Variable High Pass Filter

LowQCab

Joined Nov 6, 2012
4,186
""
If using a Noise-Cancelling-Type Electret-Element is feasible,
You may not need any special High-Pass-Filter-Circuitry,
which may ultimately result in superior Sound-Quality.

Is this possible ?, or
are You restricted to using a commercially-available Lapel-Mic ? ""


A Single-Wire Shielded-Cable is all that is needed to power any Electret-Microphone-Element.

Standard "Phantom-Power", ( if available from your Mixer ),
can be used to Power your Interface-Box,
while still using a very small Single-Wire-Shielded-Cable from the Box to the Mic.

A 9-Volt-Battery, or a Stomp-Box-Board-Power-Supply, will also work just fine.

If You want to use long-Cables,
it's a very good idea to have the Interface-Box attached to the Guitar-Strap.
An Electret-Mic-Element will not perform well pushing a Long-Cable.
For pushing a Signal through Long-Cables
You will need an Amplifier to provide a Low-Impedance-Output in to the Cable.

Do You intend to incorporate "Phantom-Power" functionality into your Box ?,
and will it be the standard ~48-Volts ?,
or do You intend to use a Custom type of Phantom-Power ?

A "2-Box" solution may be the best bet,
one on the Guitar-Strap, and one on the Pedal-Board,
this way You can use any standard generic Guitar-Cable between the 2 Boxes,
and have as much Clean-Gain as You need, with zero loss of Fidelity.
And, the Pedal-Board-Box can be larger to
accommodate 3-Way-Tone-Controls as well as Gain/Volume.

If You expect all of this to work with a commercially-available Microphone
You will need to provide the Operator's-Manual, or PDF with all the Specs.
However, I still highly recommend a
Noise-Canceling-Microphone-Element for your application.

In any case, ANY Microphone used should NOT be rigidly attached to the Guitar-Body.
Some type of Foam Mount needs to be fabricated which will securely hold the
Microphone suspended approximately ~1-inch below the Strings.
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Thread Starter

rpschultz

Joined Nov 23, 2022
416
I’ve been searching around for “noise canceling lapel mics”, and can’t find any. Feel free to make suggestions in that regard, sounds interesting!
 

Thread Starter

rpschultz

Joined Nov 23, 2022
416
I understand the guitar strap idea, but no guitarist is going to mess around with that. If it’s that important to get a power source closer than a 15’ cable, they’ll just put a 9v in the guitar. Then that is a personal preference, some guys want as little in the guitar as possible, so power from the pedalboard is ideal.
 

Audioguru again

Joined Oct 21, 2019
6,748
A Single-Wire Shielded-Cable is all that is needed to power any Electret-Microphone-Element.
Cheap 2-wires electret mics use the Jfet in the common-source mode so that its output level is a little high then it overloads and produces distortion at about 100dB and louder. I measured 120dB in a Disco that did not sound very loud.

The Microphone Linkwitz Mod (look it up) shows how to re-wire a cheap electret mic using the Jfet as a Source Follower that needs 3 wires and can be put inside a Very Loud drum or piano and maybe in a geetar and not produce overload distortion.
I do not know if there is a mic made like that.
 

LowQCab

Joined Nov 6, 2012
4,186
I have the PDFs outlining the modifications required of most Electret-Mics
from Texas-Instruments, which allow extremely high SPL levels,
but the ultimate SPL limitation is a mechanical-clearance issue that
causes the Diaphragm to "bottom-out",
and, of course, some Electret-Mic designs make the necessary modifications impossible.
I'll attach the PDFs I have if anybody is interested .........
--------------------------------------------------------------------------------------------------------------

Electret-Microphones .........
~99% of them are "Omni-Directional" designs,
this is regardless of whether or not they are in bare-Element-form or
a finished Consumer-Product with a Housing, Cable, and Plug.

The other ~1% are "Noise-Cancelling" designs.
These are normally only available in a "Headphones-with-a-Boom-Mic-attached" form.
This is because they sound very "thin" ( no Bass ) if they are further than
maybe ~6-inches from the Sound-Source,
but they are very good at canceling unwanted Environmental-Noise.

Either style of Mic is available in a Bare-Element-Form,
but Noise-Cancelling designs are not normally available as
a ready to use "Lapel-Mic" with Cord and Plug.
Therefore, to use a Noise-Canceling-Electret-Element would require
the addition of a very small Shielded-Cable, which must be Soldered to the Mic.
The small Shielded-Cable should not be longer than about ~6-feet long before
it is attached to the Pre-Amplifier-Box,
by way of direct-soldering to the Circuit-Board,
or via a 1/8" Plug & Jack connection.

The Pre-Amplifier-Box may be powered by a 9-Volt-Battery,
or, by way of Phantom-Power from a larger Box which also contains Tone and Level-Controls.

The smaller-Box, and the larger-Box, may be connected together by any type
of standard Guitar-Cable with 1/4" Plugs on each end.

The Pre-Amplifier-Circuit-Board does not need a Box if
it is glued, or otherwise attached, to the Interior of the Guitar-Body,
but in this case, a hole must be drilled in the Guitar-Body to
accommodate a 1/4"-Jack for a Standard-Guitar-Cable-Plug.

There is a wide variety of different designs of 1/4" Jacks for Solid-Body-Electric-Guitars
that will work equally well for an acoustic Guitar-Body.
Plastic / Metal / Recessed / Angled / etc., or just a plain 3/8" hole.
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Attachments

Audioguru again

Joined Oct 21, 2019
6,748
A 2-wires electret mic has a Jfet (high impedance current sink) parallel with its biasing resistor which is from 2.2k to 10k.
Then simulate it with a low impedance signal generator in series with a 2.2k to 10k resistor.
 
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