Re: Alctron MA-1 Schematic question

#37262
Edited

So, is a preamp needed in such an application and, if so, what kind of preamp?

_________________________________________________________

NO.  You should not require a pre amp for the SM58 and your transceiver.  A pre amp is likely to overload the input state on the transceiver - inline pre amps typically provide between 20 and 30 dB gain, which is not required for this application.  

The SM58 has a medium-hot output level (open signal voltage on the product data sheet) and it should drive the rig well enough without assistance.  Do not worry about matching impedance - that is rarely needed on modern circuits  (google this and you will learn a lot!)  Also, avoid - do not use - the 5v BIAS (not phantom) bias voltage intended to power FET type computer gaming headset microphones and the like.  You will likely have an unbalanced connection, so the bias voltage does not become or act or even seem like phantom voltage which only works as a phantom on a balanced cable/input.  I say unbalanced, because pins 4 and 5 carry mic signals, without a third pin to ground.  The schematic indicates one is signal and the other is shield, although I rather doubt that is the case as the cable has 8 internal twisted pair conductors, and none are shielded per se.   

The FT900 has a front panel 8-pin modular, RJ45  network type connector - you need to be careful how you wire that .  It should expect a dynamic cartridge per spec sheet - see link below.  I believe it uses the standard Yaesu Hand Microphones MH-31A8J hand mic, which has a dynamic cartridge.  Your Yaesu user manual should have pin out charts for all connectors, which will guide you in building a suitable cable / connector.  Otherwise, vendors on eBay.com and elsewhere sell suitable cable adapters to mate the XLR on the SM58 with the 8-pin modular, RJ45 connector on the rig.  You will also have to pay attention to the PTT connections, as the microphone on-off switch (if present) will only disconnect the mic from the rig - it will not activate the transmitter as a PTT switch - at least not without substantial re-wiring!  

K8JHR

Schematic for your mic can be found here:

Re: PiP capsule hum

#37261

Could be that the mic power gets shorted out.? You could try a big electrolytic cap instead, shorting the hum to ground but not the DC.

Or just connect the mic to both inputs.

-Scott

Show quoted text

On 2/23/25 23:44, Casey via groups.io wrote:

Thanks Jerry and Scott! -- when I tie the unused wire from the plug to ground as suggested, the mic goes silent - meaning totally dead with no signal at all being recorded.

So, currently the live channel is going to tip, and ring is disconnected, resulting in hum, but joining ring to ground it goes dead, so I assume a mono plug won't help.

I have crudely tried joining signal to ring (in addition to tip) but it didn't seem to make a difference. I also crudely tried a 10k resistor between ring and ground (with no signal connection to ring) and it also made little difference (maybe like 2dB less hum, but didn't really help.) But I did both of these things in a hack way; just holding the exposed wires (using a plastic-handled tool so my hands weren't pinching the joint directly). I can try a more "real" version if it would seem useful.

Any ideas on a next move?

Some other notes in case they reveal that I am doing something dumb:

- mic cable is two conductors inside a braided copper shield; I use both of them joined to carry the signal from the mic (since I don't need both)

- mic is not shielded besides its factory metal enclosure, which AFAIK is adequate for PiP mics

- joint between mic cable and the pigtail leading to the plug (maybe 10mm) is not totally shielded: maybe this is my issue? Similarly, where the cable joins the capsule is not fully shielded (maybe 6mm). I had assumed these spots (which are small) might be irrelevant, but maybe I was naive.

- I mention again in case it's a clue: a different stereo PiP mic (one mic wired to tip, one to ring) works without hum, though the signal level seemed poor

- no idea what voltage the PiP supply is but I could measure if useful

Thanks for any further thoughts!

-c

On 2/23/25 19:22, Jerry Lee Marcel via groups.io wrote:

What about grounding the unused channel?

Le 24/02/2025 à 01:01, Casey via groups.io a écrit?:

Hey all -- I have a project I'm working on that involves a raspberry pi, a cheap USB audio interface <>, and a small electret capsule (JLI-61A <>) powered from that interface via PiP.

Everything works, but there is 60Hz mains hum.

