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Merging three Capsules on two Preamps?!

 

Hi all,
I would like to create a little circuit box that merges the signals of two ambient mics (L/R) with a single vocal mic (M) before entering the preamps.
So I can record stereo ambient and vocal simultaneously on my sony cassette 2 Track cassette recorder.
The recorder has two decent mic preamps without phantom power.
Is that possible? How would a circuit like this look like?

I was thinking of using two omni primo capsules for ambient and a XLR input for the extra vocal input (potentially condenser +48V).

Ideally there would be a single switch or potentiometer with which I can switch from only ambient, to only vocal mic, and some in between settings.

Is there someone that could help me out with a circuit sketch??

And what would be the easiest way to add phantom power to that device? The whole rig is intended to be used in the field and with batteries.
I could install 9V block batteries or also 3,7V Lipo batteries as power supply.

Any help is greatly appreciated!

Thanks?
M
 

Merging two omnis down to mono might not sound that great. They generally don't downmix to mono very nicely.?

J

On Tue, 11 Feb 2025 at 13:27, martenberger92 via <martenberger92=[email protected]> wrote:
Hi all,
I would like to create a little circuit box that merges the signals of two ambient mics (L/R) with a single vocal mic (M) before entering the preamps.
So I can record stereo ambient and vocal simultaneously on my sony cassette 2 Track cassette recorder.
The recorder has two decent mic preamps without phantom power.
Is that possible? How would a circuit like this look like?

I was thinking of using two omni primo capsules for ambient and a XLR input for the extra vocal input (potentially condenser +48V).

Ideally there would be a single switch or potentiometer with which I can switch from only ambient, to only vocal mic, and some in between settings.

Is there someone that could help me out with a circuit sketch??

And what would be the easiest way to add phantom power to that device? The whole rig is intended to be used in the field and with batteries.
I could install 9V block batteries or also 3,7V Lipo batteries as power supply.

Any help is greatly appreciated!

Thanks?
M



--

07889727365

02036861372

3 Swimmers Lane
Haggerston
London
E2 8FR
 

You are describing a mixer. There are small ones out there that would accomplish?this. And as has been mentioned, take the two ambience capsules pan one hard right one hard left and mix the vocal in the middle. Adding them in mono may not sound good.

Jules

On Tue, Feb 11, 2025 at 7:27?AM martenberger92 via <martenberger92=[email protected]> wrote:

Hi all,
I would like to create a little circuit box that merges the signals of two ambient mics (L/R) with a single vocal mic (M) before entering the preamps.
So I can record stereo ambient and vocal simultaneously on my sony cassette 2 Track cassette recorder.
The recorder has two decent mic preamps without phantom power.
Is that possible? How would a circuit like this look like?

I was thinking of using two omni primo capsules for ambient and a XLR input for the extra vocal input (potentially condenser +48V).

Ideally there would be a single switch or potentiometer with which I can switch from only ambient, to only vocal mic, and some in between settings.

Is there someone that could help me out with a circuit sketch??

And what would be the easiest way to add phantom power to that device? The whole rig is intended to be used in the field and with batteries.
I could install 9V block batteries or also 3,7V Lipo batteries as power supply.

Any help is greatly appreciated!

Thanks?
M



--
Best Regards,

Jules Ryckebusch

214 399 0931
 

There's a way to make a passive battery box that could bias 3 electret capsules and has the "mono" capsule feeding both the L and R outputs, but it would have a bit of loss from a resistive mix matrix, and it wouldn't really have the blend control you wanted. And it wouldn't provide any XLR input(s) with phantom.
?
You could build a mini mixer with 3 XLR mic inputs; there are many balanced mic preamp circuits out there, including with phantom... but since you can buy decent little mixers for not much more than it would cost to DIY one it, it would seem pointless.
?
And all this effort to feed a cassette recorder? (hey, i have a SONY Walkman Pro cassette recorder somewhere, but it had its day, and we've moved on)
?
Your best move is probably to put your money into a new (or used) digital recorder that will record from 4 mics, so no external box or mixer required. A starting point would be ZOOM - such as their H4n Pro, H4E,? H5, or H6E recorders. Also Tascam.
 

Thanks for your view on this.

I have a Zoom, also a Sound Devices Mixpre10ii and many decent mics, so its not really about High fidelity or practicality here.
It's more about creating something playful and analog in nature just for the sake of it.

Yes I have been thinking also about using three electret capsules instead, too. However I would like the XLR input idea better.

I am aware that in a way I am describing a mixer yes. But I want this setup to be as small and light-weighted as possible and also battery powered.
besides I don't know any compact 3 channel XLR mixer with phantom power.
And the preamp quality of the tape recorder is really good, I dont want to decrease on quality...
Thats why I just want to switch between Stereo AB and Mid Mic or merge them.?
?
BTW: If you dont need your Sony walkman anymore, I'd happily take care of it and feed it with heartfelt music?
 

