LA500 opto comp leveling amp BUILD THREAD 500/51X

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taliska
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Joined: Thu Sep 19, 2013 5:58 am

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

Post by taliska »

Joe Malone wrote: No those numbers are relevant to the testing only at that time. To match a pair of LA500 it is best to order them together or let us know at the time so we can keep a match set for the unit you have for a month or so.

If ordering a second LA500 at a later date let us know in comments when ordering that you are trying to match a existing LA500. Also you need to let us know if you have a green or red output transformer.

You can remove a opto from your original LA500 comp U1 position to U2 in the new comp and split the new optos from the 2nd LA500 into both U1 positions as we will super match this new audio pair for you so you end up with a matched pair.
Ok, great. Good to know! :)

Kaz

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

Post by taliska »

Hi Joe,

Just been doing a few more bits on the MAC part of the kit and have reached a point of uncertainty regarding the trim pots.

I think my confusion might be down to it being a slightly older version of the kit, as I had noticed earlier that the R14 value wasn't marked with the updated value in this thread. Obviously I placed the newly recommended value instead (the background info I'm giving is just for completeness).

Anyway, the trim pot issue is that in the guide, it says that the 20k (203) trim pot has been replaced with a 1k (102) trim pot...however, in my kit I have:

1 x 203
3 x 102

which obviously means that I can follow the current guide and install a 1k trim pot for the 20k slot, but then I won't have a 1k pot available for the link mod part of the build (I will have a left over 20k trim pot instead).

Even though I've been following the errata up to this point, is it OK to do it the old way instead, and install the 20k trim pot for the meter or will that cause problems?

Cheers,

Kaz

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

Post by Joe Malone »

taliska wrote:Hi Joe,

Just been doing a few more bits on the MAC part of the kit and have reached a point of uncertainty regarding the trim pots.

I think my confusion might be down to it being a slightly older version of the kit, as I had noticed earlier that the R14 value wasn't marked with the updated value in this thread. Obviously I placed the newly recommended value instead (the background info I'm giving is just for completeness).
The MAC board has the 51X value on the PCB. If using in a 500 rack must be changed to 1k8
Anyway, the trim pot issue is that in the guide, it says that the 20k (203) trim pot has been replaced with a 1k (102) trim pot...however, in my kit I have:

1 x 203
3 x 102

which obviously means that I can follow the current guide and install a 1k trim pot for the 20k slot, but then I won't have a 1k pot available for the link mod part of the build (I will have a left over 20k trim pot instead).

Even though I've been following the errata up to this point, is it OK to do it the old way instead, and install the 20k trim pot for the meter or will that cause problems?
We have only just changed over to all 1k (4 x 1k trim pots). If you kit has a 20k trim pot use it for the Meter 0VU as normal. The extra 1k trim pot is for stereo matching mod.

If you are only building a single LA500 then you can use either the 20k or spare 1k for the Meter 0VU trim pot.
Joe :-)
JLM Audio
Capturing Audio without Injury

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

Post by taliska »

Joe Malone wrote: The MAC board has the 51X value on the PCB. If using in a 500 rack must be changed to 1k8
Oh ok. That was me just being dense. I read it as a general build note rather than a 51x/500 option thing. Don't I feel silly as I am in fact building for 51x! :oops: (time to de-solder)
Joe Malone wrote: We have only just changed over to all 1k (4 x 1k trim pots). If you kit has a 20k trim pot use it for the Meter 0VU as normal. The extra 1k trim pot is for stereo matching mod.

If you are only building a single LA500 then you can use either the 20k or spare 1k for the Meter 0VU trim pot.
Ok great. That clears everything up!

Thanks for the help Joe!

Kaz

dipfrik
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Joined: Thu Nov 21, 2013 5:42 am

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

Post by dipfrik »

Hey Joe,

seems that only 1 of the 5k1 resistors for R4/R6 (INX5 PCB) was in the package. (one 470R to much)
Can i substitute R6 with a 4.7k 1% that i have available here?

Thanks, Sven

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

Post by Joe Malone »

dipfrik wrote:Hey Joe,

seems that only 1 of the 5k1 resistors for R4/R6 (INX5 PCB) was in the package. (one 470R to much)
Can i substitute R6 with a 4.7k 1% that i have available here?

Thanks, Sven
Yes you can use 4k7 but R4 = R6. So you can use either 2 x 4k7 or 2 x 5k1.

