Phantom power and Helix

rschultz · #1 09-19-2022, 06:08 PM

Hi,

Been using a Helix Stomp to run dual source setups, but I don't think it can supply phantom power (for a mic). What's an easy way to accomplish this? The simplest preamp that can supply phantom power?

Thanks

Bob Womack · #2 09-19-2022, 06:14 PM

How about THIS? $28.68 at Sweetwater.

Just phantom power.

Bob

Cuki79 · #3 09-21-2022, 01:38 PM

You also need a preamp…

Eventide mixing link?

rschultz · #4 09-22-2022, 06:36 AM

So I've tried a TON of pickups, but never a mic. Can the mic be on the RING and be powered externally? Normally an internal active pickup has to be on the TIP to be switched. But an externally powered one shouldn't matter, right? So just wire the mic to the RING and ground?

Doug Young · #5 09-22-2022, 06:35 PM

I've been chatting with Ryan about this offline, but for anyone following this, it's important to understand that there are 2 (at least) different powering schemes for condenser mics. "Phantom Power" is an approach that uses 3 wires and (usually) 48 volts. It's what you use with studio condenser mics, etc, with XLR connectors. What is typically used as internal guitar mics in dual source systems are electret condenser mics, which use a 2 wire scheme known variously as "bias power", "a-b power", "T power", or "plug-in power". This is a bias voltage that can be applied to the same wire that produces the signal. So with one of these mics, you typically wire the mic to the ground and ring of a TRS (aka "stereo") jack, and plug it into a guitar preamp that provides the bias voltage on the ring - usually around 9 volts.

These approaches are similar in that they both provide electricity to the mic, but different enough that you can't just use either one - a bit exaggerated, but think of it like the way you plug your toaster into the 110 wall socket, while you power your flashlight from a battery, or your iPhone from a USB cable. All of these are "electricity" and you can convert between them with the appropriate gizmo in some cases, but you can't just plug your toaster into a flashlight battery, etc.

I get asked about this often enough that I created a blog post on my website detailing how I added a mic to a K&K system:

https://dougyoungguitar.com/blog/blo...l-mic-to-a-k-k

it's a *very* easy thing to use if you have the right gear - the right mic wired the right way, a TRS jack and cable and a preamp that supplies the required bias power to the ring. It gets complicated/confusing if you are cobbling together parts that don't work together.

rschultz · #6 09-22-2022, 08:48 PM

So can I just stick a 9v battery across the 2 wire scheme shown in your blog post?

Or, if I have 48v, how do I step that down to 9v? If I knew the mic current, I could calculate a bleed resistor… maybe.

Doug Young · #7 09-22-2022, 09:38 PM

Quote:

Originally Posted by rschultz

So can I just stick a 9v battery across the 2 wire scheme shown in your blog post?

Or, if I have 48v, how do I step that down to 9v? If I knew the mic current, I could calculate a bleed resistor… maybe.

Yes, you could build adaptors. Here are some electret circuits, I think the simplest would be fine. Could be powered by a battery or by a pedal power supply. Basically with a resistor and a blocking capacitor:

https://www.epanorama.net/circuits/m..._powering.html

You could also build some sort of voltage divider and use only the hot side of a phantom power source. I actually have an adaptor - XLR male to 1/4 female that I had someone build for me. Not really sure what they did and it's kind of sealed up so its hard to look. I assume just a few resistors. You'd have to figure out any current issues, but it shouldn't be hard. I tested mine, but have never actually had any occasion to use it.

Seems a bit clunky, tho, compared to just plugging into a preamp intended to support this, but you could probably wrap it up in a way that's not too bad.

Bob Womack · #8 09-23-2022, 04:26 AM

Ah, he didn't capitalize "dual source" so I didn't know he was referring to Baggs. T-power. Oh, my. I haven't run that since the '80s. Phantom power standards were still settling down at that point. Our Neve consoles had no phantom so we worked with external supplies. Different mics, different power supplies. Sennheiser began appending the power system used to the name of the mic, ie. "MKH416-P48." That was helpful. OF course their MKH816 shot gun was simply MKH816 and you had to know that it used T-power. Back in the mic locker we've got forty-seven year-old T-power supplies, many with belt clips.

Recently, during a clean-out, an AKG N46E P48 supply fro the early '70s was deemed surplus. It and I had a long history together starting around 1981, so it was given to me.

Wow, I'm dating myself.

Bob

rschultz · #9 09-23-2022, 05:58 AM

Quote:

Originally Posted by Doug Young

Yes, you could build adaptors. Here are some electret circuits, I think the simplest would be fine. Could be powered by a battery or by a pedal power supply. Basically with a resistor and a blocking capacitor:

https://www.epanorama.net/circuits/m..._powering.html

Wow, that is an awesome reference... gonna study that. Love the graphics!!!