Connecting a capsule

[pasarski]

[

It's not necessarily better, unless you have an actual (technical) requirement to use that topology.

...

That's how I see it also. There's just seem to be bias for the direct connection to the gate/grid amongst many. I have also seen that keeping the connecting wire as short as possibe is beneficial. I definitely won't hurt but I haven't yet heard a difference in the few centimeters of difference in the wire lengths.

 

[Khron]

There's just seem to be bias for the direct connection to the gate/grid amongst many.

Well, why WOULD someone insist on adding components in series with a signal, if it can be avoided by just swapping a couple wires around (even in the design phase)? And have the added expense, and running the extra risk of those components (or the extra solder joints) failing, or picking up more noise than otherwise, etc?

 

[MagnetoSound]

But if it was just a filter cap you could omit it altogether. Omit/short it and the mic makes no sound. How I see it, it blocks the polarization voltage from going to ground and completes the loop for the audio signal, and thus is as much in the signal path as in the other hookup scenario.

So yeah I'm still puzzled but I don't want to derail this thread too much. Maybe I just accept that the direct connection is better or start a new thread if I can't get over it

Opinion is divided on the AC path thing.

I happen to agree, without the AC ground reference behind the backplate, the backplate will try and follow the signal on the diaphragm because of the very high impedance of the polarisation circuit (this is how capacitors work, after all. Two plates with a charge between them will fluctuate together at high impedance).

The cap from backplate to ground keeps the backplate voltage stable (at uV level) at improves output clarity by an audible amount. Thus, the backplate cap is certainly in the signal path.

Others disagree, and it seems churlish to try to force the point. Experiment, and decide for yourself.

 

[abbey road d enfer]

The cap from backplate to ground keeps the backplate voltage stable (at uV level) at improves output clarity by an audible amount. Thus, the backplate cap is certainly in the signal path.

We're used to think of signals as voltages, but actually it's current that counts, and it runs in a loop. That's why ground paths, amon other things, count a lot, and decoupling caps as well.

 

[abbey road d enfer]

[

That's how I see it also. There's just seem to be bias for the direct connection to the gate/grid amongst many. I have also seen that keeping the connecting wire as short as possibe is beneficial. I definitely won't hurt but I haven't yet heard a difference in the few centimeters of difference in the wire lengths.

The main reason for keeping high-Z nodes as short as possible is to avoid leaks due to dirt and to minimize noise pick-up. It doesn't influence the intrinsic performance of the circuit, though.

 

[pasarski]

Well, why WOULD someone insist on adding components in series with a signal, if it can be avoided by just swapping a couple wires around (even in the design phase)? And have the added expense, and running the extra risk of those components (or the extra solder joints) failing, or picking up more noise than otherwise, etc?

I think one reason to put the cap between the capsule and the gate is that you get protection for the JFET in the case the capsule shorts out. For my DIY mics I don't find it necessary.

 

[pasarski]

The main reason for keeping high-Z nodes as short as possible is to avoid leaks due to dirt and to minimize noise pick-up. It doesn't influence the intrinsic performance of the circuit, though.

For sure. One aspect of it that a I've been contemplating though is, that if a use wire of same length as the widht of my finger and I grab that wire with my fingers I might make the sleeve (edit: insulation) conductive all the way vs. if the wire was a little longer. Shouldn't grab the wires with bare fingers of course in the first place.

 

[abbey road d enfer]

For sure. One aspect of it that a I've been contemplating though is, that if a use wire of same length as the widht of my finger and I grab that wire with my fingers I might make the sleeve conductive all the way vs. if the wire was a little longer. Shouldn't grab the wires with bare fingers of course in the first place.

I don't really understand your concern. Do you think that when you grab a wire you actually shield it?

 

[pasarski]

I don't really understand your concern. Do you think that when you grab a wire you actually shield it?

I have to admit that when I read what I wrote it is (again) not making sense. I meant I might make the sleeve conductive by touching it. If it touches the base plate of the headbasket that might be a problem if the finger print goes from capsule to there. If I touch a longer wire in the middle and only make the middle section conductive I might just get away with it. I think I might think silly things sometimes.

 

[abbey road d enfer]

What "sleeve" do you think you make "conductive"?

 

[pasarski]

What "sleeve" do you think you make "conductive"?

I mean the plastic that is around the wire. I'm not a native English speaker so maybe it's a wrong word for it sorry. Insulation?

 

[abbey road d enfer]

OK. Sleeve is the correct word, insulation is correct too. The sleeve is plastic. Touching it doesn't make it conductive.
Unless you have very dirty fingers...

 

[pasarski]

OK. Sleeve is the correct word, insulation is correct too. The sleeve is plastic. Touching it doesn't make it conductive.
Unless you have very dirty fingers...

