MAC Rack kit Build Thread from October 2016 with slow attack led

[asidd]

hello again, I'm on the SCv3 pcb and the kit comes with two 10R resistors that don't seem to have a place on the board. The build photo has a place for them in the corner but my pcb instead indicates two 1uF caps.

I'm assuming the resistors are not needed on this board?

[Joe Malone]

hello again, I'm on the SCv3 pcb and the kit comes with two 10R resistors that don't seem to have a place on the board. The build photo has a place for them in the corner but my pcb instead indicates two 1uF caps.

I'm assuming the resistors are not needed on this board?

You are correct the parts kit is shared between the LA500A and MAC so there are some extra parts.

You will not need the 2 x 10R. The newer PCBs have 78L & 79L regs instead. Follow the pcb overlay on the pcb you have.

Be careful to put the 78L12 & 79L12 in the correct places and DIP8 opamps around the correct way.

[asidd]

Hello again, when connecting the SCv3 to the chassis, how should we connect the board to the meter? The photos show the meter tabs lining up with the pads on the pcb -- do we eventually solder them directly? Or do we connect them with wires in a similar way to what the older design shows?

Also, at what point in the build should we go ahead and solder all of the switches to the SCv3 board? The photos show one foot soldered, which I assume is to hold it in place until future steps are completed.

Lastly (just to be sure), the switches can go in either way, correct? The on/off/on nature seems like this is the case.

[Joe Malone]

Hello again, when connecting the SCv3 to the chassis, how should we connect the board to the meter? The photos show the meter tabs lining up with the pads on the pcb -- do we eventually solder them directly? Or do we connect them with wires in a similar way to what the older design shows?

Also, at what point in the build should we go ahead and solder all of the switches to the SCv3 board? The photos show one foot soldered, which I assume is to hold it in place until future steps are completed.

Lastly (just to be sure), the switches can go in either way, correct? The on/off/on nature seems like this is the case.

The MAC sc PCB is made to go under the 4-meter metal tabs and sit flat against the back of the meter. Solder a couple of the toggle switch legs so the PCB stays flat with the meter and doesn't touch the back of the pull pot switches on the pot PCB. Then just bent the 4-meter tabs down and solder them to the PCB. Then if everything looks in the right place solder off the rest of the toggle switch legs.

[asidd]

Apologies, I've deleted my original post as I think I've answered my question.
I'm now just wondering how the Link function works on the MAC. It seems to almost "stack" the settings (GR and Ratio) rather than one channel dictating the stereo settings (what I'm used to). Slow Attack and Makeup Gain seem to be independent.
Is this correct? I just want to check that I've assembled it properly. Thanks again for all the help.

[Joe Malone]

Apologies, I've deleted my original post as I think I've answered my question.
I'm now just wondering how the Link function works on the MAC. It seems to almost "stack" the settings (GR and Ratio) rather than one channel dictating the stereo settings (what I'm used to). Slow Attack and Makeup Gain seem to be independent.
Is this correct? I just want to check that I've assembled it properly. Thanks again for all the help.

The link works like most vintage comps like LA2A & 1176 it just joins the side chains so both comps have to be set the same settings before linking. Only since modern VCA comps with DC controls have comps handed control over to one channel.

[saxmonster]

Hello,
Just curious what is the difference and over all sound quality with this stereo rack version vs two LA500A link together. Besides the obvious of not taking two slots up on my lunch box, which is a good reason for me, lol and its $80 bucks or so more that two la500a's. I know that this rack version comes with 2 opamps on each channel what does that do to the sound vs on having one like the la500a has. Sorry for the questions as I am still learning all the little details. I will be using this as a stereo compressor on my 2 buss.

-Scott

[Joe Malone]

Hello,
Just curious what is the difference and over all sound quality with this stereo rack version vs two LA500A link together. Besides the obvious of not taking two slots up on my lunch box, which is a good reason for me, lol and its $80 bucks or so more that two la500a's. I know that this rack version comes with 2 opamps on each channel what does that do to the sound vs on having one like the la500a has. Sorry for the questions as I am still learning all the little details. I will be using this as a stereo compressor on my 2 buss.

-Scott

Basically no real tone difference at all. The form factor is the only real difference. The rack runs on +/-24v with JLM99v input just as no DIP8 runs on that voltage anymore. This in theory gives more headroom but both LA500A and MAC can output +28dBu which is about the limit of the output transformer and way more than any A/D can handle. The input opamp only runs into a 47k load so the LA500A uses a NE5532A as it will run Class A into that 47k load so if hard to tell a difference between the input JLM99v and NE5532A.

[saxmonster]

Thanks Joe,
I will be selling my original LA500 with the slow mod to help fund getting the MAC Rack kit so to save space in my 51X rack for other future items, lol. I see you have one kit in stock, not sure how long it will take to sell this LA500 I have but will you be getting new stock in if this one rack that is left sells out?

Thanks again.
-Scott