LA-4 Help Thread!

[benlindell]

Good call, just printed it out and the scales aren't long enough, I think I designed it for 270 for some reason, the rest of the panels I've done have been but this one I guess I forgot to change. I also tested the ratio scale and it works fine for lorlins.

 

[benlindell]

The image and files have been updated

AI File:http://twin-x.com/groupdiy/albums/userpics/LA-4_Front_Design_ai.zip

 

[Luny Tune]

"Ratio", "Output" and "Link" are not centered relative to their corresponding holes. Neither is "Lindell Audio" and "Dual LA-4". "Lindell Audio" looks good where it is though!

 

[Rob Flinn]

Seems a little odd to put in a 20V transformer to feed circuitry that has a 18V limit. I can't say what may have burnt in the process.

The 7818 datasheet states that it will regulate anything from 21 -35v down to 18v. Since the rectified 20v ( x1.41 ) when smoothed will be about 28v this is well within spec so long as it's not getting too hot, or you are trying to draw to much current.  It is true that the more voltage you are dropping across the regulator the less it's current capability, but you are probably going to be alright with an La4a board.  Obviously it is less wasteful of power if you had a lower voltage feeding the regulator.

 

[benlindell]

Hey guys. Got the replacement parts in today and the channel is working, not burning. I changed the 15ohm resistors, and the bd139 and bd140 there and also put in a edcor 600:600 transformer. It's compressing and sounding fine. the only problem I'm having is the meter works fine on +4 but on GR it just hangs at -15 and reacts as it compresses. I've messed with the 0 adjust and the tracking and the highest I can get it is -15db. Any ideas? like I said for +4 it's working perfectly.

Also I'm wondering if it was my OEP transformer doing something weird. I had it wired for 1:1, did I do it right? I had + -> S1, S2 -> F1, - ->F2 on the primary and + -> S1 and S2, - -> F1 and F2

 

[Matthew Jacobs]

the only problem I'm having is the meter works fine on +4 but on GR it just hangs at -15 and reacts as it compresses. I've messed with the 0 adjust and the tracking and the highest I can get it is -15db. Any ideas? like I said for +4 it's working perfectly.

Which opto are you using? I tried to read your previous posts to find out. Is it the NSL-32? if so have you adjusted R13 or the trimmer?
Other things to check are the resistor values and voltages around IC4.

Also I'm wondering if it was my OEP transformer doing something weird. I had it wired for 1:1, did I do it right? I had + -> S1, S2 -> F1, - ->F2 on the primary and + -> S1 and S2, - -> F1 and F2

I used OEP transformer in my build. When I first installed them I was getting an extremely low level and distorted output. I can't remember what I did, but I messed around with the way I had them wired up until it worked.

J

 

[Luny Tune]

Seems a little odd to put in a 20V transformer to feed circuitry that has a 18V limit. I can't say what may have burnt in the process.

The 7818 datasheet states that it will regulate anything from 21 -35v down to 18v.

You're right. Sorry! My bad.

 

[benlindell]

I'm using the NSL-32, I've been tweaking all the trimmers and the only one that seems to do anything is the 500ohm that's in the middle, next to the 250k, which by the schematic is the zero-adjust. all the rest have no effect on the meter.

 

[Matthew Jacobs]

I'm using the NSL-32, I've been tweaking all the trimmers and the only one that seems to do anything is the 500ohm that's in the middle, next to the 250k, which by the schematic is the zero-adjust. all the rest have no effect on the meter.

I just measured the voltage of my GR signal unloaded and I'm getting a range from 0.9V to 1.87V. (Forgot to mess with the tracking pot)

I hope this helps you trouble shoot your unit.

J

 

[Piotr]

Hi !

For my stereo unit pictured a little earlier in the thread, I've followed the original manual's calibration procedure. Everything is explained in detail, not the way manuals are made anymore... The only thing is the order of the calibration procedure which I'm not completely sure about. I've tried a logical order which seems to be the way to go.

I've started by adjusting the mechanical "O" of the Sifam Vus I'm using, as stated in the manual and then the "O VU" in GR position. I then calibrated the ratio trim so that my next calibrations were exact. I then proceeded with all calibrations that I repeated twice, both because it was fun to do and to double check...

A good idea is to use a DAW (I'm using Pro Tools) with a good metering system. I've used RN Digital's Level Meter. It's also a good idea to mesure input/output signals in detail with a multimeter reading RMS, so that you can double check on the level that's comming in/out (O dBu for example should read 0,774 V rms).

