Phantom Power Supplies - all the same or quality differences?

[Corran]

I find myself in need of 2 channels of phantom power. I am torn with getting either the ART Phantom II or a nicer unit like the Stewart Audio PM-4.

I'm worried mostly because I plan on using these with a pair of Earthworks SR-77s. They are adamant about getting a full 48 volts.

But are there really any big differences in these units? Would the cheap Samson S-phantom cheap unit be alright?

I might be over-thinking this. I talked with a Sweetwater guy and I was almost sold with the ART except it is a wall-wart unit. But so is everything else! I'd love to find a supply with a standard IEC cable rather than a wall-wart, but I can't find any.

Any suggestions? Let me know if it really doesn't matter. Or where I could find a nice unit with an IEC power cable.

[xhavepatiencex]

when I needed two channels of external phantom power, I bought an apex app22 it was rather cheap. No wall wart. Works fine. As far as quality between different units I do not really have any idea.

[Corran]

I looked that model up. In the specs it says "48v, +/-2v". That's what I'm scared of, that my Earthworks mics won't like the change in voltage.

Thanks though!

I also see "frequency response" as a spec! How can the power supply effect this? Another thing I worry about, if it does actually differ between units.

[Birdi]

Actually you do need to be mindful... a cheap ass 2 channel one that I had years ago was fine with a single U87ai, but it wasnt happy to also power another condenser at the same time. cant remember what the other condenser was off hand...

or get an electronics dude to build you one?

Bird

[nosebleedaudio]

There are several things to consider, the voltage only is easy. How well is it decoupled is more important. The matching of the 6.8K resistors is VERY important...
I would take a well designed integrated phantom any day, one that is part of the design of the pre...
I say this because I have seen poor wiring/layout of a few outboard phantom supplies.
My point is JUST because it has exactly 48volts is not the main thing...
My question is; what mic pre do you have that does not contain phantom??

[Corran]

I have a pair of ADM pres that I just got from a guy here. I wanted them mainly for ribbon mics, but my ribbon obsession has subsided and I'd like to use them as a nice pre for my orchestral sessions that I'm using a pair of SDCs. Anyway, they are from a board and have no phantom. I always planned to just buy a stand-alone phantom supply, I just didn't realize it was such a hassle!

[LaChunkyStudio]

20-725 EMO PHANTOM POWER SUPPLY E725

This unit is the business. IEC power socket too.
Bound to be someone in US who sells them.

[littlelabs]

Beware most outboard phantom power supplies have poor quality electrolytics caps to block dc ...blocking dc is a good thing.. if your mic pre doesn't like it (this would only be with an input transformer-less pre which didn't take precautions) , but remember you are listening through those caps. The P48, IEC 61938 spec is 48v +- 4 v.
J

[Corran]

Most have cheap components...so does that mean I'm screwed no matter what? I guess I should just get the cheapy Samson then.

Anyone have these Stewart Audio PP supplies? It seems they are the nicest but still have a wall-wart!

The EMO unit looks nice, if I could get one. Very expensive though.

[joelpatterson]

What a can of worms you've opened, Bryan! And this is the kind of stuff I don't really want to think about!

[Corran]

Well Joel I would consider a "can of worms" to more along the line of many opinions, all different, screaming and yelling, etc. I just want a little opinion on some gear...that's not so bad is it?

[dbbubba]

My friend has a Stewart four channel phantom unit.
He uses all kinds of boutique mics with it and all kinds of esoteric mic pres.
Everything he sends me sound quiet as anything I have ever heard.
I'd buy one, but I build my own.

You need to be as concerned with the available amperage the supply can supply as well as the voltage.
A phantom supply that can't handle much amperage draw will have voltage sag.

Buy the Stewart and you'll be happy.

[Corran]

Perfect, thanks!

[dbbubba]

A Stewart with an AC line cord and NOT a wall wart.

[Corran]

Ack! Where do I find that?? All the models I've seen have the wall-wart.