I believe the the audio interface is providing a stereo 1/8" jack, but it mixes to mono internally - the computer is only provided a mono capture by the audio interface. (If I use a different set of stereo PiP mics that I made which are wired to a stereo plug, there is no hum, and both capsules hear audio in the result, but the overall signal is weak.)

The mic capsule is wired to a stereo plug (using shielded lav cable), but the signal only goes to one channel of that plug, so I presume the disconnected channel is just feeding in hum, is mixed with the signal in the interface, and that explains the hum in the result.

Does my diagnosis sound correct? If so, what would you recommend? Should I just wire the signal from the mic to both the tip and sleeve of the plug, or will that mess up the interaction with the capsule somehow? Or would it be smarter to get a mono plug?

Thanks!

-Casey

-- 
---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
"I have ceased distinguishing between the religious and the secular,
for everything is holy"  - Joe Henry

Alctron MA-1 Schematic question

#37260

I wrote:?

>Is this really the original schematic or a fake copy.

Original poster Dan answered:?

>Unknown. This is one I found from multiple net sources, but the origin was not stated.?

That schematic needs then to be seen as a fake copy imo due to the fact that real?

manufacturers schematic always afaik or as I have seen in practice has the manufacturers?

name / logo somewhere and other pertinent information put there that there should be?

no need to think that this is not the real deal.

Original poster Dan asked:?

>So, is a preamp needed in such an application and, if so, what kind of preamp?

>To be used with a Ham Radio like the Yaesu 900

Nothing that you put in your email works at all with Yaesu 900.

You need this to be used with the Yaesu 900:

https://www.amazon.com/MH-31A8J-Handheld-Microphone-FT-817ND-FT-897DM/dp/B0D9NT2CJ3

----------

Best regards,

Goran Finnberg
The Mastering Room AB
Goteborg
Sweden

E-mail: mastering@...

Learn from the mistakes of others, you can never live long enough to
make them all yourself.??? -?? John Luther

(\__/)
(='.'=)
(")_(") Pyret, Ranglet, Aron, VovVov, Nero, Smurfen & Pussin:RIP

Re: Alctron MA-1 Schematic question

#37259

开云体育

An in-line preamp such as the Alctron or FETHEAD is certainly NOT suitable, if only because they need 48V phantom power.
Why do you think you need a preamp? Have you tried connecting directly the SM58 to the input? It should work. Now, maybe if it works but has not enough "juice", you may have to add a preamp, but you would not need much gain. The SM58 delivers about 2mV at normal speech level at a distance of about 2ft, so with close talk, it should be OK for the required 7mV for full excitation.

Le 24/02/2025 à 06:38, Dan KE6PO via groups.io a écrit?:

Show quoted text

[Edited Message Follows]

On Thu, Feb 13, 2025 at 02:37 AM, Goran Finnberg wrote:

Is this really the original schematic or a fake copy.
Unknown. This is one I found from multiple net sources, but the origin was not stated.?

However, the circuit seemed suspicious, which led to my question. The FET info makes better sense now, yet the design purpose is only inferred. I am trying to solve a practical problem here...

For example:?

?

Given a dynamic (moving coil) microphone like the Shure SM58,

To be used with a Ham Radio like the Yaesu 900,

The radio includes some signal processing/compression for the mic input,

48V Phantom power in not supplied per se, but 5VDC is available on the mic connector,

The radio assumes a balanced mic input and has a 600ohms Zin,

The SM58 has a Zout of 300ohms,

According to the SM58 wiring diagram, the mic cartridge uses a transformer interface to the XLR connector.

So, is a preamp needed in such an application and, if so, what kind of preamp?

Any help here is appreciated.

TIA,

Dan?

Re: PiP capsule hum

#37258
Edited

I have tried to get rid of this hum many times, both with ultrasonic mic or normal audio. It is the raspberry Pi and the cheap sound card that will make it impossible. There are two solutions.
1. Power the raspberry from batteries or from a power bank and the hum will be gone. ?Try it! It is easily done.
2. Buy a cheap XLR balanced sound card, single channel, usually ca 50 €. Use Phantom Power and simpleP48 for your capsule and the hum will be gone. In this case you can power the Pi with a power adapter from mains 220V.
All other things I tried, grounding, shielding, shorter cables, longer ones....it never worked.

