LA-4 Help Thread!

[Luny Tune]

I see you found the right thread: http://www.groupdiy.com/index.php?topic=34012.msg419117#msg419117

But remember that the thread is not an order tread. Just a "feeler" from Gustav. You'll soon be able to order boards in Gustav's normal "shop":
http://www.groupdiy.com/index.php?topic=10776.0

 

[3nity]

Luny did you worked the on the pcb yet?
You said you probably do a better layout??
theres someone saying some hole pads are just to small??

Hoping to get mine!!!

Thanks.

 

[michal_k]

Hi,

did you use that schematic from manual you linked in the first post? Is an output trafo necessary?

 

[Luny Tune]

It does work without an output transformer. That's confirmed by a guy on our danish groupdiy forum. BUT I have no idea how that affects output impedance of the thing.

On the layout that Gustav is using this time I did make the holes for trimmers and the rectifier bridge bigger.

 

[Luny Tune]

We have just discovered an error in my adaptation!! Audio Ground is simply missing in the sidechain!!

This is easily corrected though by connecting the Threshold pot's CCW pin with the Output pot's CCW pin!

I haven't discovered any change in sound character after correcting this BUT when compressing REALLY hard it had a tendency of "jumping" as it was letting go of the signal and then grabbing on again... That's over after connecting Audio Ground to the side chain.

I will throw this in the documentation as soon as possible!

 

[mylesgm]

hi,
are there any boards left?

M

 

[Luny Tune]

I see you found the other thread.

Here's a suggestion. Read as a minimum the first post in the thread you're posting in. Then you won't ask questions like "Are there any left?" in a thread that is a feeler to see if anyone is interested in the boards.

You'll have to watch this thread http://www.groupdiy.com/index.php?topic=10776.0 for when the boards are actually up for sale.

Gustav's boards are really good quality boards so I can recommend his boards for other projects too when you dig into those.

Enjoy! The LA-4 is awesome. Check the first post in this thread when you're starting to assemble and get the pdf-files. (Wait until you need them to get the latest versions. I have a couple of corrections/additions that aren't included yet.)

 

[SIXTYNINER]

hi luny
then when pcb become ready foe "delivery"....
they will be fully updated?
cheers
6T9R

 

[Luny Tune]

With the boards that Gustav is selling now you'll still have to fix the missing Audio Ground, but holes for trimmers and the rectifier bridge are made bigger.

We've discovered that when using the NSL-32 opto you need to modify the circuit a bit. Instead of the 500Ω Ratio trimmer you should put in a 2K5Ω trimmer. I believe a 1K trimmer would be just fine, but I have only tested with a 2K5 trimmer and that works perfectly.

Alternatively, you can solder a 20K resistor in parallel with R13 (82K) and compensate that way instead. A guy on the danish groupdiy did that succesfully.

Other than that there are no "updates" necessary to have a true-to-the-original circuit.

 

[geoff004]

We've discovered that when using the NSL-32 opto you need to modify the circuit a bit. Instead of the 500Ω Ratio trimmer you should put in a 2K5Ω trimmer. I believe a 1K trimmer would be just fine, but I have only tested with a 2K5 trimmer and that works perfectly.

And all this time I though it was just me.

I finally swapped out the NSL-32 in my unit with the NSL-6910 + 10mm red LED and it sounds wonderfully amazing (superlative superlative).  No distortion even when smashing.
My suggestion is to use the NSL-32 for opto 2 and the 6910+LED for opto 1.
I also put a TLE-2074 in the IC1 position and it sounds so smooth.

 

[fucanay]

Should the resistors be 1/4 watt or 1/2 watt? I know the schematic calls for 1/2, but is that because that is all that was available or because it's needed?

Matt

 

[SIXTYNINER]

We've ............................................. with a 2K5 trimmer and that works perfectly.

And all this time I though it was just me.
I finally swapped out the NSL-32 in my unit with the NSL-6910 + 10mm red LED and it sounds wonderfully amazing (superlative superlative).  No distortion even when smashing.
My suggestion is to use the NSL-32 for opto 2 and the 6910+LED for opto 1.
I also put a TLE-2074 in the IC1 position and it sounds so smooth.

HEY
Any cool picture about?
6T9R

 

[Luny Tune]

Should the resistors be 1/4 watt or 1/2 watt?

