[dac64]

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[Rob Watts]

John Franks came up with the name Dave - I had to convert it into a suitable acronym! My Dad was a Dave, and John's brother is Dave too. But we wanted something fun - the high end takes itself far too seriously. It's just about enjoying music more at the end of the day.

 

[CaptainFantastic]

Hi Rob, I am a Mojo and Hugo 2 owner. I like your products. Performance, quality, aesthetics. I guess I voted with my wallet by buying the Hugo 2 after I experienced the Mojo and I am resolutely keeping both although working from home most of the time now and for the foreseeable future.

My honest question to you revolves around my intention to take my use of the Mojo a notch up, to enjoy it even more. I am looking into purchasing the Poly. I realize that you are not the head of the finance department at Chord, nonetheless you must have a good idea on the following point/question:

Why is the Poly priced at 650 EUR/GBP/USD or thereabout? I understand the price for the Mojo and the Hugo 2 – the research, the amazing in-house technology development, the sheer amount of work that went into creating them. But the Poly just enables wireless streaming. These kind of devices are usually very, very affordable. Sure, this had to be something customized for the Mojo, but at the end of the day, I cannot imagine the amount of work that went into it compares to developing the actual Mojo. What’s so special in the Poly that could help me wrap my mind around the 650 EUR price tag? It’s not that I can’t afford it, I just need to justify it to myself -- not feel like I am getting ripped off in a situation where a company feels like they have a captive customer base for these add-ons.

Thanks!

 

[Rob Watts]

Poly wasn't my project and so I asked Matt Bartlett from Chord and I got this reply:


"I would reply that very much like the DAC products Poly was designed from the ground up.
In order to build a complex streaming platform that was able to be incredibly low powered
so it could run on batteries whilst still having enough processing power to run services such as
Roon is very complicated. Other manufacturers tend to use similar OEM platforms that have
compromises in terms of performance and power management.
With Poly we wanted to provide a pure battery powered product to give the lowest noise possible
when feeding a digital signal into Mojo.
As yet I don't think there is another manufacturer that has been able to develop a completely
portable headless streaming platform that can run from batteries for many hours and provide
very high resolution playback. Hence the reason why the technology is more expensive than
perhaps other products you might see on the market."

 

[CaptainFantastic]

OK, thanks for getting the answer Rob. Appreciated.

 

[feddar]

Agreed on points 1 and 2.

As to RF filters, this is a complex area; also 22dB reduction would not be enough to eliminate the issue; also it's rated using a 50 ohm load which is not what one would get in practice. That said, best thing to do is to give it a listen; if it sounds warmer then run with it. I had no benefit with using batteries on TT2 though, but each system is different.

As to BNC cables, clip on ferrites helped with Blu 2; but they sounded worse with the Hugo M Scaler, due to the improved isolation on the BNC outputs. A simple way to improve the SQ is using 2m of BNC cables rather than 1m. The cable length is important (longer length is greater inductance to 2GHz impedance for ground loop currents is greater), so to a much lesser amount cable construction. Solid core 2GHz ferrites do work and will give the largest improvement and I use Wave cables myself.

Running the M scaler on batteries does indeed improve the situation and solves the BNC cable issues as batteries (you need to run it isolated completely from the mains) severs the ground loop from M scaler to TT2; thus RF currents can't flow into the DAC ground plane, and the problem is solved.

I should stress that this is very much surface finish of the icing on the cake - it's a significant difference on an AB test, but the scale of the change is forgotten about after a few days.

Happy listening!

Thank you very much for your response, explanations, and suggestions.

Yesterday, I tried using a battery to power the M scaler, with the TT2 plugged into the wall. Wow, it sounds even better! I am now wondering whether using another battery for the TT2 would help even more. According to my understanding of your explanation, it should not, right? Also, using ferrites on the BNC cable at this stage should not help either, correct?

I do have a couple more questions, if you don’t mind.

Here is the battery I am using.

Should I use the battery’s ac output (on the right) to the M scaler’s power adapter (this is what I am doing now), or use the battery’s 12V dc output (on the left) direct to the M scaler? I am worried about setting this up incorrectly and frying the M scaler, but if that may help the sound even more, I’ll give it a try.

I prefer to turn off the units after listening, as I keep them where I sleep, and the M scaler’s light can be distracting at night. I am wondering why you decided to keep the M scaler light on at all times, and why you decided not to include a power switch.

I noticed on the manuals that I should be powering on the units in a specific order (M scaler first, then TT2), otherwise there could be damage. If they go on together (ie both plugged into a powerbar, which is then turned on), could that cause damage? Also, do they need to be unpowered in any order as well?

Thanks yet again,

Fed

 

[Triode User]

Yesterday, I tried using a battery to power the M scaler, with the TT2 plugged into the wall. Wow, it sounds even better! I am now wondering whether using another battery for the TT2 would help even more. According to my understanding of your explanation, it should not, right? Also, using ferrites on the BNC cable at this stage should not help either, correct?

I do have a couple more questions, if you don’t mind.

Here is the battery I am using.

