LA500 opto comp leveling amp BUILD THREAD 500/51X

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

Postby Joe Malone » Sat Jan 31, 2015 11:50 am

Miscend wrote:Hi,

I just finished my first ever build, it worked the first time when I plugged it in too, thanks to the really good instructions on this thread. If anyone's just staring out, like I did, I recommend they pick up DIY synth kit to practice with - they're dead cheap and they teach you not to make mistakes with soldering.


Anyhow I'm now stuck on calibrating the VU meter. I have to idea what to do here. If I set the Test Oscillator in Logic X to make a 1KHz sine, at what level do Logic 's output meters need to peaking at?


Switch the comp to VU and put in a 1kHz tone until you measure 1.23vac between pin 2 and pin 3 of the output XLR of the LA500 rack slot. Then adjust the VU trimpot for 0VU.

You can also measure the 1.23vac between pin 2 and pin 4 of the LA500 edge connector
Joe :-)
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Sat Jan 31, 2015 11:55 am

Franklin wrote:Hi Joe,

I finished the pair and they sound wonderful! I'm really happy with them.
I did the calibration process and everything went according to your instructions.

I do want to verify, when I do the stereo link, they jump a little more than 1db in opposite directions. Is this acceptable or do I need to do the stereo match mod? They sound fine, it does not sound like one is compressing more than the other - I only used my ears though, no meters.

Also, one of my VU meters has some small cracks in the inside around the lower right screw. Could you send me a replacement? I can return this one to you.

Thanks,
Franklin


Send me a photo so I can see what you mean and your order number or shipping address.

If it is the scale we can send you one of these. The meter comes apart easily by pulling the back round section up or down and it will unclick form the square front. Scale just slides in and back just clips on.
Joe :-)

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

Postby Lud » Mon Feb 02, 2015 12:08 am

Joe Malone wrote:
Lud wrote:Hi Joe, i'm asking some help cause my second LA500 is not working, although things seemed easier to make compare to the first one :

So, when engaged, the vu meter is not iluminated although it responds well. Sound is passing through the unit without being processed even though the signal seems to pass through all the path due to the vu meter and knobs which respond.

If you have any idea of what is going on and how to fix it i'll be pleased.

Cheers . Lud.


If the meter led doesn't light then the bypass relay will not operate so the comp will not be switched in. Add a wire across the back of the meter shorting out the two LED terminals to see if the comp switches in then, If so the led has been blown and will need replacing.


Hi Joe, i've shorted the meter's led but that did not change anything. Same behavior. The comp seems to work but no sound's processed. What else can i do?

Thanks. Lud.
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Miscend
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Miscend » Mon Feb 02, 2015 4:17 am

Joe Malone wrote:
Miscend wrote:Hi,

I just finished my first ever build, it worked the first time when I plugged it in too, thanks to the really good instructions on this thread. If anyone's just staring out, like I did, I recommend they pick up DIY synth kit to practice with - they're dead cheap and they teach you not to make mistakes with soldering.


Anyhow I'm now stuck on calibrating the VU meter. I have to idea what to do here. If I set the Test Oscillator in Logic X to make a 1KHz sine, at what level do Logic 's output meters need to peaking at?


Switch the comp to VU and put in a 1kHz tone until you measure 1.23vac between pin 2 and pin 3 of the output XLR of the LA500 rack slot. Then adjust the VU trimpot for 0VU.

You can also measure the 1.23vac between pin 2 and pin 4 of the LA500 edge connector


Ok thanks, its fully setup in the rack now. I did not expect it to sound this good. It really is something special.

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

Postby Joe Malone » Mon Feb 02, 2015 9:39 am

Lud wrote:
Joe Malone wrote:
Lud wrote:Hi Joe, i'm asking some help cause my second LA500 is not working, although things seemed easier to make compare to the first one :

So, when engaged, the vu meter is not iluminated although it responds well. Sound is passing through the unit without being processed even though the signal seems to pass through all the path due to the vu meter and knobs which respond.

If you have any idea of what is going on and how to fix it i'll be pleased.

Cheers . Lud.


If the meter led doesn't light then the bypass relay will not operate so the comp will not be switched in. Add a wire across the back of the meter shorting out the two LED terminals to see if the comp switches in then, If so the led has been blown and will need replacing.


Hi Joe, i've shorted the meter's led but that did not change anything. Same behavior. The comp seems to work but no sound's processed. What else can i do?

Thanks. Lud.


Can you hear the back relay click on and off when you switch from off to VU or off to GR?

The bypass relay circuit only has the GR/OFF/VU switch + 1k8 resistor and 12v relay in it.

Your photos don't show me any clear shots around the switch soldering and 1k8 resistor on the MAC.

