LA500A opto comp leveling amp BUILD THREAD 500/51X

[bpark919]

Hello,

I finally figured out what I was doing wrong in the calibration process. I was measuring out pins 1 and 2... not 2 and 3. DOH! Got the thing calibrated, and its working awesome except for one issue: any makeup gain added after about 10 o clock on the makeup knob is noisy enough that the recording is unusable, and anything after 12PM is completely horrendous. I saw in a previous post that there could have been due to faulty op-amps or something but I'm having trouble finding that exact post now. Wondering if it could be the same issue. Thanks!

[Joe Malone]

Hello,

I finally figured out what I was doing wrong in the calibration process. I was measuring out pins 1 and 2... not 2 and 3. DOH! Got the thing calibrated, and its working awesome except for one issue: any makeup gain added after about 10 o clock on the makeup knob is noisy enough that the recording is unusable, and anything after 12PM is completely horrendous. I saw in a previous post that there could have been due to faulty op-amps or something but I'm having trouble finding that exact post now. Wondering if it could be the same issue. Thanks!

With threshold & Makeup fully turned down CCW does the comp output stay at the same level when switching from off to GR or VU?

At 1Khz you should be able to get about +26 to +28dBu which will overload any known A/D. What output level does the distortion start at?

What input level is the audio at?

If the audio is clean with no makeup and comp in GR or VU then the opamp is fine.

[AntonioGarage16]

Hi Joe!
Finished building my LA500A last week. One of the most straightforward and simple DIY builds I have ever had the pleasure to work on. Everything went smoothly with building and setting up and the unit has been working 100% fine. I'm already using it on the lead vocal for this EP I'm mixing!

Today an issue arose, the compressor is working as it should but the light on the VU meter stopped working, it turns on for a fraction of a second when I set the center switch to meter gr or VU but it doesn't stay lit. The compressor still compresses as it should, it's only the VY light that's not working.
Any idea of what might be the cause?

Best Regards,
Antonio

[Joe Malone]

Hi Joe!
Finished building my LA500A last week. One of the most straightforward and simple DIY builds I have ever had the pleasure to work on. Everything went smoothly with building and setting up and the unit has been working 100% fine. I'm already using it on the lead vocal for this EP I'm mixing!

Today an issue arose, the compressor is working as it should but the light on the VU meter stopped working, it turns on for a fraction of a second when I set the center switch to meter gr or VU but it doesn't stay lit. The compressor still compresses as it should, it's only the VY light that's not working.
Any idea of what might be the cause?

Best Regards,
Antonio

HI Antonio

Great to hear you like the LA500A build

Sounds like the LED has failed for some reason and gone short circuit if the comp is still working. The meter snaps apart between the square and round sections and scale slides out to reveal a 5mm clear white led. We have the LED on the webshop of a dollar or two but really It can be replaced with any 5000Mcd or more similar 5mm white led.

Let me know if you need any more info.

[AntonioGarage16]

Hi Joe!
Finished building my LA500A last week. One of the most straightforward and simple DIY builds I have ever had the pleasure to work on. Everything went smoothly with building and setting up and the unit has been working 100% fine. I'm already using it on the lead vocal for this EP I'm mixing!

Today an issue arose, the compressor is working as it should but the light on the VU meter stopped working, it turns on for a fraction of a second when I set the center switch to meter gr or VU but it doesn't stay lit. The compressor still compresses as it should, it's only the VY light that's not working.
Any idea of what might be the cause?

Best Regards,
Antonio

HI Antonio

Great to hear you like the LA500A build

Sounds like the LED has failed for some reason and gone short circuit if the comp is still working. The meter snaps apart between the square and round sections and scale slides out to reveal a 5mm clear white led. We have the LED on the webshop of a dollar or two but really It can be replaced with any 5000Mcd or more similar 5mm white led.

Let me know if you need any more info.

Thank you for helping out!
I'll get one from my local electronics shop. Sorry for my ignorance, but what should the LEDs voltage be? The local shop has 3000Mcd LEDs with 12V operational voltage, and 5000Mcd LEDs with 2.6V operational voltage. I'm clueless about which one is the right one.

[Joe Malone]

Hi Joe!
Finished building my LA500A last week. One of the most straightforward and simple DIY builds I have ever had the pleasure to work on. Everything went smoothly with building and setting up and the unit has been working 100% fine. I'm already using it on the lead vocal for this EP I'm mixing!

Today an issue arose, the compressor is working as it should but the light on the VU meter stopped working, it turns on for a fraction of a second when I set the center switch to meter gr or VU but it doesn't stay lit. The compressor still compresses as it should, it's only the VY light that's not working.
Any idea of what might be the cause?

Best Regards,
Antonio

HI Antonio

Great to hear you like the LA500A build

Sounds like the LED has failed for some reason and gone short circuit if the comp is still working. The meter snaps apart between the square and round sections and scale slides out to reveal a 5mm clear white led. We have the LED on the webshop of a dollar or two but really It can be replaced with any 5000Mcd or more similar 5mm white led.

Let me know if you need any more info.

Thank you for helping out!
I'll get one from my local electronics shop. Sorry for my ignorance, but what should the LEDs voltage be? The local shop has 3000Mcd LEDs with 12V operational voltage, and 5000Mcd LEDs with 2.6V operational voltage. I'm clueless about which one is the right one.

You want the 5000Mcd 2.6v type

[AntonioGarage16]

Hey Joe,

Thanks for the info.
I attempted to replace the led but ended up damaging the VU mechanism.
How can I buy a replacement VU?
I don't see it in the store.

Best regards,
Antonio

[Joe Malone]

Hey Joe,

Thanks for the info.
I attempted to replace the led but ended up damaging the VU mechanism.
How can I buy a replacement VU?
I don't see it in the store.

Best regards,
Antonio

Ok what got damaged ?

Link to meter on webshop

https://www.jlmaudio.com/shop/jlm-34mm-vu-meter.html

[AntonioGarage16]

It was the mechanism inside the VU.
When I desoldered the faulty LED it dropped behind the mechanism and while removing it I accidentally puled and strained a very thin wire that connects to the back of the magnet, now the needle doesn't move properly.
Anyway, the compressor is still fully operational and now the VU LED works, the only issue is that now I can't get an accurate reading on the VU.
I'll be getting a replacement VU because I don't think it's possible to fix the damage.
Thank you for your helping.