No I want to Merge a Stereo AB with a Mono Mid/vocal mic.

I want to be able to switch between:

Stereo AB, Stereo AB + mono Mic, Mono Mic?

And if I can have some degree of balancing the mono mic with the stereo that be great too. Maybe just with an adjustable pad circuit.
 

On Tue, Feb 11, 2025 at 10:29 AM, <martenberger92@...> wrote:
I am aware that in a way I am describing a mixer yes. But I want this setup to be as small and light-weighted as possible and also battery powered.
It still seems that your goals are in conflict:
  • XLR in with phantom power
  • high performance
  • mix controls or switching
  • small, lightweight, simple, portable, battery-powered
?
But anyway. Off the top of my head, a first approach to DIY might look like this:
  • crib some of the circuitry including opamp from the Opti-Alice project to buffer the raw capsules, to make one balanced mic preamp, and for post-mix makeup gain if necessary
  • battery supply (6v or more) from alkalines or rechargeables for the opamps
  • a charge pump, or 6x 9v (the rectangular PP3 type) for phantom power
besides I don't know any compact 3 channel XLR mixer with phantom power.
There are portable analog mixers available in the pro and semi-pro market. The Saramonic SR-PAX1 is a two-input mixer with phantom which might be a good starting point for modification, or combine two. Or their Smartrig+ mixer. I think Rolls offers similar mixers.
?
In the used market, the SHURE FP32 or FP33 can often be had for $200 or less. These are 3 mic in, stereo out, with phantom. Heavy little suckers.
?
 

On Tue, Feb 11, 2025 at 11:33 AM, kennjava wrote:
Opti-Alice
Sorry, the right project name is OPA-Alice
 

The FP33 looks indeed like the one device that I would need. But it's also on the heavy side. I had some slightly bigger Audio Development stuff, but mobility and lightweightedness are King for this project.

So thanks for pointing out my conflict, I am relaxing into just using three electret capsules and then merging them.

I assume the best way would be using the OPA Alice circuit on all three capsules and then merging on them right?

Would it be better to merge before the OPA Alice circuit on the capsules side, or after between the OPA circuit and the XLR Preamps?

It seems I could relatively easy add a attenuator Pad into the the Mid Mic so I would have some degree control in merging mode.

Thanks for the feedback!
 

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The ?OPA Alice is designed for capsules without a FET, to run off of Phantom power, and to drive balanced signals into a mic preamp or recorder. It really isn’t applicable for this application?
Best Regards,

Jules Ryckebusch?

On Feb 11, 2025, at 12:50, martenberger92 via groups.io <martenberger92@...> wrote:

?
The FP33 looks indeed like the one device that I would need. But it's also on the heavy side. I had some slightly bigger Audio Development stuff, but mobility and lightweightedness are King for this project.

So thanks for pointing out my conflict, I am relaxing into just using three electret capsules and then merging them.

I assume the best way would be using the OPA Alice circuit on all three capsules and then merging on them right?

Would it be better to merge before the OPA Alice circuit on the capsules side, or after between the OPA circuit and the XLR Preamps?

It seems I could relatively easy add a attenuator Pad into the the Mid Mic so I would have some degree control in merging mode.

Thanks for the feedback!
 

On Tue, Feb 11, 2025 at 02:08 PM, Jules Ryckebusch wrote:
The ?OPA Alice is designed for capsules without a FET, to run off of Phantom power, and to drive balanced signals into a mic preamp or recorder. It really isn’t applicable for this application?
Hi Jules,
?
I only suggested the OPA-Alice as inspiration - it showcases a suitable opamp for battery-powered use, some practical considerations around single-ended powering, and then I'd expect the OP or whoever to use standard audio opamp practice when designing the required blocks.
?
I didn't mean to imply that the complete OPA-Alice would be a drop-in solution. Sorry if that wasn't clear.
 

Forgive me if i'm way off base,? but couldn't you use your?Sound Devices Mixpre10ii multi inputs to record and "mix" your channels post production?

On Tuesday, February 11, 2025 at 02:50:01 PM EST, kennjava <ken@...> wrote:


On Tue, Feb 11, 2025 at 02:08 PM, Jules Ryckebusch wrote:
The ?OPA Alice is designed for capsules without a FET, to run off of Phantom power, and to drive balanced signals into a mic preamp or recorder. It really isn’t applicable for this application?
Hi Jules,
?
I only suggested the OPA-Alice as inspiration - it showcases a suitable opamp for battery-powered use, some practical considerations around single-ended powering, and then I'd expect the OP or whoever to use standard audio opamp practice when designing the required blocks.
?
I didn't mean to imply that the complete OPA-Alice would be a drop-in solution. Sorry if that wasn't clear.
 