Here are a couple of usefull links:

http://www.rane.com/note169.html
http://www.sengpielaudio.com/calculator-db-volt.htm
http://www.gearslutz.com/board/mastering-forum/387136-i-need-correct-rms-meter.html

 

[juanjovincenzo]

Hi guys
I found three series of Silonex NSL32: NSL32, NSL32 SR2 & NSL32 SR3. What is the best NSL32 to use with LA-4???? or don´t feel the sound diferences between those??.

http://www.alliedelec.com/Images/Products/Datasheets/BM/SILONEX_INC/SILONEX-INC_ACTIVES-AND-PASSIVES_6995014.PDF
http://www.alliedelec.com/Images/Products/Datasheets/BM/SILONEX_INC/SILONEX-INC_ACTIVES-AND-PASSIVES_6993010.PDF
http://www.alliedelec.com/Images/Products/Datasheets/BM/SILONEX_INC/SILONEX-INC_ACTIVES-AND-PASSIVES_6993012.PDF

So I get some NSL32serie for my LA4 and KROC compressor, but I want the best sound.
I will try with the NSL6910 and the red led too, but I want to know what is the best optocoupler NSL32 to choose.

Thanks a lot
regards
Juanjo

 

[Luny Tune]

Hey Guys, just wanted to double check I'm doing a few things right.

1. I just want to leave this in the Low range, I just connect 2 and 3 correct?

2. For the OEP Transformer, to wire it as 1:1 I do what I did in the image?

Don't think you ever got an answer to this, did you?

1. Well, that depends...what do you mean by Low Range? I think the label on this switch is confusing. Once the switch is there you quickly learn what it does in which position. But to decide beforehand you must think of the switch as one that accommodates for level of the input signal. If the signal is high enough to overload the circuit, put it in "High" position. If the signal is too low for you to work with, put it in the "Low" position.

Now, for a constant "Low" position, just connect 2 and 3. For a constant "High" position just don't connect anything to 2 and 3.

2. I've connected the OEP A262A2E like this. The attatched picture is made from yours and is a bottom view. A is the tranny's original Primary side and B is the Secondary side. I use it backwards:

"To Transformer +" to B1
"To Transformer -" to B4
B1+2 is shorted
B3+4 is shorted

A4 to "From Transformer +"
A1 to "From Transformer -"
A2+3 is shorted.

Screen pin is connected to ground.

 

[benlindell]

Still having meter problems. I measured the voltages and am just getting a max of .2V. I tried putting a 22k across the 82k and it had no effect. I'm using the NSL32 and a sifam AL29. Any ideas what it may be?

 

[benlindell]

Does it matter at all that I didn't use sheilded cabling? I have pads 11, 15, and 9 with no connections.

Also I should note that it was showing zero when I was having power problems earlier, I have now replaced all BD139s and BD140 and also the TL074s. still not workin

 

[craigmorris74]

I've got a couple of transformers out of a Urei graphic EQ, and wondered if they would be suitable for this project.  They are 12614's. 

Thanks,
Craig

 

[Rybow]

Love the layout Ben! Looks very cool. How are you planing on implementing it? Are you doing all the cut outs yourself? Silkscreen on the front panel? I can't wait to check out a picture when its all done.

Big thanks to Helterbelter for finding linking me to the OEP a262a2c. Just got it in the mail a couple days ago. I just need the meter to arrive, and then I can start final assembly.

Another thanks to chapstick, and my sincere apologies for hacking up all the ones in my house. They are going to a better place.

 

[helterbelter]

I just need the meter to arrive, and then I can start final assembly.

[thumbs up icon !!!]
;D

 

[Rybow]

Well, went to the post office to pick up a package today, and it was my Hairball meter!!! 

I only ordered it last week, and had it sent regular mail. I thought it would take forever. What an awesome day!  ;D

No more typing, time to get to work.

 

[Matthew Jacobs]

Does it matter at all that I didn't use sheilded cabling? I have pads 11, 15, and 9 with no connections.

Also I should note that it was showing zero when I was having power problems earlier, I have now replaced all BD139s and BD140 and also the TL074s. still not workin

No it shouldn't. I didn't use shielded cables and my unit works fine.

So from what I understand, your unit compresses and passes audio. Your meter works fine for +4 but sits at -15 in GR mode.

As you mentioned you are only getting .2V (I get 1.87V max on mine) it seams like you don't have enough current going to your meter for the needle to rest at 0dB.

I think you need to check your components around IC4, the op-amp that drives the meter. So R48, R49, R50, R51, R52. If you got any of these resistors wrong by accident, your current feeding your meter may be affected.

Would you like me to measure some of the voltages around this IC on my unit for you to compare yours too?

Let me know.

J

 

[benlindell]

ha, yes, i relooked at those resistors and it appears there's a 82k instead of 8.2k, not giving the opamp enough power, probably causing the problem, I'll get that replaced tomorrow and write back.

Looking further, I seem to have placed a 8.2k instead of 82k as well