LA500 opto comp leveling amp BUILD THREAD 500/51X

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

Post by Joe Malone »

Joe Malone wrote:
vernois wrote:Hi Joe, I sent a couple of pictures to your "sales" email address. It's the only one I could find. If you get a chance, could take a look? Thanks, Gavin
Ok I will check the photos over this weekend and let you know what I find.
HI vernois

Please check the 2 red circles on the photo i resent back to you. I cannot see if the 2 pads in one circle are joined by a small short or not. But it looks that way in the photo.

Also reflow the blob solder joint in the second red circle. Top of PCB looks fine as does the repair to the bottom of the PCB.
Joe :-)
JLM Audio
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vernois
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Post by vernois »

Hi Joe, I received the comp board to replace the one I was having issues with, so that unit is working. Unfortunately while testing between the known working one and the new one, and to my infinite frustration the working one stopped working. It's again an issue with the MAC board, as I've swapped boards and known working op amps and IC's. The VU on this unit shows that it's working, when I turn up the GR the meter reacts as expected, as when I turn up the Makeup Gain. The problem is there's no affect on the output. This comp did work at one point, and I did retouch most of the solder pads, plus there's continuity on all pins of the port. It just seems that the output is getting cut at some point.
If you've got any ideas I'd love to hear them.
Thanks, Gavin

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

Post by Joe Malone »

vernois wrote:Hi Joe, I received the comp board to replace the one I was having issues with, so that unit is working. Unfortunately while testing between the known working one and the new one, and to my infinite frustration the working one stopped working. It's again an issue with the MAC board, as I've swapped boards and known working op amps and IC's. The VU on this unit shows that it's working, when I turn up the GR the meter reacts as expected, as when I turn up the Makeup Gain. The problem is there's no affect on the output. This comp did work at one point, and I did retouch most of the solder pads, plus there's continuity on all pins of the port. It just seems that the output is getting cut at some point.
If you've got any ideas I'd love to hear them.
Thanks, Gavin
This sounds simply like the R14 mod needs to be done as talked about on this thread up the page and is in the build info as well.

R14 should be changed from 2k7 to 1k8 in all 500 series LA500 versions otherwise the output relay may fail to switchover from bypass.

This will make the comp seem to function correct on the meter but no change will be heard at the output as it is still in bypass or sometimes the relay will half switch and you will get very low level output with no low end.
Joe :-)
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kante1603
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Joined: Wed Jan 20, 2010 6:12 pm

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

Post by kante1603 »

Hi Joe,

just wanted to show my little progress of my Compressor-Rack for lead-vocals on my next musical.
Building was as easy as can be-again!No issues at all,amazing.....
I want to advise something concerning trimming the meters:When doing it please let the units heat up for some minutes,the meters will slightly drift otherwise.And repeat the procedure 2 or 3 times,you´ll have them spot-on then.Good idea to keep one eye closed when staring at the needle!
Here´s a pic of my "sixpack",and I think I´ll fill up the gap under the 2 blank panels early next year (Yes,I love these guys!).

Merry Christmas to you all and a happy and healthy new year,

Cheers,

Udo :D

P.S.:Good idea "sealing" the tiny transformer wires (that's hot glue,no?).
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saxmonster
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Post by saxmonster »

Hi Joe and Guys,

I am in the process of building my LA500 but a little bug popped up. I have finished the Red Pcb and was looking over my solder points and notice that there is barley not even a hairs width between the one leg of R25 and C8. I can hardly see any read and when I check continuity between the solder blobs there is continuity. Is this true should there be continuity between a leg of R25 and a leg of C8? According the the schematic one leg of each goes to ground and the others are connected to an IC or some thing down the line but the other leg of each connects to that same line running over to something else. I just don't want anything to blow up when I first fire it up. it does seem like the gold contact of the two are touching but I should have checked it out before I soldered.

Thanks in advance,
-Scott

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

Post by kante1603 »

Hi Scott,

R25 and C8 do connect there after the schemo,so yes,all good!

Have fun,

Udo :wink:

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

Post by saxmonster »

Cool beans

Thanks
Udo

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

Post by saxmonster »

Ok Guys,

I did the mod to the newer pot design. The 2 x 200k pot. I bent the 6 front legs and soldered them in pairs and used 2 leads to connect the 2 out of 3 rear pairs together but do i really need to run wires to the comp / link headers or can i just leave the shunt on it since it will be a mono compressor and not a stereo pair yet? Or should I do it and be done with it and if I get a second one I won't have to worry about doing the mod to the first one. If i continue with the linking mod should i also do the matching stereo pairs blue pot installations or just save the pot for later use when I get another la500.


Thanks
Scott

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

Post by kante1603 »

Hello Scott,

Joe is having some days off,from what I've seen he'll be back next week.
Let's see if I can help you (forgive me Joe :D ).
The pot:It's a dual pot,2 x 200 k log.Paralleling both forms the 100k log that we need in this circuit.You can find the info in the schematic for the mac pcb on the left side of the page.

