Re: ESD protection for HiZ inputs?

开云体育

I’m using the diodes ?am as this is text book protection for opamps ? Can’t speak to FET’s or a >10M input impedance?

Best Regards,

Jules Ryckebusch?

On Oct 5, 2024, at 16:04, Richard Lee via groups.io <ricardo_lee@...> wrote:

?
Dunno about piezo amps @ about 10M but for a LN condensor mike over 1G, the diodes must have VERY low leakage.

?

1n4148 far too leaky and noisy.? Guru Scott Wurcer liked a smoke alarm FET used as a diode.? Another 'diode' for this is the BE junction of an old fashioned LN BJT like BC214 or 2n5087.

?

Schottkys have very poor leakage which gets worse with time.? The latest THAT 1510/12 datasheets for microphone preamps recommend cheapo 1n4003GP (Glass Passivated).? I've personal experience of Schottky protection diodes going noisy in several MOTU Travelers withing 12 mths and indeed all da MOTU designs cured by replacing with 1n4003

?

Dunno if 1n4003 will protect Jule's piezo amps.

Re: ESD protection for HiZ inputs?

#36882

Am 05.10.24 um 23:04 schrieb Richard Lee via groups.io:
I've personal experience of Schottky protection
diodes going noisy in several MOTU Travelers withing 12 mths and indeed
all da MOTU designs cured by replacing with 1n4003Never noticed anything like that with my traveler MK3. Then again, I use
it mostly for recording... errr... noise, i.e. street scenes and
industrial ambiences.

Are these diodes in the mic amps?

Ralf

--
Ralf R. Radermacher  -  K?ln/Cologne, Germany
Blog  : 
Audio : 
Fotos : 

Re: ESD protection for HiZ inputs?

#36881

Dunno about piezo amps @ about 10M but for a LN condensor mike over 1G, the diodes must have VERY low leakage.

?

1n4148 far too leaky and noisy.? Guru Scott Wurcer liked a smoke alarm FET used as a diode.? Another 'diode' for this is the BE junction of an old fashioned LN BJT like BC214 or 2n5087.

?

Schottkys have very poor leakage which gets worse with time.? The latest THAT 1510/12 datasheets for microphone preamps recommend cheapo 1n4003GP (Glass Passivated).? I've personal experience of Schottky protection diodes going noisy in several MOTU Travelers withing 12 mths and indeed all da MOTU designs cured by replacing with 1n4003

?

Dunno if 1n4003 will protect Jule's piezo amps.

Re: ESD protection for HiZ inputs?

#36880

开云体育

thanks. So it works with a 1M input impedance.

How high input impedance can you do this before diode leakage starts messing with the fet bias or lowering the input impedance?

BTW I have built the circuit I linked to and it works ok, but I'm not sure if it sounds quite as good as without the diodes, nor how much ESD protection I'm actually getting.

Which schottky diodes did you use? what current capability and reverse voltage?

there's no point in protecting the fet only to blow the diode which I fear could happen with the tiny 1N4148.

On 05/10/2024 21:01, Jules Ryckebusch wrote:

Show quoted text

Yes!!! I just did this with my piezo buffer for my hydrophones. You need Shottkey diodes. See this?

Best Regards,

Jules Ryckebusch?

On Oct 5, 2024, at 14:55, thet via groups.io <parenthetical@...> wrote:

?I hope this is OK to ask here as it isn't exclusively a mic question but a general electronic question that might be applicable to some mics.

Consider a fet input with a high impedance, that is connected to a exposed bare wire or RCA type plug, because it needs to be unplugged from the source.

This could be for a piezo pickup with an input impedance of 5-10M or it could be for a condenser mic with an impedance of 1G

Do I need to protect that bare fet gate from ESD it might encounter in the world?

here's a schem to illustrate:

I have naively added diodes but I'm not sure if they will actually lower the input impedance which obv I don't want. The real-life behaviour of diodes at high impedances is beyond my current level of understanding.

I'm also not sure if 1N4148 are big enough to offer much protection.

Nor am I sure if R1 offers any protection.

Could any of the experts here talk me through what would be wrong with the attempts at ESD protection in this schematic?

alix dynamic mics as donors?

#36879

Has anyone here tried either of these dynamic mics from AliExpress?

Fifine K669D

Maono PD100

They look like solid bodies, I'm curious if they come apart easily and how good they would be as donor bodies.

Re: ESD protection for HiZ inputs?

#36878

开云体育

Yes!!! I just did this with my piezo buffer for my hydrophones. You need Shottkey diodes. See this?

Best Regards,

Jules Ryckebusch?

Show quoted text

On Oct 5, 2024, at 14:55, thet via groups.io <parenthetical@...> wrote:

?I hope this is OK to ask here as it isn't exclusively a mic question but a general electronic question that might be applicable to some mics.

Consider a fet input with a high impedance, that is connected to a exposed bare wire or RCA type plug, because it needs to be unplugged from the source.

