[taipan254]

That is extremely ironic given the stance of Rob Watts on linear power supplies:

Yup - I was one of the guys that asked questions at that lecture.

First off - Rob is an extremely nice guy and was very kind to offer up his time and perspectives to me before and after both lectures he gave. I was so appreciative of his time.

Rob has very strong opinions on linear power supplies. And Rob believes that a car battery is among, if not the very best, power source for most devices. I personally find his battery implementation in Mojo 2 sufficient.

My understanding of the counter-argument to removing the battery and using an external power supply (say a supercapacitor-based design or a high-quality LPS) is that it disables the battery management features in the FPGA, thereby reducing noise. God knows if that works and frankly I'm not at the point where I want to experiment with that. Maybe some day. That being said, Rob even admitted in this lecture that were he designing Dave today, he would not use the same power supply that he included in the Dave. My guess is that his next DAC will have a very hardcore, highly designed and spec-ed SMPS that is highly resilient in the face of, if not immune to, EMI and RFI.

My basic approach to maximize the sound quality I'm getting out of Mojo 2: run as much as I can off of batteries. Mojo 2's battery works for my usecase. My headamp runs off a battery + inverter. When I'm mobile, I'll run off USB to my phone (sufficient for RFI / EMI mitigataion as both are "floating" / powered off batteries). If I'm not upsampling and on a PC, I'll use the Mojo 2's optical input - nearly immune to source jitter and full galvanic isolation so no nasties coming through. When I upsample, I use a SRC-DX, but that doesn't have full galvanic isolation from the source.

My next project: building a battery-based dedicated music server after I get my home network set up (wish me luck: I'll be running ethernet cables in my walls and terminating them!).

 

[folkguy]

Is it easy or tricky to use car batteries for audio? I've seen Rob mention it a few times now, wonder how you'd configure it and if it's potentially dangerous. If anyone here knows I'd love a reply or DM, links to resources appreciated too, I'll be doing my own research anyway.

 

[freaknout]

My next project: building a battery-based dedicated music server after I get my home network set up (wish me luck: I'll be running ethernet cables in my walls and terminating them!).

May or may not suit you but I use a battery powered WiiM Mini as an isolated streamer.

 

[MarkParity]

Is it easy or tricky to use car batteries for audio? I've seen Rob mention it a few times now, wonder how you'd configure it and if it's potentially dangerous. If anyone here knows I'd love a reply or DM, links to resources appreciated too, I'll be doing my own research anyway.

You don't need a car battery as such, its used as just a generic term for a 12V Lead Acid battery.

I would use a SLA style battery myself as they are much safer, you won't end up with battery acid everywhere if it tips over. Put a fuse, 500mA should do the job, close to the battery terminals. Insulate everything and you should be OK.

Edit:
Just to clear up any confusion, this wouldn't work for Mojo 2 as it uses a 7.4V LiPo battery, this car battery approach is really for 12V devices like TT2. The moment a regulation circuit is added to the 12V battery it really defeats the whole point. Perhaps you could use a 6V SLA battery for Mojo 2 but I have no idea if that would work of if you'd risk blowing something up.

An SLA battery for reference:

 

[taipan254]

Is it easy or tricky to use car batteries for audio? I've seen Rob mention it a few times now, wonder how you'd configure it and if it's potentially dangerous. If anyone here knows I'd love a reply or DM, links to resources appreciated too, I'll be doing my own research anyway.

Here's what I know:

Car batteries, and other batteries like LiFEPO4 batteries, typically run on 12 volts DC output. Typically, they offer very low output impedance, thereby supplying power to devices very quickly. They also are "floating" and not connected to earth ground. Different ground potentials cause EMI and RFI noise. If you have a component (like a DAC) that runs off of a 12V input, you can hook the car battery or LiFePo4 battery up to the device directly via a DIY cable. Of course, when the battery is drained, you will need to recharge it and that requires some different hardware, and lots of plugging and unplugging of cables.

