[flyte3333]

I find them interesting. It’s also interesting why you’re asking them too, if you see what I mean. You must think a lot about it.

Asking why USB input gets warmer than TOSlink input? There's literally nothing for me to think about... just reach out my hand and feel the difference in heat...

When I listen to music (like now) my brain activity is ultra low - I'm in cave man mode

 

[ZappaMan]

Asking why USB input gets warmer than TOSlink input? There's literally nothing for me to think about... just reach out my hand and feel the difference in heat...

When I listen to music (like now) my brain activity is ultra low - I'm in cave man mode

It’s a good question, you have a lot of good questions lol, jk.

 

[flyte3333]

It’s a good question, you have a lot of good questions lol, jk.

Ha, cheers.

If I ask lots of good questions with cave man intelligence, imagine if I had half a brain !

Anyway I'm glad you find the questions interesting.

For those that don't there's always a bunch of other threads to read... https://www.head-fi.org/forums/

 

[miketlse]

Hi @Rob Watts

Does Mojo's USB interface (and associated circuitry) consume significantly more power than TOSLink interface (and associated circuitry)?

Is that why my Mojo gets quite a bit warmer with USB input, versus TOSlink? Mojo's is kept on the wall charger at all times at the moment. I'm never charging from low battery power because I know that will give off a lot of heat.

What's the difference in power consumption between USB and TOSlink? Do you have ball park figures? Just out of general interest only.

Just search the thread. Rob has answered the question at least once already.

 

[flyte3333]

Just search the thread. Rob has answered the question at least once already.

Done the search mate... USB consumes ~0.3W... TOSlink will be lower but can't find ball-park figure for TOSlink... hence the question to @Rob Watts ...

Thanks for your helpful input though...

 

[miketlse]

Done the search mate... USB consumes ~0.3W... TOSlink will be lower but can't find ball-park figure for TOSlink... hence the question to @Rob Watts ...

Thanks for your helpful input though...

Combining information from posts from Rob and John:

• Listening to music generates 1.7W (The power consumed by the FPGA is 475 mW - less than a third of the power used in total)
• charging from red generates another 0.91W
• trickle charging at blue generates another 0.107W
• The issue is power consumption; adding an extra SPDIF decoder module in the FPGA would add to power loss, and everything about Mojo is power. At the design time, there was no M scaler, so I had no inclination of the transformational possibilities at that time of the M scaler; saving a few mW of power was simply more important. https://www.head-fi.org/threads/hug...-official-thread.885042/page-26#post-14404378

https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/page-1429#post-12797997
https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/page-993#post-12463183

 

[flyte3333]

Combining information from posts from Rob and John:

• Listening to music generates 1.7W (The power consumed by the FPGA is 475 mW - less than a third of the power used in total)
• charging from red generates another 0.91W
• trickle charging at blue generates another 0.107W
• The issue is power consumption; adding an extra SPDIF decoder module in the FPGA would add to power loss, and everything about Mojo is power. At the design time, there was no M scaler, so I had no inclination of the transformational possibilities at that time of the M scaler; saving a few mW of power was simply more important. https://www.head-fi.org/threads/hug...-official-thread.885042/page-26#post-14404378

https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/page-1429#post-12797997
https://www.head-fi.org/threads/chord-mojo-dac-amp-☆★►faq-in-3rd-post-◄★☆.784602/page-993#post-12463183

Still no info about optical decoding power consumption vs USB’s ~0.3W ...

It will be less but how much less. As per my original question, just asking Rob out of general interest.

 

[miketlse]

Deleted

 

[flyte3333]

No doubt you will claim that this analysis is complete rubbish, but YMMV.

Of course I wouldn’t claim that.

But it still doesn’t answer my original question to Rob about why USB feels quite a bit warmer thank TOSlink... Maybe it’s something else...

Maybe it’s more like 1.8W vs 1.6W?

