LA500 opto comp leveling amp BUILD THREAD 500/51X

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greenote
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby greenote » Wed Aug 10, 2016 3:51 pm

Greetings, I have completed the build and performed the calibration on VU and GR, however the threshold doesn't seem to function. The unit is passing audio and the Make up gain is working.

I checked continuity from threshold pot wires and PCB.
Any suggestions?

thanks
Todd

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Joe Malone
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Thu Aug 11, 2016 8:15 am

greenote wrote:Greetings, I have completed the build and performed the calibration on VU and GR, however the threshold doesn't seem to function. The unit is passing audio and the Make up gain is working.

I checked continuity from threshold pot wires and PCB.
Any suggestions?

thanks
Todd


HI Todd Ok first things to check the MAC PCB has the optos in the correct way? Dot on side of opto should go to -K

Is the opamp in the correct way around ? Also are either of the 2 10R resistors on the MAC pcb burnt?

If not sure post some some well lit in focus photos here of the whole comp but mainly a few angles of the MAC pcb and wiring so I can check them over.
Joe :-)
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greenote
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby greenote » Fri Aug 12, 2016 5:59 am

Optos appear to be in correctly. Lettering appears as in the build guide. I checked the 10R's as I had blown those on another build. R14 replaced with 1.8k.

IMG_5298.JPG
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Fri Aug 12, 2016 8:00 am

greenote wrote:Optos appear to be in correctly. Lettering appears as in the build guide. I checked the 10R's as I had blown those on another build. R14 replaced with 1.8k.

IMG_5298.JPG


Ok the switch soldering needs resoldering with more solder as half look like dry joints.

Also the 100uF under the opamp has burst so needs to be replaced.

I need to see the threshold pot wiring and let me know the voltages at all pins of the OPA32604AP on the MAC measured to 0v.
Joe :-)

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Chops
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Chops » Fri Jan 27, 2017 7:41 am

Hi there,

I've calibrated my LA500 and everything sounds great but I'm just wondering if my meter is working correctly...

If I run a 1k sine at 1.23vac into the unit (3:1, HPF flat, makeup fully CCW), and adjust the threshold for 5db GR, when I change the ratio to 5:1 I then get just over 10db GR and then at 10:1 I get just a little more. Is this correct? It seems a bit jump between 3:1 and 5:1 but not much between 5:1 and 10:1.

Also, 1.23vac works out at -14dbfs in Pro Tools, but when I'm hitting around and above that region in Pro Tools the VU meter is not hitting 0, it's more like 5 and just above, I can't actually get it to 0...

This was my first build and my first hardware comp so I just want to make sure everything is ok as I'm a bit of a novice in this regard.

Thanks.

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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Fri Jan 27, 2017 9:28 am

Chops wrote:Hi there,

I've calibrated my LA500 and everything sounds great but I'm just wondering if my meter is working correctly...

If I run a 1k sine at 1.23vac into the unit (3:1, HPF flat, makeup fully CCW), and adjust the threshold for 5db GR, when I change the ratio to 5:1 I then get just over 10db GR and then at 10:1 I get just a little more. Is this correct? It seems a bit jump between 3:1 and 5:1 but not much between 5:1 and 10:1.

Yes that is correct as the simple way the ratio works increases the sidechain gain. So switching up ratios will require less threshold for the same compression amount. Also the compression knee becomes harder at higher ratios so the compression cuts in harder making greater gain reduction.

Also, 1.23vac works out at -14dbfs in Pro Tools, but when I'm hitting around and above that region in Pro Tools the VU meter is not hitting 0, it's more like 5 and just above, I can't actually get it to 0...

As long as you are measuring 1.23vac at the output of the LA500 when setting the VU meter to 0VU the setting will be correct as 0VU = +4dBM. If you play music at the same level settings it will be lower than a pure tone and the fact the VU meter has a 300mS attack and release make it a average meter ignoring any peaks. Average level of music is always lower than a pure tone. But if you are recording at the correct level of average 0VU = +4dBM then you should easily get to 0VU on the meter and more since 0VU is 14dB under 0dBFS. If you watch peak led level meters you will often set to low a recording level.
Joe :-)

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Chops
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Chops » Fri Jan 27, 2017 10:17 am

Ok, great.

Thank you.

kante1603
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby kante1603 » Mon Mar 20, 2017 4:42 am

Two more done,worked from start,no issues at all.
These are the last two LA500 kits on earth,hahaha,my #s 9 &10.

twomore.JPG


Will soon show a pic of them together with my #1 to #8.

Have fun,

Udo.
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Mon Mar 20, 2017 8:41 am

kante1603 wrote:Two more done,worked from start,no issues at all.
These are the last two LA500 kits on earth,hahaha,my #s 9 &10.

twomore.JPG

Will soon show a pic of them together with my #1 to #8.

Have fun,

Udo.


HI Udo
Great to hear they went together well and worked perfectly after going around the world twice :-)

Looking forward to the 10 x LA500 photo :-)

All the best.
Joe :-)

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kante1603
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby kante1603 » Tue Aug 29, 2017 2:52 am

Joe Malone wrote:HI Udo
Great to hear they went together well and worked perfectly after going around the world twice :-)

Looking forward to the 10 x LA500 photo :-)

All the best.

Hi Joe,

excuse me,but I totally forgot to show pictures!
Although it´s an old thread meanwhile it might be that one or the other gets inspired by this…..?
All modules are modified to "Slow Attack",are adjusted and form nicely matched pairs.
Here we go,my "Comps-To-Go"-case:
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kante1603
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby kante1603 » Tue Aug 29, 2017 2:56 am

Some more…...
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Tue Aug 29, 2017 10:37 am

kante1603 wrote:Some more…...


Fantastic Udo thanks :-)

I would like to use some of these photos up on our facebook page if that is ok with you?

https://www.facebook.com/jlmaudio1
Joe :-)

JLM Audio

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kante1603
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby kante1603 » Tue Aug 29, 2017 4:54 pm

Joe Malone wrote:
kante1603 wrote:Some more…...


Fantastic Udo thanks :-)

I would like to use some of these photos up on our facebook page if that is ok with you?

https://www.facebook.com/jlmaudio1

Absolutely Joe,thank you.Sorry for not having better pics,I'm no photographer and only have an old and cheap camera.

Best regards,

Udo.

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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby G-Sun » Sat Oct 21, 2017 2:07 am

Hi!

My meter-light died.
How may I replace it?

kante1603
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby kante1603 » Sat Oct 21, 2017 2:43 am

G-Sun wrote:Hi!

My meter-light died.
How may I replace it?


Hello G-sun,

the squared and the round part can be detached.Take care when doing that,gently tear them apart.No brutal force please,or you might damage the meter or bend the needle.
Then gently tear apart the white inlay.
After that you can reach the led.Take care while unsoldering and soldering a new one in,also watch polarity.

Have attached a pic,hope that helps.

Meter opened.JPG


Best regards,

Udo.
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