What if you have AC powered devices? Buy something like this - a high quality pure sine wave inverter connected to a battery with a battery management system already integrated in one box. I hook my amp up to this. This has AC outlets, a 12VDC outlet, and numerous USB outlets operating a 5VDC 2A. It also has a photovoltaic charging input, but you can charge this thing off of AC from your wall while you sleep. Of course, you are limited by the power one of these things can provide, so it isn't great for powering say a Nelson Pass Designed Speaker Amp that runs in Class A and consumes hundreds of Watts per hour. But it can manage a headphone amp and other devices very easily.

 

[MarkParity]

Here's what I know:

Car batteries, and other batteries like LiFEPO4 batteries, typically run on 12 volts DC output. Typically, they offer very low output impedance, thereby supplying power to devices very quickly. They also are "floating" and not connected to earth ground. Different ground potentials cause EMI and RFI noise. If you have a component (like a DAC) that runs off of a 12V input, you can hook the car battery or LiFePo4 battery up to the device directly via a DIY cable. Of course, when the battery is drained, you will need to recharge it and that requires some different hardware, and lots of plugging and unplugging of cables.

What if you have AC powered devices? Buy something like this - a high quality pure sine wave inverter connected to a battery with a battery management system already integrated in one box. I hook my amp up to this. This has AC outlets, a 12VDC outlet, and numerous USB outlets operating a 5VDC 2A. It also has a photovoltaic charging input, but you can charge this thing off of AC from your wall while you sleep. Of course, you are limited by the power one of these things can provide, so it isn't great for powering say a Nelson Pass Designed Speaker Amp that runs in Class A and consumes hundreds of Watts per hour. But it can manage a headphone amp and other devices very easily.

The problem with devices like power stations is they have regulators (SMPS) built in, you are not connecting directly to a DC power source, you may as well use any other 100-240V PSU.

 

[585046]

deleted

 

[Daniel Johnston]

The problem with devices like power stations is they have regulators (SMPS) built in, you are not connecting directly to a DC power source, you may as well use any other 100-240V PSU.

This ^

Adding to this, inverters can create tremendous amounts of noise. I used to plug my Naim into a UPS. On battery mode, there was 2X more EMI noise (based on meter) than plugged into AC. And, noise was in general higher plugged into the UPS than the wall outlet itself.

Granted it wasn't terribly expensive, but it did use the aforementioned 12V lead acid battery. I think the take away is direct DC power and DC power converted to AC via inveter are not equivalent. You'd be better of with using a good quality SMPS from the wall rather than a possibility noisy inverter.

 

[Hypops]

I read that the Mojo 2 turns off after 10 minutes of inactivity. I would use it mostly in desktop mode at my computer, so would I have to turn it on again every time I'm away for more than 10 minutes or would it only auto-turnoff after I remove it from the USB hub?

Difference seems to be if it's plugged into an audio source or not. Mine only shuts off by itself when it's powered on and not plugged into anything.

 

[taipan254]

The problem with devices like power stations is they have regulators (SMPS) built in, you are not connecting directly to a DC power source, you may as well use any other 100-240V PSU.

This ^

Adding to this, inverters can create tremendous amounts of noise. I used to plug my Naim into a UPS. On battery mode, there was 2X more EMI noise (based on meter) than plugged into AC. And, noise was in general higher plugged into the UPS than the wall outlet itself.

Granted it wasn't terribly expensive, but it did use the aforementioned 12V lead acid battery. I think the take away is direct DC power and DC power converted to AC via inveter are not equivalent. You'd be better of with using a good quality SMPS from the wall rather than a possibility noisy inverter.

Inverters can indeed generate noise and do utilize SMPS equipment. As Rob Watts mentioned in the video posted above, SMPS can offer numerous benefits, but they have to be designed well. The quality and implementation of the inverter matters a lot. I most certainly agree with @MarkParity that, when devices allow for a 12VDC input, connecting said devices directly to a battery without a regulator in between is generally preferrable (depending on the regulator, of course! There are some high quality ones out there, and lots of crappy ones).