Re: PiP capsule hum

#37257

开云体育

Thanks Jerry and Scott! -- when I tie the unused wire from the plug to ground as suggested, the mic goes silent - meaning totally dead with no signal at all being recorded.

So, currently the live channel is going to tip, and ring is disconnected, resulting in hum, but joining ring to ground it goes dead, so I assume a mono plug won't help.

I have crudely tried joining signal to ring (in addition to tip) but it didn't seem to make a difference. I also crudely tried a 10k resistor between ring and ground (with no signal connection to ring) and it also made little difference (maybe like 2dB less hum, but didn't really help.) But I did both of these things in a hack way; just holding the exposed wires (using a plastic-handled tool so my hands weren't pinching the joint directly). I can try a more "real" version if it would seem useful.

Any ideas on a next move?

Some other notes in case they reveal that I am doing something dumb:

- mic cable is two conductors inside a braided copper shield; I use both of them joined to carry the signal from the mic (since I don't need both)

- mic is not shielded besides its factory metal enclosure, which AFAIK is adequate for PiP mics

- joint between mic cable and the pigtail leading to the plug (maybe 10mm) is not totally shielded: maybe this is my issue? Similarly, where the cable joins the capsule is not fully shielded (maybe 6mm). I had assumed these spots (which are small) might be irrelevant, but maybe I was naive.

- I mention again in case it's a clue: a different stereo PiP mic (one mic wired to tip, one to ring) works without hum, though the signal level seemed poor

- no idea what voltage the PiP supply is but I could measure if useful

Thanks for any further thoughts!

-c

On 2/23/25 19:22, Jerry Lee Marcel via groups.io wrote:

Show quoted text

What about grounding the unused channel?

Le 24/02/2025 à 01:01, Casey via groups.io a écrit?:

Hey all -- I have a project I'm working on that involves a raspberry pi, a , and a small electret capsule () powered from that interface via PiP.

Everything works, but there is 60Hz mains hum.

I believe the the audio interface is providing a stereo 1/8" jack, but it mixes to mono internally - the computer is only provided a mono capture by the audio interface. (If I use a different set of stereo PiP mics that I made which are wired to a stereo plug, there is no hum, and both capsules hear audio in the result, but the overall signal is weak.)

The mic capsule is wired to a stereo plug (using shielded lav cable), but the signal only goes to one channel of that plug, so I presume the disconnected channel is just feeding in hum, is mixed with the signal in the interface, and that explains the hum in the result.

Does my diagnosis sound correct? If so, what would you recommend? Should I just wire the signal from the mic to both the tip and sleeve of the plug, or will that mess up the interaction with the capsule somehow? Or would it be smarter to get a mono plug?

Thanks!

-Casey

Re: Alctron MA-1 Schematic question

#37256
Edited

On Thu, Feb 13, 2025 at 02:37 AM, Goran Finnberg wrote:

Is this really the original schematic or a fake copy.

Unknown. This is one I found from multiple net sources, but the origin was not stated.?

However, the circuit seemed suspicious, which led to my question. The FET info makes better sense now, yet the design purpose is only inferred. I am trying to solve a practical problem here...

For example:?

?

Given a dynamic (moving coil) microphone like the Shure SM58,
To be used with a Ham Radio like the Yaesu 900,
The radio includes some signal processing/compression for the mic input,
48V Phantom power in not supplied per se, but 5VDC is available on the mic connector,
The radio assumes a balanced mic input and has a 600ohms Zin,
The SM58 has a Zout of 300ohms,
According to the SM58 wiring diagram, the mic cartridge uses a transformer interface to the XLR connector.
So, is a preamp needed in such an application and, if so, what kind of preamp?

Any help here is appreciated.

TIA,

Dan?

Re: PiP capsule hum

#37255

开云体育

What about grounding the unused channel?

Le 24/02/2025 à 01:01, Casey via groups.io a écrit?:

Show quoted text

Hey all -- I have a project I'm working on that involves a raspberry pi, a , and a small electret capsule () powered from that interface via PiP.

Everything works, but there is 60Hz mains hum.

