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Yeah the above-described solution would have two separate mics with independent outputs, a volume knob for each, and no master level. This adjustment would be nice when transitioning between a piece with sustained chords in the left hand and a single reed set activated on the right, vs. staccato on the left and doubled or tripled reeds on the right, etc. I don't play a single style of music so it's hard to use a one-size-fits-all, set-and-forget approach. It's also nice to have separate outputs so that, as Ilya said, a sound engineer can override my decisions if needed. (Also handy for recording...)

There is no doubt that individual control of the respective level of left-hand (chords) and right-hand (keyboard) is mandatory. It's even true with conventional close-micing.

I realized that this list has helped me before on this question: is a level control on Simplest P48 as simple ?

The 120k resistor should be halved in order to make sure the capsules receive enough voltage for pentode operation. Pentode operation is mandatory for correct mixing operation.
However the balance between both capsules depends on good matching of the capsules, so some kind of comparison/matching is necessary.

And there's a noise penalty but probably not relevant in this application?

The acoustic pressure in the accordion is high enough to make nay noise issue moot.

My simple test with a single Primo simplest P48 didn't seem to clip; any chance I might want to use one of the lower-gain/higher-SPL-tolerance varieties of Simplest P48, given how loud accordions can be? I'll keep testing...

I have never had any clipping issue with the standard lapel mics that I used when they were the only convenient source of electret capsules.

Sorry, I'm jumbling a few different things into the same thread... I'll try to be more clear. My ideal is described above -- independent channels with independent level controls. Besides that, there are a few other ideas:

1) a mini-mixer (not accordion-specific: just an all-purpose mixer) that can supply phantom (or PiP?) to, say, two or maybe three channels, with a gain control for each, and output a single signal, perhaps at XLR mic-level, perhaps the whole thing running on phantom (if that's even possible.) There are products akin to this so it might not be worth DIY'ing, and I'm sure there are schematics out there already; I have not yet searched. Recommendations welcome. In cases where the dual-output accordion channels aren't needed, this would be handy to mix to one signal to send to the board. This would also be handy as a mini mixer for any other applications: voice/guitar, or combining mics when field recording into limited inputs, etc.

2) a mixing topology that could take various electret capsules and mix them together into a single output, with trim pots, etc; this would have the advantage over "parallel multi-capsule Simplest P48" in that you could adjust levels of the individual capsules to dial in the response. This might be for accordion or other acoustic instruments with multi-capsule systems, if a single output is desired. Bonus points for battery-free phantom powering. This could be used for the entire accordion (left and right hands, balancing capsule levels as appropriate) or for a single side of the accordion. I don't need this, personally, at least not now, but maybe others would appreciate it.

3) a mixing topology that takes two "channels", where each channel might be a single electret capsule or a combination of capsules (e.g. a channel represents the right or left hand of the accordion), and provides a balance and master level, akin to what you and JLM and others are talking about. I don't need this personally but the world would be better with this schematic in it.

Putting all these requirements within the constraints of phantom power is a little challenging and requires some brains agility, but I reckon it is feasible.
However, integrating that in an accordion seems hardly doable, so it would be an external box with 3 or 4 cables going to the accordion.
When the definition of the product(s) is settled, I can draw a schematic, even layout a PCB. It's not too difficult.

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but if I were asked what my ideal accordion mixing circuit would be it would be two XLR jacks, each with an associated pot to control level.

Do you mean two separate mics each with their own output? So no actual mixer at all? the mixing is done on the main mixer for the gig? That's easy. Easier than a single master volume and balance pot actually. Also two XLR leads means twice the power available - no problem.

But then you don't have a master volume for the whole instrument. Do you really need to adjust the balance on the fly?

Yeah the above-described solution would have two separate mics with independent outputs, a volume knob for each, and no master level. This adjustment would be nice when transitioning between a piece with sustained chords in the left hand and a single reed set activated on the right, vs. staccato on the left and doubled or tripled reeds on the right, etc. I don't play a single style of music so it's hard to use a one-size-fits-all, set-and-forget approach. It's also nice to have separate outputs so that, as Ilya said, a sound engineer can override my decisions if needed. (Also handy for recording...)

