LA500A opto comp leveling amp BUILD THREAD 500/51X

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

Postby nenett » Tue Mar 29, 2016 3:42 pm

And here are some more photos. Thanks again for your help with this.
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G-Sun
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby G-Sun » Sat Apr 02, 2016 9:50 pm

I put in a dip-socket and Burr Brown OPA 2604
and took out the JLM 99V

Worked fine on install,
but now it's something wrong.

Anything I should watch out for?
Voltages or anything that should be connected different?

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

Postby Joe Malone » Mon Apr 04, 2016 11:10 am

nenett wrote:And here are some more photos. Thanks again for your help with this.


I cannot see a short on there at all. So my thoughts are that the rack has a damaged power supply from a previous short or overload.

Best is probably to try another module in the rack to see if it works fine.

Or ship us the rack and module to us to get it going for you.

Email me if you are going to send it to us.
Joe :-)
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Re: LA500A opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Mon Apr 04, 2016 11:12 am

G-Sun wrote:I put in a dip-socket and Burr Brown OPA 2604
and took out the JLM 99V

Worked fine on install,
but now it's something wrong.

Anything I should watch out for?
Voltages or anything that should be connected different?


The OPA2604AP can be plugged in with no changes with output transformer.

The OPA2604AP will run the output transformer but not very well.

You don't say what is wrong now so no idea on what the problem could be.
Joe :-)

JLM Audio

Capturing Audio without Injury

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

Postby G-Sun » Tue Apr 05, 2016 3:30 am

Joe Malone wrote:
G-Sun wrote:I put in a dip-socket and Burr Brown OPA 2604
and took out the JLM 99V

Worked fine on install,
but now it's something wrong.

Anything I should watch out for?
Voltages or anything that should be connected different?


The OPA2604AP can be plugged in with no changes with output transformer.

The OPA2604AP will run the output transformer but not very well.

You don't say what is wrong now so no idea on what the problem could be.

Thanks for your reply!

I've experienced some different behaviour,
so I'm a little unsure if it has been cable-problems or something,
but here is today's findings:

- There's a volume difference bypassed vs. engaged (thres. and gain full CCW)-.
Like 3 or 6db or so.
- There's a tone-difference. Engaged is thin.

Last day the sound was really broken. Like low and distorted.

On first install the sound was clear and good.

I have a few ICs more,
and will try another one.

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

Postby Joe Malone » Wed Apr 06, 2016 12:23 pm

G-Sun wrote:
Joe Malone wrote:
G-Sun wrote:I put in a dip-socket and Burr Brown OPA 2604
and took out the JLM 99V

Worked fine on install,
but now it's something wrong.

Anything I should watch out for?
Voltages or anything that should be connected different?


The OPA2604AP can be plugged in with no changes with output transformer.

The OPA2604AP will run the output transformer but not very well.

You don't say what is wrong now so no idea on what the problem could be.

Thanks for your reply!

I've experienced some different behaviour,
so I'm a little unsure if it has been cable-problems or something,
but here is today's findings:

- There's a volume difference bypassed vs. engaged (thres. and gain full CCW)-.
Like 3 or 6db or so.
- There's a tone-difference. Engaged is thin.

Last day the sound was really broken. Like low and distorted.

On first install the sound was clear and good.

I have a few ICs more,
and will try another one.


Since the fault keeps changing I would be check all your soldering. Clean the bottom of the PCB's with isocol and a old toothbrush and resolder any bad soldering will fix 90% of problems.

Bypass and comp in output with makeup & threshold at minimum should be the same level.
Joe :-)

JLM Audio

Capturing Audio without Injury

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

Postby G-Sun » Wed Apr 06, 2016 9:01 pm

Joe Malone wrote:
Since the fault keeps changing I would be check all your soldering. Clean the bottom of the PCB's with isocol and a old toothbrush and resolder any bad soldering will fix 90% of problems.

Bypass and comp in output with makeup & threshold at minimum should be the same level.

Thank you!

I believe there's a drive-issue when I connect to my FMR RNLA.

So, if I just don't chain them together LA500 > RNLA it should be ok.
Sounds good alone :)

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

Postby Joe Malone » Thu Apr 07, 2016 9:42 am

G-Sun wrote:
Joe Malone wrote:
Since the fault keeps changing I would be check all your soldering. Clean the bottom of the PCB's with isocol and a old toothbrush and resolder any bad soldering will fix 90% of problems.

Bypass and comp in output with makeup & threshold at minimum should be the same level.

Thank you!

I believe there's a drive-issue when I connect to my FMR RNLA.

So, if I just don't chain them together LA500 > RNLA it should be ok.
Sounds good alone :)


The RNLA is unbalanced in but with TRS socket. So plugging a balanced transformer out into this leaves the output open circuit on one side so you will only get a bit of high frequncy bleeding to the RNLA. Use a XLR to mono guitar jack cable and it will work fine.
Joe :-)

JLM Audio

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

Postby G-Sun » Thu Apr 07, 2016 4:57 pm

Joe Malone wrote:The RNLA is unbalanced in but with TRS socket. So plugging a balanced transformer out into this leaves the output open circuit on one side so you will only get a bit of high frequncy bleeding to the RNLA. Use a XLR to mono guitar jack cable and it will work fine.

Thank you!
Yes, I've never quite understood the unbal part of the FMR. It's supposed to be semi-balanced or something.
Works fine with other gear in this regard,
but, yes, that makes sense.

So, its:
xlr1 > jack sleeve
xlr2 > jack tip
xlr3 > not connected
?

And my setup with balanced jacks through pathcbay was shorting 1 to 3?

