Step down transformer wattage question
Old 4th November 2007
  #1
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Thread Starter
Step down transformer wattage question

Hi,

I am building a pedalboard which has both a Radial JDV and a Radial X-Amp, each of which runs off its own 110V US power adapter.

The rating on each adapter is as follows:
JDV: input 120V AC 60Hz (no wattage listed); output 21V DC 500ma
X-Amp: input 120V AC 60Hz 12W; output 15V DC 400ma

I am trying to minimise the weight of the board as it's heavy enough already, and I was wondering if it is safe to run both adapters off the same 100W step down transformer (I'm in Ireland so I'm using 220V power) or should I have a separate transformer for each unit?

I'm using one of these step down transformers:
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=270180191369

Is it as simple as adding up the wattage of each adapter and making sure it is within the rating of the transformer? In which case, the X-amp is rated at 12 watts, and though the JDV's adapter doesn't specify its wattage it could hardly be more than 80 watts, right?

any advice gratefully appreciated :)
Old 4th November 2007
  #2
Gear interested
 

Thread Starter
Upon reflection I think I'd be best contacting Radial and asking them. I'll report back here in case anyone's interested.
Old 4th November 2007
  #3
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mark mcg's Avatar
 

Quote:
Is it as simple as adding up the wattage of each adapter and making sure it is within the rating of the transformer?
This is what I was told with my American gear and using a step-down transformer when I lived in Germany. Despite that once I subconsciously plugged a Delta Labs delay straight to the wall! stike Just a fuse to replace though!

Mark
Old 4th November 2007
  #4
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CoteRotie's Avatar
 

Quote:
Originally Posted by 2GAT123 View Post
Hi,

I am building a pedalboard which has both a Radial JDV and a Radial X-Amp, each of which runs off its own 110V US power adapter.

The rating on each adapter is as follows:
JDV: input 120V AC 60Hz (no wattage listed); output 21V DC 500ma
X-Amp: input 120V AC 60Hz 12W; output 15V DC 400ma

I am trying to minimise the weight of the board as it's heavy enough already, and I was wondering if it is safe to run both adapters off the same 100W step down transformer (I'm in Ireland so I'm using 220V power) or should I have a separate transformer for each unit?

I'm using one of these step down transformers:
Find 240V to 110V Step-Down Transformer / Adaptor - 100W on eBay within, Other Consumer Electronics, Consumer Electronics (end time 04-Nov-07 21:00:00 GMT)

Is it as simple as adding up the wattage of each adapter and making sure it is within the rating of the transformer? In which case, the X-amp is rated at 12 watts, and though the JDV's adapter doesn't specify its wattage it could hardly be more than 80 watts, right?

any advice gratefully appreciated
Yes, you're safe using the one transformer. The transformer with no wattage listed is putting out 10.5 Watts, so even if it was only 50% efficient it would only draw 21 watts. So with a large safety margin you're drawing 21+12 Watts or 33 W. Now even supposing the power factor isn't unity, there's no way you're going to approach 100VA so you're safe with the 100W transformer.

Regards,

John
Old 4th November 2007
  #5
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Thread Starter
Quote:
Originally Posted by CoteRotie View Post
Yes, you're safe using the one transformer. The transformer with no wattage listed is putting out 10.5 Watts, so even if it was only 50% efficient it would only draw 21 watts. So with a large safety margin you're drawing 21+12 Watts or 33 W. Now even supposing the power factor isn't unity, there's no way you're going to approach 100VA so you're safe with the 100W transformer.

Regards,

John
Thanks a million John, that's exactly what I needed to hear.
I wasn't sure about how to work out how much it draws but that makes perfect sense. Much appreciated!
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