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

[monobass]

Hi,

Has anyone done a sidechain HPF mod on the SA-3A?

Thanks

So I guess no one did? Is it viable on this unit? Am I asking a dumb noob question?  ;D

 

[leitrim_lad]

Hey there, im just wondering if you could help me, i seem to be having a problem with one of the channels. the right hand side channels keeps seeming to cut out every now and again.. i could be in the middle of tracking something  and next thing it just goes, when i have to turn the gain nob up nearly full it kicks in again and starts to work for a while. Any ideas on what it might be?

Thanks in advance

 

[earl]

Just a guess here try swapping out the t4 with the other one?

 

[leitrim_lad]

cheers earl ill give that a go and see if it does anything

 

[ruckus328]

Hey there, im just wondering if you could help me, i seem to be having a problem with one of the channels. the right hand side channels keeps seeming to cut out every now and again.. i could be in the middle of tracking something  and next thing it just goes, when i have to turn the gain nob up nearly full it kicks in again and starts to work for a while. Any ideas on what it might be?

Thanks in advance

Tried to respond last night but forum seemed to be down, anyone else have problems?

Anyways, suspect it's either a dodgy pot, or bad solder joint or cable/crimp job.  I don't think it has anything to do with your T4. 

Swap the pots to rule that one out.  If that's not it then output cable to XLR would be my next suspect, or the cable going to the pot (that's the only two cables it could be imho).  Otherwise just crack open the schematic and trace the signal with a multimeter, only a couple dozen parts in audio path, so shouldn't take long at all to pinpoint the problem.  I'd start at the output connector on the board (J10) and work your way back.  Somewhere between there and the Pot (J5) is your issue.  Obviously wait until the problem occurs to attempt this troubleshooting.  I'd get the unit out of your rack and get the lid off so it's sitting there waiting for troublshooting when the issue occurs.  Best of luck.

 

[monobass]

hey ruckus328, any comment on my sidechain HPF question?

 

[miketeachesclass]

I'm done stuffing the boards, and am ready to start wiring.

Is it critical that the 18g wire from the IEC inlet to front panel be shielded?  I've got a ton of 18g wire, but none of it is shielded.  I've also got a ton of 22g shielded cable.  I'm planning to mount the toroid on the side of my case, unless someone has a compelling reason I shouldn't. 

Thanks,
Mike

 

[ruckus328]

I'm done stuffing the boards, and am ready to start wiring.

Is it critical that the 18g wire from the IEC inlet to front panel be shielded?  I've got a ton of 18g wire, but none of it is shielded.  I've also got a ton of 22g shielded cable.  I'm planning to mount the toroid on the side of my case, unless someone has a compelling reason I shouldn't. 

Thanks,
Mike

22 Gauge wire is not safe for the mains wiring, it should be 18 gauge minimal.  You don't need shielded wire there, however since this is mains AC there is a very high likelyhood it will cause hum in your unit depending on how you wire things.

No issue with mounting transformer on the side, just be sure your side panel has good ground connection with the other pieces of your enclsoure.

 

[miketeachesclass]

Thanks.

Is it just me, or is it hard to find 18ga shielded cable?  Where is everyone getting theirs?

I suppose I will probably just try it and run the 18ga wires along the side of the case, as far away from everything else as possible. 

Thanks,
Mike

I'm done stuffing the boards, and am ready to start wiring.

Is it critical that the 18g wire from the IEC inlet to front panel be shielded?  I've got a ton of 18g wire, but none of it is shielded.  I've also got a ton of 22g shielded cable.  I'm planning to mount the toroid on the side of my case, unless someone has a compelling reason I shouldn't. 

Thanks,
Mike

22 Gauge wire is not safe for the mains wiring, it should be 18 gauge minimal.  You don't need shielded wire there, however since this is mains AC there is a very high likelyhood it will cause hum in your unit depending on how you wire things.

No issue with mounting transformer on the side, just be sure your side panel has good ground connection with the other pieces of your enclsoure.

 

[miketeachesclass]

Well, I ended up shielding a pair of 18ga wires.  I took a 2' length of canare star quad (it's got a braided shield), and did the following:

1) strip the jacket completely
2) work the inner 4 conductors out of the shield (leaving you with nothing but the braided shield)
3) put 2 conductors of 18ga wire in the braided shield.
4) heat shrink the hell out of it to make sure the shield won't short to anything
5) check continuity between both 18ga wires and the shield to make sure nothing is shorted.

We'll see how it goes!

Mike

Thanks.

Is it just me, or is it hard to find 18ga shielded cable?  Where is everyone getting theirs?

I suppose I will probably just try it and run the 18ga wires along the side of the case, as far away from everything else as possible. 