I believe the the audio interface is providing a stereo 1/8" jack, but it mixes to mono internally - the computer is only provided a mono capture by the audio interface. (If I use a different set of stereo PiP mics that I made which are wired to a stereo plug, there is no hum, and both capsules hear audio in the result, but the overall signal is weak.)

The mic capsule is wired to a stereo plug (using shielded lav cable), but the signal only goes to one channel of that plug, so I presume the disconnected channel is just feeding in hum, is mixed with the signal in the interface, and that explains the hum in the result.

Does my diagnosis sound correct? If so, what would you recommend? Should I just wire the signal from the mic to both the tip and sleeve of the plug, or will that mess up the interaction with the capsule somehow? Or would it be smarter to get a mono plug?

Thanks!

-Casey

Re: PiP capsule hum

#37254

Equivalent to a mono plug would be connecting ring and sleeve together on the stereo plug.? So you could try that.? If it seems to change the signal level from the microphone, change the direct connection to a resistor (say around 10k ohms).

-Scott

Show quoted text

On 2/23/25 18:01, Casey via groups.io wrote:

Hey all -- I have a project I'm working on that involves a raspberry pi, a cheap USB audio interface <>, and a small electret capsule (JLI-61A <>) powered from that interface via PiP.

Everything works, but there is 60Hz mains hum.

I believe the the audio interface is providing a stereo 1/8" jack, but it mixes to mono internally - the computer is only provided a mono capture by the audio interface. (If I use a different set of stereo PiP mics that I made which are wired to a stereo plug, there is no hum, and both capsules hear audio in the result, but the overall signal is weak.)

The mic capsule is wired to a stereo plug (using shielded lav cable), but the signal only goes to one channel of that plug, so I presume the disconnected channel is just feeding in hum, is mixed with the signal in the interface, and that explains the hum in the result.

Does my diagnosis sound correct? If so, what would you recommend? Should I just wire the signal from the mic to both the tip and sleeve of the plug, or will that mess up the interaction with the capsule somehow? Or would it be smarter to get a mono plug?

Thanks!

-Casey

-- 
---- Scott Helmke ---- scott@... ---- (734) 604-9340 ----
"I have ceased distinguishing between the religious and the secular,
for everything is holy"  - Joe Henry

PiP capsule hum

#37253

开云体育

Hey all -- I have a project I'm working on that involves a raspberry pi, a , and a small electret capsule () powered from that interface via PiP.

Everything works, but there is 60Hz mains hum.

I believe the the audio interface is providing a stereo 1/8" jack, but it mixes to mono internally - the computer is only provided a mono capture by the audio interface. (If I use a different set of stereo PiP mics that I made which are wired to a stereo plug, there is no hum, and both capsules hear audio in the result, but the overall signal is weak.)

The mic capsule is wired to a stereo plug (using shielded lav cable), but the signal only goes to one channel of that plug, so I presume the disconnected channel is just feeding in hum, is mixed with the signal in the interface, and that explains the hum in the result.

Does my diagnosis sound correct? If so, what would you recommend? Should I just wire the signal from the mic to both the tip and sleeve of the plug, or will that mess up the interaction with the capsule somehow? Or would it be smarter to get a mono plug?

Thanks!

-Casey

Re: Windows XP installation disk

#37252

Take a look at

Am Fr., 21. Feb. 2025 um 03:44?Uhr schrieb Cram via <mitchell.cram=[email protected]>:

Show quoted text

You can turn the nag screen off for activations - it's worked for me when using xp on a virtual machine (I too have had to run legacy software in the past).

Not necessarily exactly what you asked, but should point you in the correct direction. There are plenty of xp ISO downloads on legit sites (you've never really needed an "authentic MS disc").??

Re: Windows XP installation disk

#37251

You can turn the nag screen off for activations - it's worked for me when using xp on a virtual machine (I too have had to run legacy software in the past).

Not necessarily exactly what you asked, but should point you in the correct direction. There are plenty of xp ISO downloads on legit sites (you've never really needed an "authentic MS disc").??

Windows XP installation disk

#37250

Does anyone have a Windows XP install disk they could give or sell me? ?Or a copy with the password decrypted.

?

I need a pukka XP machine to run the software I wrote myself in da last Millenium. ?Yes. ?I've tried the various Virtual machines but none of them give me the functionality I need. ?To put this into perspective, I run a DOS window under Win 98 on the XP machine.