The switches on the back of the pot are just needed if you want to comfortably link the compressors for stereo operation by just pulling the knob on the front instead of needing to link them internal of your rack.In a 51x rack e.g. you put in a jumper between the modules you want to link.On other racks you can switch this on the back,sometimes it's even needed to solder a bridge.Generally the switch replaces the jumper which makes the connection to pin 6 on the " goldfingers"( the link bus).
It's up to you,easy way is to just leave the jumper in or even leave it open as long as you work in mono.More comfortable is to run the two wires as you have the transformer still not installed.You'll be set then for later stereo operation super easy.
I did this on all of my builds,it's a three minutes work.If you want to add the wires later you need to get the transformer out to access the header ( but it's no biggie,one idc plug and two screws).

The stereo matching mod is only useful when two units are off in showing gain reduction by more than +/-1dB.The mod is then done on the unit that shows the higher gain reduction on the meter.
So not needed for your mono compressor now.

I hope I was able to help you so far,

Best,

Udo.

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

Post by saxmonster »

Ok I will do the mods and just not the stereo matching pot. I am almost ready to fire it up and calibrate it. Just one last question I can't find any info on where the red led should be installed. Unless i missed it somewhere.

Thanks Udo for your tips, they are on the money.

-Scott

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

Post by kante1603 »

saxmonster wrote:Ok I will do the mods and just not the stereo matching pot. I am almost ready to fire it up and calibrate it. Just one last question I can't find any info on where the red led should be installed. Unless i missed it somewhere.

Thanks Udo for your tips, they are on the money.

-Scott
The led is not used,it's a left-over part from the mac opto comp kit.Remember this kit is " composed" of two parts,the mac kit contains additional parts for building a compressor in a rack etc.
The led is for showing "compressor in" and is replaced by the (led-) lights inside the vu meter in this build.

Cheers,

Udo.

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

Post by saxmonster »

Thats what I thought, thanks.

Calibration went pretty easy. I measured the 1k tone out of my digital performer that goes out my 2408MKII interface and with the fader at 0 it measured 1.9VAC so I lower the fader to -3.8 to get the volts down to 1.23 on the MOTU2408MKII output. I then sent it into the LA500. It seemed that I had to turn the VU pot a bunch inorder for it to read 0. Everything else was pretty easy to align. I then ran a prerecorded sax track with no compression on it or eq into the LA500 and the GR meter setting was working great and moving around alot with the different ratio and moving the knobs but when i flip the switch to the VU meter setting it was hardly moving. I then pumped some commerical cd tracks throught the la500 and saw how the vu meter responded to that and made sure the highpass filters worked ok. I just have to check the output of the la500 when the 1k tone goes through it with nothing compressing and make sure i am getting 1.23vac out of it.
Anything else I should do? Gonna look at really calibrating my system output to make sure when the fade it at zero it puts out 1.23vac.


Thanks

PhotogRob
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Joined: Wed Jan 09, 2013 5:52 pm

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

Post by PhotogRob »

Finished my pair of LA500 comps... very nice.
Image

After reading this thread, here is how I calibrated. Is this the best way?

Using Nuendo, I created a sine wave file that goes to absolute zero (max amplitude). Fed that playback through my MOTU 24I/O. I used my multimeter, attached to the hot/cold pins until I got 1.23v A/C on it. This became my reference (which is substantially less than max absolute amplitude). Then, feeding that into the LA-500, I did the alignment procedure described in this thread.

Is this the best way to align them?

campbellj503
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Joined: Tue Feb 12, 2013 9:49 am

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

Post by campbellj503 »

I had emailed Joe with some questions regarding the LA500 kit I’m working on and he asked me to bring the discussion in here so here goes!

I’m a beginner and this is only my third or fourth DIY project. Having completed the kit, I put it into my 500 series rack and fed a 0dB, 1kHz tone into the LA500. I’m using Avid’s signal generator in pro tools, and a Saffire Pro24 DSP for my audio interface. I’ve got the LA500 set to the settings described in the calibration steps of the build thread. When I try to adjust the Meter 0VU trim pot to bring the meter to read 0 in the VU metering setting the trim pot seems to have no effect on the position of the needle in the meter. I’ve tried endlessly to adjust the trim pot with no change in needle position. I’m able to set and adjust the meter when it’s in “Meter GR” just fine, and the balance trim pot also seems to work when metering gain reduction. I’m not sure if this behavior is due to problems in my soldering or if the Meter 0VU trim pot could be a faulty component. Anyways, here are answers to questions that Joe asked in response to my original email along with pictures of the PCB’s + components.

Thanks in advanced for any help!

Q: Does the meter actually move down hard under -20 when you switch to
VU or is it just the same VU reading as in the off position? If it move down
hard when switched to VU you have some wires reversed to the meter.
A: It is the same VU reading as in the off position. If does not move past -20.

Q: Are you going to run this in 51X or 500 mode? You have the 2k7 on the MAC PCB so I presume 51X as this should be 1k8 for 500.
A: I have since clipped the 2k7 and will be using it in a 500 series rack.

Q: Can you hear the compressor working when listening to the output?
A: Yes, the compressor is able to attenuate the signal if I turn the threshold knob up.

Q: Does the makeup control add gain to the output?
A: Yes, the makeup control seems to be functioning normally as is able to add gain to the output.

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

Post by Joe Malone »

Sorry just realized somehow had been subscribed from this thread :-(. I will go back up the page and start answering questions. Sorry for the delay in replying.
Joe :-)
JLM Audio
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