Thanks,
Mike

I'm done stuffing the boards, and am ready to start wiring.

Is it critical that the 18g wire from the IEC inlet to front panel be shielded?  I've got a ton of 18g wire, but none of it is shielded.  I've also got a ton of 22g shielded cable.  I'm planning to mount the toroid on the side of my case, unless someone has a compelling reason I shouldn't. 

Thanks,
Mike

22 Gauge wire is not safe for the mains wiring, it should be 18 gauge minimal.  You don't need shielded wire there, however since this is mains AC there is a very high likelyhood it will cause hum in your unit depending on how you wire things.

No issue with mounting transformer on the side, just be sure your side panel has good ground connection with the other pieces of your enclsoure.

 

[tom f]

Hi,
we have finished the built of our first SA-3A.
After sending Audio through the unit for the first test, I noticed a significant high frequency boost (a little bit like an exciter)
and loss at bass frequencies in both channel when comparing to bypass.

The input level on Gain on 10 (when in 30db gain mode) is to soft for compression (no Gain Reduction audible and visible)
although Peak Reduction is on 10 too.

Do you know a solution for this and can tell me where I can find instructions for the calibration of the SA-3A?

Thanks a lot for your help and time.
Tom

 

[ruckus328]

Only calibration is to set bias voltage as printed on the board - adjust VR1 for 12-13V DC at TP1.

Adjust VR2 to 0 out the meter in G/R.

I noticed a significant high frequency boost (a little bit like an exciter)
and loss at bass frequencies in both channel when comparing to bypass.

The input level on Gain on 10 (when in 30db gain mode) is to soft for compression (no Gain Reduction audible and visible)
although Peak Reduction is on 10 too.

Do you know a solution for this?

Since it's the same problem on both boards than safe to say an assembly error, but impossible to say what, could be anything.

Did you follow all assembly instructions at beginning of the thread?

Did you space the Input transformer & metal can transistors off of the board?

Otherwise, check every component for correct value & orientation, check all wiring is correct.

 

[tom f]

Hi Ruckus,
thanks for the information.
For the first audio test we used an asymmetric cable.
After switching to symmetric cable the unit sounds right. 

Tom

 

[dandeurloo]

I finished building mine!  Sounds sweet and is super quite!  Thanks Ruckus. 

 

[sr1200]

This compressor should win the "is it on?" award.  It's transparent up to a point.

 

[sage]

Hi there

just a quick question since I am no expert I rather be safe than sorry....

I have a Power Transformer Toroidal TRIAD VPT30-830

loooking at the specs downloaded from their site it shows that  for 115VAC input it needs to be in PARALLEL mode which will generate 15.0 VAC.... so the conection to the unit would be :

INPUT (From Electricity 115V) BLUE and Brown jumping Blue to Violet, GRAY to BROWN
OUTPUT (in series straight to the PCB for 30 VAC output) Black and Yellow, jumper Black to Orange, Red To Yellow

is there a drawing that anyone has which is crtistal clear on HOW TO CONNECT this Toroidal correctly ?

Thank you so much !

Sage

 

[AlbertoM]

Hi all! it's been a while since my last post, that means I've been very busy. I had a problem with the gain reduction metering, it wasn't accurate, I was told to play with r13 and today we (my tecnician and I) have managed to set it right, we have changed r13 for a 100k trimmable resistor and trimming VR2 and the new 100k trim pot we've succeeded, now everything is perfect!.

Thanks again for the project and help.

Cheers.

Alberto.

 

[ktfstudio]

Just want to give this a thumbs up. This kit is just seamless, no headaches at all. Been working the SA-3A for about a month now and I have nothing but praise. No disappointments.
Thanks

 

[dandeurloo]

I just got some T4B's from Drip that are regular speed so I re-calibrated my unit.  I found that R13 should be a trim pot in order to get the Meters to track properly with the Drip T4b's.  No idea if this is need for originals T4B's or not.  If you need this a 50-100K trimpot should be more then enough to get the meters tracking perfect.  I didn't measure what the final adjusted value was but I know its was lower than 39k.  So I think 50k will work. 

I also added a switch to the 604 1/2 w output termination.  So know I can switch that in and out from the front panel as well. 


Again I love this comp!  Sounds great, easy build.  Everyone needs one.  Thanks Ruckus.

 

[sage]

Hi There

I am all done but I do have a very sensitive gain pot - when we feed +4 and reading ZERO on VU meter the pot is at 1.5.... any suggestions? This happens on BOTH channels NOT in stereo mod - also it is as sensitive in STEREO...
Is this normal?

This is on NORMAL - no mod or 50db switches are engaged

sage