This could be for a piezo pickup with an input impedance of 5-10M or it could be for a condenser mic with an impedance of 1G

Do I need to protect that bare fet gate from ESD it might encounter in the world?

here's a schem to illustrate: https://halfshavedyaks.xyz/forumimages/fetbuffersm.png

I have naively added diodes but I'm not sure if they will actually lower the input impedance which obv I don't want. The real-life behaviour of diodes at high impedances is beyond my current level of understanding.

I'm also not sure if 1N4148 are big enough to offer much protection.

Nor am I sure if R1 offers any protection.

Could any of the experts here talk me through what would be wrong with the attempts at ESD protection in this schematic?

ESD protection for HiZ inputs?

#36877

I hope this is OK to ask here as it isn't exclusively a mic question but a general electronic question that might be applicable to some mics.

Consider a fet input with a high impedance, that is connected to a exposed bare wire or RCA type plug, because it needs to be unplugged from the source.

This could be for a piezo pickup with an input impedance of 5-10M or it could be for a condenser mic with an impedance of 1G

Do I need to protect that bare fet gate from ESD it might encounter in the world?

here's a schem to illustrate: 

I have naively added diodes but I'm not sure if they will actually lower the input impedance which obv I don't want. The real-life behaviour of diodes at high impedances is beyond my current level of understanding.

I'm also not sure if 1N4148 are big enough to offer much protection.

Nor am I sure if R1 offers any protection.

Could any of the experts here talk me through what would be wrong with the attempts at ESD protection in this schematic?

Re: choosing SimpleP48 resistors

#36876

It's so obvious with hindsight  . . . Mea culpa,  . . .
________________________________________________

NO WORRIES, old man.  Just use your Daily MULLIGAN and all is instantly forgiven and forgotten !!   /  James    :-)

Re: choosing SimpleP48 resistors

#36875
Edited

Jerry (and pmfalcman) is (are) of course right.

?

By all means measure your P48V and 9V before doing the arithmetic.? Da P48V is specifically important as many so called Prosumer 'P48' devices may be much less.? I ask people to do this in simpleP48.pdf to give tested values for various capsules.

?

Please keep sending me these test results for simpleP48.pdf for those (shock horror !!) who are MicBuilding without a multimeter.

?

But we are shooting at a broad target; 5 - 10V.? Drawing Fig 6 in FETbias.doc has highlighted the consequences of just using E24 resistors.? It has also prompted me to personally go again for 5V instead of 10V .. something I keep vacillating between. :)

?

I have to resist making the circuit more complex to 'cure' its shortcomings.? But then my failing eyesight and deteriorating soldering skills won't let me fit even one extra bit inside a male XLR.

?

There's also an even simpler circuit but IMHO, this sacrifices stuff like simpleP48's excellent RFI/EMI immunity etc .. lesser known features that distinguish good mikes from great mikes.

Re: choosing SimpleP48 resistors

#36874

开云体育

A more elaborate answer would take several pages of discussion, so "yes".

Le 29/09/2024 à 15:17, pmfalcman a écrit?:

Show quoted text

Jerry - so, I understand, your answer to my question is:?

"It doesn't matter"

Right?

Re: choosing SimpleP48 resistors

#36873

Jerry - so, I understand, your answer to my question is:?

"It doesn't matter"

Right?

Re: choosing SimpleP48 resistors

#36872

"Tolerance analysis" is the correct wording.

Re: choosing SimpleP48 resistors

#36871

开云体育

For a start, the "9V" in the equation is not cast in bronze. One may argue that 7V or 5V is better than 9V, if only because no FET is equal to another, and noise performance would dictate to go towards the lower side. Before reaching a critical (partially destructive) value, increasing Vgs increases noise (due to the GS junction reverse current).

In addition, designing something that requires perfect voltage source or zero-tolerance components is bad practice.
If you want to pursue that way, you should run a susceptibility analysis, based on the cumulative effects of all the variables in the circuit.
It's a whole branch of electronic design.

Le 29/09/2024 à 11:53, pmfalcman a écrit?:

Show quoted text

Richard - thank you for the info and thinking how to make life easier for simple, electronically dumb individuals like me.

?

But... (there's always a "but" - this is a rule of the Universe) - the 48V and 9V are only a beautiful, easy approximations.

In practice, as you perfectly well know, this "48V" varies from one recorder to another (usually lower). And the "9V," even in a fresh battery is not equal to 9V.

Therefore, shouldn't we measure and use real voltages in this equation?

?

"The Total Resistance has 48 - 9 = 39V"

?

Or the differences are so minuscule in the final outcome that they do not matter?

?

Cheers

Re: choosing SimpleP48 resistors

#36870

Richard - thank you for the info and thinking how to make life easier for simple, electronically dumb individuals like me.

?

But... (there's always a "but" - this is a rule of the Universe) - the 48V and 9V are only a beautiful, easy approximations.

