SA-3A (LA-3A Clone) Support Thread

[mulletchuck]

I wanted to see if anyone could verify some stuff regarding the Mod/Classic and 30/50 switches.  the following is a table showing switch configuration, and the subsequent gain setting to achieve unity with peak reduction set to 0.  I'm feeding the unit with a -12dbFS 1khz sine signal from my DAW, and the interface is set to deliver a +4dBU signal when given a 0dbFS signal.  I'm not sure what the actual voltage coming out of the daw is.  All of the values listed below are based on the meter reading in Apogee Maestro.  So, if I saw -12 going out, i turned the gain knob until the inputs said -12.  GR was

Mod  30db:  Gain @ 7
Mod  50db:  Gain @ just past 2
Classic 30:    Gain @ 1.6
Classic 50:    Gain @ 0.7

Gain reduction amounts, in Compress mode, Peak Reduction all the way up, gain knob set to unity gain. 

Classic 50:  24db of Gain reduction
classic 30:    8-9db of Gain Reduction
Mod 50:      23db of Gain Reduction
Mod 30db:    8-9 db of Gain Reduction

Gain reduction amounts, in Limit Mode, P/R @ 10, Gain @ Unity:

mod 30:  9.5 db GR
Mod 50:  28.3 db GR
Classic 30:  9.7 db GR
Classic 50:  29 db GR

Are you guys getting similar results?

 

[North]

Is there anything special to note  about building /calibrating a mono unit - such as replacing the stereo adjust pot for a 10K resister, etc.?

 

[rob61]

Finished my build. Is there a calibration procedure for the VR3 HF Contour?

 

[rob61]

Here is a photo of my build.

 

[TmBaBt]

Hi guys,

I think I was one of the last guys to buy the SA3A kit before they stopped.  Finally getting to build it now with a friend.  I've searched this forum and the Serpent Audio site for the step-by-step setup/test guide (the one you do before stereo calibrating the boards), but I can't find it.

I'm sure it was a PDF or something on the Serpent Audio site when it was available.  Can someone upload here?
Thanks

 

[mulletchuck]

There isn't a setup guide.  You pre-trim the trimmers that go on the PCB, and that's it.  the schematic says what to trim them to. 

 

[North]

I just finished my mono unit and took my time building to be sure it was right. Powers on ok, has great input/output volume and is dead quiet. The problem is that there is no gain reduction in audio or at the meter. The mod and 30/50 switches work. The unit seams to be fine in all regards except that there is no gain reduction. Any one else run into this? Thanks

 

[rainton]

It is most likely the "stereo adjust" and the "limiter response" trimmer.
This also happened to me with my first LA2A build - if they're not set correctly you'll
Get no compression.

Try turning both of them fully clockwise until you hear a slight click.

If you still get no compression try turning both of them fully counterclockwise...
(Depends on their orientation - how you installed them - and assuming you installed the trimmers with the same orientation, otherwise you might have to go through turning one of them fully cw while you turn the other one fully ccw or vice versa)

Hope that helps

 

[North]

Thanks rainton it worked  Funny thing - I turned the stereo adjust trimmer both ways the other night and didn't get any compression. BTW Which is the limiter  response trimmer? I had believe the stereo trimmer is normally supposed to be at full CCW but I went full CW to get it to function. I only saw one way to orientate the pot so I don't know.  :-\Strange but anyhow its working and very quiet. Its a little sensitive as the gain is pretty hot/aggressive while the peak reduction seems to just start to kick in at 6 on the dial. I guess I'll play with it some more before screwing down the lid but would like to get the gain less aggressive and get the peak reduction adjust to kick in earlier somehow. I noticed that I have to really crank the input for the Classic/30 setting to get it to see compression. Normal? Thanks again!

 

[rainton]

Sorry, on ruckus' pcb it's not labeled "limiter-response" but "bias adjust" - I got it mixed up with the original LA2A schematic...
This is the trimmer that decides how the compressor reacts...so this trimmer should usually be around the middle position - but you could of course adjust to taste 

regarding the gain - the LA2A/3A has tons of gain. Did you feed it with a signal from your DAW? Make sure you don't use 0dbfs from your DAW as a reference!
That's way too hot - 0dbu is usually around -16 to -20dbfs  - but you most likely know that - just wanted to make sure 

 

[North]

Actually with the bias at 12.5, it seams to be pretty good so I just left it. I also did attach the shields to the XLR's and it is dead quiet. I used a Kenetek T4B and am very pleased. I feed the SA3A direct from the preamp before it hits the daw to prevent overs going in. I'll need to add to my patchbay for inserts as well as I can see where this shines compared to my plugins. I got a chance to really test it out the other night and I must say- this thing is fantastic. Its very transparent on vocals which was my main reason for building. Even on program material , it retains the clarity and the highs usually lost in other comps when trying to tame levels. This thing is a keeper!! Thanks so much Ruckus for making this project available to diy, you did an awesome job!!

 

[North]

My mono build. Front Panel Express was awesome to work with!

 

[North]

Case is Par-Metal. Very stellar.

 

[mulletchuck]

Why didn't you build a stereo box??

 

[North]

well..honestly I really didn't need one at this time. I may get another pcb just in case I change my mind  I have other projects in the fire that I need to throw $$ at as well

 

[Pran]

Is it still possible to get the PCBs and faceplate from somewhere? LA-3As are my favourite compressors and I'd really love to do this build.

 

[ding]

My mono build. Front Panel Express was awesome to work with!

North, do you have the fpd file for that mono build? I would love to get that going. Also where is everyone getting their EA-11184 and T4B. I see Hairball has the EA-11184 but without the frame.

 

[Dr Gris]

For T4B you could try Drip, Kenetek, IGS, evilBay....
David Kulka (member here) at Studio Electronics has lots of cool parts.

Best
//M

 

[ding]

I don't think Drip sells the T4Bs any more, evilBay has bumpkis, I'll check out the rest.

BTW North, what is that material for that neve 3415? Is that the Blue anodized aluminum from front panel express?

 

[rainton]

I think Drip does still them - you just have to ask them for it.
I bought one 2 months ago