Jump to content

USB-C power input on MixPre 6 II - voltage specs?


Grant
 Share

Recommended Posts

It's a longer story than needs to post here, but bottom line is : I need to fabricate a cable that brings battery power into the USB-C power port on this new mixer. Q : does anyone know the acceptable range of DC input voltages? The only power arrangement I can fabricate here, while waiting on shipments, will put aprox 14.4 volts into the port, way higher than the 5 V DC that comes with the wall power supply. (as everyone probably knows, the mixer/recorder will give aprox 60 mins run time with the standard 4xAA power module).

 

Standing by with cable cutters and soldering iron!

 

Grant.

Link to comment
Share on other sites

TL;DR: Don't without a voltage regulator.

 

USB-C is a USB port, I imagine they haven't added a voltage regulator because USB is just 5 V. 

 

USB-C can go higher but some negotiation between is involved.

 

As a desperate measure play with the battery terminals, which can get 7.5V (NP-F battery packs). Again, regulate. 

 

Link to comment
Share on other sites

How many volts does the mixer want (operating range), how many amps is its max consumption, and why did the mixer not come with this cable?

 

Looking up specs on USBC cables, I see a Power Delivery spec (USB-PD) that is safe up to 20 volts, max of 3 amps. They claim all USB-C cables are capable of this.  If you believe this, you’re safe at 14 volts and a few amps.

 

25 minutes ago, borjam said:

TL;DR: Don't without a voltage regulator.

 

Obviously we don’t know the voltage needed here, but is there a specific product you’d recommend?  Seems like there is a lot of cheap options for a little DC voltage regulator.

 

Going OT:

 

I ask because I’ve been wanting an AC voltage regulator at home to keep my guitar amps running at a constant voltage (120 volts) but no one seems to make that.  My wall voltage dances between 116 volts and 123 volt, and is never constant.  Folks on the guitar forums tell me I need to build it.

Link to comment
Share on other sites

1 hour ago, Izen Ears said:

Going OT:

 

I ask because I’ve been wanting an AC voltage regulator at home to keep my guitar amps running at a constant voltage (120 volts) but no one seems to make that.  My wall voltage dances between 116 volts and 123 volt, and is never constant.  Folks on the guitar forums tell me I need to build it.

Perhaps this, depending on your amp's current draw? https://www.apc.com/shop/us/en/products/Line-R-1200VA-Automatic-Voltage-Regulator/P-LE1200

Link to comment
Share on other sites

The easy way to do this is find a suitable USB-C car charger, and use the circuit board from it. Despite car power being nominally 12V, it can actually vary within the same range you'd find from common location sound batteries. A good quality car charger will already have protections for over and under voltage, and if it supports USB PD, then it will have the communications interface for negotiating the higher voltages used in that spec. 

Link to comment
Share on other sites

16 hours ago, Allen Rowand said:

I have that unit and it does not ensure a steady output, it just protects against short dips.  I have a variac with a voltage display and that shows me how much my wall voltage changes in real time, and it’s not significantly different with or without that box.  I asked about a box that supplies steady voltage on the forums, and it was explained how complicated and heavy that would be, and how I’d need to build it.  I didn’t question them!  It sounded super complicated, tons of caps and inductors and chip-controlled switchers and all kinds of components.  It wasn’t simple.  Basically a computer-controlled variac that instantly responds to input changes. (Far beyond any skill set I’ll ever have.)
 

If any genius here has different information I’m all ears!  I would *love* to be able to run my 60s amps on 115 steady volts.

Link to comment
Share on other sites

Grant, like everyone said you should regulate down to 5v. But I see in the manual that the power supply is rated for 15w so that’s 3amp. Not so common to find a 12v to 5v car battery charger that allows more than 2,5A. 

Also regulating down from 14,5v to 5v with a linear regulator is going to generate some heat and loss/waste of energy so you might want to find a good switching regulator that operates in a frequency high enough to not generate noise in your machine. If I remember correctly it must be at least twice the sample so 192k x2= 384k, if you find one above 500kHz that should be ok, 1mega even better.

 

Link to comment
Share on other sites

Grant, the USB-C port can be easily powered by a PD power bank that supplies the correct voltage. If you only have access to a 14v source then best practice would be to purchase Hirose equipped battery sled that can accept 10-20v.

Link to comment
Share on other sites

On 4/17/2022 at 6:01 PM, Izen Ears said:

How many volts does the mixer want (operating range), how many amps is its max consumption, and why did the mixer not come with this cable?

 

Looking up specs on USBC cables, I see a Power Delivery spec (USB-PD) that is safe up to 20 volts, max of 3 amps. They claim all USB-C cables are capable of this.  If you believe this, you’re safe at 14 volts and a few amps.

 

USB-C is a complex beast. Normal USB-C is 5.0 volts. Period.

 

Power delivery is a special specification implemented only on some devices (like Macs, some USB-C monitors, phones...)  but it is not mandatory.

 

Devices implement some kind of negotiation to enable PD. Other than that, USB-C is 5.0 V. I wouldn't dare to do an expensive experiment and I would ask Sound Devices. But it is safe to assume that MixPres don's support PD and in that case the expected voltage on the USB-C port is 5 V. I am not sure if some form of over voltage protection or regulation is mandatory on USB-C ports but I wouldn't assume it beforehand.

 

This is a question you should ask Sound Devices.

 

Your best bet is to use the battery terminals, connecting a regulator to them. There is even a Hirose adapter designed to fit like the battery caddy and it includes a voltage regulator.

 

I wouldn't worry much about power noise. I am pretty sure Sound Devices filters the USB-C power input thoroughly.

 

 

Link to comment
Share on other sites

  • 4 weeks later...

Only noise I could foresee is a ground loop if you are recording to computer with other things that may not share ground, say with some guitar pedals or bus powered synths going into the mixpre as the interface or a separate port. Then a usb splitter cable makes sense to me

 

as for usb, the entire proposition sounds so sketchy to me. Not just in fatal powerdowns and corrupted cards, but in risks to the mixpre itself. And it sounds like it ought to be a terrific, light, option, and then I consider the stress on the port, the chances of picking the cable wrong over and over again, the lack of warnings, etc…

 

to this day, I don’t see any consensus around cables. They will be stiff, right angles are out of the question, and let’s face it, they won’t last in a bag, you are loosing a port…just not worth the grief

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...