JLM BAD Pre (help) No mid tones or bass

[Jeppe M]

Hey folks.
I just finished my JLM BAD Kit yesterday. When i tested it out there where no mid or lows comeing through to my recorder. It sounds like there is a high pass filter at about 3 khz (maby even higher) which makes the preamp more or less useless. There is no noise, and no other problems except the high pass effect. I have connected the Z regulator and a master output pod to my BAD and it has 2 JLM99v opamps and the OEP input transformer. I have the on / off power switch connected as well. All the extras (Z pot, output pot, on / off switch) seems to work.

I Really hope you guys have some info as to what might be wrong.

Thanks. Jeppe

[Joe Malone]

Hey folks.
I just finished my JLM BAD Kit yesterday. When i tested it out there where no mid or lows comeing through to my recorder. It sounds like there is a high pass filter at about 3 khz (maby even higher) which makes the preamp more or less useless. There is no noise, and no other problems except the high pass effect. I have connected the Z regulator and a master output pod to my BAD and it has 2 JLM99v opamps and the OEP input transformer. I have the on / off power switch connected as well. All the extras (Z pot, output pot, on / off switch) seems to work.

I Really hope you guys have some info as to what might be wrong.

Thanks. Jeppe

As always I can fix 99% of problem with a couple of large in focus well lit photos of the top and bottom of the PCB and your wiring either to my email or here.

The high pass effect is usually when using a input or output transformer with a unbalanced input or output that does pull pin 3 of the XLR to pin 1 ground as this leave the transformer open one end so only some capacitive effect get out of the preamp to the next stage which sounds like some high frequency bleed only.

Also one of the biggest mistakes I see is a input or output XLR wired the same left to right when the wirng should be a mirror image as pin 1 is on the opposite sides of female and male XLR's.

[Jeppe M]

Hey Joe. Thanks for the quick response... I'll check it out... For what it is worth, the high frequencies sounds amazing

[Jeppe M]

Hey Joe. Heres some pics. I hope you can spot the error. Thanks!

[Jeppe M]

Hey Joe. It looks like the Software cuts off som of the pics. You can follow this link to my Photobucket page. The only pics are of the Preamp:
http://s871.photobucket.com/albums/ab27 ... e_sushi82/

[Joe Malone]

Hey Joe. It looks like the Software cuts off som of the pics. You can follow this link to my Photobucket page. The only pics are of the Preamp:
http://s871.photobucket.com/albums/ab27 ... e_sushi82/

HI Jeppe easy one. You just need to add the missing wire jumper between -1 and +2 on the JLM111DC output transformer to make the output circuit complete and you will have a working mic pre amp.

[Jeppe M]

Awesome! Thanks!

[Jeppe M]

Hey Joe. It seems to be working... Thanks.

[Joe Malone]

Hey Joe. It seems to be working... Thanks.

Cool