I think in the high z part of the mic it can. It's not wise to touch anything with bare hands there.

Edit: And yes, my fingers are very dirty sometimes

 

[abbey road d enfer]

I think in the high z part of the mic it can.

No way.

It's not wise to touch anything with bare hands there.

For other reasons. It's very hard to make plastic conductive without chemistry.

 

[pasarski]

No way.

For other reasons. It's very hard to make plastic conductive without chemistry.

Hmmm
https://groupdiy.com/threads/microphone-noise-hiss-question-for-the-mic-guys.19765/post-231387

Edit: Of course I didn't mean that the fingerprint makes the plastic conductive. But it makes a conductive layer on the plastic. I thought that that would be obvious but I will try to be more precise with my inadequate English.

 

[abbey road d enfer]

Hmmm
https://groupdiy.com/threads/microphone-noise-hiss-question-for-the-mic-guys.19765/post-231387

Edit: Of course I didn't mean that the fingerprint makes the plastic conductive. But it makes a conductive layer on the plastic.

It may, but it will not result in conduction to the conductor wire that's inside.

 

[pasarski]

It may, but it will not result in conduction to the conductor wire that's inside.

Of course it can. You must know that the conductor wires come out at the ends of the insulating plastic? It would be really hard to solder them if they didn't. So if the stain makes a path from plastic to the wire it will result exactly that.

Anyways, I wonder why is it so much easier for some people to latch onto a side remark or bad phrasing of mine rather than try to talk about the main topic?

I have seen countless times mentioned here and on other forums that a direct connection to the gate/grid (which really needs a cap between capsule and ground, even though some question that) is better than cap on the gate/grid (with other side of the capsule grounded). I always believed that to be true but lately started question that and want to know more about the theory behind it.

This far nobody has been able to explain it in a way I and my dirty fingers understand it. Instead there has been unbelievable amount of (deliberate?) misunderstanding and effort to lead the conversation off track. Love this forum regardless and I'm happy to be back here <3

 

[Khron]

This far nobody has been able to explain it in a way I and my dirty fingers understand it.

That "understand" is a very unusual spelling of the word "accept"

But I'm not sure you've yet answered why you feel(?) / think that insisting on putting a non-ideal component IN SERIES with a very delicate signal source, is more desirable than relegating said non-ideal component to a far more "pedestrian" and undemanding / less crucial role, while achieving (at least) the same net result, if not even a better one... Of course, assuming the rest of the circuit topology allows for it.

 

[pasarski]

Opinion is divided on the AC path thing.

I happen to agree, without the AC ground reference behind the backplate, the backplate will try and follow the signal on the diaphragm because of the very high impedance of the polarisation circuit (this is how capacitors work, after all. Two plates with a charge between them will fluctuate together at high impedance).

The cap from backplate to ground keeps the backplate voltage stable (at uV level) at improves output clarity by an audible amount. Thus, the backplate cap is certainly in the signal path.

Others disagree, and it seems churlish to try to force the point. Experiment, and decide for yourself.

This is super interesting. In a simulation you can short the cap from backplate (or a membrane, capsule is symmetrical) to ground it seems. Doesn't make a big difference, only affects the low frequencies which is expected. So in a way @Khron is right, it's a filter cap.

Still, you definitely can't omit it, there has to be a path to ground (surprisingly though you get a really weak signal in simulation even if you leave the other side of the capsule floating; the mic wouldn't be usable though). So it's definitely in the signal path as I see it.

I Can't judge clarity from the simulation and have to try it in real life when I get back home (travelling atm) but I believe what is written above makes sense. Also if it was good practice to leave it out we would have seen mics implemented this way. So it's not JUST a filter cap imo.

Edit: Of course you can't short the cap to ground because there will be no polarization voltage then fell for a simulation (and red wine).

(This is the circuit I used for the simulation, a really basic common source circuit built in a Behringer B1 using the stock capsule. C2 is the capacitor of interest. You can't omit it but you can short (edit: bypass?) it to ground (with possible side effects). If you wonder about the 100 meg resistors and the low value coupling and bypass caps: it's meant to be hand held and used for really close miked vocals and it really seems to do that quite well.)

 

[pasarski]

That "understand" is a very unusual spelling of the word "accept"

But I'm not sure you've yet answered why you feel(?) / think that insisting on putting a non-ideal component IN SERIES with a very delicate signal source, is more desirable than relegating said non-ideal component to a far more "pedestrian" and undemanding / less crucial role, while achieving (at least) the same net result, if not even a better one... Of course, assuming the rest of the circuit topology allows for it.

I don't know why you think I insist that.

Edit: maybe the post above clarifies what I mean? Not trying to insist anything