Should I use the battery’s ac output (on the right) to the M scaler’s power adapter (this is what I am doing now),

In order to produce the mains voltage from the battery, your Motomaster Eliminator will use an inverter circuit. These are switching circuits and they generally output a very noisy mains voltage. It is not normally recommended to run sensitive electronic equipment off inverters unless the inverters employ good quality filtering and I doubt that the Motomaster Eliminator does that. It is perhaps testament to the quality of the supplied Chord HMS power supply quality that it coped so well with this almost certainly very dirty mains voltage from the Motomaster Eliminator (assuming of course that your 'Wow' moment was not just due to noise induced artifacts). Better would be to run the HMS off the DC output of the Motomaster Eliminator or better still just to use a plain 12v battery.

Chord would say that there is no benefit in running the TT2 off a battery if you already have the HMS connected to a battery because the real power supply to the TT2 is the super caps inside it rather than what you plug into the TT2.

 

[Rob Watts]

Triode User beat me to it!

Yes run the M scaler from the 12v, and don't worry about TT2 - once the current path is completely broken, breaking it twice won't help any further.

Make sure the battery is isolated from ground or the mains too.

 

[feddar]

Triode User beat me to it!

Yes run the M scaler from the 12v, and don't worry about TT2 - once the current path is completely broken, breaking it twice won't help any further.

Make sure the battery is isolated from ground or the mains too.

Thanks again.

Just to clarify, once the M scaler is on 12V battery, the BNC change shouldn’t matter any longer, correct?

Also, I noticed on the manuals that I should be powering on the units in a specific order (M scaler first, then TT2), otherwise there could be damage. If they go on together (ie both plugged into a powerbar, which is then turned on), could that cause damage? And do they need to be unpowered in any order?

 

[Rob Watts]

Yes - if the capacitance of the battery to ground is low, and this will depend upon siting and the physical size of the batteries. Certainly with the PowerAdd power bank, it went to barely or not audible - but your circumstances may be different!

It does not matter on powering up or down order in terms of causing damage. But perhaps you may get a pop or click if TT2 is not last on first off. That might cause damage problems with ultra sensitive IEMs on high gain mode - hence the advice in the manual.

 

[feddar]

Yes - if the capacitance of the battery to ground is low, and this will depend upon siting and the physical size of the batteries. Certainly with the PowerAdd power bank, it went to barely or not audible - but your circumstances may be different!

It does not matter on powering up or down order in terms of causing damage. But perhaps you may get a pop or click if TT2 is not last on first off. That might cause damage problems with ultra sensitive IEMs on high gain mode - hence the advice in the manual.

Please excuse my ignorance, but I don’t know what you mean by a low battery capacitance to ground. If the battery is not plugged into the mains, how can there be capacitance to ground?

Would you be able to suggest a PowerAdd battery?

Thanks for clarifying the power on/off issue. That makes sense. I always have my headphones disconnected when powering on or off anyhow.

 

[Rob Watts]

So any metallic object will have a capacitance to ground - we call this ground parasitic capacitances. So for example, two 100mm square parallel plates separated by 1m has a capacitance of 0.088 pF; and a 100mm square plate 1m above an infinite perfect ground plane is 1.26pF. A 100 mm square battery sitting on a wooden desk will have a capacitance to ground of something like 0.1pF as ground in a house isn't a perfectly conducting medium. Now you may think 0.1pF isn't much, but its an impedance of 796 ohms at 2GHz! Fortunately, it's a high enough impedance not to be a SQ issue. Also, the impedance of your floor will be higher than this too.

The proof of course is in the listening, and using a battery for the M scaler pretty much eliminates SQ changes with BNC, so the isolation from a Poweradd battery bank is effective enough.

The one I use is no longer available, but this looks promising:

https://www.amazon.co.uk/dp/B078XRB...olid=3H6TO0MDSGPOK&psc=1&ref_=lv_ov_lig_dp_it

 

[feddar]

Thank you very much. I will get one. Looks like the 50,000mAh version is a bit cheaper in Canada.
https://www.amazon.ca/Krisdonia-50000mAh-Batterie-Portable-Type-C/dp/B074N1B15F?ref_=ast_sto_dp

I assume this would be just as good. I hope I’m not missing something here...

Edit:
Looks like they are 3A, but the included adapter is 4A. That could be a problem, correct?

 

[dac64]

So any metallic object will have a capacitance to ground - we call this ground parasitic capacitances. So for example, two 100mm square parallel plates separated by 1m has a capacitance of 0.088 pF; and a 100mm square plate 1m above an infinite perfect ground plane is 1.26pF. A 100 mm square battery sitting on a wooden desk will have a capacitance to ground of something like 0.1pF as ground in a house isn't a perfectly conducting medium. Now you may think 0.1pF isn't much, but its an impedance of 796 ohms at 2GHz! Fortunately, it's a high enough impedance not to be a SQ issue. Also, the impedance of your floor will be higher than this too.

If I'm not misunderstood the above:

A. a wooden rack to house the equipment is a better option
B. keep away all metallic objects from the equipment as far as possible
C. wooden floor is best for hifi a bit way off now!

 

[Rob Watts]

No I just said wood in the sense of a non metallic surface. Any non conductive surface will do - and a steel rack is OK if it isn't earthed! It's the connection to mains earth that is the key here. I think I am guilty of encouraging you to overthink this a bit - the key is breaking the connection to the mains, and a battery does this perfectly - it's just 99.9% and not 100% - but that last 0.1% is not worth chasing...