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microphone for H120

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Datman:
These are the schematics of my mono and stereo preamps.

The mono one is for a "two track" recording of a mono mic, like a Shure SM58 or a Sennheiser e835 i.e. for interviews. Circuit is inside the XLR connector; on the other side a stereo mini jack plug goes to the H120 input.

Don't worry about the L and R inputs connected together: it's safe!

The stereo preamp is for a stereo mic like a Sony MS907. The circuit is inside a thermoplastic tube on a mini jack socket; on the other side, a stereo mini jack plug goes to the H120 input.

Capacitors could be electrolythic (polarized) or not. Plastic film capacitors are better, but bigger.

Power is drawn from the H120 input.  

The gain is about 14dB, that is 14dB better in s/n ratio...

The output is not a line level signal, but a stronger mic level.

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Datman:
Mono and stereo schematics

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petur:

--- Quote from: perik on August 23, 2006, 12:00:04 PM ---I know that, but it seems to be possible on the H3x0 to change the impedance on that jack so the one and the same jack can work as both mic-in and line-in.
--- End quote ---

No it's not.

In the original iriver firmware, the selection between line-in and ext-mic only changes the range of gain that is presented.

The mic power is always available on the plug and is around 3.7V (depends on your battery charge).

That said, I have no idea how the inut impedance looks like, but iirc, there's a schematic on the input stage in the wiki (iriverport -> h1x0 hardwardware schematics)

Your only option is to get a sensitive mic, for that, you need to ask guys that know a lot about mics. Or start mailing several mic companies for advise.

Peter

EDIT: I saw you've posted your question at taperssection.com in the mean time. Hope you'll find the answer that gives you your perfect recording experiance.

perik:
ok thanks for all replies.


--- Quote ---Mono and stereo schematics
--- End quote ---
DATMAN,
have u built that preamp? how does it sound?

Dick,

--- Quote ---The OKM and surely other mics work very well with H120/140 and do not require a separate pre-amp.
--- End quote ---
what about those OKM microphones. What level do u need to have the gain in rockbox for recording very quiet sounds, for example if u put the mic between to person who are sitting and talking, or even the sound from a newspaper?
I have noticed some hizz in the H120 above 20-25 in gain.

I think I will go for a preamp. Think I go for the Denecke AD20. Any comments on that preamp?

Thanks

Perik

Datman:
I have built a stereo preamp for using with a Sony 907 stereo mic and a mono preamp for using with a Shure SM58 or a Sennheiser MD431 or e835.

Sound is very good! (But a single transistor, with a correct polarization, couldn't sound bad...)

S/n ratio, as expected, is about 14dB better.

H120 input impedance is about 2kOhms. Preamp gain = collector load / emitter load = 2k/390=5;
20 log5=14dB.
In the mono preamp, collector load is the half of 2kOhm, then emitter resistor shall be 180 Ohm (390/2=195, but standard value is 180) to have the same gain.

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