I realized that this list has helped me before on this question: is a level control on Simplest P48 as simple ? And there's a noise penalty but probably not relevant in this application?

My simple test with a single Primo simplest P48 didn't seem to clip; any chance I might want to use one of the lower-gain/higher-SPL-tolerance varieties of Simplest P48, given how loud accordions can be? I'll keep testing...

2 fullsize XLR jacks and two pots with knobs is bulky to mount though and if it is to be permanently mounted in the accordion cover needs quite large holes.

Yeah, I imagined mini-XLRs (or TRS, but I have bad luck with them), going to short adapter cables, to full-size XLR.

?(A flexible phantom-powered "mini-mixer" that provides 2 or 3 phantom-powered XLR jacks/connections and a level pot for each sounds great, but I don't know if the per-channel power limitations of P48 make that idea ridiculous.)

I don't understand this, do you mean separate outputs for each mic on the accordion? Or do you mean an external standalone phantom powered mixer unit with 3 inputs and one output?

Sorry, I'm jumbling a few different things into the same thread... I'll try to be more clear. My ideal is described above -- independent channels with independent level controls. Besides that, there are a few other ideas:

1) a mini-mixer (not accordion-specific: just an all-purpose mixer) that can supply phantom (or PiP?) to, say, two or maybe three channels, with a gain control for each, and output a single signal, perhaps at XLR mic-level, perhaps the whole thing running on phantom (if that's even possible.) There are products akin to this so it might not be worth DIY'ing, and I'm sure there are schematics out there already; I have not yet searched. Recommendations welcome. In cases where the dual-output accordion channels aren't needed, this would be handy to mix to one signal to send to the board. This would also be handy as a mini mixer for any other applications: voice/guitar, or combining mics when field recording into limited inputs, etc.

2) a mixing topology that could take various electret capsules and mix them together into a single output, with trim pots, etc; this would have the advantage over "parallel multi-capsule Simplest P48" in that you could adjust levels of the individual capsules to dial in the response. This might be for accordion or other acoustic instruments with multi-capsule systems, if a single output is desired. Bonus points for battery-free phantom powering. This could be used for the entire accordion (left and right hands, balancing capsule levels as appropriate) or for a single side of the accordion. I don't need this, personally, at least not now, but maybe others would appreciate it.

3) a mixing topology that takes two "channels", where each channel might be a single electret capsule or a combination of capsules (e.g. a channel represents the right or left hand of the accordion), and provides a balance and master level, akin to what you and JLM and others are talking about. I don't need this personally but the world would be better with this schematic in it.

Thanks for reading, all thoughts welcomed and appreciated,

-c

On 05/06/2022 16:58, Casey via groups.io wrote:

I continue to resist the temptation to use this group as my personal on-call product design team,

well I'm happy to discuss it as whatever I learn will be of use to me for other things. However my knowledge of mixers is limited.

but if I were asked what my ideal accordion mixing circuit would be it would be two XLR jacks, each with an associated pot to control level.

Do you mean two separate mics each with their own output? So no actual mixer at all? the mixing is done on the main mixer for the gig? That's easy. Easier than a single master volume and balance pot actually. Also two XLR leads means twice the power available - no problem.

But then you don't have a master volume for the whole instrument. Do you really need to adjust the balance on the fly?

2 fullsize XLR jacks and two pots with knobs is bulky to mount though and if it is to be permanently mounted in the accordion cover needs quite large holes.

?(A flexible phantom-powered "mini-mixer" that provides 2 or 3 phantom-powered XLR jacks/connections and a level pot for each sounds great, but I don't know if the per-channel power limitations of P48 make that idea ridiculous.)

I don't understand this, do you mean separate outputs for each mic on the accordion? Or do you mean an external standalone phantom powered mixer unit with 3 inputs and one output?

Le 05/06/2022 à 17:58, Casey via groups.io a écrit?:

JLM wrote:

I have noted that the difference between omni and cardio capsules inside is just that the latter have less bass.

Huh, I would have thought that proximity effect would mean more bass from the cardioid?

At best, proximity effect extends the LF response to that of a comparable omni.

JLM wrote:

I have noted that the difference between omni and cardio capsules inside is just that the latter have less bass.