?

Machines that have XP drivers are all more than 10 yrs old. ?I found one but I lent my pukka XP install disc to a friend who promptly lost it???

Re: Circuit for PiP EM272

#37249

thank you everyone for clearing things up.

Re: PCB for ambisonic mic with 9V power supply

#37248

Yes - sorry about the typo!? The ones I used are definitely the JLI-140A-T.

Re: PCB for ambisonic mic with 9V power supply

#37247

On Wed, Feb 19, 2025 at 03:42 PM, David Platt wrote:

The guts now consist of four JLI-240A-T capsules

Do you mean JLI-140A-T capsules? I have a few of those. They're nice.

?

Thanks for sharing your circuit.

Re: PCB for ambisonic mic with 9V power supply

#37246

See the attached ZIP (KiCAD 8 project with schematic and board layout, Gerbers, and a PDF of the schematic).? It might be suitable for you to use, either as-is or as a starting point for changes.?

?

A couple of years ago I was gifted with a "long past its use-by date" Philips stereo microphone.? The old dynamic elements were (I decided) quite useless by modern standards, and the foam had turned to goo and powder, but the shielded enclosure and stand were nicely built and in great shape.? I decided to experiment, gut it, and rebuilt it as a full-field microphone.

?

The guts now consist of four JLI-240A-T capsules, glued into a 3D-printed holder I built using OpenSCAD.? It's based on a basic pattern I found here in MicBuilders, with a graceful branching Bezier-curve support structure which fits into the screw-locked metal shaft in the microphone base.

?

I decided I did want a proper phantom-powered balanced drive for it, so I implemented one of the standard two-transistor circuits using a small PC-board layout (.86" wide by 1.26" long).? This is small enough that I could place four of them around the support shaft, wire them to the mics and to four (Electronics Flea Market surplus) XLR cables, and fit everything comfortably inside the case and shield.? I laid out the boards to suit the parts I had on hand - all surface-mount except for the two 1 uF film capacitors, for which I used through-hole parts I had handy.? I'm sure the boards could be made smaller, using SMT caps and 0805 or 0603 resistors.? I used BC856 transistors because I had a bunch of them in a samples box;? there are many other types which should work fine.

?

OshPark delivered 6 boards, in about two weeks, for under $11... hard to beat!

?

The result - it works, and with the shield closed there's no detectable hum pickup.? I got distracted by other projects and haven't done anything more than confirm the mic's basic functionality, but considering that it's using a standard sort of circuit and decent capsules I don't expect that there are any horrible surprises waiting (he said, walking confidently towards a cliff :-) )

?

ElectretPreamplifier.zip

Re: Circuit for PiP EM272

#37245

Hi
Everything is fine with + capsule on + jack and ground capsule on ground jack.
The assembly of the technical sheet is already inside the recorder

Re: PCB for ambisonic mic with 9V power supply

#37244

开云体育

No need to duplicate requests.
SimpleP48 is adequate for balanced lines of less than 20 meters. Does not require PCB's.

Le 18/02/2025 à 13:01, martenberger92 via groups.io a écrit?:

Show quoted text

Hi all,

I'd like to build a first order ambisonic 9V electret microphone, that I can travel with.

Balanced outputs is important since I will need cable lengths of 6m and longer.

What are the smallest form factor PCBs available for a project like this?
Are there any SMD based circuits openly available?

Thanks and I wish you all a lovely day!
M

Re: Circuit for PiP EM272

#37243

开云体育

The Sony PCM10, as well as all other products that provide PIP, include the protection capacitor and resistor.
Addding them would not have any benefit.

Le 18/02/2025 à 10:34, dampfus.hansus via groups.io a écrit?:

Show quoted text

Hello fellow mic builders,

I've soldered some cables to the EM272 capsules, with + to signal and GND to GND. My Sony PCM M10 provides 3V of PiP.?

?

Should I also solder in the circuit from the data sheet, with a resistor from GND to Signal and a capacitor to the Mic in?

If so what are the benefits? Is it true that I could damage the recorder through not filtering the DC voltage?

?

Thank you very much!?