Let me know what voltages to 0v you get on each end of the 1k8 resistor with the switch off and GR and VU?
Joe :-)

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

Postby Lud » Tue Feb 03, 2015 5:46 am

[/quote]

If the meter led doesn't light then the bypass relay will not operate so the comp will not be switched in. Add a wire across the back of the meter shorting out the two LED terminals to see if the comp switches in then, If so the led has been blown and will need replacing.[/quote]

Hi Joe, i've shorted the meter's led but that did not change anything. Same behavior. The comp seems to work but no sound's processed. What else can i do?

Thanks. Lud.[/quote]

Can you hear the back relay click on and off when you switch from off to VU or off to GR?

The bypass relay circuit only has the GR/OFF/VU switch + 1k8 resistor and 12v relay in it.

Your photos don't show me any clear shots around the switch soldering and 1k8 resistor on the MAC.

Let me know what voltages to 0v you get on each end of the 1k8 resistor with the switch off and GR and VU?[/quote]

Hi, to be honest i did not know where to place my multimeter tip and i don't have the extender cable kit :-( so i've tried but without succès. Then, i did notice that the first 1k8R's pin did not seemed to be well soldered so i put a bit more of solder, and... Here it is, that beautiful LA500 sound!
So i put back the meter led wires... and it did not work again which mean that the meter led doesn't work.
Could you send me a valid vu meter or maybe there's a way to change the led?
In any case thanks a lot for your precious help and your great products!
Cheers.
Lud.

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

Postby Joe Malone » Tue Feb 03, 2015 9:18 am

Lud wrote:
Hi, to be honest i did not know where to place my multimeter tip and i don't have the extender cable kit :-( so i've tried but without succès. Then, i did notice that the first 1k8R's pin did not seemed to be well soldered so i put a bit more of solder, and... Here it is, that beautiful LA500 sound!
So i put back the meter led wires... and it did not work again which mean that the meter led doesn't work.
Could you send me a valid vu meter or maybe there's a way to change the led?
In any case thanks a lot for your precious help and your great products!
Cheers.
Lud.


Cool good to hear you got it to work and like the sound. Make sure you have the led wires the correct way around? You can try both ways as it is safe to do so.

If the led doesn't light when the unit is switched to VU or GR then the LED has been blown. The LED does turn off when switch is in off. All LED are tested here before shipping.

Led is easily removed by pushing or pulling the round back section of the meter up or down as it will unclip from the screwed in square part of the meter.

Slide the scale up and you will see a 5mm white LED facing vertically mounted on 2 solder posts.
Joe :-)

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

Postby Franklin » Wed Feb 04, 2015 3:50 am

I sent you the photo @ sales@jlmaudio.com

Joe Malone wrote:
Franklin wrote:Hi Joe,

I finished the pair and they sound wonderful! I'm really happy with them.
I did the calibration process and everything went according to your instructions.

I do want to verify, when I do the stereo link, they jump a little more than 1db in opposite directions. Is this acceptable or do I need to do the stereo match mod? They sound fine, it does not sound like one is compressing more than the other - I only used my ears though, no meters.

Also, one of my VU meters has some small cracks in the inside around the lower right screw. Could you send me a replacement? I can return this one to you.

Thanks,
Franklin


Send me a photo so I can see what you mean and your order number or shipping address.

If it is the scale we can send you one of these. The meter comes apart easily by pulling the back round section up or down and it will unclick form the square front. Scale just slides in and back just clips on.

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Joe Malone
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Posts: 1572
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby Joe Malone » Wed Feb 04, 2015 3:19 pm

Franklin wrote:I sent you the photo @ sales@jlmaudio.com

Joe Malone wrote:
Franklin wrote:Hi Joe,

I finished the pair and they sound wonderful! I'm really happy with them.
I did the calibration process and everything went according to your instructions.

I do want to verify, when I do the stereo link, they jump a little more than 1db in opposite directions. Is this acceptable or do I need to do the stereo match mod? They sound fine, it does not sound like one is compressing more than the other - I only used my ears though, no meters.

Also, one of my VU meters has some small cracks in the inside around the lower right screw. Could you send me a replacement? I can return this one to you.

Thanks,
Franklin


2 new scales sent today
Joe :-)

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

Postby Lud » Fri Feb 06, 2015 4:01 am

Cool good to hear you got it to work and like the sound. Make sure you have the led wires the correct way around? You can try both ways as it is safe to do so.

If the led doesn't light when the unit is switched to VU or GR then the LED has been blown. The LED does turn off when switch is in off. All LED are tested here before shipping.

Led is easily removed by pushing or pulling the round back section of the meter up or down as it will unclip from the screwed in square part of the meter.