While I have not tested more than the bluetti inverter I own (it was suggested to me by an audio retailer whose ears I trust), my audio set up sounds markedly clearer using batteries (for DC devices) and the bluetti battery and inverter (for AC devices) relative to the AC power coming out of my wall. I do repeated tests at many times of the day (just to distract from my day-to-day work to make sure).

I can't be certain I know why I'm getting better listening results using the batteries and inverter. Various hypotheses I cannot in any way definitely (i.e., without a doubt) prove:

• Power quality from grid-linked AC outlets varies by time of day (power usage is higher during daytime hours - coincidentally usually when my the listening experience is worse).
• Grounding schemes in vary on a home-by-home basis (Michael Fremmer just got his house re-grounded - fun video here). Therefore not all AC lines offer the same performance due to the differences in grounding.
• The Batteries and AC Inverter are "floating". This "air gap" from shared ground isolates the audio devices from noise generated by other devices (like microwaves and washing machines) that travel on the AC line and ground.
• Unknown Unknowns - I have no idea, but in my Brooklyn apartment, I could pick up low-level ham radio signals! I have no idea why this was the case. This problem actually led me down the power isolation rabbit hole.

At the end of the day, all I can do is compare my listening experience vs. different set ups I have experienced (either in my house, at CanJams, or at friends' spots). I'm just sharing my experience in the hopes it benefits others!

 

[Daniel Johnston]

While I have not tested more than the bluetti inverter I own (it was suggested to me by an audio retailer whose ears I trust), my audio set up sounds markedly clearer using batteries (for DC devices) and the bluetti battery and inverter (for AC devices) relative to the AC power coming out of my wall. I do repeated tests at many times of the day (just to distract from my day-to-day work to make sure

In my case, I can't tell you if there were any audible differences between the UPS, UPS on battery and using inverter, or direct from wall AC. I used it originally to keep my Yggdrasil powered on when I moved the portable cart it was on from my living room to the office when we had company. It morphed into using with the Naim because I was under the impression that battery power via inverter was cleaner than AC. It wasn't until I got some EMI filters and and EMI measuring device that I found the noise.

I agree that DC direct has the least chance of EMI and should sound the best.

 

[Hypops]

I use an LPS with my Mojo 2 more for peace of mind (and because I had an unused and compatible LPS lying around). But can’t say I can hear a difference between that, a cheap wall wart SMPS, and running off of battery. By contrast, I do get audible improvements with better quality interconnects. In other words, if the LPS does lower the noise floor, it’s more marginal than (much cheaper) interconnect upgrades.

 

[NYer718]

Right.

I'd bet that in 90% of Mojo2 users tweak the bass or highs a bit but almost never change the mids.

I guess I'm the 10%

I set my Mojo 2 eq to
Red -1
Yellow +1
Green +1
Teal -6

Crossfeed OFF

These make my Sony MDR EX1000 sound somewhat closer to my Sennheiser HD650

 

[NYer718]

Yoo friends. I kinda pulled the trigger on a Mojo 2 with the leather case included for 500 Euros.

Question: Ive been browsing through this 600 page thread and im lost in the flood of information:

I have a Samsung S23 Ultra with USBC C port.

Does the cable need any specifics or, is any USB C to USB C fine?
Any recommendation for a cable that can be bought in Europe/Germany?

Cheers

I highly suggest the iFi 90 Degree USB-C to USB C

 

[lolhero]

I use an LPS with my Mojo 2 more for peace of mind (and because I had an unused and compatible LPS lying around). But can’t say I can hear a difference between that, a cheap wall wart SMPS, and running off of battery. By contrast, I do get audible improvements with better quality interconnects. In other words, if the LPS does lower the noise floor, it’s more marginal than (much cheaper) interconnect upgrades.

Forgive me for stupid question, but what are the interconnect upgrades you mention?