LA-4 Help Thread!

[substitute]

Nice one!  Sounds like your regulators are ok, they're only speced to step up or down the voltage by a little bit, meaning they want to see about 18v so they can spit out exactly 18v.  So if you're giving them 9v and they're stepping it up to 12v that seems normal. 

By the way substitute, I checked out your MILA. Looks pretty sweet! I haven't had a chance to check out your sound file yet, but I'll try in the next couple of days.

thank you, point to point stuff is really fun. 

 

[pedroplanet]

Here's an ugly sketch of the off-board wiring that i drew for myself. Maybe someone can make a better one....
NO guarantee that it's correct, but I´ve wired and tested my comp and it seems to work.
I haven't calibrated it though.

So CHECK with the SCHEMATIC. If someone finds an error, please let me know.

Link to the pdf: http://www.bitterend.se/LA4-Offboard-Wiring.pdf

does anybody knows if this is 100% correct??

 

[Rybow]

From what I can see while checking this against the schematic, it does seem correct. I am going to be wiring up my unit in the next couple of days using the drawing, and I'll let you know when I get that done. It certainly makes the off board wiring a boatload easier to understand.

 

[MrZpliff]

Mine works fine so it should be ok. i haven't had the time to make a decent frontpanel yet, so it's been on hold for a while.

 

[Rybow]

First of all, I owe a big thanks to a lot of you guys for all the help. Especially to Luny Tune, Helterbelter, Briomusic, Gar381, Substitute, MrZpliff (the drawing rules dude), and Matthew Jacobs for all the advice and patience you guys have given me. I owe you all a beer!
Luny Tune. Dude. I had never even heard of an LA 4 until being directed here from the Brewery. Thanks so much for sharing this project. I really enjoyed building it!

Yes. I have one channel completed, and yes, it F@*$ing works baby! Whose house? Ryan's house!  ;D
No fizz, no bang, no white smoke, no meter light. Yup, I still have to figure that one out. Took me 7 hours to finish the wiring today, and I got about 30 minutes to mess with it until I had to head to the day job. I haven't been able to adjust it yet, but I just want to make sure it would pass audio, and that there was no crazy hum or anything like that. No hum, and strong signal. 
I DI'ed a guitar to test it out, and this thing sounds spectacular! A-freakin-mazing! Since its not adjusted yet, the LA 4 was crushing my signal, pinning the GR meter all the way down on every ratio, and it still sounded freakin awesome. The distortion was there for sure, but I liked it, and I could get it relatively clean. Gave a really nice texture. The guitar sounded amped to me with some nice weight behind it. Absolutely gorgeous tone!
Thanks to everyone one last time. I'll post a couple pics and more details once I clean it up and adjust it. Can't wait to try it on Vocals!

 

[substitute]

Cheers!

 

[MrZpliff]

Nice to hear ! It was ten years since my first and only visit to Vancouver, so maybe it's time to over and have that beer

One GOLD-medal yesterday, cross country skiing, soon time for some hockey.
The Sedin-brothers will rule, I hope.

 

[Rybow]

Come by anytime. Ale or Stout? I've never been to Sweden before though, so maybe it's time for a vacation!

I hope the Sedin brothers are happy with silver. 

 

[Rybow]

Well its not good stuff today, but I am still happy with it. Here is where it stands:

#1- I measured the resistance on the LDR's. One of them is null until signal comes in, the other is constantly varying resistance. When I apply a signal to it, it just keeps jumping around. I think I'll have to replace that one.

#2- My threshold control is super sensitive. A 1 mm movement results in massive GR. I have yet to adjust it with a test tone though, so this may be cleared up when I get to that.

#3 The distortion that I was liking last night is getting a little ugly. I am getting the same situation as others where as soon as the signal hits the threshold, the distortion comes in. Are there any more clues as to which resistors should be 1/2 watt? I have everything below 470 as 1/2 watt right now.

Other than these small issues, I am digging this limiter! Once I get it all smoothed out, it should be awesome!

 

[Luny Tune]

Hi, and you're very welcome! ;D

Did you remember this from my assembly notes:
"Due to a design error which means that the sidechain circuit is not connected to ground on the
board itself, you must connect the two CCW positioned pins on the Threshold and Output
potentiometers with a piece of wire. This connects the sidechain to ground."

Without that connection you may get some rather erratic behaviour.

Distortion will behave as it's supposed to when the unit is adjusted properly.

PS: I have just gotten two original blackface LA-4 in for a recap job. This far I've tested it against my diy ones showing very very little difference if any at all taking into consideration that it's extremely difficult to set them up exactly alike. I would have NO problem whatsoever recording a song with the original comping a bass guitar hard and then later redo the second verse and chorus using a diy LA-4 and no one would ever be able to tell what was made with which one and where I had punched in and out.

There MAY BE a very slight difference in the attack time but I'm gonna get to the bottom of it by a bit of thorough lab testing, setting both versions up with test tones and measuring levels here and there, and then determine what happens where.

I will certainly post my findings here.

My latest experiment is to add a Lundahl input tranny and replace the TL074 in the sidechain with an MC33079. The tranny adds a kinda 1176 coloring to it and I'm not quite sure yet but the mc33079 appears to let it handle transients a little differntly....and I think I like it better. So far I'm sort of live testing it. I just put it in there and I'm letting reality show which version I'm chosing when working on actual mixes for clients. That's kinda how I chose if all or any other gear stays or goes in my setup.

I'll be sure to post what I think.

 

[Rybow]

Hey Luny! Great to hear your DIY LA 4 stacks up to the original, and those mods you are doing sound very interesting indeed! I may have to try them out when I get my second channel stuffed.

