LA-4 Help Thread!

[maxime]

very cool box!

just a quick question
are those meters good enough for the la-4?
http://be01.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=0220368

http://docs-europe.electrocomponents.com/webdocs/0add/0900766b80add73a.pdf

thanks for your help

Maxime

 

[Luny Tune]

They will all work. I use the smallest circular ones in my 1U dual LA-4.

 

[maxime]

thanks a lot
best

Maxime

 

[Matthew Jacobs]

Hi Everyone

It's me again.

My meters finally arrived from Canford today.

I've never had to install a meter before and was just wondering if I have to use a 3K6 resistor somehow attached to the meter? Does it go in series or in parallel across the meter? Do I even need to use it or is the LA4 circuitry designed so that the meter works without any resistor.

I am using the Sifam AL29WF. Can someone please tell me if I can hook it up directly as in Lunytune' diagram or do I need a resistor in series or parallel.

Many Thanks

J

 

[Luny Tune]

The circuit is designed for the meter. Note the 3K6 rsistor in the schematic in the output section.

@Maxime
I forgot to mention that you need 4 Germanium diodes to make a rectifier bridge for each of those meters. They have to be of the Germanium type to minimize voltage drop through them and you need the bridge to enable the meters to show VU.

 

[Matthew Jacobs]

Thanks Luny Tune for the quick reply.

OHHHH thanks what R46 is doing in the circuit....

Stupid me.... 

J

 

[maxime]

thanks luny tune for your help,

now I know that some VU meters are actually DC meters..
I found what I 'd call the cheapest vu meter:
It looks exactly as the RS components "anders electronics". it's probably the same.
http://cgi.ebay.co.uk/1x-VU-Meter-55x48mm-FSD-200ua-45mm-dia-Hole-3933_W0QQitemZ120483400854QQcmdZViewItemQQptZUK_BOI_Electrical_Components_Supplies_ET?hash=item1c0d5ecc96

happy diy

Maxime

 

[Rob Flinn]

I suspect that the meter you are looking at has no diode bridge, which means you will need to add one for it to work in the +4 & +8 modes.  You may also need to mess around with it in GR mode, because its sensitivity may not work if it's directly dropped into circuit.

 

[Luny Tune]

I forgot to mention that you need 4 Germanium diodes to make a rectifier bridge for each of those meters. They have to be of the Germanium type to minimize voltage drop through them and you need the bridge to enable the meters to show VU.

And GR mode is not a problem.

 

[maxime]

Thanks for the input. I 'll fiddle with it and and tell about it.
anyway the meter will be for GR only ..
best

Maxime

 

[Luny Tune]

The LA-IV.pdf has been updated.

The BOM now focuses on the diy way to make the optos and NSL 32 is mentioned as an optional replacements.

I've added tips and comments.

Oh and I removed the extra 47Ω from the BOM...

 

[mpc3000limited]

I dont know if this was asked before but what are the dimensions for the PCB?

 

[Luny Tune]

Euroboard. 100x160mm.

 

[Rybow]

Hey everyone,

Well, I am getting close to beginning assembly, and I have an IC question. I am really trying to buy as many parts locally as I can, but I can't seem to locate the TL 074CP in town. I can get the TL 074 CD, TL 074 CN, and TL 074 IN. Any of these workable? Or should I just order up the TL 074 CP.

Thanks!

 

[Luny Tune]

They're all TL074 chips and will work. Just make sure you don't order SMD parts and that the chips you get is 14 pin DIL (Dual In Line) ones. That is 7 pins on each side of the chip.

 

[Rybow]

Thanks for the info on those chips. I did a search and found about 10 different varieties of the same chip, but I shouldn't have any issues getting the right one. Alright, off tomorrow to pick up the rest of the parts and order transformers.

By the way, thanks for updating the PDF file in the first post Luny. Much appreciated!

 

[Rybow]

A stupid question. In the BOM the ceramics are listed as 1 MODUL or 2 MODUL. I have scoured the internet trying to find out what that means, and I have come up with nothing. Every time I type MODUL in, Google suggests that I change it to module. So, what does MODUL mean? Edit: Sorry, I found it earlier in the thread. 1 Modul = 2.54mm.

Thanks, and sorry if this is a really dumb question. I am putting together my order for Mouser, and I want to make sure that I order the right capacitors.

I have learned quite a bit about this stuff recently, but I have one other question that may also be dumb. The voltage rating on capacitors denotes the maximum voltage that can be put through it before damage incurs. However, is there any downside to having way too high of a voltage rating? Say putting a 500V capacitor where a 50V capacitor is needed? Thanks again!

 

[gyraf]

Downside would be the larger physical sizes of packages for higher-voltage devices. But if they fit the PCB, no problem.

Jakob E.

 

[briomusic]

AFAIK modul relates to the leg spacing of the ceramics:
1 modul = 2.5mm
2 modul = 5mm

 

[Gachet]

Hi Luny,

I've just finished the building and calibrating of a pair of those la 4 clones and they sound great even better than my original urei la 4 silverface...I believe it's because components are brand new...

I'm still having an issue when connecting the units in stereo mode.compession becomes huge and strange!!!
As I am writing I'm thinking at connecting the stock urei with my clones to find out witchone is wrong.

I can't do that right now because i'm away from the studio.

Another question is :
Can someone explain me the function of ic3b and ic3a and the expected behaviour , output polarities and voltages?

thanks for this project luny