PZT's Desk Mic - some home brew!

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CharlieM0PZT
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PZT's Desk Mic - some home brew!

Post by CharlieM0PZT » 05 May 2009, 22:27

Finally got around to taking a few of pictures of my home-brew desk microphone. Using mostly junk-box items, this is now known as my "Five Quid Desk Mic" 8)

The Electret Capsule and RG-213 "Gooseneck"
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The Desk Mic on the desk: click here for a larger image
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Desk Mic close-up:
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At present there are 2 PTT switches: Momentary, and latching. There are 2 phono sockets for external microphone and remote-PTT (ie: footswitch).

The completed unit will feature an all-in-one mic amp/gate/compressor device, the SSM2167. At present, I'm just using an NE5534 op-amp to give me a bit of gain (to allow for the 12" distance between PZT's gob and the mic), plus there's a very basic hard limiter/clipper which is not ideal but a start.

The noise-gate will be essential - it'll cut-out any shack ambience such as fan noise, room acoustics (to some degree) and give the right processing, will make for a nice sound. There will be some EQ control - This will comprise of 2 sets of fixed resistors (and possibly the same for the compression rate) that can be switched to "DX" or "Local" - in others words: A fairly aggressive+gated sound for DX SSB whilst a more relaxed sound is offered for local and FM working.

Whilst I already had a small metal box available, I decided to spend £3 on an "ice blue" translucent ABS case from Maplin. It's kind of see-through so there's some incentive to make the insides look pretty :lol: I'm already thinking about re-working this into a "console box" - the kind with a sloping front so I can have a few extra controls like EQ and perhaps a VU meter - Sort of like the W2IHY gizmos but for beer money!

Bedtime reading: M0PZT's Five Quid Desk Mic
Charlie

CA148
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Re: PZT's Desk Mic - some home brew!

Post by CA148 » 06 May 2009, 08:40

Looks very nice indeed matey, you may want to start selling a few on Ebay, well impressed.

CharlieM0PZT
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Re: PZT's Desk Mic - some home brew!

Post by CharlieM0PZT » 06 May 2009, 09:47

Yours for £50 :lol:

Seriously - they are simple to make. A bit "big" for an Intermediate course project (due to the drilling etc) but the basic circuit is a very simple non-inverting op-amp with a small amount of gain. With the SSM2017 chip, I'm hoping to do a DF4ZS and put something inside a standard fist-mic.

Electret capsules are the best to use - although they vary in terms of quality considerably. At around £1 each, it may be worth getting a couple to experiment with. I tried the circuit with an old dynamic vocal mic (a £10 Argos jobby) and as expected the microphone was pretty quiet but with some gain adjustment it sounded OK.

A mate of mine has a Behringer Shark DSP which he doesn't use so I may borrow that for a bit and see what I can do with something "proper". Sadly I no longer have much of my broadcast gear such as expensive processing, studio microphones etc.. If you want to see how much fun you can have splattering your audio across the bands, check out http://www.nu9n.com/home.html ;)
Charlie

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Re: PZT's Desk Mic - some home brew!

Post by MuddyFox » 06 May 2009, 13:13

Nice one charlie :D
Looking forward to seeing this console being built/growing!
I can imagine it now... starts of as a desk mic and spreads out as other boxes are joined on, then .......... it looks like the cockpit of the space shuttle! hi hi
Good skills
M6RKY

CharlieM0PZT
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Re: PZT's Desk Mic - some home brew!

Post by CharlieM0PZT » 06 May 2009, 20:31

...and here's how it sounds:

M0PZT's Desk Mic Audio Clip

A bit of clipping but not bad for a 12" distance between mic and gob :lol:
Charlie

CharlieM0PZT
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Re: PZT's Desk Mic - some home brew!

Post by CharlieM0PZT » 07 May 2009, 21:53

...and these will be the front+rear panels for the Mk2 "console" version:

Image

Designed with Serif DrawPlus4.0 8)

I've opted to have the compression ratio adjustable via the front-panel aswell as an FM/SSB switch to tailor the EQ. The actual microphone will be mounted on my shelf - After further tests with a dynamic vocal mic and some more electret capsules, I have found that electrets give a higher noise-floor and with several EQ tweaks - I think I prefer the dynamic mic.

CPC order time 8)
Charlie

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Re: PZT's Desk Mic - some home brew!

Post by CharlieM0PZT » 11 May 2009, 15:34

New console box arrived today - took some out to make a start. A few more holes need to be drilled, such as the 8-pin mic socket and perhaps some VFO up/down buttons if I can find some nice ones. I plan on using the 5-pin DIN to connect to the computer for data modes - There'll be an "inhibit" switch to stop the PC from keying the radio as well as muting the soundcard output.

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I'd forgotten how delicate work it is filing aluminium!
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The circuit is working fairly well, albeit on breadboard... There's plenty of room inside the box so I may add a voice-recorder module for contest work 8) CPC also do some decent DJ-stlye goosenecks (either in black or silver) for 1/3 the price of Maplin. These are the 5/8" type, unless I take apart an old paging/intercom desk-mic I've no idea where to find "skinnier" ones that I can use.
Charlie

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108xx002
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Re: PZT's Desk Mic - some home brew!

Post by 108xx002 » 18 Feb 2018, 09:17

Resurrecting an old thread :D
I looked on your page charlie and u mention using a SSM2166 for use as a noise gate, I am interested if you have a diagram on this.
Being a ham has benefits...certain religions stay away from me.
Day in and day out swl to same QRM from the same ops but on a different date.
If at first you do not succeed...it's because you never tried hard enough...

SgtBilko302
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Re: PZT's Desk Mic - some home brew!

Post by SgtBilko302 » 18 Feb 2018, 13:44

Any good Jason.
MXRNoiseGate.gif
One Knob Noise Gate.png
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108xx002
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Re: PZT's Desk Mic - some home brew!

Post by 108xx002 » 19 Feb 2018, 11:53

SgtBilko302 wrote:
18 Feb 2018, 13:44
Any good Jason.

MXRNoiseGate.gif

One Knob Noise Gate.png
Thanks OM
Being a ham has benefits...certain religions stay away from me.
Day in and day out swl to same QRM from the same ops but on a different date.
If at first you do not succeed...it's because you never tried hard enough...

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