External Power Supplies revisited

[Delaware Dave]

1 hour ago, TJ Cornish said:

I have not collected any data, but I suspect 15W isn’t enough to run a lot of keyboards, and a 5v supply is very limiting as well - pro level boards that can push +12dBU or better can put more than a 5V swing on the outputs. Very basic opamps are fed by +15v/-15v, and good pro stuff with headroom probably a lot more, so that means step up conversion in the board for those functions, not to mention the heat of modern processors and more than one keyboard with fans.

 

The full-fledged USB-C spec probably is enough - that can negotiate up to 48v/240 watts, however as you mention, now you have a connector where it looks like you can use any supply, but only high-current laptop-style USB-C bricks will work.

most of the professional line of keyboards i've owned (non controllers) have used  somewhere between 35-45 watts of power historically (Kurz, Korg, Yammie, Gem, Ensoniq).

[stoken6]

3 hours ago, TJ Cornish said:

I suspect 15W isn’t enough to run a lot of keyboards, and a 5v supply is very limiting as well - pro level boards that can push +12dBU or better can put more than a 5V swing on the outputs. Very basic opamps are fed by +15v/-15v, and good pro stuff with headroom probably a lot more, so that means step up conversion in the board for those functions, not to mention the heat of modern processors and more than one keyboard with fans.

I was thinking along similar lines. High-spec outputs, a big touchscreen, or complex audio processing typical of pro-level boards may require over 15W - but those are the kinds of beasts that are already, and would continue to be, fitted with internal PSUs. (Kronos is basically an entry-level laptop in a keyboard-shaped box). EDIT @Delaware Dave's comment above puts pro-level keyboards at around 40w.

 

At the other end of the scale, controller keyboards can be bus-powered on USB 5v 500mA = 2.5W. Somewhere in between would suit a 15W power draw. To pick an example at random: Yamaha CK61 specs a 11w power requirement https://uk.yamaha.com/en/products/music_production/stagekeyboards/ck/specs.html. And that's with 2x 6W onboard speakers.

 

Cheers, Mike.

[The Real MC]

5 hours ago, stoken6 said:

USBC "current mode" offers 5v at 3A = 15W. Enough for a keyboard without (or with modest) built-in speakers. USB-PD offers even more (at the expense of standards complexity).

 

Peeking around my studio, that is a gross underestimate.  Very few of my keyboards is less than 15W, and many designs use higher voltage rails than 5V.  Yes you can use converters but they add to the current demand.  You can quickly exceed the 3A limit.

 

"USB-PD at the expense of standards complexity" you're right back to the problem of wall-warts

[stoken6]

3 minutes ago, The Real MC said:

"USB-PD at the expense of standards complexity" you're right back to the problem of wall-warts

To some extent. If I could power keyboards from (say) a standard 65w laptop USB power supply, that's an improvement over having a different, proprietary PSU for every keyboard. The challenge with USB-PD is poor ratification of standards and labelling when it comes to the different standards supported by devices, PSUs and cables. 

 

And as I mentioned earlier, high-specification, high-power-draw boards tend to have internal PSUs to start with, so the problem doesn't arise. It's with the budget/midrange, cost-sensitive models that I think USB provides an opportunity. 

 

Cheers, Mike.

[CEB]

I never put 2 and 2 together.  I like the Roland D-05.  It is a D-50 with better fidelity output.  But my only knock against the synth the low volume output.  It is usable.  I run the volume on max.  It is a MIDI slave of the Kronos but I run the the D-05 output into the audio line input of the FA-06.  That gives me a gain stage if I need it.    It is powered by 5v USB.  The USB power would explain the lower volume output I suppose.

[Jim Alfredson]

57 minutes ago, The Real MC said:

 

Peeking around my studio, that is a gross underestimate.  Very few of my keyboards is less than 15W, and many designs use higher voltage rails than 5V.  Yes you can use converters but they add to the current demand.  You can quickly exceed the 3A limit.

 

"USB-PD at the expense of standards complexity" you're right back to the problem of wall-warts

It's also inefficient to attain higher voltages from low voltage sources. 

IEC with internal supplies is the way to go unless you're talking about controllers, minikey stuff, etc.

[marino]

On 1/4/2024 at 10:38 PM, Dave Bryce said:

What does when you were born have to do with preferring internal power supplies over wall warts? 🤔

 

I admire your restraint...

