[bhjazz]

I guess the question is: how much is too much!

The plugin wallwart for my phono preamp has died. Dunno why. It's an AC AC Adapter: 16VAC/250ma. And I can't seem to find a reasonable replacement online. The closest I have found is 16VAC - 1A. Seems like overkill. Would this burn up the phono preamp or just be able to supply more current on demand?

Perhaps I should look for something closer...

Thanks!

(tunes tonight: the 70s! Sly & The Family Stone just went by...)

 

[Nemo de Monet]

It'll be fine - what the rating is, is what the power supply can supply, not what whatever it's connected to will receive.

 

[adamus]

the only thing you have to watch for with overated transformers is that they will produce slightly high voltage if not used to near their rating

 

[n_maher]

Quote:

Originally Posted by adamus /img/forum/go_quote.gif the only thing you have to watch for with overated transformers is that they will produce slightly high voltage if not used to near their rating

Slightly high may be putting it nicely. Last night I was testing a 12VDC/300mA wallwart with an amp that draws ~60mA. The wallwart puts out 22VDC unloaded and almost 19V when loaded by the amp. Lesson - be very careful overspecing current capacity on a wallwart.


jazz, you might try something like this - 412-215042 - and hope that by overspecing the current you raise the output voltage enough to get to the 16V level but don't go too high.

I'd also probably open the thing up and have a look at where the AC is going once it gets inside.

 

[bhjazz]

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif I'd also probably open the thing up and have a look at where the AC is going once it gets inside.

Well I hadn't thought about what would happen if the voltage started creeping up. Yikes! I'll try to find something closer.

I did manage to get the cover off, but it really is a simple design: input is soldered to the blades (that get plugged into the wall) and output soldered directly to the wire with the output barrel plug.

All right, then. Thanks!

 

[nikongod]

what phono-stage is it?

Its also worth note that Nate's case was a DC wall-wart, where you are using AC. There will still be a little voltage excess because of under loading the transformer, but probably not as bad.

 

[bhjazz]

A Pro-Ject "The Phono Box" circa 2001. I was going to attempt ordering the part from them but they seem to have moved to a 20V/200ma model for all of their gear now....then again, I suppose I could ask.

Wouldn't the AC creep with higher current like the DC version?

 

[n_maher]

Quote:

Originally Posted by bhjazz /img/forum/go_quote.gif Wouldn't the AC creep with higher current like the DC version?

Yes, but as Ari said generally not as much. Also, the wallwart I linked to is only a 400mA unit so it's not overspeced to the degree the other wallwart you were looking at was.

 

[bhjazz]

Quote:

Originally Posted by nikongod /img/forum/go_quote.gif There will still be a little voltage excess

Quote:

Originally Posted by n_maher /img/forum/go_quote.gif Yes, but as Ari said generally not as much.

Gah! I'm a dork. That's what I get for trying to respond while at work!

Thanks for the clarification. I'll dig in a bit more. Much appreciated!


EDIT: Just sent some email to Sumiko. Just can't find too much that's close. Ah well. The journey is the fun part, right?

 

[bhjazz]

I Punted.

Sent some email off to Sumiko/Pro-ject and they are getting me in touch with a local dealer to get the replacement part. I wonder where they got these in the first place? If nothing else, the original wallwart will make it easier to sell the preamp in the future.

Anyway, problem (almost) solved. Vinyl will return to my audio room very soon...

 

[nikongod]

Quote:

Originally Posted by bhjazz /img/forum/go_quote.gif I wonder where they got these in the first place?

lowest bidder who will put the project label on it

not trying to be offensive, but thats probably how it went.

I dont know if your up for DIY'ing a transformer, but there are some cool instructions on the web for this kind of application. Stuff with better output filtering to keep RF noise and other junk hanging out on the wall line from sneaking through the transformer.

 

[bhjazz]

You're probably right. Well, at least they bought a few extra...

Yes, I was thinking of DIYing a PS for this. Funny you should mention that. I did find a few places that had a transformer with closer specs, but of course it was the raw transformer. I even reviewed Tangent's Tread but realized that the output is DC. If you have a few links, feel free to post them. I think it would be fun throw one together and see what I can get out of the admittedly basic preamp. Thanks!

 

[nikongod]

link

will need some modification to suit specific needs.

more links

 

[bhjazz]

Good deal! I'll search around a little tonight and see what else I can find. Those designs were simpler than I expected so I can pretty easily take this on.
Thanks for the links.