LA-4 Opto DIY

[Ptownkid]

Ok, I've read over this thread a few times now, and I don't understand why you went through the trouble of making the opto's instead of using the nsl32?

I know I must be missing something...

 

[Luny Tune]

I'm just a romantic, Ptownkid. That's the main reason.

And then to see if there IS a difference. Even a small one. And there is...and it is very small. I'd say that adjusting the LA-4 just right and to your liking is much more important than which opto you use.

(Well, I'm sure there are optos out there that wouldn't fit. I've tested only relevant ones.)

Also there are shops on the net and in real life who charge you ridiculous prices for the two LEDs and a pair of LDRs. About time we demystify these optos and end that trend. If someone's got the originals and want to maintain the look of them inside and out, just replace the broken opto(s) with a standard red LED and an NSL6910 LDR. And maybe it's just the LED that's dead. Solder out the LDR and run a signal through the machine and see if the LEDs start blinking. If it doesn't, just replace the LED. No need to pay $95 for replacements... (The LEDs are in series so they both light up or none of them do. Just replace the pair.)

 

[Ptownkid]

What is the original part number that costs $95?

BTW, excellent work man!!!

 

[solderspongebob]

Here's an idea for a neat container. Pull apart an electrolytic capacitor of suitable dimensions!

Prise open the end of the case with a small screwdriver and pull out the rubber stopper and capacitor roll (best wear some latex gloves whilst handling this).

Use the rubber stopper for the LDR, and drill two small holes in the end of the can. Heatshrink the legs of the LED and push them through the can holes. Then push the rubber stopper end back in and fold over the end of the casing.

Should look quite neat.

BTW, where did you find the DIY LA4-A project? I did a quick search, but came up with nothing.

 

[helterbelter]

or a TL starter in aluminum can. Maybe they'll be too big though.... (I don't know the dimensions of the opto).

 

[Luny Tune]

BTW, where did you find the DIY LA4-A project? I did a quick search, but came up with nothing.

I couldn't find it anywhere either so I made it, dude!! ;D hehehe

 

[Luny Tune]

What is the original part number that costs $95?

http://cgi.ebay.com/Complete-Electro-Optical-Attenuator-Kit-for-UREI-LA-4_W0QQitemZ280293642418QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item280293642418&_trksid=p3286.m20.l1116

 

[jrfred453]

I just installed two 2 NSL-6910s in a silver face LA 4 that I bought that was used as a parts unit. I'm slowly getting it back together. Anyway it sounds great with those optos and it wasn't hard on the wallet either. Thanks for the tips.

Now i just need to find a top and bottom cover.....

 

[mac]

Hey Luny Tune,
in that ebay listing they say "Please note that general stock LED’s should not be used in the LA-4 optical circuit."

any ideas what they might be referring to??

Cheers - and awesome work by the way!! 

 

[kazper]

Technically speaking it probably has to do with the light wavelength that LED emits and or if they have a diffusor or not.

But it's probably put there so the average joe would spend $100 on $8 worth of parts. Dave is a nice guy and honestly thats a fair price for all the effort put into having it all from a single source IMO. Especially if your up keeping a real deal machine and "don't want to mess with the value of the thing"

Back to Red LEd, they do vary and I'm sure that can effects just how the compressor does it's magic.

Red LED property's
Wavelength (nm)610 < λ < 760
Voltage (Vdc) 1.63 < ΔV < 2.03
Materials
Aluminium gallium arsenide (AlGaAs)
Gallium arsenide phosphide (GaAsP)
Aluminium gallium indium phosphide (AlGaInP)
Gallium(III) phosphide (GaP)

 

[Luny Tune]

I lean mostly towards Kazper's second point. They're blowing smoke up our butts.

I have just a couple of days ago been offered to borrow an original blackface for a couple of days and I promise to test them against eachother thoroughly!

I'm gonna test different opamps, optos and trannies and the whole adjustment procedure.

 

[mac]

Thanks Chaps...

They're blowing smoke up our butts.

LOL

I have just a couple of days ago been offered to borrow an original blackface for a couple of days and I promise to test them against eachother thoroughly!

I'm gonna test different opamps, optos and trannies and the whole adjustment procedure.

Look forward to this...

if they have a diffusor or not.

Any thoughts on the "science" to focusing or diffusing the LED's? I have noticed that different ones I have played with seem to have different focal lengths. Have you observed any difference in terms of light coverage over the LDR's?

mac