Intel on mic pre low-cut circuits!

[kags]

This was discussed long ago and linked here - check out the third post…

https://gearspace.com/board/geekzone/356482-easy-diy-passive-filter.html

 

[ruffrecords]

You don't need two in series in each leg unless you want to switch frequencies (but even that only requires pairs of 3.3uF capacitors). For 80Hz you need just a pair of 6.8uF caps.

How big they are will depend on tere voltage rating. You do not need anything more than 100VDC working parts. These are readily available in a 15mm lead pitch:

https://www.farnell.com/datasheets/3673887.pdf

Cheers

Ian

 

[djmiggymigz]

Ahhh okay I dont know why I couldn't find those but with the part number there it is!

Also I deleted the post you were responding to because I realized what I had drawn up would have the exact opposite effect I was thinking! Thanks for the datasheet!

Would 63VDC be acceptable? I dont think there would be any DC after the output transformer.. is that correct?

 

[My3gger]

63VDC should be more than enough because VAC rating for 3,3u and 6,8u capacitors from TDK datasheet is 40V. AC is your audio signal. There's a lot of reading about AC rating of capacitors used in audio circuits.

 

[ruffrecords]

Ahhh okay I dont know why I couldn't find those but with the part number there it is!

Also I deleted the post you were responding to because I realized what I had drawn up would have the exact opposite effect I was thinking! Thanks for the datasheet!

Would 63VDC be acceptable? I dont think there would be any DC after the output transformer.. is that correct?

63VDC would probably do. As you say there is no dc there but there is ac (the signal) so the ac rating is important. 40VAC rating is usually sufficient.

Cheers

Ian

 

[djmiggymigz]

63VDC would probably do. As you say there is no dc there but there is ac (the signal) so the ac rating is important. 40VAC rating is usually sufficient.

Cheers

Ian

Sweet thank you! I found some Wima's that work. They're kind of chunky (11mm wide) but I got them on my board layout no problem!

 

[djmiggymigz]

Okay tapping back in here for some double checking before I order my PCB's.

is a reasonable assumption they are intended to look like a 600 ohm load. So use 600 ohms as R and set the frequency to 80Hz and out will pop the capacitor value

So with this logic, does this layout look correct? I have it routed so that switch on routes the signal thru the caps -> output trim and with it off the signal goes straight from the tx to the output trim. And I've doubled the value of the caps to account for the caps being in series with each other in context of the signal.

For added context, I'm using this attenuator from CAPI that IS (confirmed) reading a constant 600ohm.

If i'm understanding this correctly, in the context of the RC Filter I'm using the output trim as my R value right? Meaning I don't need to add resistors to the circuit.

Let me know if the screenshot of the schematic is low quality and I'll get a better one uploaded.

 

[djmiggymigz]

Anyone have a sec to look at this? As long as this Hi-Pass circuit looks like it'll function properly, I'm going to order my boards!

 

[gyraf]

Should work

Try to solder up the parts and see if it lives up to your expectations

 

[djmiggymigz]

Sweet thank you!! I'll try to breadboard just to confirm.

 

[JohnRoberts]

Sweet thank you!! I'll try to breadboard just to confirm.

Old school designers always breadboard new/different circuits to confirm.

This can be challenging with some modern ICs that are only available as SMD, but your circuit looks bread board-able.

JR

 

[zzzzz]

Looks like it will work to me. You could even lay out a PCB using the footprint for CAPI’s attenuator and put your switch and caps on the same board depending on the application.