LA500A opto comp leveling amp BUILD THREAD 500/51X

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nicsmith
Posts: 1
Joined: Wed Dec 11, 2019 3:53 am

Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby nicsmith » Fri Dec 13, 2019 9:25 am

Hi there!

I built a LA500 and to my amazement it worked straight away. It sounded fantastic, I was super happy with it and was gleefully using it as my main vocal compressor on the way in. I had it up and running for about 3 weeks. Since then I've had some issues. At some point the Rupert Neve R6 container I had it in seemed to develop a fault or at least showed a fault code (all power LEDs flashing intermittently) and no power was being supplied to any of the units. The needle pulsed slightly and the light came on intermittently with the flashing of the power LEDs of the R6 unit.

A few days later after testing it and trying to get in contact with RND about the R6 it just started working again. The LA500 functioned normally, all was well and I just thought heck, weirder things have happened.

A few days after that, it continued to appear like it was working. The needle still moves in accordance with the amount of gain reduction applied, the unit lights up, theoretically it all seems to be working, except, there is no output. Just nothing coming out.

Signal comes through perfectly in bypass. Needle moves in accordance with gain reduction and input signal, and make up gain controls. Simply no output.

Very small amount of bleed when gain is boosted drastically on interface, but predominantly electrical noise signal.

I'm hopefully sending the R6 in for a look over soon but waiting on a ticket and details from RND, they suggested perhaps an electrical issue or problem with the power supply. Regardless, I'm not the most amazing circuit builder and I wanted to check if you thought perhaps I may have made any mistakes with the build that could have caused this electrical fault in the first place. Sadly I have no alternative rack to test any of them on atm. If it's relevant perhaps, my EMS Neve 1073LB unit is not transmitting phantom power but is otherwise working fine as well as an API 560a unit, so I wonder if the two issues might be connected in some way.

Any thoughts?

Many thanks!

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Joe Malone
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Tue Dec 17, 2019 12:46 pm

nicsmith wrote:Hi there!

I built a LA500 and to my amazement it worked straight away. It sounded fantastic, I was super happy with it and was gleefully using it as my main vocal compressor on the way in. I had it up and running for about 3 weeks. Since then I've had some issues. At some point the Rupert Neve R6 container I had it in seemed to develop a fault or at least showed a fault code (all power LEDs flashing intermittently) and no power was being supplied to any of the units. The needle pulsed slightly and the light came on intermittently with the flashing of the power LEDs of the R6 unit.

A few days later after testing it and trying to get in contact with RND about the R6 it just started working again. The LA500 functioned normally, all was well and I just thought heck, weirder things have happened.

A few days after that, it continued to appear like it was working. The needle still moves in accordance with the amount of gain reduction applied, the unit lights up, theoretically it all seems to be working, except, there is no output. Just nothing coming out.

Signal comes through perfectly in bypass. Needle moves in accordance with gain reduction and input signal, and make up gain controls. Simply no output.

Very small amount of bleed when gain is boosted drastically on interface, but predominantly electrical noise signal.

I'm hopefully sending the R6 in for a look over soon but waiting on a ticket and details from RND, they suggested perhaps an electrical issue or problem with the power supply. Regardless, I'm not the most amazing circuit builder and I wanted to check if you thought perhaps I may have made any mistakes with the build that could have caused this electrical fault in the first place. Sadly I have no alternative rack to test any of them on atm. If it's relevant perhaps, my EMS Neve 1073LB unit is not transmitting phantom power but is otherwise working fine as well as an API 560a unit, so I wonder if the two issues might be connected in some way.

Any thoughts?

Many thanks!


The LA500A only uses the +/-16vdc and only about 60mA per rails so is very easy to run and way under the API VPR standard. If the VU meter is still running it proves all the electronics is working. Only part after that point between the output XLR is the JLM111DC output transformer. Basically check the JLM99v is plugged in fully and all 10 pin headers are fully plugged in. Plus your soldering is all clean and no solder joint has been missed.

I would try another 500 rack to see if it works fine in there. Sounds like your rack power supply is SMPS type and has failed.
Joe :-)
JLM Audio
Capturing Audio without Injury

CasinoDeathfish
Posts: 1
Joined: Mon Jan 06, 2020 11:48 pm

Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby CasinoDeathfish » Fri Mar 13, 2020 9:56 pm

Greetings.

Quick question. I've built a single LA500A. Great kit, great instructions. It went together pretty quickly and easily. The problem I've run into and can't seem to solve has to do with an issue I discovered when calibrating my unit. 1Khz tone passes through and I can measure 1.23vac on output. VU meter trim adjustment has no effect on VU meter; it stays all the way left. GR meter adjustment works as expected and I can adjust it to 0db. Threshold control allows me to adjust for 5db compression. Balance trim adjustment also has no discernible effect. Switching between VU and GR show needle all the way left for VU and back to 5db for GR. Running an audio signal through the unit in GR mode shows the compressor working with meter action clearly responding to changes in threshold and audio signal, so it would seem the unit is functioning, although I was not actually LISTENING to the output signal but rather watching it on my multimeter.

I then thought to test the VU and Balance trim pots and discovered they both were not working or measuring properly.

I've replaced BOTH the VU and Balance trim pots (1k) and have confirmed they are good. All voltage measurements with the opamps are correct as is voltage coming into the unit.

Thoughts?

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Joe Malone
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Location: Brisbane, Australia
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Sat Mar 14, 2020 1:54 pm

CasinoDeathfish wrote:Greetings.

Quick question. I've built a single LA500A. Great kit, great instructions. It went together pretty quickly and easily. The problem I've run into and can't seem to solve has to do with an issue I discovered when calibrating my unit. 1Khz tone passes through and I can measure 1.23vac on output. VU meter trim adjustment has no effect on VU meter; it stays all the way left. GR meter adjustment works as expected and I can adjust it to 0db. Threshold control allows me to adjust for 5db compression. Balance trim adjustment also has no discernible effect. Switching between VU and GR show needle all the way left for VU and back to 5db for GR. Running an audio signal through the unit in GR mode shows the compressor working with meter action clearly responding to changes in threshold and audio signal, so it would seem the unit is functioning, although I was not actually LISTENING to the output signal but rather watching it on my multimeter.

I then thought to test the VU and Balance trim pots and discovered they both were not working or measuring properly.

I've replaced BOTH the VU and Balance trim pots (1k) and have confirmed they are good. All voltage measurements with the opamps are correct as is voltage coming into the unit.

Thoughts?


Ok check the toggle switches gave all there legs soldered properly to the pcb or send me some photos to check them. Often see solder that has not taken to the pcb at all so one switch position doesn’t work. Also common is not all legs of the 10 pin headers soldered on pot and SC pcb. If stuck Email me clear in focus well lit photos of the assembled comp with no 99v fitted so I can see the top sides of the pcbs. Also remember these are 25 turn trim pots so may take several turns to see any change.
Joe :-)

JLM Audio

Capturing Audio without Injury

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