going at full blast)?

Just talking technical mechanisms for sound quality being affected, not necessarily listening tests.

How does no ground currents relate to the DAC sensitivy to airborne RF?

Airborne RF specifically

Cheers!

 

[Rob Watts]

It's difficult to imagine how airborne RF is going to induce currents in Dave's ground plane, considering how well screened Dave is in its thick solid aluminium chassis.

We need current through the ground plane to set up voltages - and it is these voltages that the analogue electronics pick up. So no current, no voltage on the ground plane, no pick-up... The common mode noise, won't affect the analogue electronics at all.

 

[xxx1313]

I can also report that I hear a difference, using ferrites on the (silver) USB cable between SP1000 and Dave. However, I have an Iso Regen in between, powered by an Sbooster BOTW. This could be responsible for some RF pickup (even though I have ferrites on the power cable as well), but it still sounds better than straight from SP1000. The Wurth ferrites mentioned by Rob and others are better than the cheap Topnisus ferrites, imho. Less brightness, deeper soundstage. Dave is already great without ferrites etc., but one wants to hear the Dave at its best.

 

[jonstatt]

I am using a Bluesound Node 2 with optical to the Dave. The Node is connected via WiFi. I like the Node because it is compatible with Roon. I don’t have files greater than 192kHz. But what magical optimisations am I missing out on by not spending more on a streamer or posh Ethernet cable?

 

[penguin69]

My listening tests revealed no change with ferrites on USB cables at all. But differing sources may give different results. I know some posters have reported improvements. Also, battery mode operation should mean no ground loops, so no current flow into the ground planes, then no RF noise pick-up in the DAC and so no problem... This has been validated by listening tests.

Rob,

You mentioned way back in the early pages of this thread that you considered the USB input preferable (slightly) to the Toslink input.

This was obviously based on listening tests; however, were you able to establish the technical reason(s) for this? Toslink receivers have traditionally been criticised for jitter, but I am pretty certain that your design eliminates that jitter.

Regards
penguin140369

 

[Rob Watts]

Yes I vaguely recalled that - it does indeed sound slightly brighter and I put that down then to the benefit of USB in that it gets the clock from the FPGA. But I have changed my mind on this now, as Hugo 2 USB sounds the same as optical when using headphones (it's like Dave when driving a power amp). So actually that indicates that the timing issue is not actually a benefit, as the DPLL eliminates the source jitter. So on Dave, because of ground loops, and the fact that the galvanic isolation lets a small amount of RF into the ground plane via the isolators 2pF of capacitance, now my explanation is down to increase in noise floor modulation from the RF, making it sound a tiny bit brighter.

 

[penguin69]

Yes I vaguely recalled that - it does indeed sound slightly brighter and I put that down then to the benefit of USB in that it gets the clock from the FPGA. But I have changed my mind on this now, as Hugo 2 USB sounds the same as optical when using headphones (it's like Dave when driving a power amp). So actually that indicates that the timing issue is not actually a benefit, as the DPLL eliminates the source jitter. So on Dave, because of ground loops, and the fact that the galvanic isolation lets a small amount of RF into the ground plane via the isolators 2pF of capacitance, now my explanation is down to increase in noise floor modulation from the RF, making it sound a tiny bit brighter.

Thanks Rob for the reply.

If source jitter is eliminated by the phase locked loop, then - all things being equal - shouldn't the optical connection be as good as if not better than the USB connection for 16/44.1? Or is that simplistic?

I note that the ES9038 Pro has a pin to change the DPLL settings (I think there are 15 or 16 available settings), which hints that there could be some compromising of quality in order to reduce chances of dropout. I'm guessing a little bit here as this capability of the Sabre chip isn't well described.

Thanks again.

 

[Rob Watts]

Yes optical is the best input - its really a question of getting the other inputs to match optical.

 

[flyte3333]

It's difficult to imagine how airborne RF is going to induce currents in Dave's ground plane, considering how well screened Dave is in its thick solid aluminium chassis.

We need current through the ground plane to set up voltages - and it is these voltages that the analogue electronics pick up. So no current, no voltage on the ground plane, no pick-up... The common mode noise, won't affect the analogue electronics at all.

Thanks Rob!

Based on this, then if Dave were directly powering PASSIVE speakers, i.e. only Dave's power supply involved therefore there's no ground or power supply 'loop' , then could Dave's housing THEORETICALLY be made of plastic and still suffer zero effects from airborne RFI, even if a mobile USB source was used with all it's wireless radios active on full blast??

And the same for someone using Dave purely with headphones with a mobile USB source?

Before anyone falls off their chair reading this, I'm not suggesting Dave should be made of plastic . I'm just trying to use this example to close the loop (pun intended) on my understanding of when airborne RFI is of concern, and when it's not.

Cheers in advance.