Small Inline Mic Preamp Solutions?

[James Palanza]

So, I decided this deserved its own thread. I'm trying to come up with a method for powering a better lav such as a countryman b3 when used with a Zoom h1 in the pocket of lets say, the groom. With this in mind, nothing really large is going to work. I only need like 6 volts, but I can't find anything really discrete.

Should I just switch to a different lav?

[Greg Miller]

"Is that an H1 in your pocket, or are you just glad to see me?"

Why stuff an H1 into the groom's pocket, when you could use something smaller and more discrete, like a DR-03?

And by "like 6 volts" exactly what voltage are you looking for? The DR-03 does provide "in line power" that is adequate for a lot of unbalanced electret mics.

[James Palanza]

Haha, I figured the H1 was small enough. Also countryman b3 omni specs suggest 3 to 12V @ 200mA . I read the h1 is putting out about 1.5 volts or so.

ALSO i keep hearing of hiss/noise issues with the tascam its, the dr-03 and the dr-08. Hence why I thought the h1 would have to work.

http://taperssection.com/index.php?topic=144774.0 an example

prob going to go with the dr-08 and see for myself how it sounds.

[Greg Miller]

First of all, I get the impression that those guys on tapers session are a little weak on the technical side. One guy suggests connecting an electret mic to the line input of the recorder. That will never work because an electret mic requires "plug in power" and a line input jack will not provide that. An electret mic contains a FET used as an impedance converter, and without the DC supply voltage, no discernable audio will come out of the FET.

Second, that Olympus mic is incredibly cheap. It's a stereo mic, so divide the price by two, and you'll realize that it is a pair of $25 microphones. $25 microphones are not going to sound good.

You cannot directly compare the specs for the B3 with the specs (or lack thereof) for that Olympus mic. The olympus is unbalanced and requires "plug in power" on its audio lead. The B3 is a professional mic, and the specs you show are for a professional balanced configuration, which needs "phantom" power on both of the balanced audio leads. It's an entirely different powering scheme. You could not connect any balanced mic directly to the DR-03, DR-05, DR-07, DR-08, or H-1... those all have unbalanced inputs with "plug in power."

The DR-03 "plug in power" is approximately 2.4 volts. Indeed, that may be too low for some unbalanced electret mics... you really need to check the specs for each given mic. The DR-08 appears to be nearly identical, so I suspect that its voltage is probably the same. DR-07 voltage is also ~ 2.4 volts.

Again, where did you find this requirement of "like six volts"? Certainly the balanced B3 won't work on "like six volts" ... the spec sheet says 9 to 48 volts (balanced) phantom power. But, again, that balanced mic won't work directly with any of the recorders you're considering. (Indeed, there may be an unbalanced version of the B3, made for use with a radio pack, etc... I don't have that info at my fingertips.

It would be worthwhile for you to do some more intelligent research on mics. If you want a "single box" solution (i.e. only one device in the groom's pocket... not an extra preamp and not a battery box, etc., then you need to locate a good quality unbalanced mic that will work reliably at low voltage... if it works on 2 volts or so then you can use it with numerous different recorders.

[James Palanza]

My statement of "like six volts" was just to get the point across that the b3 needs more than the little voltage provided by the h1, etc, without going into specifics. Just being general here. Yeah I'm going to just switch to a lav with a much smaller voltage req such as the rode I mentioned in the other post.

Good information though all around, I'll admit I don't have nearly as much mic knowledge as I'd like to have.

[Greg Miller]

Aside from talking about specific voltage, you always need to remember that there are two entirely different mic & powering schemes.

Professional mics usually have balanced signal wiring, so there are two audio leads, plus an additional shield/ground. Phantom power was conventionally 48 volts, although some mics will work on less (for example the B3 spec says 9 volts is the lower limit). And some mixers/recorders do not provide the full 48 volts.

Any other mics ("prosumer" all the way down to Radio Shack) have unbalanced signal wiring: just one "hot" audio lead, plus the shield/ground. "Plug in power" is usually somewhere between 2 volts and 10 volts... there is no universal standard.

If you try (using some sort of passive adapter) to connect a phantom-powered mic to an unbalanced "plug in power" recorder, you'll most likely get no audio whatsoever.

If you try (using some sort of passive adapter) to connect a "plug in power" mic to a recorder with balanced phantom powering, you'll most likely fry the mic! (However, some manufacturers do make correct adapters that allow using their "PIP" mics with a true phantom mixer/recorder.)

Dynamic mics (becoming more and more of a rarity these days) require no powering, and connecting them to either type of power may damage them. Ribbon mics (usually quite good, but rather esoteric, and also physically fragile) also should not be connected to either type of powering.

Is there a dealer near you who will let you try a Pin Mic, and return it if you change your mind?

[Tom Morrow]

The rode page says, of the 1/8" connector that fits into the h1: "The MICON-2 is designed to connect to a standard 3.5mm stereo minijack, with a power supply of 1V minimum."

[Greg Miller]

Which Rode page was that?

I'm looking at the Pin Mic page RDE Microphones - PinMic

It says "P48 through MiCon-5 adaptor, 2V~5V through all other MiCon adaptors."

Are they giving out different specs on different pages? Or were you looking at some mic other than the Pin Mic that the OP is talking about?

[James Palanza]

Tom is referring to the standard lav from rode i believe.

[Robert Turchick]

Just gonna throw this out there cause it saved a producer's arse and blew me away how good it sounded... Drop an iPhone in the grooms jacket and forget the lav. The situation occurred when the producer who shoots interviews had an issue with her Sennheiser wireless and needed a quick solution while interviewing a doctor.

But...to get back to the OP, check This out ...

Radio Design Labs Radio Design Labs STM-3 High Gain Microphone Preamplifier - 35 to 75 dB Gain Microphone Preamps at Markertek.com

I've used several RDL items and while tiny, they work. Don't forget you need the power supply too.
You could Velcro this to the back of the h1.

Enjoy!

[Greg Miller]

Originally Posted by James Palanza

Tom is referring to the standard lav from rode i believe.

If I go to the rode homepage, then drill down to their standard lav, the specs I see on that page are as I quoted above: 2V ~ 5V.

I am curious to see the page you found that said "1 volt minumum." Can you give me the URL for that page?

[Greg Miller]

I contacted RODE concerning the apparent discrepancy, between the "2V ~ 5V" spec, and the "1 volt" spec that Tom mentioned (above).

RODE replied as follows:
"The Micon 2 is the 3.5mm connector, it can be used with our current range of products that require 2-5V which are the Pin Mic, Lav and Headset. The connector screws onto the cable that comes with the microphone. There is a mistake on our website which should have the voltage as 2V minimum."

So disregard that previous "1 volt" figure that Tom quoted, according to Rode that's a mistake on their website.

At any rate, any of those three RODE mics should work OK with the DR-03, -05, -07, -08 as they provide approximately +2.4 volts DC on the mic connector.

[Tom Morrow]

Just to clarify, where I saw that 1V spec was on the page for the Micon-2 connector:

RDE Microphones - MiCon-2

But I would suspect Rode's email is correct and 2V+ would be more likely to work.

[James Palanza]

Ah most excellent. Well, case solved haha. Thanks a lot for all of the helpful responses.

[Richard Crowley]

I believe this is exactly what Mr. Palanza was asking for...
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