Otherwise I can send some 5k1 to you.

Remind me next order and I will add something extra in instead of leave something out :-(
Joe :-)
JLM Audio
Capturing Audio without Injury

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

Post by dipfrik »

Yes you can use 4k7 but R4 = R6. So you can use either 2 x 4k7 or 2 x 5k1.
Fine. I will use two 4k7 that i have here. No need to send the 5k1's ;)

Thanks for the quick help!

Cheers, Sven

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

Post by dipfrik »

4 nights & 4 modules later - power on - everything works like a charm.
Thanks for the awesome kits Joe!

…ready for tracking now ;)
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Joe Malone
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Post by Joe Malone »

dipfrik wrote:4 nights & 4 modules later - power on - everything works like a charm.
Thanks for the awesome kits Joe!

…ready for tracking now ;)
Cool great to hear. And thanks for posting the photo as well :D 8)
Joe :-)
JLM Audio
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dimmyrock
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Post by dimmyrock »

Hi
I recently bought and started building The LA500 and need a pic of the reverse side (solder side) of the Mac pcb as i have managed to over heat one off the "through hole" soldering positions and the silver laminate has come off on both sides. I just need to see wear the track goes so i can solder the two positions together. There pics of the component side on the forum but no solder side in full.

Your help would be appreciate :D

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

Post by Joe Malone »

dimmyrock wrote:Hi
I recently bought and started building The LA500 and need a pic of the reverse side (solder side) of the Mac pcb as i have managed to over heat one off the "through hole" soldering positions and the silver laminate has come off on both sides. I just need to see wear the track goes so i can solder the two positions together. There pics of the component side on the forum but no solder side in full.

Your help would be appreciate :D
See below images
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Joe :-)
JLM Audio
Capturing Audio without Injury

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

Post by dimmyrock »

Excellent!!!

Cheers

Glen

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

Post by zendrum »

Hello Joe-

A bit of feedback on the LA500 kit. A pretty quick build for someone experienced with soldering - no problems at all!

Calibration went well also. I started out measuring my converter output to get 1.23VAC, but this became cumbersome rather quickly. I generally use -18dbFS as 0vu throughout my studio, so I used a tone generator to output a -18dbFS signal to the LA500. From there, the calibration instructions in the build thread were easy to follow.

The sound? Wow! I've never used a hardware LA2A before. Smoothest vocal comp I've ever heard! And very easy to dial in. You can't make this thing sound bad!

Thanks for the great kit, and for answering my questions!
2014-02-03 11.33.24.jpg
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thestaylor
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Re: LA500 opto comp leveling amp BUILD THREAD 500/51X

Post by thestaylor »

Hi friends.

I'm new to electronics so bare with me. I've built an LA-500 and the VU meter keeps drifting off after I calibrate it to 1.23 vac. On GR mode, the meter drifts above 0VU after I've calibrated it. And on VU mode the meter always sits between -10 & -7. After the most recent calibration, the meter changed after I swapped another module in my 500 rack.

Thanks in advance for your help,

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

Post by kante1603 »

thestaylor wrote:Hi friends.

I'm new to electronics so bare with me. I've built an LA-500 and the VU meter keeps drifting off after I calibrate it to 1.23 vac. On GR mode, the meter drifts above 0VU after I've calibrated it. And on VU mode the meter always sits between -10 & -7. After the most recent calibration, the meter changed after I swapped another module in my 500 rack.

Thanks in advance for your help,

Sam
Hello Sam,

hope I can help.
If the meter moves in vu mode when you apply some music to it and it does audible compression when in gr mode the circuit seems to work o.k.
There seem to be two things that were not done properly:

1.: Let the circuit heat up for a while,say 20 to 30 minutes otherwise the meter will drift off.Then do the zero dB adjustment to your prefered refernce level,normally +4dB.Seriously,when I switch on my rack all of my eight compressors' vu zero readings are too high in cold state.After some minutes they all fall back to zero spot on precisely!

2.:After having done the full adjustment for gr it seems that the balance procedure wasn't done correct.Please refer again to the procedure on page 1 in this thread.The goal is to get the needle sit in the same spot in both vu and gr mode when toogling between them.This will be somewhere on the scale,not precisely at zero or -5......
It's very important not to alter any of the other switches or the pots or your generator output level while doing it.

Best regards,

Udo.

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