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.

On 04/06/2022 11:44, Jerry Lee Marcel wrote:

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.

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.

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...

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...

I'm scheming on making internal mics for my accordion using Simplest
P48. Using just a single internal mic would greatly emphasize some
notes over others, so a typical design uses multiple mics internally
and blends them.
I thought to use parallel capsules in a standard Simplest P48
circuit... some questions, if anyone has thoughts:
1) a standard accordion is about 18-20" (~48cm) wide. That means
wide-spaced mics would be about 12" ~= 1ms apart, which comes to comb
cancellation with first node at about 500Hz... I wonder how the
average accordion pickup system deals with this... simply ignores it,
maybe? Judicious spacing of mics to make a less offensive cancellation
pattern? Corrective EQ?
2) if e.g. I put multiple 5024's in parallel in a Simplest P48, I
don't need to make any other adjustments to the circuit (resistor
size, cap size), correct?
3) would using many capsules in parallel, say four or six, alleviate
comb filtering by averaging out the cancellations, or make things
worse? Simplistic testing simulations shows that the cancellation
pattern is somewhat unpredictable, and sometimes ugly, but I wonder
how this goes in practice...
Thanks!
-Casey

Thanks thet --

You don't say if it is a piano accordion or B/C system or some other type, but reed layouts may vary, so consider the reed layout.

It's a piano accordion, so the reeds are linearly arranged. Doing some tests (with a single Primo omni Simplest P48 inside the right-hand side) I do hear a strong difference for the reeds near the mic, as expected.

I would think two mics on the keyboard and one or two on the bass would be sufficient.

Glad to hear that this and Jerry's experience accord with each other.

There are better circuits than P48 that aren't really much more effort if you are going to the trouble of installing multiple mics in an accordion.

Interesting... what did you have in mind? I have made so many S-P48's and they've been great, and given how simple and effective they are, and that I don't need low noise performance in this application, Simplest P48 seemed the natural choice?

If you draw the circuit you intend we can comment better on the mixing - seems to me in a mixer each capsule needs its own resistor into the summing amp, just shorting together the capsule fet outputs seems wrong to me.

Yeah the plan was to literally parallel multiple capsules on a standard P48 circuit, so, .

IIRC it has been discussed a couple times here that this works (and gives a little less noise) so it seemed like the easy way to deal with mixing the signals from the capsules without having to engineer some kind of active mixer as well... but I have no idea if there are subtle consequences, so let me know if I'm missing something.

-c

On Jun 3, 2022, at 4:08 PM, Casey via groups.io <mbuilders@...> wrote:

?

Thanks thet --

You don't say if it is a piano accordion or B/C system or some other type, but reed layouts may vary, so consider the reed layout.

It's a piano accordion, so the reeds are linearly arranged. Doing some tests (with a single Primo omni Simplest P48 inside the right-hand side) I do hear a strong difference for the reeds near the mic, as expected.

I would think two mics on the keyboard and one or two on the bass would be sufficient.

Glad to hear that this and Jerry's experience accord with each other.

There are better circuits than P48 that aren't really much more effort if you are going to the trouble of installing multiple mics in an accordion.

Interesting... what did you have in mind? I have made so many S-P48's and they've been great, and given how simple and effective they are, and that I don't need low noise performance in this application, Simplest P48 seemed the natural choice?

If you draw the circuit you intend we can comment better on the mixing - seems to me in a mixer each capsule needs its own resistor into the summing amp, just shorting together the capsule fet outputs seems wrong to me.

Yeah the plan was to literally parallel multiple capsules on a standard P48 circuit, so, .

IIRC it has been discussed a couple times here that this works (and gives a little less noise) so it seemed like the easy way to deal with mixing the signals from the capsules without having to engineer some kind of active mixer as well... but I have no idea if there are subtle consequences, so let me know if I'm missing something.

-c

I'm scheming on making internal mics for my accordion using Simplest P48. Using just a single internal mic would greatly emphasize some notes over others, so a typical design uses multiple mics internally and blends them.

I thought to use parallel capsules in a standard Simplest P48 circuit... some questions, if anyone has thoughts:

1) a standard accordion is about 18-20" (~48cm) wide. That means wide-spaced mics would be about 12" ~= 1ms apart, which comes to comb cancellation with first node at about 500Hz... I wonder how the average accordion pickup system deals with this... simply ignores it, maybe? Judicious spacing of mics to make a less offensive cancellation pattern? Corrective EQ?

2) if e.g. I put multiple 5024's in parallel in a Simplest P48, I don't need to make any other adjustments to the circuit (resistor size, cap size), correct?

3) would using many capsules in parallel, say four or six, alleviate comb filtering by averaging out the cancellations, or make things worse? Simplistic testing simulations shows that the cancellation pattern is somewhat unpredictable, and sometimes ugly, but I wonder how this goes in practice...

Thanks!

-Casey