Microphone FET selection

[sodium05]

Hi everyone. I'm trying to build a relatively cheap and high quality microphone for voice chat applications like skype and discord. In that, i've decided to follow Nordic Audio Labs simplest condenser setup found here: simple condenser mic . I plan on using a jli 2555 capsule as it's pretty high performing and quite cheap. As I'm new to the scene, I don't know much about electret microphone circuitry. Using his schematic, what N FET would you guys recommend I use with the capsule?

 

[RuudNL]

The jli 2555 doesn't have an internal FET, so it won't work as shown in the video.
You could use an external FET, such as the 2SK30, but in that case you also need a high value resistor from gate to ground.
Or use a 2SK596, that already has an internal gate resistor.

 

[sodium05]

The jli 2555 doesn't have an internal FET, so it won't work as shown in the video.
You could use an external FET, such as the 2SK30, but in that case you also need a high value resistor from gate to ground.
Or use a 2SK596, that already has an internal gate resistor.

Thanks! Yeah I'm aware it doesn't have a FET. I'll check your recommendation out though! I don't quite understand how a FET is chosen. Does the capsule have any influence on the FET, other than whether it has one or not? Also, a video I watched recently that uses this capsule and a custom preamp recommended a 2N4416 transistor. Any idea why that would be chosen over the 2SK596? The 2SK596 seems like the easy answer.

Also I'm on Digikey putting in an order for a few (I might make some mics for a few friends as well. Do you know if there's a difference between versions A, B, and C?: 2SK596 Digikey

EDIT: You can only buy them from DigiKey in packs of 5000+. Going to look elsewhere.

 

[MikelLikesIt]

AliExpress has them, just got some delivered yesterday. Good luck with your project. If you are looking for impedance converter circuit boards check out Pcbway.

 

[sodium05]

AliExpress has them, just got some delivered yesterday. Good luck with your project. If you are looking for impedance converter circuit boards check out Pcbway.

Do you know if I should grab type A B or C?

 

[MikelLikesIt]

Well I don’t know it you have a choice on Ali, but if fets are marked like transistors, the higher number is higher gain.

 

[sodium05]

Would a 2SK170BL work? These seem to be much easier to acquire stateside.

 

[Drosselmeier]

Нужен резистор на 1 гиг

 

[RuudNL]

Do you know if I should grab type A B or C?

There is even a D and E version!
The differences (Idds) are explained on page 553 of the datasheet.

 

[sodium05]

There is even a D and E version!
The differences (Idds) are explained on page 553 of the datasheet.

Oh I just meant, around Idd am I looking for? I don't really know what parameters to look at when considering FETs.

I'd rather try and get something stateside. Any idea if there are other viable alternatives?

 

[k brown]

2SK660 also doesn't require gate resistor.

 

[MikelLikesIt]

Would a 2SK170BL work? These seem to be much easier to acquire stateside.

Where woukld I look for them?

 

[sodium05]

Where woukld I look for them?

Lots of places. Mojotone, ebay, etc... most are like 10 shipping. Google them.

Stateside, they're expensive tho.

 

[MikelLikesIt]

Lots of places. Mojotone, ebay, etc... most are like 10 shipping. Google them.

Stateside, they're expensive tho.

I tried AliExpress, they were not real. But they were inexpensive.

 

[ccaudle]

Where woukld I look for them?

Linear Systems has LSK170 variants that are compatible replacements for the original 2SK170.
JFET page at Linear Systems

 

[MikelLikesIt]

Linear Systems has LSK170 variants that are compatible replacements for the original 2SK170.
JFET page at Linear Systems

And cheap enough at around $4. I’m just starting to do SMT, did a few fets the other day. Doing some ICs today.

 

[kramerb1]

Linear Systems jfets are available here: www.trendsetter.com/lsk189-to-92-3l.html

 

[sodium05]

If I grabbed a simple audio card from amazon, does anyone know of any extremely simple amplifying circuits I could use to connect the capsule? I want to make a usb version as well as my almost complete xlr version.

 

[abbey road d enfer]

Linear Systems has LSK170 variants that are compatible replacements for the original 2SK170.

Beware that LSK170 have rather high input capacitance (Cgs), about 2pF. This is to put in perspective with the capsule's capacitance. This can be partially mitigated by use of bootstrap, but it makes the circuit somewhat more complex.
2N4416 has only about 2-3 pF Cgs, which explains why it's a favourite.

 

[abbey road d enfer]

Would a 2SK170BL work? These seem to be much easier to acquire stateside.

See previous post.