I need help finding a wall-wart for a portable amp

[aphex]

Here are the specs from the manual; http://www.iiki.org/outgoing/portaac.jpg

50+ mA, 6-28v DC

 

[Zepper]

http://www.bgmicro.com has a good selection of that type of supply. But you'll also need to know the size of the barrel connector it needs - they aren't all the same. Good they gave the polarity though... Radio Shack usually has a wide selection but pricey as always. But some of their models have an adapter on the end and you can pick the size of barrel connector you need as an add-on. May be worth the extra cost to you...

You'll probably want a regulated linear rather than switching unit for an audio application.

jameco.com and allelectronics.com usually have a selection too.

.bh.

 

[aphex]

Thanks for the info.

I swung by Ratshack and they showed me the highest they had, a 12v 500mA AC to DC power supply - $18.99 w/ a free tip (they said $7 value). I would prefer to go as high as possible (the manual says the sound gets better the higher you get towards 28v).

I'll check out BGMicro right now.

In regards to the last comment - Whats the difference between linear / switching? Are you referring to those that are one voltage vs. those that can switch between different voltages?

And am i correct in reading that it needs a 'positive polarity'?

 

[aphex]

Actually, someone just pointed me to this; http://www.jameco.com/webapp/w...10001&productId=174861

Only issue, i would have to solder on a tip that fits. I have a soldering iron, is it difficult to do?

 

[myocardia]

I'd personally grab two cheap 12v wall warts, then series them. The manual for your amp says you can use anything between 6 & 28v, and 12v supplies in series will give you 24v. The reason I'd do it that way is becaus 28v suppies are ~$50, and the 12v you can find just about anywhere for $10 each.

 

[aphex]

And chances of me burning down my house with two 12v in series without ever having done that before?

 

[myocardia]

Originally posted by: aphex
Actually, someone just pointed me to this; http://www.jameco.com/webapp/w...10001&productId=174861

Only issue, i would have to solder on a tip that fits. I have a soldering iron, is it difficult to do?

That's a good price. And no, it isn't hard to do, but you'll have to be careful that you do it right, because you can mess up the amp, if you get the wires backward.

 

[aphex]

Hmmm, could there really be a discernible difference in sound quality from a 12v to a 24v power supply?

I would prefer just stick with the easy $19 one from ratshack, but if there is a noticable difference in SQ by going up to a 24v, then by all means i'll go that route.

 

[Zepper]

The polarity of barrel connectors are Pos on pin or Neg on pin. From the diagram, the one you need is Pos on pin. The Jameco one looks good - hope the size of the connector is correct, the polarity is. All the higher voltage may give you is better ability to handle large transients w/o distortion. Depends on the slew rate of the amp whether the snap to the transients is there. But you don't want to overdrive the outputs.

.bh.

 

[myocardia]

Originally posted by: aphex
And chances of me burning down my house with two 12v in series without ever having done that before?

Zero, unless you start the fire with the soldering iron. BTW, Wal Mart sells 12v wall warts for ~$10 each. Well, they used to, I'm not sure if they still do.

 

[Modelworks]

I would hope they are doing some regulation of the supply at the input.
I'm guessing though that they are just feeding it directly to an opamp that has a 28v voltage limit, not a good design to use, because voltage will effect the output swing.

If they aren't regulating then yes 28v would technically have better range than 12v.

 

[aphex]

Hmmmm.... I dunno, the amp sounds great to me with a single 9v battery, so i assume even the 12v will sound great as well. 24v, hmmmm, i dunno. lol.

 

[John]

Email Jan: meier-audio@t-online.de

 

[Zepper]

WM doesn't sell regulated wall warts for no $12. those are floating outputs - voltage depends on load...

Switching PSUs chop the incoming sine wave into a high frequency square wave so you can get some hash at the output that you don't want on the DC lines of audio equipment - much lighter than linear units due to the lighter weight transformer you can use with high frequencies.

Linear is the old-fashioned heavy, low freq. transformer to full-wave bridge rectifier to filtering components to voltage regulator IC then perhaps more filtering components, then on to the output.

.bh.

 

[myocardia]

Originally posted by: Zepper
WM doesn't sell regulated wall warts for no $12. those are floating outputs - voltage depends on load...

I never said they sold regulated 12v wall warts for $10. I said they used to sell 12v wall warts for $10. And since he found a place to buy a 24v regulated for $25, that's obviously what he should buy.

 

[Zepper]

Well, myo, OP needs a regulated wall wart per his link, so I'd just assumed that any unit suggested would meet his requirements...

.bh.

 

[aphex]

thanks guys - this was the one at radioshack that the guy was telling me would work.

Hmm, decisions decisions...

 

[aphex]

Actually, not i'm reading some reviews of people using the 30v ratshack power supply without any issues (they contacted the manuf. and he said it can actually go up to 32v).

Waiting to hear back from Jan as to the definitive answer

BTW - thanks everybody thus far!

 

[Zepper]

The Radio Schlock one doesn't claim to be regulated but since it's only 12V, it probably won't float above a safe number, but if you measure while connected to your amp it will probably read higher than 12V as the load isn't very high.

.bh.

 

[aphex]

http://www.radioshack.com/prod...p?productId=2049692&cp

Thats the one another Porta Corda III user used on his usb enabled model, i'm trying to find out if it will work on mine as well.

 

[Zepper]

At that point you may as well get the one from Jameco. It is regulated and will probably cost less even with shipping than that one. It doesn't say it is regulated either and there is always the chance of bumping the switch to 30V, but I suppose you could always glue the switch in place...

.bh.

 

[aphex]

well I meant he was actually using it at 30v

 

[Zepper]

Yikes!

.bh.

 

[aphex]

Originally posted by: Zepper
Yikes!

.bh.

I just got this response from Dr. Jan

Your amp will have no problem with a 30V supply. Theoretically
the amp can go upto 32 V.

28V is just a little bit more save.

Cheers

Jan

But with an unregulated power supply, how much can the voltage vary? quite a bit?

What actually would effect the voltage?

 

[Zepper]

The lower the draw of the load (in Amps), the higher the voltage. Since your load is only 1/10th of max, then it will be running at whatever the max is. Maybe they have a =/- x% tolerance range on that thing, but it's not in the specs online. Regulated are usually +/- 5 or 10%, so I'd assume an unreg. one could go beyond that.

.bh.