In practice, as you perfectly well know, this "48V" varies from one recorder to another (usually lower). And the "9V," even in a fresh battery is not equal to 9V.

Therefore, shouldn't we measure and use real voltages in this equation?

?

"The Total Resistance has 48 - 9 = 39V"

?

Or the differences are so minuscule in the final outcome that they do not matter?

?

Cheers

Re: choosing SimpleP48 resistors

#36869

Thank you for the further information, Richard. I surmise then that the short between source and gate shown in Fig 1 is internal to the capsule. I look forward to using this really simple method.

-John

On Saturday, September 28, 2024 at 11:51:49 PM CDT, Richard Lee via groups.io <ricardo_lee@...> wrote:

The 5 - 10V is between the terminals on the capsulei ... NOT on the XLR

?

The 'new' method obviates messing about with a zillion resistors or pots.

Re: choosing SimpleP48 resistors

#36868

The 5 - 10V is between the terminals on the capsulei ... NOT on the XLR

?

The 'new' method obviates messing about with a zillion resistors or pots.

Re: choosing SimpleP48 resistors

#36867

For my devices, the Zoom H6 Essential and PUI 5024, I constructed a Simple P48, and the chosen resistor value is 75K.

Show quoted text

On Sun, 29 Sept 2024 at 12:08, dog hot <zushi000@...> wrote:

I had explored this issue before, but later gave up. I don't know how the perfect bias voltage of 9V for the PUI5024 microphone is generated. However, when connecting the PUI5024 to different devices, the voltage on the two pins is different when using a 6.8k ohm resistor. Later, I chose a 20k ohm potentiometer, rotated it, and measured with a multimeter to find the resistance value that could create a 9V voltage between the two pins when used with my recording device. Then, I bought a fixed resistor based on that value.

On Sun, 29 Sept 2024 at 11:54, Richard Lee via <ricardo_lee=[email protected]> wrote:
On Sat, Sep 28, 2024 at 05:32 PM, John Thaden wrote:

Can I even set up the easy test condition of Fig. 1 if my electret is two-lead, for instance, PUI AOM 5024? I then only have access to the drain and to the already internally connected gate and source and I don't know how they are connected internally.

Fig 1 in FETbias.doc is exactly applicable to PUI 5024

Is the 6k8 resistor in the equipment providing the 48 volts? It is standard?

Yes.? The 2 x 6k8 is standard for 48V Phantom Power

Re: choosing SimpleP48 resistors

#36866

I had explored this issue before, but later gave up. I don't know how the perfect bias voltage of 9V for the PUI5024 microphone is generated. However, when connecting the PUI5024 to different devices, the voltage on the two pins is different when using a 6.8k ohm resistor. Later, I chose a 20k ohm potentiometer, rotated it, and measured with a multimeter to find the resistance value that could create a 9V voltage between the two pins when used with my recording device. Then, I bought a fixed resistor based on that value.

Show quoted text

On Sun, 29 Sept 2024 at 11:54, Richard Lee via <ricardo_lee=[email protected]> wrote:

On Sat, Sep 28, 2024 at 05:32 PM, John Thaden wrote:

Can I even set up the easy test condition of Fig. 1 if my electret is two-lead, for instance, PUI AOM 5024? I then only have access to the drain and to the already internally connected gate and source and I don't know how they are connected internally.

Fig 1 in FETbias.doc is exactly applicable to PUI 5024

Is the 6k8 resistor in the equipment providing the 48 volts? It is standard?

Yes.? The 2 x 6k8 is standard for 48V Phantom Power

Re: choosing SimpleP48 resistors

#36865

On Sat, Sep 28, 2024 at 05:32 PM, John Thaden wrote:

Can I even set up the easy test condition of Fig. 1 if my electret is two-lead, for instance, PUI AOM 5024? I then only have access to the drain and to the already internally connected gate and source and I don't know how they are connected internally.

Fig 1 in FETbias.doc is exactly applicable to PUI 5024

Is the 6k8 resistor in the equipment providing the 48 volts? It is standard?

Yes.? The 2 x 6k8 is standard for 48V Phantom Power

Re: choosing SimpleP48 resistors

#36864

Hi Richard,

?

Can I even set up the easy test condition of Fig. 1 if my electret is two-lead, for instance, PUI AOM 5024? I then only have access to the drain and to the already internally connected gate and source and I don't know how they are connected internally.

?

Also, I'm not clear how this instruction works (or I guess I mean why it works), regardless of whether two- or three-lead:

?

The Total Resistance has 48 - 9 = 39V across it so? ?Total Resistance = 39V / ‘Idss’

Then?R1?(in SimpleP48.doc & pdf)?for Vds 9V?is? ? ?R1 = Total Resistance – 6k8

Is the 6k8 resistor in the equipment providing the 48 volts? It is standard?

?

Sorry, struggling here a bit,

?

-John