D-LA2A Support Thread

[schrobbelbop]

IGS T4Bx http://www.igsaudio.com/t4bx

Compared some tubes:

12AY7's give this unit more richeness in mid and mid/lows
12AX7's are really clean.

25K pot mod is very helpfull for better gain control

 

[Deepdark]

didn't knew those cells. I use Kenetek ones.

 

[schrobbelbop]

when i play music true it and make a transfer meas it shows its like cutting highs max 3 db's more then lows. with its cross point around 500, why doesnt it show up with pink noise running true it? i think it has to do with combination of cell and filter network.


Also calibrated gain reduction on the meters that was off with its 33K standard resistor.

 

[Chad]

Hey there. I'm really close to finishing my D-la2a, just having some trouble getting the sucker to compress
It passes audio and when I take the cover off the T4B and shine a light on it I get compression and meter ducking. At Pin 3 I'm only getting between .1v and .7v AC so it's probably not enough to set the lights off in the T4B I'm guessing, apparently supposed to be getting around 100v??? . I'm getting around 20v AC before C11 (10nf).  Any ideas why there is not enough signal coming to Pin 3? All my DC voltages seem to be good at the test points. Thanks

 

[schrobbelbop]

Hi chad, i had the same on one channel. it was the socket not connecting good enough to my cell's pinns. so check your soldering and tighten the socket pins. and measure on the pcb 3/4 pins. i sqeeuzed the socket's pinns a bit together with some pliers and all was fine!

 

[Chad]

Ok I sorted my problem and my D-la2a is alive!
It was my stereo link cables, when plugged into there sockets they were inhibiting signal getting to Pin3 on the opto cell, after days of troubleshooting I unplugged them and suddenly got signal on the Pin. Cant be bothered figuring out the stereo link problem so will just run in dual mono mode! Stoked, hope this helps someone.

 

[schrobbelbop]

Nice! enjoy. and it sounds like you're shorting something with your stereo link cabling.

 

[schrobbelbop]

Sidechain trimmer mod:

Removed the R137 trimmer. i wanted to have a switchable sidechain HPF on the frontpanel.
But look at the curves when i used resistors. Since it is somekinda RC filter i started experimenting
with some caps instead of resistors. and that gave me more usefull sidechain response.

Now i have  a 4,7nf and 10nf or Jumpered (flat response) and gives me the following compression curves:



Also swap around some tubes between channels to match L/R . it made my freq response in almost 0.2db's matched without having matched tubes.

 

[ENS Audio]

Hello, I have a question about which Edcor transformers to order for the dual LA2A compressor.  On the BOM it calls for

Input WSM600/15K
Output WSM15K/600

But over at Don Audio they recommend the

Input  XSM600/10K
Output  XSM10K/600

Could anyone clarify which set I should purchase for the Silent Arts dual LA2A?

Thanks.

 

[JW]

Anybody know if I can use a Yamaha PM1000 console meter in the DLA2A? I successfully did it with a G1176. I don't think there is anything special about the LA2A meter, but . . . . I thought I'd ask before I go cutting my front panel for it. Here is a link to Hairball talking about using it in the 1176 (closest thing to relevant I can think of to link) http://groupdiy.com/index.php?topic=26375.0

But anyway, I don't know the make of the meter. It doesn't say. The above link has pictures. ?????

 

[QNote]

Hi all!

I'm currently about finished with a D-LA2A build and have been video-journaling some of the process.  Here's a link to the first video introducing the build.  There are three videos in the series currently posted...

https://www.youtube.com/watch?v=nbZ67QpT-nQ

As of this past weekend, the unit is up and running.  No problems, as of yet, other than one of my new tubes was bad out of the box.  Swapped it out and all good.  I'm about to post video number four (4)  this week illustrating the calibration/tracking of the VU/GR meter by the proper selection of R125/R225.  There will be six or seven videos in all, with the last video showing the unit in use in the studio.

I may share some photos later.  Enjoy the videos and let me know your thoughts!

Prentice

The build is also journaled here...
https://www.facebook.com/TyndallElectronics/

 

[fragletrollet]

Cool videoblog!

 

[Floti]

Hi! Just a stupid and fast question.. Was meaning to change the neon lamp for a diode, but the scheme keeps me confused about that. Does the zener go direct to ground? See attached picture! Thanks!

 

[[silent:arts]]

Does the zener go direct to ground? See attached picture!

Yes

 

[Floti]

Thanks!

 

[MicDaddy]

Some turd is asking $4995 USD for one of these claiming that "the designer" made it...    :  I got booted from the group over stating the price was crazy high.

 

[QNote]

I've posted a video illustrating how to select the proper values of R125/R225, as well as covering a few other related topics.

https://www.youtube.com/watch?v=M-lXJtmLrd8

More videos to come!  Subscribe if you're interested.

 

[QNote]

Thought I would post a few pictures of the completed unit.  And, before the questions come, the unit does not have "switchable" transformer bypass or T4B fast/slow switching...yet. 

Here's the front view...

And, an inside view...

And, another...

And, another...

And, finally...

 

[QNote]

when i play music true it and make a transfer meas it shows its like cutting highs max 3 db's more then lows. with its cross point around 500, why doesnt it show up with pink noise running true it? i think it has to do with combination of cell and filter network.

I have found, in my case, that using my grounded shield wire to the limit/comp switch for channel 2 was causing a slight roll-off of the high frequencies.  If I ungrounded the shield, everything was okay, but there was some hum and buzz.  I've temporarily left it unplugged until I try another type of shielded mic cable.

Also, the frequency response of the unit is not flat during compression...only with no compression.  The T4 module reacts differently at different frequencies.

Also calibrated gain reduction on the meters that was off with its 33K standard resistor.

My channel one ended up using an 18K and channel two used a 12.2K. 

 

[saxmonster]

Cool videos Prentice,

Gonna have to go back and recheck my calibrations on this beast and see if the are up to spec.  Know a lot more now than I did before and your videos are a nice refresher, hahahah,  Might have to up grade from edcore to sowters.  Might also put on a bigger heat sink and move it to the side of the case like you did.  Also how will you compensate for heat and the meters not staying at zero once the unit warms up?  That is so annoying to me.

-Scott