TwentyTrees
Well-known member
If memory serves, I think the "FP" indicates "front panel" here, ie it's mounted off board - would that make sense in context?
LA-4 Help Thread!
- Thread starter Luny Tune
- Start date
Help Support GroupDIY Audio Forum:
culteousness1
Well-known member
That`s correct. Please follow the wiring guide in Luny Tune`s original docs.
IIRC, the resistor connects to some potentiometer lug.
Cheers,
Carsten
Rybow
Well-known member
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
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
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pedroplanet
Well-known member
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?
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?
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?
Attachments
![Soldering Iron Kit, 120W LED Digital Advanced Solder Iron Soldering Gun kit, 110V Welding Tools, Smart Temperature Control [356℉-932℉], Extra 5pcs Tips, Auto Sleep, Temp Calibration, Orange](https://m.media-amazon.com/images/I/51sFKu9SdeL._SL500_.jpg)
..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.
Did not receive an email...
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.
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Rybow
Well-known member
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
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
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LA 4 revisited -- old thread, I know.
But the stereo clone unit has sat unused for quite some time, so I finally salvaged the Vactrols and put NSL32 into the circuit.
Using NSL32 requires some adjustment -- described somewhere above. Had traced resistances at 1mA, 2.5mA, 5mA, 7.5mA and 10mA to find closest opto pairs for L and R / GR and VU.
First impression is sounding good.
Calibration is a pita and not fully done yet, cos first I want to try adding a few things.
But the stereo clone unit has sat unused for quite some time, so I finally salvaged the Vactrols and put NSL32 into the circuit.
Using NSL32 requires some adjustment -- described somewhere above. Had traced resistances at 1mA, 2.5mA, 5mA, 7.5mA and 10mA to find closest opto pairs for L and R / GR and VU.
First impression is sounding good.
Calibration is a pita and not fully done yet, cos first I want to try adding a few things.
Ratio 1.5:1 -- or whatever
Not interested in clone personally. Rather need something that gets used. Limiter settings of 20:1 12:1, 8:1 and 4:1 see use. The soft 2:1 setting does not. Too much. So I added an extra ratio setting by splitting R33 in half.
1K is tacked in parallel onto R33 (1K) on underside of board. A 500R goes onto the rotary. This too is a soft setting but 'bites' much less. Maybe it's just the NSL32 being more aggressive. Either way.. ... Better even on rotary would be 4:1 (hard), 1.5:1 (soft), 2:1 (soft)...
Here's the schematics (no change)
Here's the added resistors
Not interested in clone personally. Rather need something that gets used. Limiter settings of 20:1 12:1, 8:1 and 4:1 see use. The soft 2:1 setting does not. Too much. So I added an extra ratio setting by splitting R33 in half.
1K is tacked in parallel onto R33 (1K) on underside of board. A 500R goes onto the rotary. This too is a soft setting but 'bites' much less. Maybe it's just the NSL32 being more aggressive. Either way.. ... Better even on rotary would be 4:1 (hard), 1.5:1 (soft), 2:1 (soft)...
Here's the schematics (no change)
Here's the added resistors
Stereo Link – variable mono
The stereo link as per schematics is ‘just’ a mono maker (L+R) feeding the SC, meaning when linked, the detectors can't 'see' anything stereo in the music and they 'feel' mono buildup.
To achieve a better balance between either a wonky stereo image (unlinked, Dual Mono) or instruments on pogo sticks (linked, “Single Mono”, i.e. two channels to mono into both SCs), I added a blend pot, actually a (guitar) pot with push-pull switch for easy dialing-in and quick AB'ing.
For virtually full channel separation (0.1dB), I measured more than 600K are needed -- too high for a sensible feel on any pot I tested. Finally settled on a measured 109K61 (A100K pot plus nearest 9K53 fixed). This yields from fully mono-linked on one side of the pot to almost separated channels (other end of pot). The pot switch then gives fully separated (classic Dual Mono). The leeway and effect of the pot naturally depends on the music material, but also on the THR and RAT setting.
Sorry for dirty scribbles. Thing on top left is meant to be a switch, not a cap.
The stereo link as per schematics is ‘just’ a mono maker (L+R) feeding the SC, meaning when linked, the detectors can't 'see' anything stereo in the music and they 'feel' mono buildup.
To achieve a better balance between either a wonky stereo image (unlinked, Dual Mono) or instruments on pogo sticks (linked, “Single Mono”, i.e. two channels to mono into both SCs), I added a blend pot, actually a (guitar) pot with push-pull switch for easy dialing-in and quick AB'ing.
For virtually full channel separation (0.1dB), I measured more than 600K are needed -- too high for a sensible feel on any pot I tested. Finally settled on a measured 109K61 (A100K pot plus nearest 9K53 fixed). This yields from fully mono-linked on one side of the pot to almost separated channels (other end of pot). The pot switch then gives fully separated (classic Dual Mono). The leeway and effect of the pot naturally depends on the music material, but also on the THR and RAT setting.
Sorry for dirty scribbles. Thing on top left is meant to be a switch, not a cap.
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Output pot actually calls for swapping out for rotary for easier set up. THR does not!
But too lazy right now. Instead, I slugged the output pots for unity gain at exactly 12 o'clock. Set and forget for now.
Hi/Lo input switch migrated to back of unit. That switch is a widow maker
Also dropped VU level switch. Don't need. I know what I feed into the unit. Meter now shows GR only.
But too lazy right now. Instead, I slugged the output pots for unity gain at exactly 12 o'clock. Set and forget for now.
Hi/Lo input switch migrated to back of unit. That switch is a widow maker
Also dropped VU level switch. Don't need. I know what I feed into the unit. Meter now shows GR only.