Huh, I would have thought that proximity effect would mean more bass from the cardioid? I guess in the semi-enclosed region that doesn't really matter?

thet wrote:

Can the trace be easily cut to turn it into a 3 wire capsule with the source separated from ground?

Yeah, the 5024 can be cut/"linkwitzed" in this way.

thet wrote:

Are there different 5024s with different specs?

Re: the HD-R vs HD-F-R I believe the "F" just means there is felt on that capsule and they are otherwise identical.

I continue to resist the temptation to use this group as my personal on-call product design team, but if I were asked what my ideal accordion mixing circuit would be it would be two XLR jacks, each with an associated pot to control level. I'm often playing music in situations where I'm my own sound person (or the sound person is asleep at the board) and being able to control both the balance and the independent level of each hand would be best. My ideal circuit would run on phantom power (i.e. no battery; not sure if realistic). (A flexible phantom-powered "mini-mixer" that provides 2 or 3 phantom-powered XLR jacks/connections and a level pot for each sounds great, but I don't know if the per-channel power limitations of P48 make that idea ridiculous.)

Thanks for listening. :-)

-c

apologies, that must have changed when I wasn't paying attention

here it is:

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You can't attach documents to the mails. You need to upload them to the Files or Photos folders.

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OK, I have no expertise in mixer resistance networks which is what this comes down to. I drew 5 versions and don't like any of them all that much.

But to start discussion what about this?

The green areas are the capsules, each wired as a source follower with separated ground. (sorry GND symbol was omitted on top capsule) The 9v supply is derived from phantom in the usual way.

The values shown are merely to start discussion, I don't know the likely output impedance of the capsule fets

The output buffer could be an opamp instead of the source follower shown, and that might allow the removal of its input capacitor as the resistance network would be referenced to virtual ground.

An alternative way to make a balance trim would be to use a trimpot as the source resistor on one or both capsules, and take signal from the wiper.

I see: I thought the mics would be mounted inside the bellows. If not then my comment becomes irrevelant.
I'd be surprised that cardioid capsules change anything in feedback prevention.

Le 04/06/2022 à 11:48, ilya dontsov a écrit?:

It may be useful to have separate outputs for left and right hands. The final balance can be made at the mixing desk.

Certainly, in order to accomodate for different styles, different players...

Le 04/06/2022 à 11:27, thet a écrit?:

For an accordion mic is capsule balance a set and forget thing?

Yes.

ie could it be a trimpot on the board, and with limited range, just to make minor adjustments to almost balanced levels?

Correct.

Or does it need to be a full on 100% balance pot that is accessible to the player during a gig?

No need for that.

It may be useful to have separate outputs for left and right hands. The final balance can be made at the mixing desk.

As for a mic array. indeed, since the mics are inside, it should be possible to get away with 2-3 mics per side.

For an accordion mic is capsule balance a set and forget thing? ie could it be a trimpot on the board, and with limited range, just to make minor adjustments to almost balanced levels?

Or does it need to be a full on 100% balance pot that is accessible to the player during a gig?

I agree stick to the omni capsules for the reasons Jerry gave.

As far as designing a mixing preamp system, it might help to have specs on the specific fet in the specific capsule that you want to use. You mentioned 5024s - does anyone have specs on the fet?

(I really wish you could get little electret omni caps without fets, it would make designing good preamps a lot easier to use known good parts)

Can the trace be easily cut to turn it into a 3 wire capsule with the source separated from ground?

If I were starting from scratch I'd probably be tempted to deign around a primo EM273

I have some 10mm omnis that are supposed to be good but I can't remember what they are, they look like pics of 5024s though.

ie here:

and here:

Are there different 5024s with different specs?

Le 04/06/2022 à 03:36, Casey via groups.io a écrit?:

Thanks -- are you thinking that there might be some near-DC signal fluctuation from these pressure changes?

Eletret capsule do not pass absolute pressure, only its variations.

But I do wonder about cardioid capsules just for the sake of preventing on-stage feedback...

When put inside a cavity, mics become omni regarding what's outside of the cavity. Feedback resistance is governed by distance. The capsules are very close to the reeds and inside the pressure field.