The sidechain ground is in place, but I believe I know whats happening. I think my LA 4 is locked at 20:1. When I left it, the ratio control does not affect GR, ratio trimmer doesn't seem to affect GR, the threshold issue described above, and the waveforms I recorded with it all point to a 20:1 ratio. The peaks of the waveforms were all exactly the same level except the odd transient that got through.

Need to shorten the wiring in a lot of places, so I'll take a look at the ratio control while I do that. I also think I may have wired my overload LED wrong. I was hitting it with massive signal, and it didn't blip once. I did fix my meter lamp though. Its shining brightly!

Oh the joys of DIY!

 

[goldenGeek]

I finally got around to stuff my 2 boards and I'm just done wiring up the first channel. A simple test revealed that my output and threshold pots are probaby wired wrong... when you say for instance ccw, do you mean ccw from the front or back of the pot? When I turn up the output the volume goes down and when I turn up the threshold the threshold goes up - is this supposed to be like this or did I mess it up (I'm not surprised if I did ) And it also seems like the ratio switch also is somewhat wrong, but I'm not sure. It seems like it's compressing the most when turned to position 1 (ccw) and the least at position 5 (cw). If I compare my Lorlins with the drawings earlier in this post it seems like my numbers goes the other way around, did I maybe get the wrong swithes? The meter switch on the other hand seems okay - ccw to cw: GR +4 +8... I don't have a good VU at the moment so I havent gotten around to real tests yet, I will go get one at my storage later today. Right now I'm using an old Roland VU from a PA120 mixer/amplifier. It gives an idea of what goes on, but it's probably totally wrong voltages.

Another thing: do you HAVE to have a VU hooked up? I usually just use the VUs to check if we're sort of in the right place and then use my ears to do the rest. I was thinking of putting just 1 VU in my dual/stereo box. Would that be okay, or does the circuit demand a VU? I was also thinking of making it switchable between the 2 channels.

On the wiring-drawings earlier in this post some of the wires were marked as shields, I've read that this can be leaved out but since I only had shielded wire at hand I thought I'd ask. For instance wire/point 11 is marked as shield, but where do you connect the other end?? Maybe a stupid question, but I'm still in training

Edit: I can't seem to find what values to use for LEDs... any hints?

 

[substitute]

do you mean ccw from the front or back of the pot?

usually folks mean from the front.

When I turn up the output the volume goes down and when I turn up the threshold the threshold goes up

just switch pins 1 & 3 on the pot.  Wiper is always the center or pin 2, but the others vary from manufacturers, so sometimes you just have to try it one way and if it doesn't work switch it.

On the wiring-drawings earlier in this post some of the wires were marked as shields, I've read that this can be leaved out but since I only had shielded wire at hand I thought I'd ask. For instance wire/point 11 is marked as shield, but where do you connect the other end??

only one end is supposed to connected, connecting both would create a ground loop.

As far as the VU's go, I guess whatever floats your boat.  I'm not really big on VU's either, they're expensive, the square holes are a pain to cut etc...

Maybe try calibrating using your multimeter, or DAW meters.

 

[Rybow]

Edit: I can't seem to find what values to use for LEDs... any hints?

I used a 2.2K 1/2W resistor for my power LED. Works great! I have been told you can use anything from 1K to 4K depending on how bright you want it. On my VU meter lamp, I used 2 330 ohm 1/2 watt resistors in parallel as current limiters. I don't think you ned anything on the overload LED's as those are set up to light when you level is too high.

I don't know if you need a VU meter hooked up, but if you use one VU meter for both circuits, you may not be able to get the GR meter tracking adjustment to work out on both channels.

Good luck!

 

[Rybow]

Well, here it is! I still need to clean up the wiring a little bit, but it is fully functional. Channel 2 is so transparent, you can't even see it!! 

I rewired all the controls except for the meter switch (it worked already). I had them hooked up with quick connectors before, but hardwired it this time around. I noticed lower noise and better performance, but my meter still seems a little sluggish on the decay. Not sure if that is just the 6910's decay. I still have a tiny bug in the ratio, but I'll get that sorted at some point. Can't wait to get channel 2 in there!

 

[Matthew Jacobs]

I still have a tiny bug in the ratio

You know position 1 is a soft knee and behaves completely different to the other positions right?

Just checking....

Nice build man!!!

J

 

[Rybow]

I still have a tiny bug in the ratio

You know position 1 is a soft knee and behaves completely different to the other positions right?

Just checking....

Nice build man!!!

J

Thanks Matthew! I hope to get the other channel done soon. Then it will look really great!

I know that 2:1 ratio is much different than the others. I haven't done too much experimenting with it yet, but it sure does suck down the gain. I was running through the calibration as best as I could, but my Ratio trimmer doesn't seem to work. I checked the trimmer, and it appears fine. The ratios do seem to impart a different sound after I rewired it. I think I'll swap out the IC just to see if that helps, and then I'll check the photocells. I am also going to run through calibration again.

This is my first hardware compressor, so I do need some time to get used to using it. I did some vocal recordings on it yesterday, and I loved how it sounded!

 

[Rybow]

I just thought I'd ask this before charging at my LA 4 with soldering iron in hand. Is it possible that 2 6910's can be too far out of spec from each other? I measured both with the LA 4 powered off. One was  around 74Kohms, and the other was around 104Kohms. I made absolutley sure that no light was leaking into them.

Thanks!

 

[3nity]

Does anyone knows a part number for the Trimmers on digikey?
I'm having a hardtime finding them in Digikey!!

Thanks.

 

[3nity]

Alirght i found those but they are 9mm not 10mm!!

Any thoughts?