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Viewing topic "PA-150 adapter extension for MX88"

     
Posted on: February 19, 2018 @ 10:33 AM
Chewie5150
Total Posts:  14
Joined  02-19-2018
status: Regular

First of all, Hello there. I’m new around here and will make this my first post. I recently bought the MX88 after doing a lot of research for what my needs are and decided this over the Moxf8.  I didn’t need the sequencer and computer connectivity was high on my list etc. 

My one complaint would be how short the ac adapter cord is.  Wondering if anyone has used anything like this:

https://www.superpowersupply.com/super-power-supply-ac-dc-adapter-cord-with-10ft-foot-extension-for-yamaha-pa130-pa-150-pa150-dgx-200-electronic-digital-piano-midi-keyboard-plug.php

Seems to be the correct one and the specs seem to line up but wanted to check with the community here to see if anyone has any experience using this or similar product.

Cheers

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Posted on: February 19, 2018 @ 11:47 AM
5pinDIN
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Chewie5150 - 19 February 2018 10:33 AM

First of all, Hello there. I’m new around here and will make this my first post.

Welcome to the forum.

 

Chewie5150 -

I recently bought the MX88 after doing a lot of research for what my needs are and decided this over the Moxf8.  I didn’t need the sequencer and computer connectivity was high on my list etc. 

My one complaint would be how short the ac adapter cord is.  Wondering if anyone has used anything like this:

https://www.superpowersupply.com/super-power-supply-ac-dc-adapter-cord-with-10ft-foot-extension-for-yamaha-pa130-pa-150-pa150-dgx-200-electronic-digital-piano-midi-keyboard-plug.php

Seems to be the correct one and the specs seem to line up but wanted to check with the community here to see if anyone has any experience using this or similar product.

I have no experience with the product you’ve linked to. Offhand, I don’t see a need for it. An ordinary AC extension cord, or a power outlet strip, could be used at the input side of the PA-150. Or, just a power adapter extension cable could be purchased for use with the PA-150 output.

Google “power adapter extension cable” (without the quotation marks). Just make sure to get one with the proper plug inner and outer dimensions. I also suggest not getting one longer than necessary, to keep possible voltage drop to a minimum.

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Posted on: February 19, 2018 @ 02:43 PM
Chewie5150
Total Posts:  14
Joined  02-19-2018
status: Regular

It’s the way my studio space is setup.  The keyboard is a good 6-7 feet away from the wall.  My old MO8 had a different power supply which had nearly twice the length of this adapter. I ordered that extension and will run a quick test with the multimeter to see if there are any voltage drops

Thanks for the reply

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Posted on: March 03, 2018 @ 08:54 AM
Chewie5150
Total Posts:  14
Joined  02-19-2018
status: Regular

update here: I got an extension lead which gives me roughly 10 feet and used a multimeter to verify no drops in voltage

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Posted on: March 03, 2018 @ 08:58 AM
5pinDIN
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Chewie5150 - 03 March 2018 08:54 AM

update here: I got an extension lead which gives me roughly 10 feet and used a multimeter to verify no drops in voltage

Not that I’d expect a significant drop from a 10 foot extension (providing it’s of sufficient wire gauge), but where did you measure the voltage, and what was the supply connected to at the time?

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Posted on: March 03, 2018 @ 12:07 PM
Chewie5150
Total Posts:  14
Joined  02-19-2018
status: Regular
5pinDIN - 03 March 2018 08:58 AM
Chewie5150 - 03 March 2018 08:54 AM

update here: I got an extension lead which gives me roughly 10 feet and used a multimeter to verify no drops in voltage

Not that I’d expect a significant drop from a 10 foot extension (providing it’s of sufficient wire gauge), but where did you measure the voltage, and what was the supply connected to at the time?

So it was just a simple comparison I did with my mutlimeter on the power supply which was plugged into the wall outlet. measured at the end of the barrel.

second test was using the extension and measuring at the end of its barrel.

the readings were identical

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Posted on: March 03, 2018 @ 01:58 PM
5pinDIN
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Chewie5150 - 03 March 2018 12:07 PM

So it was just a simple comparison I did with my mutlimeter on the power supply which was plugged into the wall outlet. measured at the end of the barrel.

second test was using the extension and measuring at the end of its barrel.

the readings were identical

Sorry, but that comparison won’t determine voltage drop that might occur when an operating MX is connected. Just for the interest of anyone wondering why…

The MX draws about 3/4 of an amp. Your meter, even if it’s an inexpensive one, will draw a small portion of that, and a decent one will draw about one millionth of an amp at 12 volts. That’s intentional, because the concept when measuring is to affect the circuit as little as possible. In other words, unlike the MX, the meter provides a very minimal “load”.

Voltage drop is determined by multiplying current by resistance. A few ohms of resistance when the current is 3/4 amp can drop the voltage by several volts. Even two ohms could cause about a 1.5 volt drop. That same resistance, when the current is determined by what the meter draws, won’t cause a noticeable change in the meter reading.

See https://en.wikipedia.org/wiki/Voltage_drop

Nevertheless, as I said previously, with a reasonable length and sufficient wire gauge, the drop can be acceptable.

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Posted on: March 03, 2018 @ 02:50 PM
Davelet
Total Posts:  43
Joined  07-27-2017
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I’d be quite cautious about using a 10 foot extension on the low-voltage side. Far better a 10-foot extension on the mains side for the reason 5pinDin mentions (IR voltage drop). Why can’t you do this again?

