JLM AUDIO

All missing parts arrived this morning and everything is ok.
But,
I assembled second unit and calibrated the voltage carefully and on tests the first channel is having a problem. It looks like it lacks half the gain and sound much "thinner", same thing happens on its DI.
Second channel works as expected.
I can't find right now what could be the problem. I included the pictures.

Problem solved, thanks to Joe's advice I looked at the terminals on the output XLR and measured infinite resistance between pin 2 and 3. Upon examination I discovered that contact wasn't established on the red wire as terminal screw was holding on isolation instead on the metal wire.

Hi Joe,

Two quick questions:

-I noticed one of the BAX83VN's I received is missing the 680pF polystyrene cap to the right of the 470uF. Will that be an issue? I'm not sure if it was an accidental omission or not.

-I'm using Ed Anderson's EA-10468 transformers (http://www.hairballaudio.com/catalog/pa ... ransformer) on the input of my 1290's. Hairball Audio uses a 4K7 load resistor and a 180pF zobel cap with the EA-10468 on the input of their pre's. Should I follow-suit or omit those?

Thanks!

PeterBregman wrote:Hi Joe,

Two quick questions:

-I noticed one of the BAX83VN's I received is missing the 680pF polystyrene cap to the right of the 470uF. Will that be an issue? I'm not sure if it was an accidental omission or not.

-I'm using Ed Anderson's EA-10468 transformers (http://www.hairballaudio.com/catalog/pa ... ransformer) on the input of my 1290's. Hairball Audio uses a 4K7 load resistor and a 180pF zobel cap with the EA-10468 on the input of their pre's. Should I follow-suit or omit those?

Thanks!

Sorry they should all have the 680pF cap. This would seem to have been missed and since it is a 2nd stage RF bandwidth limiting it didn't show up in module testing. Send me a photo of the 4 modules so I can see which type of cap to send you. Fit this module closest to the blue front switch as it is easy to slide in and solder that cap later then. The module will work fine for now until the cap we send you arrives.

The 4k7 load and 180pF cap are on the 1290 module main pcb already so no other parts need to be added for the 10468.

Thanks for the answers!

Attached is a picture of all four BAX83NV's (sorry for the quality - bad lighting). As you can see, the top left one is missing the cap at the right edge of the board.

PeterBregman wrote:Thanks for the answers!

Attached is a picture of all four BAX83NV's (sorry for the quality - bad lighting). As you can see, the top left one is missing the cap at the right edge of the board.

OK cool that is perfect. Let me know if anything else is missing and I will get this cap shipped out to you ASAP

Joe Malone wrote:OK cool that is perfect. Let me know if anything else is missing and I will get this cap shipped out to you ASAP

Thanks! I don't see anything else amiss. This is easily the best customer service I've had for any product I've ever bought.

Just finished getting it all together and did initial testing. Everything is perfect aside from the channel with the missing cap oscillating at high gain levels (pad engaged, full gain, full fader). Should that be remedied once I add the missing cap, or did I screw something up? Thanks!

PeterBregman wrote:Just finished getting it all together and did initial testing. Everything is perfect aside from the channel with the missing cap oscillating at high gain levels (pad engaged, full gain, full fader). Should that be remedied once I add the missing cap, or did I screw something up? Thanks!

If you are testing with nothing plugged into the input at 75dB of gain you can get oscillation just between the in and out bleed.

Also you should twist the ribbon cable into a tight cylinder and then replug it in to the XLRIO header. Also keep ribbon and the output wires from transformer to the output XLR away from eacdh other as much a possible.

Of course when a mic is plugged in no oscillation should happen. The missing 680pF may also make this oscillation happen easier.

Joe Malone wrote:If you are testing with nothing plugged into the input at 75dB of gain you can get oscillation just between the in and out bleed.

Also you should twist the ribbon cable into a tight cylinder and then replug it in to the XLRIO header. Also keep ribbon and the output wires from transformer to the output XLR away from eacdh other as much a possible.

Of course when a mic is plugged in no oscillation should happen. The missing 680pF may also make this oscillation happen easier.

This is with a dynamic plugged in (I'm guessing the missing cap is the culprit). Thanks for the tip on twisting the ribbon cables.

FYI, the cap arrive and I installed it - no more oscillation at high gain! Thanks again for all the help.

PeterBregman wrote:FYI, the cap arrive and I installed it - no more oscillation at high gain! Thanks again for all the help.

HI Peter Cool great to hear cap arrived and fixed the problem

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Hi Joe,

I have just spent the last couple of days building the kit and taking great care with the soldering and wiring.

The left side works perfectly but the right side does not. Tried the mic in with no luck and could only get the faintest of signals through the DI (with Gain turned up high.

I adjusted the 24V before and after red wire connection - have 24v on both TREX. I have checked all my ground connections and tested point to point as much as I could. I took the board back out to check i had installed all the parts. Now running out of ideas. Doe you have a test procedure sheet for the 1290?

Thanks, Jason

jb2060 wrote:Hi Joe,

I have just spent the last couple of days building the kit and taking great care with the soldering and wiring.

The left side works perfectly but the right side does not. Tried the mic in with no luck and could only get the faintest of signals through the DI (with Gain turned up high.

I adjusted the 24V before and after red wire connection - have 24v on both TREX. I have checked all my ground connections and tested point to point as much as I could. I took the board back out to check i had installed all the parts. Now running out of ideas. Doe you have a test procedure sheet for the 1290?

Thanks, Jason

Feel free to email me some photos to check all of the wiring etc before you do any of the below

First thing is to swap the DI kits and check the fault doesn't follow the DI.

If the fault stays on the same channel then see if you have audio at the INS OUT -> point (yellow/orange wire)? If yes then preamps are working

Remove the black wire on the INS IN <- and send audio in and see if you have audio on output XLR? If yes the output amp is working

Let me know what you find

Hi Joe,

Everything seems to be working well now. I still need to do some more test tracking but the initial results are very pleasing (certainly heaps of gain). When I turn the 1290 off with the monitors still on, i get a small high pitched squeal (in the monitors) as it powers down. Is this normal behavior or do I need to check something.

Thanks, Jason