LA500A opto comp leveling amp BUILD THREAD 500/51X

Support for JLM Audio Kits

Moderator: Joe Malone

bpark919
Posts: 4
Joined: Wed Dec 16, 2020 10:17 am

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

Post by 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!

User avatar
Joe Malone
Site Admin
Posts: 1801
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

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

Post by Joe Malone »

bpark919 wrote:
Sun Jan 17, 2021 8:57 am
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.
Joe :-)
JLM Audio
Capturing Audio without Injury

AntonioGarage16
Posts: 4
Joined: Thu Feb 25, 2021 8:35 pm

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

Post by 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

User avatar
Joe Malone
Site Admin
Posts: 1801
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

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

Post by Joe Malone »

AntonioGarage16 wrote:
Thu Feb 25, 2021 9:39 pm
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.
Joe :-)
JLM Audio
Capturing Audio without Injury

AntonioGarage16
Posts: 4
Joined: Thu Feb 25, 2021 8:35 pm

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

Post by AntonioGarage16 »

Joe Malone wrote:
Mon Mar 01, 2021 2:29 pm
AntonioGarage16 wrote:
Thu Feb 25, 2021 9:39 pm
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.

User avatar
Joe Malone
Site Admin
Posts: 1801
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

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

Post by Joe Malone »

AntonioGarage16 wrote:
Tue Mar 02, 2021 9:08 am
Joe Malone wrote:
Mon Mar 01, 2021 2:29 pm
AntonioGarage16 wrote:
Thu Feb 25, 2021 9:39 pm
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
Joe :-)
JLM Audio
Capturing Audio without Injury

AntonioGarage16
Posts: 4
Joined: Thu Feb 25, 2021 8:35 pm

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

Post by 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

User avatar
Joe Malone
Site Admin
Posts: 1801
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

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

Post by Joe Malone »

AntonioGarage16 wrote:
Fri Mar 05, 2021 1:19 am
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
Joe :-)
JLM Audio
Capturing Audio without Injury

AntonioGarage16
Posts: 4
Joined: Thu Feb 25, 2021 8:35 pm

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

Post by 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.

pachi2007
Posts: 1
Joined: Sat Mar 20, 2021 7:49 pm

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

Post by pachi2007 »

Hi!
I´ve build two of this awesome comp.
One is working great ( highly recommended ) , the other still not right.

It passes audio, bypass is ok.
I can see gain reduction in the meter but it doesn´t happen at the output.

I see I need to unsolder the meter to look in the detector pcb
so I ask for advice before I commit .

Thx a lot

User avatar
Joe Malone
Site Admin
Posts: 1801
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

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

Post by Joe Malone »

pachi2007 wrote:
Fri Mar 26, 2021 6:40 pm
Hi!
I´ve build two of this awesome comp.
One is working great ( highly recommended ) , the other still not right.

It passes audio, bypass is ok.
I can see gain reduction in the meter but it doesn´t happen at the output.

I see I need to unsolder the meter to look in the detector pcb
so I ask for advice before I commit .

Thx a lot
Ok email me some photos to check over first but this will usually be soldering on U1 opto or balance pot. How far could you get with alignment procedure before having problems?
Joe :-)
JLM Audio
Capturing Audio without Injury

Taperocket
Posts: 8
Joined: Mon Sep 06, 2021 11:24 am

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

Post by Taperocket »

Hello Joe,
I just finished my La500a build and everything seems to be working except the two LEDs which aren’t lighting at all. I believe I placed the 4 resistors on that board properly and made a solid connection with the led legs, with the long leg to the + square terminal.

For calibration I sent a +4db 1000kz signal to the input, is that adequate or do I need to measure voltage from the output. Everything seemed to calibrate fine using your procedure.

Thanks,

Todd

User avatar
Joe Malone
Site Admin
Posts: 1801
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

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

Post by Joe Malone »

Taperocket wrote:
Mon Sep 06, 2021 12:00 pm
Hello Joe,
I just finished my La500a build and everything seems to be working except the two LEDs which aren’t lighting at all. I believe I placed the 4 resistors on that board properly and made a solid connection with the led legs, with the long leg to the + square terminal.

For calibration I sent a +4db 1000kz signal to the input, is that adequate or do I need to measure voltage from the output. Everything seemed to calibrate fine using your procedure.

Thanks,

Todd
HI Todd
If the leds are in the correct way and do not light when you pull the pot switches outwards check you cut off the extra leg length so that it didn't run into the pot/switch under the pcb?

+4dbu 1000kz signal to the input is correct but to get 1.23vac (+4dBu) on the output you may need to turn the +4dBu up or down 0.5dB
Joe :-)
JLM Audio
Capturing Audio without Injury

Taperocket
Posts: 8
Joined: Mon Sep 06, 2021 11:24 am

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

Post by Taperocket »

Thanks Joe,
I slightly shortened the leads and resoldered and reflowed the solder on the 4 resistors but still no luck. Any other ideas? Are these leds faulty often?

Thanks,

User avatar
Joe Malone
Site Admin
Posts: 1801
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

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

Post by Joe Malone »

Taperocket wrote:
Mon Sep 06, 2021 10:21 pm
Thanks Joe,
I slightly shortened the leads and resoldered and reflowed the solder on the 4 resistors but still no luck. Any other ideas? Are these leds faulty often?

Thanks,
Out of 1000s built here, we have never had a faulty orange or blue led.

Lots of kit builders have fitted the 10 pin headers backwards on the pot or LA500 SC pcb so wiring is wrong and lots of reversed LEDs fitted with polarity wrong way.

What DC voltage do you have across the leds is the best clue?
Joe :-)
JLM Audio
Capturing Audio without Injury

Post Reply