LA3A 500 BUILD

[peter purpose]

i saw  nielsk had the same problem with very few compression but it was a solder bridge, i double checked i don't find...

I couldn't possibly say, but check again.

 

[adrian]

after some check it seem it was a bad trimmer,
i replace it with a pot and it's ok,
i wait for an new trimmer..
i'm so exited to use this comp in the studio....

thanks for your help!

 

[adrian]

waou!!!  last days I used my finished LA3a, it's AMAZING!!! sound so good!!! especially on vocals!
gonna finish my second ASAP!!!

thank you Peter for this great project!!!
let me know if you plane an other batch!!!

some notes about my calibration process :

- whatever RV31 position is I had to keep RV28 fully CW because if i change the position when the squash is engaged the comp begin to attenuate (even without audio signal),  I presume it's ok because Peter said " R28 ... as was said before... needs to be at one end or the other.... you'll know which when you've done it. "

- RV31 about 6 turn before fully CW to avoid oscilating when squash pot is fully CW…

thank you again!!!

 

[haima]

Congrats on finishing your LA3A!

I'm loving mine.

 

[Pliplo]

man i really wanna make a couple of these! Any idea of where i could get at least pcb+bracket/panel, etc?

 

[saxmonster]

Can we start another round of orders?  If so I would be in for a stereo pair.

 

[tonycamp]

I pm'd Peter about that last week, he's not into it right now i guess. I am thinking of doing a couple of these,  http://www.jlmaudio.com/shop/index.php?_a=viewProd&productId=136  ,has anyone tried them out? Is it inappropriate for me to post this link here? If so, i'd be glad to delete the post.

Thanx

 

[mulletchuck]

sonic02 built both, send him a PM and ask him his thoughts.  that's what I did before I decided to buy the kits from buildafriend when he needed to sell his. 

 

[mulletchuck]

Has anyone thought about replacing the squash/boost pots with switches so recall is possible, along with matching settings between 2 units? 

 

[mulletchuck]

*bump*

 

[mulletchuck]

ok, so I have got my units to power on and pass audio. 

my unit doesn't compress, and the audio output is suuuuper loud if I crank up the boost knob past 25%, basically the same problems Sonic02 had.  turning up the squash knob introduces harmonics.

all op amps are getting +/-16V.  the transformers are wired correctly.  Red into 2.5, Blue into .31 etc.

I really wanna get these guys working and hear what they sound like, cuz i've been building them since June when i bought the kits off of Buildafriend.  :-(

Right now, no amount of turning of the knobs will get the EL panels to light up on either of the pair i've built.  When i crank up the boost knob, i can hear one of the transforms start to act like a speaker.  my 1073s behave that same way, btw.

 

[buildafriend]

do you own an oscilloscope?

if you made a 51x/500 series card connector extender it might be a lot easier to probe around.

does anyone else in NYC have one who you are friends with that would allow you to compare test points?

 

[peter purpose]

Have you got the el panel in the right way round?

 

[mulletchuck]

What sort of AC Voltages should I expect on the In/Out/FB pins of all the opamps?  Zayance has been helping me go thru it, but i need those voltages to track down the problem. 

Zayance did say that he saw 24VAC or so on the non-ground pin of the EL Panel.    Can someone verify that?

I'm ready to throw this thing in the trash, it's such a headache!!!! 

 

[mulletchuck]

ok, some updates:

I rebuilt the opamps with the metal can transistors lifted off the PCB.  the EL Panels light up relative to the Squash knob's position :-D    The output level is just as hot as the SA3A I just built, so I know i'm getting enough boost. 

 

[mulletchuck]

So, i'm learning that even though the EL Panels that I bought shine Blue, and that one side of them is, IN FACT BLUE, it's the white side that shines blue.   

*proceeds to flip over El Panel* 

G*D F*CKING D*MMIT IT WORKS NOW!!!!


I get a range of about 20db of compression with the squash knob and 15-16 on the other.    does that sound about right?  I'm chalking the difference up to the LDRs i used, which I got bulk from a supplier for like 1.50 each.  Definitely not matched and with a VERY large variance of resistance among them.    Also, what's up with the output level of this compressor?  both this and the SA3A have a MASSIVE output.  like, with gain cranked all the way up, it's gotta be like +28db or somethin'.  Is that just how the LA3A is? 

Funny about the meters, even though the meters in my daw show the above mentioned amount of signal change, the meters only show 8db of GR.  Oh well, at least they are working!  Time to trim the knobs with the dremel! 

 

[mulletchuck]

Alright, got 'em racked up and somethin' weird happened.  the units, with nothing else in the rack, get about 20db of compression.  when I load up the rest of the modules, the compression changed to about 5-10db.  Not sure if it's the result of when I turned the rack from vertical (for calibration) to horizontal and somethin' shifted, or what.  But it was strange. 

anyway, if someone wants to feed a signal into the unit so it shows up as -6dbFS in the DAW and then crank up the Squash knob and see what level shows up in the daw, it'd be appreciated!    Like i said in an earlier post, my first tests resulted in about 15-20db of gain reduction on my daw faders. 

 

[maq3396]

Hello all

Just becoming interested/exposed to DIY equipment
Is there any chance of a reissue of this kit or anyone wanting to part with theirs?

Thanks
Mac

 

[Nelson]

Sorry if I post wrong or something. This is not only my first post on GroupDIY, it's my first post on any forum ever.

So...
Calculating my LED resistors... Using 2v 20mA LED's but I'm not sure what the source voltage is. Is it the full 16v? If so, I'd need an 820k resistor. I did find the schematic earlier in this thread but I did not see the LED's on it, so I don't know what is feeding them or if there are diode drops to account for, etc. Perhaps I am just blind. Can anyone tell me the voltage at the LED's?

 

[Nelson]

One more... what is the 3 pin header marked "TERM" for?