[Anderton]

16 hours ago, TJ Cornish said:

The idea of USB-C as a power connection is interesting - one challenge is that there tends to be a length limit to the length of the USB-C cable - not sure I’ve ever seen one longer than 2 meters.  I sure love USB-C on laptops, though!

 

The length limitation applies primarily (but not exclusively) to data transfer. There are already USB cables that carry only power, like to charge a battery. This saves the company money (but bites you in the butt if you don't realize the cable doesn't carry data, and then wonder why when you use that cable, your XZY-1000's MIDI port can't talk to your computer!).

 

The length over which a cable can transfer full wattage depends on the wire gauge. Most USB-C/Thunderbolt 3 cables that meet USB-FI specs can support 60W charging up to at least 12 feet with no problem. The more current being drawn and the longer the length, the greater the possibility that there will be excessive resistance, especially with inexpensive cables.

 

If length is an issue, you would need an extension cord from the stage's AC outlet to whatever is supplying power over USB-C. That may actually be the best way to go anyway, because having an AC cord running across the stage seems far less fraught than using a USB-C cable. 

 

 

[Anderton]

2 hours ago, Jim Alfredson said:

It's also inefficient to attain higher voltages from low voltage sources. 

 

That's true. However, remember USB-C is a connector standard that is not tied to a particular type of data transfer or voltage. There are already devices with power supplies that push 48V, but no data, into devices with USB-C connectors.

 

Of course, then it might seem we're back to having multiple incompatible power supplies for various devices. However, the higher-voltage ones will probably be corner cases, and there will probably be some standards, too. For example, most laptop bricks provide 19-20V. So, one power supply could handle any typical laptop if it has a USB-C connector. 

 

The biggest problem I see is that labelling has to be unamibigous for cables, data transfer, and power. The USB-IF is working on that. Granted, that's a problem for what we have now as well. Hopefully, it will be less of a problem in the future.

 

[stoken6]

Thanks to @Jim Alfredson, Craig @Anderton and all the other experts on this thread.

 

Cheers, Mike.

[AnotherScott]

Nicely, external power supplies have gotten a lot smaller/lighter in recent years. I have some stuff from years ago where the external PSUs are bricks. Which also means there's a decent chance of damage if you drop one. (I did lose one that way.)

 

My Korg and Roland external PSUs are nice... light, with a decent thickness cable to the keyboard, and a removable standard or figure-8 cord for the other side. You can velcro the piece to the keyboard and have essentially the same benefits as an internal (e.g. can't forget/lose it), along with the added advantages of an external (easy replacement, lighter keyboard weight, since it seems that internals are rarely if ever found in boards with plastic chassis, possibly because of issues of meeting shielding/FTC requirements)... though you do have to make sure your case can accommodate it. I wish Yamaha would get with the program, they still ship the wall-wart style with a flimsy twisted cable.

[TommyRude]

I hate wall warts

- Signed:  Boomer

 

Why don’t we already have wireless power?  Not batteries, just magical wireless power.

- Signed:  Boomer

 

Can we get rid of cables, for everything?

- Signed:  Boomer

[stoken6]

14 hours ago, AnotherScott said:

a removable standard or figure-8 cord for the other side. You can velcro the piece to the keyboard and have essentially the same benefits as an internal (e.g. can't forget/lose it), along with the added advantages of an external (easy replacement, lighter keyboard weight, since it seems that internals are rarely if ever found in boards with plastic chassis)

I've done this. The risk is that the point where the (DC low-voltage) power cable leaves the PSU is fragile and can be easily damaged. It needs to be located carefully and potentially protected to avoid damage. 

 

Cheers, Mike.

[Mills Dude]

13 hours ago, TommyRude said:

I hate wall warts

- Signed:  Boomer

 

Why don’t we already have wireless power?  Not batteries, just magical wireless power.

- Signed:  Boomer

 

Can we get rid of cables, for everything?

- Signed:  Boomer

Where's my flying car?

-Signed: Boomer

[Delaware Dave]

15 hours ago, TommyRude said:

Why don’t we already have wireless power?  Not batteries, just magical wireless power.

 

talk to tesla .....