[Karloff70]

Don't get an ART one. Measured one and it kicks out a measly 34V........other good options would be old AKG, Neumann or Shure units.

[joelpatterson]

Well, now that you mention it... I have never ever seen worms canned, sometimes they're in a bait bucket, but usually they're just crawling along the driveway after a rain. This is some kind of Chinese delicacy, maybe?

[dbbubba]

Are the Stewarts all wall wart models?
You don't want wal warts because they don't filter that well as a rule.
They can only supply so much amperage, too.

Then I'd pop for a Shure or AKG.
The Nuemann units are $$$$ aren't they?

Like I said... I built/build my own.
I have MAYBE $120.00 invested in a hand built four mic one based on a decent Alpha 48V supply.
I'll have to either use it or adapt it for use with my JH538C console if I ever use the mic pres in it with condensers.

[Karloff70]

Originally Posted by dbbubba

Then I'd pop for a Shure or AKG.
The Nuemann units are $$$$ aren't they?

Not necessarily, if you're lucky on the ol' bay.......

The selfbuild sounds interesting though. Quite fancy a 4-way one myself. Did you get the circuit from somewhere or design it from scratch?

[atiller]

I'm a complete rookie at this stuff, so take this with a grain of salt and please someone correct me if I'm wrong-- this idea just popped into my head.

Why don't you try chaining two preamps together. Run the earthworks mics into a couple transparant pres with phantom, don't gain them at all, and then run those pres into your ADM pres that lack phantom. Wouldn't this solve the problem and at least offer your mics good phatom with very little additional colouration?

-Adam

[dbbubba]

I built it from scratch, but the actual 48V comes from an Alpha 48V supply which can be bought from DigiKey for under $50.00.
I think I studied Eddie Celetti's webpage on phantom power a bit and I did talk to him about few ideas and "improvements."

Beyond the 48V from the Alpha supply there is an extra cap and the precision resistors.

I had some enclosure for other supplies I had built for racked gear that I used for this project.
They had a power switch, fuse, indicator light from a previous power supply build.
I had built several +/- 15V supplies for some stand-alone MCI JH-110 electronics that I used for meters.
I just rebuilt one of those.

It is pretty simple build.

I have some pics of it on my other computer that isn't on the network here at the house.
I'll post them when I get time.

[Karloff70]

Originally Posted by dbbubba

I built it from scratch, but the actual 48V comes from an Alpha 48V supply which can be bought from DigiKey for under $50.00.
I think I studied Eddie Celetti's webpage on phantom power a bit and I did talk to him about few ideas and "improvements."

Beyond the 48V from the Alpha supply there is an extra cap and the precision resistors.

I had some enclosure for other supplies I had built for racked gear that I used for this project.
They had a power switch, fuse, indicator light from a previous power supply build.
I had built several +/- 15V supplies for some stand-alone MCI JH-110 electronics that I used for meters.
I just rebuilt one of those.

It is pretty simple build.

I have some pics of it on my other computer that isn't on the network here at the house.
I'll post them when I get time.

Cool, nice one! Looking forward to it. Might just do one myself.

[Corran]

Yeah, if anyone happens to have a schematic of a DIY PP supply, I'd be game to try to build it.

atiller, stacking pres is usually not a great idea. It's possible, but the noise floor would rise more than I'd like for a classical recording, which I do mostly.

[nosebleedaudio]

What do you mean my stacking pres?
A 7824 regulator with a 24volt zener in series with the ground works very good, provided you use good decoupling like any well designed supply.
Again the 6.8K resistor matching is very important as well.

[atiller]

Originally Posted by Corran

atiller, stacking pres is usually not a great idea. It's possible, but the noise floor would rise more than I'd like for a classical recording, which I do mostly.

Right, I didn't think about that at all. Good point!

[mahasandi]

I know an old thread but as a resource these guys are saying good stuff and my experience is that cheaper wall wart p48 supplies have loads of hum and are not worth it......