?
On Tue, Feb 11, 2025 at 02:08 PM, Jules Ryckebusch wrote:
The ?OPA Alice is designed for capsules without a FET, to run off of Phantom power, and to drive balanced signals into a mic preamp or recorder. It really isn’t applicable for this application?
Hi Jules, thanks for clarifying.?
I checked out your M/S mic today, where you created a figure of 8 by wiring to cardioid capsules in series. And that gave me an idea?

Couldn't I then if I want to merge Stereo AB with the Mid Mono mic wire the Mono Capsule in series with the A & B capsules?
Essentially forking the Mono Capsule and feeding it then into capsule A & B. Would that be worth an experiment?

Maybe I should add: The Stereo AB will be approx, 20 cm apart. And the Mid Mic is about 30cm closer to the source as the AB. Like a mini Decca Tree.

Then I could run this three capsule on a dual channel OPA alice board provided I have added phantom power and plug it right in my Sony Cassette Recorder.?

Btw Jules, thanks a lot for creating all this amazing content!

@James B: Yes I could use my Sound Devices Recorder and I do it all the time. But this project is really all about the fun and playfulness of old school cassette recorders. But still I want to record songs and capture the ambience simultaneously. So a Stereo AB is not gonna cut it.?
 

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No problem you can power that circuit from a 9v battery sans phantom power?
Best Regards,

Jules Ryckebusch?

On Feb 11, 2025, at 14:43, martenberger92 via groups.io <martenberger92@...> wrote:

?
?
On Tue, Feb 11, 2025 at 02:08 PM, Jules Ryckebusch wrote:
The ?OPA Alice is designed for capsules without a FET, to run off of Phantom power, and to drive balanced signals into a mic preamp or recorder. It really isn’t applicable for this application?
Hi Jules, thanks for clarifying.?
I checked out your M/S mic today, where you created a figure of 8 by wiring to cardioid capsules in series. And that gave me an idea?

Couldn't I then if I want to merge Stereo AB with the Mid Mono mic wire the Mono Capsule in series with the A & B capsules?
Essentially forking the Mono Capsule and feeding it then into capsule A & B. Would that be worth an experiment?

Maybe I should add: The Stereo AB will be approx, 20 cm apart. And the Mid Mic is about 30cm closer to the source as the AB. Like a mini Decca Tree.

Then I could run this three capsule on a dual channel OPA alice board provided I have added phantom power and plug it right in my Sony Cassette Recorder.?

Btw Jules, thanks a lot for creating all this amazing content!

@James B: Yes I could use my Sound Devices Recorder and I do it all the time. But this project is really all about the fun and playfulness of old school cassette recorders. But still I want to record songs and capture the ambience simultaneously. So a Stereo AB is not gonna cut it.?
 

So this setup could be built actually fairly simply - no need to have phantom power or anything like that. Too complicated.
?
Going back to the kind of electret capsules that kick-started the mic DIY boom, you should just be able to feed them all from a 9v battery through something like a 10k resistor to each.? Then collect your audio output through a nice big capacitor (to strip off the DC), and you've got something easily compatible with your recorder's inputs.? Unbalanced, but over a few inches or feet it won't matter.? You can do your custom summing with resistors and/or potentiometers.? There will be a little interaction, but something you will be able to cope with.
 

Hey Scott,

Pls allow me some beginners questions.
Is what you are describing similar to the simple P48 circuit just with a smaller resistor?
And would 4,7 uF be a "nice big" capacitor?
And the 9V is connected just as Phantompower would be connected?

If you could briefly sketch the schematic you suggested that would be amazingly helpful!
?
Thanks a lot!
?
?
?
?
 

If you could briefly sketch the schematic you suggested that would be amazingly helpful!
?
I've attached the Primo EM272 datasheet.? Look at the diagram on the right, that's what I'm referring to.? In the place of the 5 volt battery you can use a 9 volt battery and a higher value resistor, say around 6-10k ohms.? You can use the same battery to power all three capsules, each through its own resistor.
?
On the output side, you have an unbalanced signal with plenty of gain for a recorder.? You can put a resistor from the capacitor to your mic input, and if you connect two capsules that way you can adjust the resistor values to set the ratio between the capsules.? Or use a variable resistor, also called a potentiometer, so that you can adjust it while listening.
?
This will work with electret capsules, it does not quite give you the "XLR mic input for a vocal mic" you were referring to.? However, you could build your own vocal mic using a cardioid pattern capsule and this same approach.?
?
-Scott

EM272.pdf
EM272.pdf

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