[The Piano Man]

I can see a scenario where a keyboard could be designed such that the casing has a neat recessed area for the PSU to be housed, complete with C14 connector. Almost like one step further than what AnotherScott describes. 

[Stokely]

I had just about that same thought, though with an almost total lack of technical insight into how it might work   

Basically, an easily-replaceable internal power supply.  And for all I know, they are now...I've never had one die on me.   I do see where you'd have to open the main chassis and that seems to made pretty difficult by some of the manufacturers unfortunately.   IEC cables, yep just had one die, but I have about 30 around the house and keep several spares in my backup case.

[bfields]

I wonder if there's any potential for heat buildup if you attach the "external" power supply to the case.  Seems to me one of the advantages of an external power supply could be that heat dissipates more easily.

[Reezekeys]

My controller uses 300ma so pretty much anything can power it. On the road, I used to use USB for convenience since my laptop could provide power and get midi on one cable - until the gig we did on a huge stage where I confidently attached a USB extension cable only to see my midi data get corrupted. Now I use my wall wart for the keyboard and 5-pin midi (my Roland A800 can do either or both in any combination). I carry an extension cable for my wall wart since I sometimes can't get a quad box near my keyboard. It's been smooth sailing since.

 

Being a controller & laptop (or i-device) person, I haven't used a keyboard with built-in PSU for many years so I'm quite used to the extra pieces. What I really like about my setup is that my three external PSUs - for the laptop, A800, and my Rolls in-ears mixer – are switched mode and operate at any voltage between 100 and 240 volts. In the last 10 years I've been to the UK and Japan multiple times and all I've needed is a plug adapter.

 

In the 1980s I traveled to Europe with John Scofield and remember a gig in Poland where my setup (personal USA gear, not rented) was powered by a step-down transformer on the same circuit as the bass amp. Every time the bass player thumbed a low E, the voltage dropped and two things happened: my gear shut down for a second, then came back up - on patch #1!! So all you young 'uns complaining about yer wall warts, you don't know how good you have it! 🙂 

[wineandkeyz]

Boomer here.

 

All of my keyboards use IEC cables, but I suppose I could picture owning a keyboard that uses an external power supply if everything else about it was optimal. But it seems that many of the keyboards from the major manufacturers that use an external PS also cut corners in other ways, such as scaled down features, an inferior keybed, plastic chassis, etc. For example, compare the Roland Jupiter-80 to the Jupiter-50, Fantom series to the Fantom-0 series, or Yamaha Montage to the MODX series. So while I might look past the external PS, other factors turn me off.

[zxcvbnm098]

For those of us that started playing keys in an era where almost all keyboards had an internal PS, the subtle move over time to more and more keyboards having external PS is disappointing. 

 

To me, it's understandable for a lower priced instrument - say south of $1K - to have the external. I get it, and have worked in CE manufacturing where we utilized them for many products that were relatively inexpensive for both economic and time saving in the production of said goods. They make sense for sure at certain low price points.

 

And I will recognize that what we get for keyboards in these lower, entry-level-ish price range is pretty astounding compared to what things cost in the 80's let's say. Improvements in manufacturing and computer chips have been a boon for people like me who drooled over a Prophet 5 or other similar unobtainium instruments back in the day. 

 

But my frustration comes when something like a Kurzweil SP7 Grand with a MAP at ~$2K still comes with a external PS. I know all of the major players play follow-the-leader in these categories (not to pick on Kurzweil here), but to me that's a category where it's mainly geared toward "pro" players, and therefore should really have an internal PS. 

 

I don't know what the cutoff should be, but I'll say anything above roughly a MAP of $1500 should really get into internal PS territory. 

[kenheeter]

It's about the only thing that disappoints me on my Numa X Piano.  I did buy a spare supply with an IEC connector and a  robust DC cable which I shortened and on which I installed an angle plug. It is permanently velcroed onto the rear of the Numa X and fits into my soft case so it is   virtually an internal supply.  I've had a   Mojo 61 for years and I installed its power supply internally a long time ago. The latest version of the Mojo61 now comes with an internal supply.  

[elsongs]

For those of you dealing with Wall Wart plug real estate, I've invested in a handful of these for my studio rack. A 6-inch extension cord. A wart can go in the long end and a regular plug can go in the short end. Just $5 each at your local Lowe's or Home Despot: