Author Topic: 400mA power supply enough for a pedal which requires 600mA? (Read 6479 times)

Mann · « **on:** September 27, 2007, 11:13:03 AM »

I bought a Behringer X V-Amp (junk sale...) which seems to work - all the leds light according to the manual etc. - but I can't get any sound out of it. I've tested different cords, headphones etc. and tried different input gain settings but no sound, just hum.
I opened the thing and changed the battery (no help) . It came with a power supply which gives 9v/400mA but there's a text on the pedal that says 9V/600mA, could this be the problem or is it just a flashy paper weight?

(I do build most of my own stuff: amp, pedals etc.)

Mark Hammer · « **Reply #1 on:** September 27, 2007, 11:58:53 AM »

Is the power supply provided with the unit you bought the power supply that originally came with it, or merely a quick substitution for one that was rendered "less functional"?

Ideally, you will want to supply the current that the chassis stipulates.

And, um, one other little detail. Is there perchance a wavy line beside the 9V 600ma? I ask because I was not accustomed to that symbol and ran all over town trying to find a 10vDC adaptor for a DOD floor unit before I realized it was supposed to signify 10vAC.

If you are using a 9vDC adaptor when an AC unit is actually called for, that might be the source of your problem. Several things would likely or possibly result from that. First, AC doesn't have an orientation/polarity when it comes to the jack, so there is a possibilty that a 9VDC supply would be feeding the hot and ground to the "wrong" spot at the jack. Second, if the unit has its own on-board regulation and rectifies 9VAC up to 12.7VDC so it can be regulated down to either 12 and/or 9vdc, then feeding it 9VDC would not be enough to meet the needs of that circuit.

So, ultimately, the issue may be the power you are currently feeding it OR the power it was mistakenly fed in past.

Mann · « **Reply #2 on:** September 27, 2007, 12:19:33 PM »

I don't know about the power supply which came with the pedal if it's original or not. But this is from the power supply:

ac adaptor
pri: 230V ~ 50 Hz 6W (I'm from finland...)
sec: 9V ----- 400mA 3.6 VA

and another text: video receiver
so it can't the original

and there is the wavy line on the pedal:
9V ~
600mA

so my adapter must be of wrong type?

GibsonGM · « **Reply #3 on:** September 27, 2007, 12:44:57 PM »

As long as the chassis has the wavy line, I'd suspect you need a 9v, 600mA AC adapter....hopefully no damage has occurred to the unit because of the wrong power supply....you can always use the other one for some other project ;o)

CGDARK · « **Reply #4 on:** September 27, 2007, 12:52:09 PM »

If your adaptor is 9ac 400ma then you'll need another adaptor, because you are 200ma short of the Behringer X V-Amp specs that's why you can't get any sound out of it. So try to find a 9vac of a least 600ma or more and you are done.

CG

Dingleberry Electronics · « **Reply #5 on:** September 27, 2007, 06:25:34 PM »

Hi.

Your power adapter is totally wrong type. What I can understand from your descriptions, your pedal needs 9VAC 600ma and your power supply is giving you
9VDC 400ma. First that's 200ma too low and second it's DC not AC what your pedal requires. So get a new adapter.

And same in Finnish:

Verkkolaite on täysin väärää tyyppiä. Mitä nyt tuosta sinun kuvauksesta ymmärsin, niin sinun pedaali tarttee 600ma vaihtovirtaa ja tuo sinun muuntaja antaa 400ma tasavirtaa.
Ensiksikin se on 200ma liian vähän ja toiseksi se antaa tasavirtaa eikä vaihtobirtaa mitä tuo pedaali vaatii. Joten hommaa uus verkkolaite.

-Dingleberry

Ronsonic · « **Reply #6 on:** September 27, 2007, 07:17:23 PM »

This very problem was presented in a Yamaha service seminar. The analog section of the pedal runs on a +/- voltage and the digital just needs a +5V supply. So what they (they, being pretty much anyone who build pedals) do is feed the pedal AC and then use a bridge to get both supplies. A DC pedal will still supply the positive DC for the digital section, but the bridge can't supply the negative voltage for the analog section. So you get a symptom of a unit that boots and responds to the digital controls but just won't do audio.

Fun when the customer insists this is the power supply he's been using all along.

Ron

Paul Marossy · « **Reply #7 on:** September 27, 2007, 08:00:11 PM »

ART has made some products that require an AC power supply as well. It greatly de-mystified why my X-15 foot controller wouldn't work with a DC power supply when I noticed that the unit said AC on it and not DC. I didn't notice this until years later after I got the replacement power supply from ART.

I didn't know any better at the time as I didn't really know anything at all about electronics back then...

petemoore · « **Reply #8 on:** September 27, 2007, 10:23:56 PM »

Correct AC supply is the only way to test the units functionality.

Mann · « **Reply #9 on:** September 28, 2007, 01:22:04 AM »

Thank you for answers - I totally didn't expect ac-powered pedal. The only place it is mentioned is the pedal itself and the power I got with the pedal was totally wrong.

Paul Perry (Frostwave) · « **Reply #10 on:** September 28, 2007, 04:07:59 AM »

It's not just guitarists that get confused.
Unfortunately, manufacturers of ANY kind of plug pack tend to call them "AC Adaptors", because AC mains goes in... it's very difficult to get manufacturers to understand that I want something that puts OUT ac!
For anyone living in the USA, www.jameco.com is a good wallwart source. That's where I get the AC plugpacks for the units I sell to North America.

Mark Hammer · « **Reply #11 on:** September 28, 2007, 09:33:35 AM »

As an aside, using an AC supply has several advantages to it.

First, as with any audio appliance that has the power transformer external to the chassis and audio circuitry, you get the hum-reduction advantages (i.e., the transformer is not close enough to the audio stuff to influence it).

Second, the hardware required to convert the AC to DC is minimal, in terms of footprint, cost and weight (although there is the issue of heat dissipation on the regulating semiconductors, I suppose, if current draw is high).

Third, the circuit is powered by known regulation, as opposed to some black epoxy-encapsulated thing which purports to provide DC but one has no idea how ripple-free it may be.

Fourth, the AC can be readily converted to several DC voltages, although I suppose DC can be downregulated too.

Fifth, there is no issue regarding the polarity of the adaptor plug/jack since both contacts are equivalent.

96ecss · « **Reply #12 on:** September 28, 2007, 10:01:38 AM »

Quote from: Mann on September 27, 2007, 11:13:03 AM

I bought a Behringer X V-Amp (junk sale...) which seems to work - all the leds light according to the manual etc. - but I can't get any sound out of it. I've tested different cords, headphones etc. and tried different input gain settings but no sound, just hum.
I opened the thing and changed the battery (no help) . It came with a power supply which gives 9v/400mA but there's a text on the pedal that says 9V/600mA, could this be the problem or is it just a flashy paper weight?

(I do build most of my own stuff: amp, pedals etc.)

Hi,

I just read all the answers and something kind of jumped out at me. He said he replaced the battery and it didn't help. I'm not familiar with this unit but if it runs on battery and he replaced it, wouldn't that rule out the power supply as being the problem? Unless of course if the unit was damaged by using the wrong power supply it might not work at all. I'm not being a wise guy here, I'm just curious.

Dave

Mark Hammer · « **Reply #13 on:** September 28, 2007, 10:46:58 AM »

Not necessarily. If the battery is a rechargeable unit (and we don't know at this point), and the supply is not getting "over the hump" to generate the DC output voltage that will ultimately recharge the battery (rechargeables are sometimes sold uncharged) then it could very well be the case that a new battery fails to "work".

96ecss · « **Reply #14 on:** September 28, 2007, 11:17:42 AM »

Good point about the rechargeable. I hadn't thought of that.

Dave

Ronsonic · « **Reply #15 on:** September 28, 2007, 07:51:11 PM »

The only battery in that unit would be a lithium coin cell, and a known problem spot on some Behringer products. Some units had cheesy coin cell holders and the momentary interruptions would store garbage to the memory, so his replace battery (preferably with a soldered in one, or a better holder and reinit is the standard drill. Actually not a bad starting place for any deranged digital appliance. Of course there is the "check the wall wart first" business so maybe the battery is step two.

Ron

Paul Perry (Frostwave) · « **Reply #16 on:** September 29, 2007, 05:51:17 AM »

Quote from: Mark Hammer on September 28, 2007, 09:33:35 AM

As an aside, using an AC supply has several advantages to it.
...
Third, the circuit is powered by known regulation, as opposed to some black epoxy-encapsulated thing which purports to provide DC but one has no idea how ripple-free it may be....

There is another point, now that California (and thus the world) is making ordinary linear DC plugpacks illegal: it will still be legal to use AC output plugpacks. I guess there will bew millions of ordinary DC plugpacks available for the rest of my lifetime.. but for new stuff, there is an argument for AC & then old style diodes & regs in the FX.

Ronsonic · « **Reply #17 on:** September 29, 2007, 05:04:38 PM »

Quote from: Paul Perry (Frostwave) on September 29, 2007, 05:51:17 AM

There is another point, now that California (and thus the world) is making ordinary linear DC plugpacks illegal: it will still be legal to use AC output plugpacks. I guess there will bew millions of ordinary DC plugpacks available for the rest of my lifetime.. but for new stuff, there is an argument for AC & then old style diodes & regs in the FX.

Please tell more. What's the deal on that?

Paul Perry (Frostwave) · « **Reply #18 on:** September 29, 2007, 09:35:12 PM »

here ya go Ron:
powerelectronics.com/mag/503PET23.pdf
It's a pretty flawed concept, throwing out linear supplies & replacing them with switch mode supplies thatare
1. far more unreliable
2. prone to bursting into flame (happened to me)
3. radiate interference
4. distort the mains sine wave
5. have a much shorter life (reliability problem) so add to waste

But governments LOVE to be 'seen to be doing something' so there it is.

Mann · « **Reply #19 on:** October 01, 2007, 04:15:55 AM »

I bought a new power supply which gives 1000mA (600mA needed) but the effect does not work as it should - delay, reverb and modulation effects don't work at all only the amp simulations.
Could this 1000mA be too much?

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Author Topic: 400mA power supply enough for a pedal which requires 600mA? (Read 6479 times)