LA500 Slow attack mod

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Joe Malone
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LA500 Slow attack mod

Postby Joe Malone » Tue Oct 21, 2014 11:43 am

How to add the JLM Audio LA500 slow attack mod kit to a LA500

LA500 Slow mod kit parts list
1 x Dual 20k reverse log pot with DPDT pull switch
1 x Pot washer
1 x pot nut
1 x 100mm red wire
1 x 100mm black wire
1 x 100uF 35v or higher cap

Standard LA500 ready to mod into a LA500A.
(Your LA500 must already have a pull to link comps function in the threshold pot for this to work like below photo.)
(Only a few early LA500 comps were ever made without pull to link in the threshold )

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New makeup pot with pull switch that will replace the original 10k rev log pot
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Check pot has correct 10C20K value marked on it
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Fold 3 back pot legs forward and down 90degrees and 3 front pot legs back and down 90 degrees
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Solder 3 sets of front and back legs together to make a 10k reverse log pot
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Remove side locate tab with sidecutters
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New makeup pot with pull switch is now ready for installing in LA500
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Remove makeup pot knob. A flat metal ruler with paper tape on it between knob and the front panel works well.
Unsolder yellow and black wires form the makeup pot. Remove pot nut and slide pot out.
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Mount new makeup pot with pull switch into LA500 and do up pot nut.
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Cut blue and white compressor link wires from the threshold pot switch.
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Trim blue and white wires to correct length for soldering to new makeup pot switch.
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Strip and solder blue and white wires
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Solder blue and white wires to makeup pot switch and now pull to link compressor side chain function is on the makeup pot.
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Next we will fit the slow attack function to the threshold pot
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Fold 100uF cap legs to the right with negetive strip closest to you like below
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Fit 100uF cap to threshold pot switch as shown below with +cap to middle row and -cap to back row of terminals.
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Trim and solder one end of the red and black wires
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Red and black wire solders to points on the MAC PCB shown below.
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Trim and pre solder wires so black reaches the threshold pot terminals with the -cap lead and red reaches switch terminals closest to the threshold pot as hsown below.
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Solder wires to threshold pot switch
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Solder makeup pot yellow and black wires back on to new makeup pot. Refit makeup pot knob.
Finished LA500 slow attack mod below. This makes the LA500 into a LA500A.
Pull on threshold will engage the slow attack function.
Pull on makeup with engage the compressor side chain link function.
(We moved the compressor link function down to the makeup pot so when pulling to link the threshold balance between 2 x LA500 was not accidentally bumped out of balance. Also having the slow attack in the threshold makes it easy to quickly listen to slow attack on and off while adjusting the amount of compression)

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Joe :-)
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jensenmann
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Re: LA500 Slow attack mod

Postby jensenmann » Tue Nov 04, 2014 7:16 am

That mod is a great idea. I had problems with bass guitars on a few occations since the LA500 obviously is too fast - what a statement about an opto comp.... :D
This mod seems to perfectly adress this problem. I´m going to check it out as soon as my purse allows.
Btw, Joe, I´m still in high praises about this compressor - although honeymoon is over for quite some time now. This is a serious piece of kit. I absolutely love it and it eats my Ureis for breakfast on a regular basis as can be heard on leadvocals here: http://www.mr-winterbottom.com/
Thanks for that great comp!!!
Jens

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Re: LA500 Slow attack mod

Postby Joe Malone » Fri Nov 28, 2014 5:33 pm

:D 8)
jensenmann wrote:That mod is a great idea. I had problems with bass guitars on a few occations since the LA500 obviously is too fast - what a statement about an opto comp.... :D
This mod seems to perfectly adress this problem. I´m going to check it out as soon as my purse allows.
Btw, Joe, I´m still in high praises about this compressor - although honeymoon is over for quite some time now. This is a serious piece of kit. I absolutely love it and it eats my Ureis for breakfast on a regular basis as can be heard on leadvocals here: http://www.mr-winterbottom.com/
Thanks for that great comp!!!


:D 8) Cool
Joe :-)

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PeteJE
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Re: LA500 Slow attack mod

Postby PeteJE » Mon Dec 29, 2014 7:00 pm

Joe,
The original makeup pot instructed and showed the top pin black, and the middle and bottom pin both yellow, bridged. This photo series on the mod shows the opposite, top yellow and middle and bottom bridged with the black wire. Which is correct with this new makeup pot?
Thanks,
Pete

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Re: LA500 Slow attack mod

Postby Joe Malone » Thu Jan 01, 2015 10:28 pm

PeteJE wrote:Joe,
The original makeup pot instructed and showed the top pin black, and the middle and bottom pin both yellow, bridged. This photo series on the mod shows the opposite, top yellow and middle and bottom bridged with the black wire. Which is correct with this new makeup pot?
Thanks,
Pete

