JLM AUDIO

Audiobatik wrote:I just can't seem to find one.
-Thanks.

-Ab

The small kits that have no variable parts have no build thread as they are just simple build by the PCB overlay.

If you are trying to do something different with the FetDI like run on lower voltage or phantom power or having trouble getting it going let me know and I will do up a drawing or guide you on how to fault find etc.

Feel free to ask any questions on this thread.

The PC board indicates non polarized caps (3pc. 100µf).
These caps look like polarized caps. How should they be oriented?

Does it matter?

Thanks, Ab.

Audiobatik wrote:The PC board indicates non polarized caps (3pc. 100µf).
These caps look like polarized caps. How should they be oriented?

Does it matter?

Thanks, Ab.

Yes the latest batch of 100uF 50v caps shows a negative strip but they are actually all NON polar caps so they can all go in either way around.

Available on JLM Audio Web shop here

Hi Joe,
building these for my 1290 kit, I have the FET DI version 2 PCB.
There's a space labeled "220P" just below the vertical 2k7 resistor, but I can't find a cap or any other component included in the kit which would fit here. Is it missing, or do I not need it?
If I need it, are there other specs I should be aware of - I'll grab something locally.

Thanks,
Dan

EDIT:
I checked the DI from my BA500 I'd built and see that this should be a 220pf ceramic capacitor, right? Any minimum voltage or tolerance requirement?
My local good electronics shop has 220 pf 50v ceramic caps - possible to sub with these? Thanks Joe, sorry for the beginner's questions here.
Dan

LAST EDIT: I bought and installed 220pf 50v caps. I hope that's right. I have another issue with the build - only 1 channel which I'll post to the 1290 build forum. Thanks

This is what I ended up with in the new versio. I hope its correct. Lol

gtjumper wrote:This is what I ended up with in the new versio. I hope its correct. Lol

Looks correct except for the missing socket

Hi Joe,

I got two DI kits to do with BA500s, and am missing 4x 470 ohm resistors (2 per board), but have 2x 2.2k ohm resistors with seemingly no home. Just wondering what the deal is?

Also, why are two of the 2.2 Meg resistors starred?

-Moley

moley1390 wrote:Hi Joe,

I got two DI kits to do with BA500s, and am missing 4x 470 ohm resistors (2 per board), but have 2x 2.2k ohm resistors with seemingly no home. Just wondering what the deal is?

Please email me a photo of the parts and PCB with parts etc so I can check the values and your order number so I can line-up which batch they are from.
All FETDI kit from the latest batch check ok for correct parts so not sure why these two would be different.

Also, why are two of the 2.2 Meg resistors starred?

-Moley

The starred 2.2Meg can be made bigger in value to make higher input impedances. e.g making them 100Meg each will make a 50Meg input impedance DI which is good for piezo pickups etc.

I’m going to build the fet di into its own dedicated 500 series module. Are there any changes i need to make to run it on the 16v standard rail?

rockprocess wrote: ↑

Mon Oct 17, 2022 10:33 am

I’m going to build the fet di into its own dedicated 500 series module. Are there any changes i need to make to run it on the 16v standard rail?

The FetDI circuit will work fine across the +/-16v but the pcb 0v will be at -16v so will have to have a look at how to isolate that and reference the 500 series 0v +/-16v instead. If you do not understand what the above line means then let me know as I would have to have a think about it and draw up the best way to do it.

I had originally thought I couldn’t run the fet di from the existing 48v supply on a 500 series card pin 15, thinking I wouldn’t have enough current. That led me down this path of using pin 12 , which is 16v.

Can you tell me the current requirements for the fet di v2 and do you think a typical 500 series module 48v supply is enough to supply it?

Joe Malone wrote: ↑

Mon Jan 05, 2015 7:25 pm

moley1390 wrote:Hi Joe,

I got two DI kits to do with BA500s, and am missing 4x 470 ohm resistors (2 per board), but have 2x 2.2k ohm resistors with seemingly no home. Just wondering what the deal is?

Please email me a photo of the parts and PCB with parts etc so I can check the values and your order number so I can line-up which batch they are from.
All FETDI kit from the latest batch check ok for correct parts so not sure why these two would be different.

Also, why are two of the 2.2 Meg resistors starred?

-Moley

The starred 2.2Meg can be made bigger in value to make higher input impedances. e.g making them 100Meg each will make a 50Meg input impedance DI which is good for piezo pickups etc.

I Joe?
I would like to try the DI for piezo pickup. 100Meg resistor? Can i find it? Change all 1Meg by 100Meg?
It is possible to power DI with 9v battery?

Hi Joe,
I have a stereo1290 mic pre with the FET Di ahead of it, and on one channel I am getting Di signal to the output but not mic signal.
Trying to fault find and wondering if the SS relay might not be switching the signal correctly.
Can you supply cct for Fet Di, and/or SS relay pinout,
Thanks, Neil.

BigSkyAudio wrote: ↑

Tue Jul 25, 2023 2:11 pm

Hi Joe,
I have a stereo1290 mic pre with the FET Di ahead of it, and on one channel I am getting Di signal to the output but not mic signal.
Trying to fault find and wondering if the SS relay might not be switching the signal correctly.
Can you supply cct for Fet Di, and/or SS relay pinout,
Thanks, Neil.

HI Neil

The relay is normally on for mic input and when a jack is inserted the Sheild contact of the jack opens to turn off the relay and switch to the DI input.

The relay coil circuit is 0v via jack contact next to the front edge of the PCB to relay coil in series with 2k7 resistor to 48v. Check shield contact for DI is touching the switch contact on the jack or it will stay in DI input mode permenently. Check you have 24v across relay coil which is the 2 pins closest to the jack.