LA-4 Help Thread!

[ilfungo]

I just finished my first LA4 (NSL SILONEX 32)
sounds good with a bit of saturation with high compression ratios,it's normal?
I want to try another LA4 with Vactrol VTL5C4 / 2
I found this on Farnell (http://it.farnell.com/eg-g-vactec/vtl5c4-2/optocoupler-single-channel/dp/1652521) may work?
this model will need 2 x 1 compressor?
THANKS

 

[ilfungo]

??? ??? ???
Help!!!
how to connect VTL5C4 / 2?
I made several tests but I can not make it work

 

[Luny Tune]

Forgive me the crude drawing.

Red triangles = Not connected.

 

[Luny Tune]

I found a solution to the added noise in High position. I've added the tip below to the documentation in the first post of course.

The wires for the High - Low switch (S1, wiring points 2 and 3) tend to pick up noise when in High position.

The added noise occurs because of the long wires from the wiring points and that they just pick up noise when they’re disconnected in High position. (In the original each wire is no more than an inch long. This is not really possible to recreate with the placement of the wiring points on out PCB.)



Fix it by removing the 30 KΩ resistor just next to wiring point 3 and mount it on the outer pins on the switch (S1). This requires of course that you’re using a 3pole/2pos switch.

Audio goes through these wires so keep them short still.

 

[Rybow]

Wow Ben! Your LA 4 looks amazing! I see you mounted your PCB's side by side. Do you get any noise from the toroid? Which OT did you use?

I am still hunting for a transformer for my second channel. I was considering the EA 2503 from classic API, a Hammond equivalent, or a Cinemag. I tried emailing Cinemag a month ago, but I have yet to get a response. Where/how do you get these?

3nity- Did you ever use the Vactec VTL5C1? I remember you mentioning them in the first page. I did order a couple along with some NSL 32's to try. I was thinking of experimenting with being able to switch between the two. I was hoping to use a 2 deck 4p2t rotary switch for the optos, and then some sort of a switchable bias resistor or something. Could work. Could fail.

 

[Luny Tune]

I think it's a lot of effort for no particular difference in sound. In my experiments there was very little difference if any at all. The slightest difference in adjustment makes a lot more difference. I found the difference to be so minute that I wouldn't bother to build the optos myself if it wasn't for just that nerdy satisfaction; Building them myself.

You should at least experiment before going through the hassle of incorporating both. Who knows, you may very well be able to hear stuff I'm not.

 

[ilfungo]

Thanks Luny! ;D
I just finished the second LA4 and plays wonderfully with vactrol
problems of distortion that I had with SILONEX NSL32, have disappeared ...
I have two silver face Urei LA4 and I must say that your project with vactrol sounds very close to them ....
Luny Thank you for this wonderful PROJECT!

 

[pedroplanet]

I'm about to finish my LA-4 using VTL5C4/2 optos.
Should I use the 20KΩ resistor in parallel 82KΩ (R13) ?

 

[benlindell]

Wow Ben! Your LA 4 looks amazing! I see you mounted your PCB's side by side. Do you get any noise from the toroid? Which OT did you use?

Thanks man, I'm not getting any noise issues luckily but I arranged the mess of wires so the wires going to the pots are as far away from the toroidal as possible. I used edcor trannies.

 

[Luny Tune]

@pedroplanet
I don't think so, as it seems to be the direct replacement for the original optos without any other modifications, but maybe. No harm in trying to get it to work as is...

 

[ilfungo]

Sorry for the stupid question
could fit a layout like this?
I would like to find a way to have less problems possible?
thanks

 

[shot]

Forgive me the crude drawing.

Red triangles = Not connected.

Hm, I'm a bit confused... you would need two silonex NSL32's but according to your drawing in earlier post, if using VTL5C4/2 only one opto would do the job? What am I missing here?
???

 

[Luny Tune]

You're missing that the Vactrol is a dual opto that'll do the job of two single optos. (It contains one LED and two LDR. Shown in the attached drawing, actually... )

 

[Luny Tune]

Sorry for the stupid question
could fit a layout like this?
I would like to find a way to have less problems possible?
thanks

In theory, yes. I'm not sure if it's a good idea to let one toroidal supply two supply circuits with power or not... Someone with more expertise in that area will have to pitch in...

But I do know that I have already prepared the PCB for letting one PCB supply the other.

See? Two outlets!

 

[ilfungo]

Thanks Luny
I will try...

 

[Rybow]

I think it's a lot of effort for no particular difference in sound. In my experiments there was very little difference if any at all. The slightest difference in adjustment makes a lot more difference. I found the difference to be so minute that I wouldn't bother to build the optos myself if it wasn't for just that nerdy satisfaction; Building them myself.

You should at least experiment before going through the hassle of incorporating both. Who knows, you may very well be able to hear stuff I'm not.

Thanks Luny. The more I think about it, the more I realize that it will be a pain in the butt. I'll just try both out and see what I like. The 5C1's have a very fast decay, so I am not sure how well they will work.

I'll look into those edcor trannies Ben. Thanks for the info!

 

[ilfungo]

Hello Luny
and thanks for your help,
I use 2X18 V DC to power 4 led to the VU meter (modutec) ...
What resistance should I use to power LEDs  with 18V?
Thanks and sorry for my english....

 

[Luny Tune]

This is my best advice: http://ledcalc.com/

I can only inform you about the original design and my alterations. The rest is DIY, if you catch my drift. I simply don't know enough about it to educate anyone.

 

[gar381]

Hey ilfungo..

From Insomniaclown

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.

Maybe this will help



GARY

 

[Rybow]

Just a note on the above, I ended up with a 180 ohm 2 watt resistor on the 12V lamp in my meter. The 2 1/2 watt resistors were getting very hot.

All credit from the advice above goes to Gary, He was the one that educated me on the process.