Wall wart power supply help please !!!!!

jibreel · #1 11-20-2010, 02:59 PM

This saga started here: HELP !!! My Ebay purchased Kern came w/out a power supply. What can I use instead??
Summary: Won a Kern preamp on ebay. The end of the package came apart and the power supply was lost.
Someone with this power supply told me the exact description of what is needed:
Class 2 transformer 120VAC 60hz 30W
Output: 12VAC 1.25amp

I ordered this online: http://azsurplus.com/index.php?main_...62&language=en

On the site is reads: RH48T-1201250DU AC ADAPTER 12V 1250mA 30W CLASS 2 TRANSFORMER E2

It finally arives after two weeks from Canada and everything is correct EXCEPT it is 12VDC 1.25 amp output not 12VAC

Will this work ???? I am not going to plug it in until I know for sure.

Also, this particular adaptor is very hard to find.
Can I use one that is close?
How hard to have the power supply put inside the unit itself as some have done?

Thanks for any info !!!

dmusic148 · #2 11-20-2010, 03:08 PM

No, that won't work and may even damage the Kern.
All you need is a transformer. You should be able to get one at Radio Shack. Then you just need to wire it up- simple really.
You could put it inside the unit instead, but I suspect Kern put it in a wall wart format to prevent the possibility of the pre picking up radiated noise from the transformer.

BTW the surplus site should have specified DC, which I see they don't. But the giveaway is that they listed + and - for the different parts of the connector- an AC connector won't be labeled.

**mikeddd** · #3 11-20-2010, 03:09 PM

If your Kern preamp really requires a 12VAC supply DO NOT use a 12VDC supply or you could possibly fry it. Do you have the manual for that preamp? Can you download it to ensure it really needs AC? Any good pedal power supply like the BBE SupaCharger has 9-12VAC outs. Just a thought.

dmusic148 · #4 11-20-2010, 03:14 PM

No, that won't work and may even damage the Kern.
All you need is a transformer. You should be able to get one at Radio Shack. Then you just need to wire it up- simple really.
You could put it inside the unit instead, but I suspect Kern put it in a wall wart format to prevent the possibility of the pre picking up radiated noise from the transformer.

dmusic148 · #5 11-20-2010, 03:17 PM

Quote:

Originally Posted by mikeddd

Any good pedal power supply like the BBE SupaCharger has 9-12VAC outs. Just a thought.

Mmm...don't think so. I don't see anything anywhere that suggests it will supply AC.

bongomania · #6 11-20-2010, 03:18 PM

Quote:

Originally Posted by mikeddd

Any good pedal power supply like the BBE SupaCharger has 9-12VAC outs.

No, you've got it backwards--they mainly supply DC. There are a few that additionally have one or two AC outlets, and there are a couple that only do AC, but by and large, pedal power supplies are DC. The BBE only has DC.

**mikeddd** · #7 11-20-2010, 03:42 PM

Whoops.

My bad. I got confused. I own a SupaCharger and confused the 200MA outputs, thinking they were AC outs. Thank you for correcting me and ensuring the OP gets the right info. Didn't mean to mislead you, Jibreel. I had the best of intentions.

jibreel · #8 11-20-2010, 04:36 PM

MikeD.. no worries and thanks for trying.

And thanks to all who have responded.

I am wondering if top one here will work. I will call them on Monday.

http://www.rofu.com/misc/power.html

bongomania · #9 11-20-2010, 05:31 PM

Two things about that one: it has no cord or barrel plug, so you'd need to cannibalize those from another supply; and it's unregulated. TBH regulation may only be relevant with DC, I'm not sure about AC; but it's super-important with DC, so it's worth investigating.

jibreel · #10 11-20-2010, 05:52 PM

Quote:

Originally Posted by bongomania

Two things about that one: it has no cord or barrel plug, so you'd need to cannibalize those from another supply; and it's unregulated. TBH regulation may only be relevant with DC, I'm not sure about AC; but it's super-important with DC, so it's worth investigating.

Thanks. I do have a barrel plug and the cord would be easy but I do not know about unregulated or not.

jibreel · #11 11-20-2010, 06:03 PM

Lineman6 found this !!

http://www.mouser.com/ProductDetail/...teL%252b79c%3d

bongomania · #12 11-20-2010, 06:17 PM

The nice thing about Mouser is they are great about accepting returns, and if you end up with the wrong item, they will get an engineer on the line to help you get the right one.

fdeck · #13 11-20-2010, 07:50 PM

A regulated AC wall transformer would be an oddity. There's a good chance that if the preamp takes an AC wall wart, it's probably turning the AC into "split" DC power supply voltages internally, such as +/- 12 V . Thus there is probably good regulation inside the preamp.

Beware that there are two different center pin diameters on those *&@#$ barrel jacks. If you get the wrong diameter, it either won't fit, or won't make contact.