JLM AUDIO

I'm considering using a Mono as an on-stage preamp for gigs. I'm trying to figure whether the output would be protected against phantom power inadvertently being sent to it. Would 'accidental' phantom coming in through the output XLR potentially fry the opamps? If so, I'm guessing either blocking c...

Everett wrote: ↑

Fri Jan 26, 2024 11:38 pm

Fantastic! A little spray of pot cleaner did the trick. Both comps are calibrated and ready to go. Thanks so much for the troubleshooting help! Now I'll dive into building my FREQ500 kits.

Cool Great to hear that solved the problem

I'm not sure if resurrecting this old thread is the best place to ask this, but: Has anyone tried running AMP kits from a switching power supply instead of a transformer. For example this: https://www.aliexpress.com/item/1005005911546916.html I'm aware that there could be issues , specifically that...

I think something may be grounded on the pot pcb on the faulty comp? When I disconnect the ribbon cable on the pot pcb and measure resistance from any lead to the case, I get readings. If I do the same on the good comp, I don't. When the ribbon cable is connected, if I measure resistance from any p...

Everett wrote: ↑

Fri Jan 26, 2024 12:20 pm

Resistor readings matched on SC pcbs for both comps.

Yes looks fine. How many dB louder is this comp compared to the off position with no makeup and no threshold?

With both comp on full makeup is there still the dB difference between the comps?

Everett wrote: ↑

Thu Jan 25, 2024 5:42 pm

Ok, I swapped the BIO500T pcbs (not transformers) and the high level stayed with the faulty comp.

Ok points to the problem being on the sidechain pcb in the faulty comp. Can you take some photos of the top of that pcb so I can see all the resistor colour codes

Here are some pics of the meters after calibration with GR on and the LINK switch ON. They both were on -5db before I turned the link switch on. let me know what you think. Is this within spec? Photo Jan 21 2024, 4 46 13 PM.jpg Photo Jan 21 2024, 4 46 20 PM.jpg Not sure if these output spec look ok...

Ok, the Threshold pot measures 93k and Makeup pot 9.7k. Similar on other comp. Ok either swap the BIO500T pcbs between comps and see if the high level swaps to the other comp or stays with the current faulty comp. Or unplug the bio ribbon cable from the sc pcb on the faulty comp and do the 2 link t...

Everett wrote: ↑

Wed Jan 24, 2024 2:07 am

Ok, here are the pics. Hopefully, lighting is OK.

Ok that looks built fine. Unplug the ribbon cable going to the pot pcb and measure the threshold and makeup pots outside solder pads while pots fully CCW. Threshold should measure 100k and makeup 10k. Let me know what you measure.

Yes, both comps output level is the same as input level when switched to off. No, one of the comps output level does not stay the same when switched to VU/GR. It has more output when switched to VU and GR. Ok remove the jlm99v opamp from comp that goes higher output and send me a couple of clear we...

Hello Joe, I recently went to check calibration on my two LA500A comps and discovered an input level issue. They were built from kits over 5 years ago. I connected to an extender and from my DAW, setup a signal generator plugin to send 1k tone at -18db and set the send level at -4db. On one unit I ...

Am I right in guessing that you think the output attenuator is simply not a good idea, Joe? I found this old thread that quotes you as saying you "would never put an output control on a baby animal because it will take away from headroom and adds output damping" (https://gearspace.com/board/geekzon...

Yep just desoldered meter so it’s all good. Hope this helps. Worth if you have any pot cleaner to give the inside of the pot a tiny spray and remeasure with pot fully CCW to see if it returns to 10k. Otherwise the pot will need to be removed from the pcb and replaced. Okay so terribly slow with thi...

Thanks for your input. Just ordered two v4 PCBs so I can try to make it work. If it turns out to not work with the transformer inside the case I will put it in an external (Powerbrick like) box. PS: If anyone is interessted I will come back with my findings once I finished the powersupply exchange....

Thanks for your input. Just ordered two v4 PCBs so I can try to make it work. If it turns out to not work with the transformer inside the case I will put it in an external (Powerbrick like) box. PS: If anyone is interessted I will come back with my findings once I finished the powersupply exchange....