Yes correct the colors can go either way around as long as the correct 2 pins on the pot are connected
Joe :-)

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steveau
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Re: LA500 Slow attack mod

Postby steveau » Fri Jan 02, 2015 7:41 am

Joe,
I would like to do this mod, but since I only have one unit, and don't need the link,
can I just cut off the blue and white leads, or do they need some special termination?
Thanks,
Steven

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Joe Malone
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Re: LA500 Slow attack mod

Postby Joe Malone » Fri Jan 02, 2015 10:30 am

steveau wrote:Joe,
I would like to do this mod, but since I only have one unit, and don't need the link,
can I just cut off the blue and white leads, or do they need some special termination?
Thanks,
Steven


Yes you can remove the blue and white wires completely.
Linking the 2 pins on the LA500 will allow this comp to link to another LA500 with the link pull switch.
Leave the 2 pins on the LA500 open will stop this comp from ever linking to anything.
Joe :-)

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saxmonster
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Re: LA500 Slow attack mod

Postby saxmonster » Sat Aug 22, 2015 12:09 pm

Hi Guys,
Where can I get this Alpha 10C20K pot here in the USA. I have looked everywhere and can't find it. Do I have the wrong part number? Is it special order? I have an older LA500 and wanna complete this mod to it. Just need this dam pot, hahaahah.

-Scott

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Joe Malone
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Re: LA500 Slow attack mod

Postby Joe Malone » Sat Aug 22, 2015 9:14 pm

saxmonster wrote:Hi Guys,
Where can I get this Alpha 10C20K pot here in the USA. I have looked everywhere and can't find it. Do I have the wrong part number? Is it special order? I have an older LA500 and wanna complete this mod to it. Just need this dam pot, hahaahah.

-Scott


We have them specially made for us and the slow attack mod kit with the pot to update you LA500 is available on our website at the link below

http://jlmaudio.com/shop/la500-slow-attack-mod-kit.html
Joe :-)

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saxmonster
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Re: LA500 Slow attack mod

Postby saxmonster » Wed Aug 26, 2015 11:19 pm

Ok, thanks Joe. Will order it this week.

nicosquid
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Re: LA500 Slow attack mod

Postby nicosquid » Tue Jan 29, 2019 11:55 pm

Hello Joe,
I received the parts and performed the mod. Thanks for the ground jumper I was missing!
Everything seems to be OK, just wanted to ask if it’s normal for the compressor to take a few seconds to start working again after switching to the new slow attack position?
Thanks.

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Joe Malone
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Re: LA500 Slow attack mod

Postby Joe Malone » Wed Jan 30, 2019 11:33 am

nicosquid wrote:Hello Joe,
I received the parts and performed the mod. Thanks for the ground jumper I was missing!
Everything seems to be OK, just wanted to ask if it’s normal for the compressor to take a few seconds to start working again after switching to the new slow attack position?
Thanks.


Not usually. Send me some photos of your mod so I can check them over.
Joe :-)

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nicosquid
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Re: LA500 Slow attack mod

Postby nicosquid » Thu Jan 31, 2019 3:21 am

Joe Malone wrote:
nicosquid wrote:Hello Joe,
I received the parts and performed the mod. Thanks for the ground jumper I was missing!
Everything seems to be OK, just wanted to ask if it’s normal for the compressor to take a few seconds to start working again after switching to the new slow attack position?
Thanks.


Not usually. Send me some photos of your mod so I can check them over.


Hi Joe,
Here are some pictures.
You do not have the required permissions to view the files attached to this post.

saxmonster
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Re: LA500 Slow attack mod

Postby saxmonster » Thu Jan 31, 2019 12:26 pm

Nico,
It looks like your black wire coming off of the new Capacitor is not going to the same spot on the PCB as Joe's black wire is, in fact it kinda looks like there might be a soldering bridge there too with the soldering point above it. Hot solder might have dripped down causing it to bridge.

Also your red wire going to the leads on the threshold should be bridged I think. Just like originally but now that I look at it it looks like Joe snipped the bridge between the two front leads on the threshold pot but there is no mention of it. Maybe it just looks like it is snipped. The two leads closest to the knob. Please confirm Joe.

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Joe Malone
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Re: LA500 Slow attack mod

Postby Joe Malone » Sun Feb 03, 2019 3:33 pm

nicosquid wrote:
Joe Malone wrote:
nicosquid wrote:Hello Joe,
I received the parts and performed the mod. Thanks for the ground jumper I was missing!
Everything seems to be OK, just wanted to ask if it’s normal for the compressor to take a few seconds to start working again after switching to the new slow attack position?
Thanks.


Not usually. Send me some photos of your mod so I can check them over.


Hi Joe,
Here are some pictures.


Other wires are in the way so cannot see where both wires are soldered to the PCB
Joe :-)

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