LA500A opto comp MAY 2021 BUILD THREAD 500/51X

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billface
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by billface »

Probably the first in a series of stupid question from myself.

1) Do the J99 sockets get soldered into the board? I said on the instructions not to press them in and to use a piece of cardboard to hold them in, but now the J99 is inplace it seems a bit odd that is a bit loose.

2) I put the DIP8 socket in upside down. Any top tip on how to remove it? I have a solder sucker and some copper braid

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Joe Malone
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by Joe Malone »

billface wrote:
Mon Apr 15, 2024 10:06 pm
Probably the first in a series of stupid question from myself.

1) Do the J99 sockets get soldered into the board? I said on the instructions not to press them in and to use a piece of cardboard to hold them in, but now the J99 is inplace it seems a bit odd that is a bit loose.

2) I put the DIP8 socket in upside down. Any top tip on how to remove it? I have a solder sucker and some copper braid
Yes solder the sockets to the pcb. The 6 sockets fit the holes easy. Use a piece of cardboard to hold them in to flip the pcb and solder them on the bottom pcb side.

Don’t try and remove the dip socket unless you are very good at resoldering just put a white dot on the opposite end to remind you to put the opamp in the other way around. Best to fit the ne5532A now while you remember
Joe :-)
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billface
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by billface »


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Joe Malone
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by Joe Malone »

billface wrote:
Tue Apr 16, 2024 4:46 pm
So just to be clear, are you saying this arrangement will work?
Attach photos to your post. I cannot get to Google photos
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billface
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by billface »

Here's the pics attached (sorry got confused by the img tag function). So quick recap, I put my dip8 upside down and you said to leave it in and match the orientation with the op amp. Have I understood correctly and if so will this affect stereo matching if I put the other one in correctly.
PXL_20240416_063203933-EDIT.jpg
PXL_20240416_063343561.jpg
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billface
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by billface »

Sorry Joe,

I've just reread your post and engaged my brain. The 'other way round' means relative to the dip socket not its normal orientation

I'll flip the opamp to how i had it in the photos

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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by Joe Malone »

billface wrote:
Wed Apr 17, 2024 2:41 am
Sorry Joe,

I've just reread your post and engaged my brain. The 'other way round' means relative to the dip socket not its normal orientation

I'll flip the opamp to how i had it in the photos
You have the opamp facing the wrong way, so unplug and turn it 180 degrees
Joe :-)
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billface
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by billface »

1. Set LA to Threshold pot fully CCW, Makeup pot to CCW. Ratio switch to 3:1, Meter switch to VU, HPF switch to FLAT.
2. Apply 1kHz tone to LA500A input so you have the reference level of +4dBu (1.23vac) on the LA500A output between pin 2 & 3 of the XLR.
3. Or plug LA500A output into VU or PPM meter that is calibrated to 0VU = +4dBu. If voltage not correct adjust 1kHz generator level until correct.
4. Adjust meter 0VU trim pot for the desired level for 0VU on the meter.
5. Switch Meter switch to GR and adjust Zero GR trim pot for 0VU on the meter.
6. Turn up Threshold pot until you have 5dB of compression on the meter.
7. Switch Meter switch between GR and VU and adjust the Balance trim pot until the same reading is seen in both GR and VU.
8. You're ready to rock.

Hey I've got two of these I'm trying to calibrate and have a few questions.

1) it needs a bit more gain to get one of the units to read 1.23vac. Should that be the case? If i'm setting a slighty higher amount of gain to equal 0vu presumably i need to adjust something to balance the two units. Would that be the front needle adjuster?
2) I would like -18db from my DAW to be 0vu but at the moment -16.6db is 0VU and i can't adjust the 0vu trimpot any higher. should adjust the screw on the front of the meter?

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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by Joe Malone »

Hey I've got two of these I'm trying to calibrate and have a few questions.

1) it needs a bit more gain to get one of the units to read 1.23vac. Should that be the case? If i'm setting a slighty higher amount of gain to equal 0vu presumably i need to adjust something to balance the two units. Would that be the front needle adjuster?
2) I would like -18db from my DAW to be 0vu but at the moment -16.6db is 0VU and i can't adjust the 0vu trimpot any higher. should adjust the screw on the front of the meter?
What is 0dBFS on your DAW = to in dBu?

It would need to be +22dBu for -18dB to = +4dBu

With 1.23vac between pin 2 & 3 on the output XLR you should be able to trimpot up to +2dB on the meter.

The mechanical adjust on the front of the meter is only for setting exactly -20 on the meter when the comp is not powered up before doing an alignment
Joe :-)
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billface
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by billface »

Yes the calibration on my system was a bit out. I've adjusted and its fine now. Next question:

The stereo link requires a link between adjactent units on the rack. My rack doesn't have this facility built in but apparently I can solder a link between pin 6 on adjacent slots. Does that sound right to you? i.e is pin 6 the right one? And do I count from the top or the botton of the unit?

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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by Joe Malone »

billface wrote:
Fri May 03, 2024 12:11 am
Yes the calibration on my system was a bit out. I've adjusted and its fine now. Next question:

The stereo link requires a link between adjactent units on the rack. My rack doesn't have this facility built in but apparently I can solder a link between pin 6 on adjacent slots. Does that sound right to you? i.e is pin 6 the right one? And do I count from the top or the botton of the unit?
Calibration is best done with the module warmed up for 30mins or so. And doing it twice is a good idea for stereo match.

Yes you just need a wire between pin 6 of the 2 slots for 500 series comp. Pin 1 is at the top. Set both comps to the same switch and rough threshold settings and then pull both makeup pots outwards so both blue link leds light up. And adjust both makeup pots to get the output level needed.
Joe :-)
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billface
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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by billface »

Just doing my stereo calibirations. I don't understand what the instructions are trying to get me to do. But they seem to work in stereo with the Threshold of one unit controlling the threshold of the other. Could you perhaps do a laymans explanation of the procedure.

I have also noticed that with a 1khz sine wave at 1.228V input to both units with them both set to CCW thres & Makeup one gives aa output of 1.20V and the other 1.24V. Is that within tolerance?

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Re: LA500A opto comp MAY 2021 BUILD THREAD 500/51X

Post by Joe Malone »

billface wrote:
Mon May 06, 2024 10:19 pm
Just doing my stereo calibirations. I don't understand what the instructions are trying to get me to do. But they seem to work in stereo with the Threshold of one unit controlling the threshold of the other. Could you perhaps do a laymans explanation of the procedure.

I have also noticed that with a 1khz sine wave at 1.228V input to both units with them both set to CCW thres & Makeup one gives aa output of 1.20V and the other 1.24V. Is that within tolerance?
The cal is just setting the VU meter so 0VU = +4dBu (1.23vac) and then the second part is balancing so -5dB (5dB compression) on the VU meter = -5dB when switched to GR. The 1.24 to 1.2vac is a tiny difference but you can turn up the makeup on the lower level one slightly until you get 1.24vac on it as well.
Joe :-)
JLM Audio
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