More generally, you do need to be careful when replacing the adapters supplied with the synths with cheap adapters such as the ones you describe. The voltage, ampere and/or power ratings only tell part of the story.

All these adapters use some form of switch-mode power supply and I’m afraid that the manufacturer’s profit margins on the cheap adapters are miniscule and the manufacturers of them cut corners everywhere, and map and project component values to fractions of a cent to ensure they turn *some* profit. (Not to say the Yamaha-supplied ones aren’t overpriced by the way!) Of particular concern for any adapter providing power to an audio product is the voltage ripple, and this is always higher under higher power draw, and about which your volt meter would tell you nothing, even if the synth were plugged in (which from the sounds of it wasn’t). To analyse that you need an oscilloscope (or spectrum analyser). I can almost guarantee that the cheap adapter will have worse voltage ripple, and that can manifest itself as horrible noise on the synth’s audio outputs.

Then compound that with the IR voltage drop and the problem will be even worse. One way that corners are cut is to use the thinnest cable possible (look at the price of copper nowadays) which makes the problem worse. In fact, many manufacturers now use something called “cable compensation” where they increase the ouput voltage at the adapter output when there is a high current draw so that the voltage at the end of the cable remains the same as the additional electronics to do that is cheaper than having a thicker cable. But to do that accurately absolutely requires that the exact cable supplied with the adapter is used and not extended, as extending it means that the cable compensation at best won’t work accurately and at worse will make your power supply go unstable with disastrous results.

If you don’t mind wasting your 13 dollars giving it a go that’s fine - I am just advising caution.

(In case you’re wondering how I know all this, I used to design ICs ("chips") that went into these adapters for a living. Glad I don’t do it any longer!)

David.

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Posted on: March 03, 2018 @ 04:17 PM
5pinDIN
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Davelet - 03 March 2018 02:50 PM

[...] More generally, you do need to be careful when replacing the adapters supplied with the synths with cheap adapters such as the ones you describe. The voltage, ampere and/or power ratings only tell part of the story.

All these adapters use some form of switch-mode power supply and I’m afraid that the manufacturer’s profit margins on the cheap adapters are miniscule and the manufacturers of them cut corners everywhere, and map and project component values to fractions of a cent to ensure they turn *some* profit. (Not to say the Yamaha-supplied ones aren’t overpriced by the way!) Of particular concern for any adapter providing power to an audio product is the voltage ripple, and this is always higher under higher power draw, and about which your volt meter would tell you nothing, even if the synth were plugged in (which from the sounds of it wasn’t). To analyse that you need an oscilloscope (or spectrum analyser). I can almost guarantee that the cheap adapter will have worse voltage ripple, and that can manifest itself as horrible noise on the synth’s audio outputs.

I agree that inexpensive power adapters should usually be avoided for the reasons you’ve mentioned. I’ve seen quite a few where the filter capacitors have failed in short order, typically resulting in low output voltage and very high ripple.

Although I don’t have a schematic for the MX, I’m familiar with the design of other models that use the PA-150. The MOXF, for example, doesn’t apply the 12 volts from the adapter directly. The MOXF internal power supply has a three-terminal 9 volt regulator for the audio section, and a DC-DC converter for 5 volt digital. There’s further regulation to 3.3 volts elsewhere. Therefore, at least for the MOXF, a certain amount of ripple can be tolerated.

Interestingly, the particular 9 volt regulator used In the MOXF can remain in regulation with as little as 300mV (500mV at most) I/O voltage difference. (Not that I would suggest trying to run a MOXF on 9.5 volts!)

 

Davelet -

Then compound that with the IR voltage drop and the problem will be even worse. One way that corners are cut is to use the thinnest cable possible (look at the price of copper nowadays) which makes the problem worse. In fact, many manufacturers now use something called “cable compensation” where they increase the ouput voltage at the adapter output when there is a high current draw so that the voltage at the end of the cable remains the same as the additional electronics to do that is cheaper than having a thicker cable. But to do that accurately absolutely requires that the exact cable supplied with the adapter is used and not extended, as extending it means that the cable compensation at best won’t work accurately and at worse will make your power supply go unstable with disastrous results.

While switch-mode supplies are advantageous in terms of efficiency (and I like being “green"), the recent price of copper is probably more a factor in why linear power supplies are a rarity now. I’ve seen some power cables which at first glance appear to be of heavy gauge, but when cut reveal relatively thick plastic insulation surrounding a barely visible conductor.  ;-)

 

Davelet -

If you don’t mind wasting your 13 dollars giving it a go that’s fine - I am just advising caution.

(In case you’re wondering how I know all this, I used to design ICs ("chips") that went into these adapters for a living. Glad I don’t do it any longer!)

David.

Thanks for your comments and insight, and providing the opportunity for me to expound on the topic a bit more.

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Posted on: March 04, 2018 @ 02:59 PM
Chewie5150
Total Posts:  14
Joined  02-19-2018
status: Regular

Appreciate the clarification and explanations given above.  I’m still using the PA-150 Adapter but using the lead extension.  Perhaps I’ll get an extension cord from the mains to be safe.  Also, when i did the original post here it was for the MX but i’ve switched over to the MOXF.  Cheers

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