LA-4 Help Thread!

[TwentyTrees]

Hi!

Where is R11 (2k2) (F.P.), on the 1.0 revision board? I can't find it!!

Jay x

If memory serves, I think the "FP" indicates "front panel" here, ie it's mounted off board - would that make sense in context?

 

[culteousness1]

If memory serves, I think the "FP" indicates "front panel" here, ie it's mounted off board - would that make sense in context?

That`s correct. Please follow the wiring guide in Luny Tune`s original docs.
IIRC, the resistor connects to some potentiometer lug.
Cheers,
Carsten

 

[JAY X]

Hi!

Ok, thank you!!

I was thinking to add a below/above threshold indicator circuit i will build, as from the THAT corp design note DN132. I think a good point to connect such circuit would the output of IC5b. pin7.

Jay x

 

[Rybow]

Nice to see there is still a little action on this project from time to time. It was my first build, and so the LA4 holds a special place in my heart.

If anyone needs the docs I have them somewhere.

Regarding the Vactrols, it does suck that the supposed replacements don’t come close. I have a VTL5C4/2 in one of my channels, but it won’t adjust to give different ratios. I was hoping to grab a couple more to see if they will work better, but I think I’ll try the NSL-6910 option instead

Edit: Here a link to the docs. Let me know if there are any issues downloading them
https://drive.google.com/drive/folders/1wySIYiBNXEwFG_VA3fnQx5r3V3KrtWl5?usp=share_link

 

[pedroplanet]

I finished my La4 13 years ago using Vactec VTL5C4/2.

I had no problems calibrating ratios, but the attack is med to slow and the release is so slow - not very useable, so i ended up not using my la4 as much as would like to.

Does anyone came with a conclusion for an ideal opto solution?


I also found some Clairex CLM 6000 here on my parts stock, any experice with those?

 

[VanGenz]

I am planning to finish a "stereo" (two) LA4 that has been "in the drawer" for a long time . I downloaded a "Front Panel Designer" file many years ago which is called "Front_Parametal_1U_LA4.fpd". Does anybody know which meter this panel is designed for? The pcb is the "Levelling Amplifier IV, Rev. 1.0 Project by Torben Lysholm and Rasmus Fris". In the part list AL-29 is specified but I dont think this front panel is for AL-29?

 

[gyraf]

..Torben's project was for a single LA4 - I don't think that frontpanel is from him

 

[VanGenz]

..Torben's project was for a single LA4 - I don't think that frontpanel is from him

I am not sure who made this. But I am making a "double" LA4, and this panel which is only 1U suits me well.

 

[HerbertR]

Hi, I Pm'd you with all my docs... I ve collected about the build I ve done about 2.5 years ago all infos I could find. NSL32 are a nice substitution, but not like real Vactrols....

 

[VanGenz]

I have "fast read" all 42 pages and think the meter I am wondering about is Sifam Retro Al-15.

 

[VanGenz]

Hi, I Pm'd you with all my docs... I ve collected about the build I ve done about 2.5 years ago all infos I could find. NSL32 are a nice substitution, but not like real Vactrols....

Did not receive an email...

 

[Csiszi34]

Hello everyone!

I want to start DIY and I'm very interested in the LA-4A. I would like to ask you if anyone has a PCB design that I could buy or an existing PCB? Thanks in advance everyone!

Hi, András

 

[Rob Flinn]

Hello everyone!

I want to start DIY and I'm very interested in the LA-4A. I would like to ask you if anyone has a PCB design that I could buy or an existing PCB? Thanks in advance everyone!

Hi, András

This project is quite old now (the first post in this thread is 15 years ago) & the boards haven't been available for years. Your best option will be to post a "wanted" in the black market & see if anybody has any of the pcb's they want to sell.

 

[Rybow]

I will say that if boards ever become available again I’d be down for some.

The documentation has the etch file in it. I do have the docs still if you need it. I’m too lazy for etching my own boards haha

Kind of funny that I got a notification for this. I literally just made up some new optos using the nsl-6910 to replace the VTL5C4/2 in one of my channels