Thanks a lot for helping out :)

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

Postby Joe Malone » Sun Apr 10, 2016 7:42 pm

G-Sun wrote:
Joe Malone wrote:The RNLA is unbalanced in but with TRS socket. So plugging a balanced transformer out into this leaves the output open circuit on one side so you will only get a bit of high frequncy bleeding to the RNLA. Use a XLR to mono guitar jack cable and it will work fine.

Thank you!
Yes, I've never quite understood the unbal part of the FMR. It's supposed to be semi-balanced or something.
Works fine with other gear in this regard,
but, yes, that makes sense.

So, its:
xlr1 > jack sleeve
xlr2 > jack tip
xlr3 > not connected
?

And my setup with balanced jacks through pathcbay was shorting 1 to 3?

Thanks a lot for helping out :)


If pin 1 to pin 3 is shorted then transformer out has a full path so will work full range.
Joe :-)

JLM Audio

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

Postby G-Sun » Mon Apr 11, 2016 3:04 am

Joe Malone wrote:
G-Sun wrote:
If pin 1 to pin 3 is shorted then transformer out has a full path so will work full range.

Thanks!

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

Postby DeathMeister » Tue Apr 26, 2016 1:00 pm

Finished assembling a pair of LA500A compressors.

Everything seems to work fine in unlinked mode.

When calibrating all goes well until I link the compressors by pulling BOTH Makeup pots out.

Then:

GR on compressor A goes to 0
GR on compressor B goes to about -15
I switch the jumper on compressor B to MATCH

Now here the instructions get confusing. I continue:

On the LA500 where I switched the jumper I go back to the beginning of the calibration procedure but use the ST MATCH VU trimmer instead of the BALANCE / GR trimmer. I get it all looking good. Then I continue:

Set up both comp with 1k tone and set 0VU on meter switched to VU and turn up Threshold pot to get -5dB on meter.
2. Turn threshold pot off on modified comp (fully CCW)

What does “modified comp mean? The one I switched the jumper on? That’s the one I will turn down the THRESH pot on.

3. Link the comps. Adjust modified VU trim pot until both comps show the same VU meter readings.

When I do this one meter goes to 0 and the other to -15 or so. Both threshold/makeup pots cause the “modified” comp VU meter to move, but the other meter stays at 0 no matter what. I hesitate to start twisting additional trim pots. Can you suggest where the problem might be?

Thanks!

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

Postby Joe Malone » Tue Apr 26, 2016 1:35 pm

DeathMeister wrote:Finished assembling a pair of LA500A compressors.

Everything seems to work fine in unlinked mode.

When calibrating all goes well until I link the compressors by pulling BOTH Makeup pots out.

Then:

GR on compressor A goes to 0
GR on compressor B goes to about -15
I switch the jumper on compressor B to MATCH

Now here the instructions get confusing. I continue:

On the LA500 where I switched the jumper I go back to the beginning of the calibration procedure but use the ST MATCH VU trimmer instead of the BALANCE / GR trimmer. I get it all looking good. Then I continue:

Set up both comp with 1k tone and set 0VU on meter switched to VU and turn up Threshold pot to get -5dB on meter.
2. Turn threshold pot off on modified comp (fully CCW)

What does “modified comp mean? The one I switched the jumper on? That’s the one I will turn down the THRESH pot on.

3. Link the comps. Adjust modified VU trim pot until both comps show the same VU meter readings.

When I do this one meter goes to 0 and the other to -15 or so. Both threshold/makeup pots cause the “modified” comp VU meter to move, but the other meter stays at 0 no matter what. I hesitate to start twisting additional trim pots. Can you suggest where the problem might be?

Thanks!


OK there is something very wrong to be that different between comps as with the matched opto we supply with pairs you should only be about 1dB out and can trim that out if you want with the balance match. But they should never be close -15dB different.

Do not use the Stereo match jumper or trim pot at all until we get the comps working properly.

Did you split the U1 matched opto bag to U1 position in each LA500SC pcb in each comp?

Did you split the U2 matched opto bag to U2 position in each LA500SC pcb in each comp?

With threshold and makeup fully ccw does the bypass off and comp in output level stay the same when switching from OFF to GR or VU for both comps?

When you have -5dB GR and VU on each comp are the threshold pots in similar positions on the dial?

Also are the makeup pots in similar positions to make up the 5dB back to the same bypass level?
Joe :-)

JLM Audio

Capturing Audio without Injury

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

Postby DeathMeister » Tue May 03, 2016 10:08 am

Well we have narrowed it down.

The comp only misbehaves when stereo linked and fast attack. It's the fast attack that kicks in the problem, then the ratio seems to be almost nothing or the threshold unusually high cuz I have to pull threshold all the way CCW to get even a little GR.

I installed the optos correctly. I'll check for soldering problems around the fast/slow attack switch but any advise otherwise?

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

Postby Joe Malone » Tue May 03, 2016 2:08 pm

DeathMeister wrote:Well we have narrowed it down.

The comp only misbehaves when stereo linked and fast attack. It's the fast attack that kicks in the problem, then the ratio seems to be almost nothing or the threshold unusually high cuz I have to pull threshold all the way CCW to get even a little GR.

I installed the optos correctly. I'll check for soldering problems around the fast/slow attack switch but any advise otherwise?


I need you to answer all the above questions so I can help. Repeated below

Did you split the U1 matched opto bag to U1 position in each LA500SC pcb in each comp?

Did you split the U2 matched opto bag to U2 position in each LA500SC pcb in each comp?

With threshold and makeup fully ccw does the bypass off and comp in output level stay the same when switching from OFF to GR or VU for both comps?

When you have -5dB GR and VU on each comp are the threshold pots in similar positions on the dial?

Also are the makeup pots in similar positions to make up the 5dB back to the same bypass level?
Joe :-)

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