Slide the scale up and you will see a 5mm white LED facing vertically mounted on 2 solder posts.[/quote]


Ok, so they did not have a 5mm 12V led at the electronic store so i put a 3v with a 1k resistor. That makes the vu meter less bright and more vintage looking, and actually i like it better! (not very perceptible on the pic but that's more obvious in real)
unfortunately i've messed up at some point because the vu's needle doesn't move any more. I've twisted it and it sticks now on the glass so it can't move (i think that's what happened). I'll try to fix it.
I've tried the link mod and it works just fine! Real cool feature!

Cheers. Lud.
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thestaylor
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Postby thestaylor » Sat Feb 07, 2015 8:16 am

Hi friends. Currently having some VU issues with my LA500. It's always sounded great, but I've never been able to get to stay after calibration. Well, I recently pulled it out of the slot to rearrange some modules and when I put it back in, the VU and GR modes are both static at the same position. Photo was taken with unit in GR mode with no signal & threshold off.

Many thanks,

Sam

Photo Feb 05, 8 31 00 PM.jpg
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Musepro
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Re: LA500 R15/R16 Smoking

Postby Musepro » Sun Feb 08, 2015 1:26 am

Hey gang,

After building a few LA500s, I had an issue with the last one. R15 and R16, the 10ohm resistors on the MAC PCB, would start smoking when powered up. After thoroughly checking the build of both the MAC and JLMIO PCBs, confirming proper component placements, polarities and solder joints and measuring the output of the IO card, which ran clean and delivered the proper +15.3VDC on pin 4, -15.3VDC on pin 8, I replaced R15/R16 and tried again. Still smoked!

After going through a few more trouble shooting steps, I found that the OPA2604AP opamp on the MAC PCB was faulty! Replacing this opamp solved the issue.

So if any of you have an issue like this (or other issue you can't trace back to your build), pull the opamp to see if it solves the problem.

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

Postby Joe Malone » Mon Feb 09, 2015 11:02 am

Lud wrote:Ok, so they did not have a 5mm 12V led at the electronic store so i put a 3v with a 1k resistor. That makes the vu meter less bright and more vintage looking, and actually i like it better! (not very perceptible on the pic but that's more obvious in real)
unfortunately i've messed up at some point because the vu's needle doesn't move any more. I've twisted it and it sticks now on the glass so it can't move (i think that's what happened). I'll try to fix it.
I've tried the link mod and it works just fine! Real cool feature!

Cheers. Lud.


The white LED in the meter is a 3v type normally. You cannot add any series resistance as this will mean the bypass relay which is series with the led and 1k8 on the MAC PCB will not operate properly.

The needle is very easy to bend but usually means the black plastic set screw on the front of the meter hasn't gone back in the metal meter adjust slot properly and is putting pressure on the needle. The front set slot should be used to set the meter to -20 with no power on.
Joe :-)

JLM Audio

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

Postby Joe Malone » Mon Feb 09, 2015 11:08 am

thestaylor wrote:Hi friends. Currently having some VU issues with my LA500. It's always sounded great, but I've never been able to get to stay after calibration. Well, I recently pulled it out of the slot to rearrange some modules and when I put it back in, the VU and GR modes are both static at the same position. Photo was taken with unit in GR mode with no signal & threshold off.

Many thanks,

Sam

Photo Feb 05, 8 31 00 PM.jpg


Check the cables are plugged in fully and if the comp meters keeps moving around recheck your soldering on the MAC pcb.
Check the 10R resistors on the MAC are not burnt and that you get the +/- power rails at pin 8 and pin 4 of the OPA2604AP on the MAC pcb.

If you cannot spot anything email me some photos of the whole inside of the LA500 as well as top and bottom photos of both PCB's
Joe :-)

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

Postby Lud » Thu Feb 19, 2015 8:28 am

The white LED in the meter is a 3v type normally. You cannot add any series resistance as this will mean the bypass relay which is series with the led and 1k8 on the MAC PCB will not operate properly.

The needle is very easy to bend but usually means the black plastic set screw on the front of the meter hasn't gone back in the metal meter adjust slot properly and is putting pressure on the needle. The front set slot should be used to set the meter to -20 with no power on.[/quote]


Hi Joe, after i fixed the needle, the comp did not worked again. I really did not understand why! So i tried to switch every wires once again in every sens but things did not worked. Then i read your post about the resistance so i placed a new led without the 1kR, but still, nothing worked. I was depressed... then i try to put the comps in another LB and everything was fine! Actually that was some cables i made in the mean time that had issues. Unfortunately i definitely broke the vu meter's systeme during that messy new episode. I'll buy a new metter with my next purchase, but my comps works great.

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