LA-4 Help Thread!

[geoff004]

I'm still having an issue when connecting the units in stereo mode.compession becomes huge and strange!!!

Make sure that you add a ground where it's missing (is it IC2?) - it's not in front of me, but I remember my unit doing the same thing until I added the ground.  Also the meters would act really strange.

 

[Rybow]

Thanks for all of your help guys. I don't plan to try and drop in a whole bunch of Mundorfs on the board, but I just wanted to make sure that going over voltage wasn't a problem. It is so awesome how everyone on this message board rules!

Now, may I steal a secret from someone? I originally planned on the NSL 32 route. Make it easy. I have now decided to DIY it with the 6910 instead. I know you just take the LED, point it at the LDR, wrap something around it, and presto Opto! I was wondering what some of you cool cats were using to couple your optos. Duct tape? The heads from action figures? or are there couplers that can be purchased?

 

[Luny Tune]

There's been suggestions about those plastic endings to metal pipes, I made small tubes myself from those small 4 hour candles in aluminum foil thingys and as you said you could simply wrap them in duct tape. The latter not being very service friendly though.

The suggestions can be found out here, either in this thread or in the thread I made when making the project at first.

 

[geoff004]

Now, may I steal a secret from someone? I originally planned on the NSL 32 route. Make it easy. I have now decided to DIY it with the 6910 instead. I know you just take the LED, point it at the LDR, wrap something around it, and presto Opto! I was wondering what some of you cool cats were using to couple your optos. Duct tape? The heads from action figures? or are there couplers that can be purchased?

The 6910s fit perfectly inside a tube of chapstick.  Pull out all the innards and cut the tube in half.  Save the top - put 2 holes in it for the leads for the 6910.  Then use 10mm LEDs.  Make sure your wrap it up tight - light gets through the plastic as it is, so use some heavy tape.
They're a little tricky to fit on to the PCB but it can be done with just some creative bending of the leads.

 

[Rybow]

Cool! Thanks for the suggestions on that one! I have some chapstick lying around, as well as a bunch of other crap that might work. I'll try out a bunch of stuff.

Just thought I'd do an edit here. I bought some trimmers, but I could only find 470ohm and 220kohm ones. I am hoping that because I used all metal film resistors, this should make up for the missing ohms. Unless the thing just won't calibrate. Trying to find a 2.2uF poly cap in this city that isn't enormous is proving to be impossible, so I have to go externally. Finally got those 4.99K resistors though!

I do have a question though. I am working with one of Gustav's excellent PCB's. Where the 100pf capacitor goes, there are 3 solder points instead of 2. What is the 3rd hole for? Should I just leave it open?

Thanks!

 

[Rybow]

Bumpity bump  ;D

 

[geoff004]

I do have a question though. I am working with one of Gustav's excellent PCB's. Where the 100pf capacitor goes, there are 3 solder points instead of 2. What is the 3rd hole for? Should I just leave it open?

I'm assuming this is what the bump's about.
I'm not looking at the PCB but (if it's what I think) those holes are usually there to accommodate different sized caps.
Just make sure your cap goes between the right 2 holes.

I think the 470ohm trimmer will be ok - the 220ks are probably going to be difficult to get in to the sweet spot.  Again I'm not looking and it's been about 6 months since I was in my LA4, so I can't remember which trimmer does what.
Can't you order parts?  I'll look and see what I've got around (see, that thread I started months back about asking for stuff might be useful yet) - I don't know your location, but maybe shipping isn't much from here to there.

 

[Rybow]

Thanks Geoff. Yes, that is what the bumps about. The different size caps thing makes sense, but it's the only capacitor on the board that has this option. This is why I am confused about it. A closer look has revealed that 2 of the holes a directly connected, so I guess thats what its for.

The trimmers are a worry for me. Looking at the schematic, which I am not very good at reading just yet, the 470 ohms I have are for the ratio, common mode adjust and zero adjust, while the 220K is in the GR meter tracking position. I guess it will all come down to how tight the tolerance of all my parts is. I actually may have a 300k lying around, so it might be better if I threw that in instead of the 220k?

I am almost done populating the board! Just waiting on some capacitors and the opto's to arrive from Allied. That 2.2uF poly is a tough one to find. I almost ended up putting a non polar electrolytic in there.

 

[pedroplanet]

does anybody knows if any of theese Meters would work on LA4?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350291639687&ssPageName=STRK:MEWAX:IT
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130338184438&ssPageName=STRK:MEWAX:IT
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=130338725839&ssPageName=STRK:MEWAX:IT
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=140353649532&ssPageName=STRK:MEWAX:IT
or
http://www.dealextreme.com/details.dx/sku.7071

 

[3nity]

theres a thread on the drawing board talking about similar inexpensive meters...i'd say they no good...
Me think this is better...

http://cgi.ebay.com/VU-meter-for-recording-audio-level-warm-back-light_W0QQitemZ220529770545QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item3358994031

 

[3nity]

i have 2 boards on its way...
Now can someone post better pix of their boards stuffed and racked?
please somebody?

 

[Rybow]

I think any VU meter works, but it needs to have a germanium diode bridge and needs to 0 adjust to a 3.6K resistor in the circuit. I was originally looking at a Sifam meter, but have since decided on the Hairball VU meter. Half the price with all the good times.

I would also love to see more completed project pictures. I am hoping to get mine all done within the next 3 weeks. Longer probably. I'll certainly post some pics, but I am still waiting for parts.

 

[benlindell]

Hey Guys, just wanted to double check I'm doing a few things right.

1. I just want to leave this in the Low range, I just connect 2 and 3 correct?

2. For the OEP Transformer, to wire it as 1:1 I do what I did in the image?

Thanks guys.

 

[gar381]

Hairball meters

Look and work GREAT !!

GARY

 

[Sredna]

... I was wondering what some of you cool cats were using to couple your optos. Duct tape? The heads from action figures? or are there couplers that can be purchased?

I used heat shrink tube with 10mm red LED and 6910, just check that the LDR snuggly
fits in the tube.

 

[Rybow]

Hairball meters

Look and work GREAT !!

GARY

Those meters do look great! I can't wait to get mine. Your unit looks awesome as well! You wouldn't happen to know the dimensions for the hairball meter do you? I am getting my case today, and I am planning everything out right now. I know the cut out dimension, but that's it. How did you do your cut outs?

 

[gar381]

http://hairballaudio.com/shop/product_info.php?cPath=25&products_id=40

Hole dim:  80mm x 37mm

Front Panel Express

GARY

 

[juanjovincenzo]

Hi guys!!!

Maybe someone use 2x15V DC Supply in the LA-4???

Regards
Juanjo..

 

[gar381]

Juanjo

That is what I used.. Works fine.

GARY

 

[juanjovincenzo]

Thanks Gary

I will try

Regards
Juanjo