I have noted that the difference between omni and cardio capsules inside is just that the latter have less bass. Feedback resistance is the same.

It would be different if the mics were externally mounted.

Maybe you should consider NOT using omnidirectional capsules...
Omnidirectional microphones usually have their back chambers sealed. Your average omnidirectional capsule may have trouble dealing with the constantly changing pressure, in fact alternating between pressure and vacuum inside the accordion...

Omni capsules always have a pressure leak, in order to prevent the possible effects of change in ambient pressure.

Thanks -- are you thinking that there might be some near-DC signal fluctuation from these pressure changes? At any rate, the capsules will be on the atmospheric-pressure side of the reeds, not inside the bellows, so there shouldn't be any significant pressure swings of that nature, AFAIK.

But I do wonder about cardioid capsules just for the sake of preventing on-stage feedback...

-c

Maybe you should consider NOT using omnidirectional capsules...
Omnidirectional microphones usually have their back chambers sealed. Your average omnidirectional capsule may have trouble dealing with the constantly changing pressure, in fact alternating between pressure and vacuum inside the accordion...

On 04/06/2022 00:58, Casey via groups.io wrote:

you could check Ricardo's PDF in the files section for some more info; this link might work: /g/MicBuilders/files/Ricardo/SimpleP48/SimpleP48.pdf

Yes I just read through that. It doesn't explain the circuit straight up, but one can glean quite a lot about how it works from reading that. TBH the floating balanced operation sort of does my head in.

It seems that it *will* work with transformer inputs, though the more subtle consequences of that still give me pause.

. but I'm basically just following instructions; to build the simple mixer circuit you describe I would basically have to pester the list until it collectively designed the entire circuit for me, and I wouldn't feel good about that. So if there's some already-drawn-up way to do what you describe, that would be awesome... I would love level controls for the two sides... but my knowledge is not at a level where I can design it myself. (Also it feels a little off-topic for the list to design mixers, so I'm trying to be sensitive to that.)

Well this is something I'm also interested in. I want a compact way to mix 2 pickups for a fiddle with two hiZ piezo film pickups - so the same sort of mixer might well work for both. An accordion has a luxurious amount of space for mounting circuitry compared to a fiddle so it should be easy.

I know I could design something that would work - I'm not sure if I would think of every subtlety to completely optimise it.

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Paralleling them is using parallel fets though - I would think the matching of the fet characteristics would matter.

Actually, the FET characteristics do not matter too much, as long as the voltage across them is enough to guarantee they are in their pentode region, but the sensitivity, being usually spec'd with a +/-3dB tolerance may result in too much difference. Unless using matched capsules, the system must allow for some kind of individual adjustment, which is not compatible with the simple P48.

Considering the modest price of electret capsules, it should not be too difficult to buy a batch of 10 and match them using a simple jig.

Is there a full circuit diagram somewhere with an actual explanation of how they work? All the docs I can see seem to omit the fet from the diagram, and are vague about how it actually works. Capsule datasheets are also vague on internal connections, especially how (if?) the gate is referenced.

I can't speak to the technical side, but once logged into the groups.io website you could check Ricardo's PDF in the files section for some more info; this link might work: /g/MicBuilders/files/Ricardo/SimpleP48/SimpleP48.pdf

It just doesn't seem that hard to wire each capsule as a source follower and then mix them to a buffer amp that can give a low Z balanced output - the extra circuitry looks like a lot compared to a S-P48 but its trivial compared to the effort of fitting a pickup system into an accordion. It would allow the addition of a balance or level pot easily enough as well.

I'm sure you're right; I've built a few circuits from schematics here in the group (with lots of help from members here) and I'm not generally intimidated by that (even made my own PCB's for the DIYGenericIntFET)... but I'm basically just following instructions; to build the simple mixer circuit you describe I would basically have to pester the list until it collectively designed the entire circuit for me, and I wouldn't feel good about that. So if there's some already-drawn-up way to do what you describe, that would be awesome... I would love level controls for the two sides... but my knowledge is not at a level where I can design it myself. (Also it feels a little off-topic for the list to design mixers, so I'm trying to be sensitive to that.)

-c