I can’t guesstimate if that’s enough for the difference I feel. It depends on thermal analysis with this case design doesn’t it...

Anyway I appreciate your efforts but would ask we leave it to Rob please, as originally intended...

Otherwise it’s the blind leading the blind and we just clutter the thread.

 

[Rob Watts]

Hi @Rob Watts

Does Mojo's USB interface (and associated circuitry) consume significantly more power than TOSLink interface (and associated circuitry)?

Is that why my Mojo gets quite a bit warmer with USB input, versus TOSlink? Mojo's is kept on the wall charger at all times at the moment. I'm never charging from low battery power because I know that will give off a lot of heat.

What's the difference in power consumption between USB and TOSlink? Do you have ball park figures? Just out of general interest only.

The unused inputs are shut-down to save power, so turning on USB adds about 150 mW to the total, or increase total power by about 10% - maybe 1 deg C warmer.

 

[flyte3333]

The unused inputs are shut-down to save power, so turning on USB adds about 150 mW to the total, or increase total power by about 10% - maybe 1 deg C warmer.

Cheers Rob. I've seen you mention the USB decoder consumes 1/3 W of power though, ~0.3W ?

So is the USB decoder still consuming a tiny little bit of power, even with no USB source connected?

 

[Rob Watts]

No the USB decoder is powered down if the USB is not connected; but when USB is on, the SPDIF circuitry and SPDIF decoder (in the FPGA) is off too.

 

[flyte3333]

No the USB decoder is powered down if the USB is not connected; but when USB is on, the SPDIF circuitry and SPDIF decoder (in the FPGA) is off too.

Got it. Cheers again!

 

[flyte3333]

To understand it better, let's assume Mojo is off and charging.

Now the charger has two modes of normal operation - constant current, which is set to 330 mA, and constant voltage which is set to 8.200 V. Now when the non charging battery battery voltage is less than 8.200 V, then the charger supplies a constant current. But when the non charging battery voltage gets close to 8.200 V, then the charger switches mode to constant voltage at 8.200 V. The current that is charging the battery then slowly falls from the initial 330mA, to zero - its in the trickle charge mode now. Eventually, the non charging battery voltage hits exactly 8.200 V, the charger is in constant voltage mode of 8.200 V, no current now flows into the battery, and the charger switches off automatically. When the battery voltage falls to 8.0 volts, then the charger will return to charging. Tip - if you want to force the charger to top up Mojo's battery to 8.200 V then removing the charge USB, wait 5 seconds, reattach, and the charger will top it up to 8.200 V.

Now imagine that Mojo is on at the same time as it is charging. In this case, the battery will continue to charge until it gets to 8.200 V, and the charger is set to voltage mode and gives 8.200 V too; so no current flows into or out of the battery; but Mojo itself is drawing 180 mA of DC current, and this will simply come from the charger - so the charger will supply the needed 180 mA for Mojo. It will do this for ever, and it won't switch off. This is intended, as it means that the battery is effectively not being used to supply the bulk of the current, won't charge or discharge, is held at a safe level, and will operate like this for a very long time.

Hi @Rob Watts

This is probably the best post I could find on Mojo's two modes of normal operation.

For Mojo on and charging at the same time, 24/7, 365 days a year:

When you say battery is held at a safe level, is it at 8.200V at all times? Or does it do trickle down cycles, like the other mode of operation you described (Mojo off and charging).

Or is it safe for the battery to stay at 8.200V 24/7/365 ?

Cheers

 

[Deftone]

Hi @Rob Watts

This is probably the best post I could find on Mojo's two modes of normal operation.

For Mojo on and charging at the same time, 24/7, 365 days a year:

When you say battery is held at a safe level, is it at 8.200V at all times? Or does it do trickle down cycles, like the other mode of operation you described (Mojo off and charging).

Or is it safe for the battery to stay at 8.200V 24/7/365 ?

Cheers

Dude, go enjoy some music.