I honestly don't know.

You can hear a difference between TL074 and TLE2074? They're ridiculously expensive here but apart from a change in slew rate I don't see how you can make use of it's better specs without increasing the supply voltage.

I've ordered a couple of MC33079 to try out.

 

[geoff004]

You can hear a difference between TL074 and TLE2074?

I seemed to think so - maybe it's just in my head.
they're only $4 from mouser.

For the LDR I took a tube of chapstick (original brand) and cut it in half (I needed 2).  The NSL-6910s fits right in to the cut end.  In the top poke 2 holes for the LED.  In the bottom drill out a hole for the other LED.  Wrap well with electrical tape.

I was a little quick to say no distortion.  I built 2 stereo units - ever so slightly different.  The 1 still lacks meters.  When I changed the LDR in that one we smashed up an acoustic guitar and it sounded fantastic.  Later on I got to my other unit.  It definitely sounds better, especially at lower compression ratios, but at higher ones the distortion is still there.  Also the meter doesn't seem to track very well with mismatched LDRs.  The first one is at a studio an hour from here - I'll try to get them side by side and figure out the differences.

 

[Luny Tune]

There's quite a bit of difference when it comes to calibrating the units with different optos in.

I'm also gonna build a dual version with my 6910/LED optos and I'm gonne test both the MC33079 and I've gotten some very very cheap transformers from Musikding (TM019, TM022) I'm gonna see if I can get something decent out of. Probably not but it'll be fun to try.

Oh, the TLE2074 is $37 in the only danish shop I could find it in!!! : Guess I could find it somewhere else where it would be cheaper...

 

[Di_Sousa]

With the boards that Gustav is selling now you'll still have to fix the missing Audio Ground, but holes for trimmers and the rectifier bridge are made bigger.

We've discovered that when using the NSL-32 opto you need to modify the circuit a bit. Instead of the 500Ω Ratio trimmer you should put in a 2K5Ω trimmer. I believe a 1K trimmer would be just fine, but I have only tested with a 2K5 trimmer and that works perfectly.

Alternatively, you can solder a 20K resistor in parallel with R13 (82K) and compensate that way instead. A guy on the danish groupdiy did that succesfully.

Other than that there are no "updates" necessary to have a true-to-the-original circuit.

Hi Luny congratulations for your work in making this project possible.
I think that the unused Opamps situation is also an important "update".
Don't know if you had the change to sort it out before Gustav made the boards.

thanks

Re: LA-4 Help Thread!
« Reply #29 on: May 02, 2009, 05:50:52 am »
Reply with quoteQuote
Looking at your PCB it looks like you have two opamps unused in TL074-2. You left the pins not connected to anything which can be a source for problems (unstable?). A good practice for unused opamps is to connect the non inverting input to ground and connect the inverting in to the output.

chrissugar
I'm talking about each opamp's output.
One opamp is pins 5,6,7 and another opamp is pins 8,9,10.
Pin 5 to ground, pin 6 connected to pin 7.
Pin 10 to ground, pin 9 connected to pin 8.

So basically I'll solder some nice bridges between 6 and 7 and 8 and 9, then jump 5 and 10 to pin 12 (which traces back to ground).
Thanks! (again, please let me know if I'm off the mark)

 

[Luny Tune]

It doesn't affect the sound or behaviour of the comp in any way, so apparently it's not THAT important.

It will be fixed at some point but as you quoted me for saying there are no updates necessary to have a true-to-the-original circuit.

 

[Di_Sousa]

Thanks a lot for clearing that out Luny.

I'm really interested in doing this project.
How do you say that your DIY unit's release time compares to the original unit?

is it similar to the release of the blackface model (faster) or a bit slower release time more towards the later units?

thanks

 

[Luny Tune]

When adjusted correctly I find it very hard to tell this one from blackface reference file I have.

I really believe that the main difference between the original units is the adjustment procedure. If I want my units to sound as identical as possible I REALLY have to be absolutely anal and keep the smallest margins possible when adjusting them. Then I can get very very similar results with every machine.

 

[Di_Sousa]

thats really nice,
it's not that I want to make a copy of a Blackface or whatever gurus say it's the best,
it's just I'm not too fond on really slow release times in compressors.
(besides the Shure Level Loc, where the slow release makes a nice effect on drums)