LA-4 Help Thread!

[briomusic]

Hi all,

I am just ordering parts for this project and have a few questions:

BD139/140: there seem to be to versions, BD139-10 has B(gain, I suppose?)of 60-160 and the BD139-16 B:100-250. Same thing goes for the BD140. Does it matter and which one is preferrable?

Lorlin 2*6: are these supposed to be shorting or non-shorting?

That's all for now, thanks for any help!

 

[Luny Tune]

Doesn't matter which BD139/140 pair you go with.

The switches should be of the shorting/make before break type preferably. Haven't tried the other type myself but make-before-break ensures that it doesn't lose it's "grip" while switching...

 

[geoff004]

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?

I went through my build and replaced all 1/4 watters with 1/2 watt resistors - the distortion that was bothering me is finally gone.
With the other unit I built I used more 1/2 watt resistors from the start (I just used what I already had on hand).  My guess is that you could use some 1/4s, but I couldn't tell you which ones.
It seem that the best bet for the compressor to work as it should from the start is to just use 1/2 watt resistors all though it.

Frankly I feel like a moron for not paying more attention to the original schematic - this has been a good learning experience.
Thanks for the project Luny!

 

[kazper]

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

Good chance you would want  higher than 1/4W in the R43 and R45 positions.

 

[goldenGeek]

I`ve ordered a few of Gustavs PCBs for this project and I`m currently trying to order all the components so that I can start soldering as soon as the boards arrive   Anyway - the partlist says 1 Rectifier bridge round. I`m quite a newbie on this (I`ve only built an 1176 and racked a few mic pres previously), what do you mean by rectifier bridge round? I`m ordering most of my parts from Farnell - is anyone kind enough to put a link up here to the part that I need?

Edit: I guess what I should be asking is what values should be used, I found some components at Farnell that seems like the right stuff but they come in lots of different values. Is the case style RB-15 correct, and is 50V 1.5A okay?

Thanks for a great project and a great forum

 

[MrZpliff]

I`ve ordered a few of Gustavs PCBs for this project and I`m currently trying to order all the components so that I can start soldering as soon as the boards arrive   Anyway - the partlist says 1 Rectifier bridge round. I`m quite a newbie on this (I`ve only built an 1176 and racked a few mic pres previously), what do you mean by rectifier bridge round? I`m ordering most of my parts from Farnell - is anyone kind enough to put a link up here to the part that I need?

Edit: I guess what I should be asking is what values should be used, I found some components at Farnell that seems like the right stuff but they come in lots of different values. Is the case style RB-15 correct, and is 50V 1.5A okay?

Thanks for a great project and a great forum

I've ordered this one:
http://se.farnell.com/multicomp/am158/bridge-rectifier-1-5a-800v/dp/9381481

800V, better safe than sorry and not much difference in cost.

 

[goldenGeek]

I`ve ordered a few of Gustavs PCBs for this project and I`m currently trying to order all the components so that I can start soldering as soon as the boards arrive   Anyway - the partlist says 1 Rectifier bridge round. I`m quite a newbie on this (I`ve only built an 1176 and racked a few mic pres previously), what do you mean by rectifier bridge round? I`m ordering most of my parts from Farnell - is anyone kind enough to put a link up here to the part that I need?

Edit: I guess what I should be asking is what values should be used, I found some components at Farnell that seems like the right stuff but they come in lots of different values. Is the case style RB-15 correct, and is 50V 1.5A okay?

Thanks for a great project and a great forum

I've ordered this one:
http://se.farnell.com/multicomp/am158/bridge-rectifier-1-5a-800v/dp/9381481

800V, better safe than sorry and not much difference in cost.

Thanks

...but if you get up to 800V on the board I guess you`re in deep trouble anyway with other components?

 

[Luny Tune]

You won't be in trouble with a rectifier bridge that can take 800V.

 

[goldenGeek]

Ah, okay

I`m also wondering what the 1 MODUL and 2 MODUL on the ceramics mean...?

Edit:
Sorry for all the newbie questions, but I figure it`s best to ask than make big mistakes.
Another question has arised: Do I have to use a 2x18V transformer, or will the circuit tolerate and adjust 2x25V correctly?

 

[Luny Tune]

2x25 is too much I think. That has to do not with the rectifier but the regulators that must bring it down to the 18V rectified. The 2x25 may well be within the regulators' specs, but when 2x25 i rectified it becomes over 2x30V DC and I believe that's more than the regulators can handle.

On that note may I suggest that you put a couple of cooling plates on the regulators. The machine will work fine without but I think we're moving on the edge of what they will take and you can feel safer and probably prolong the life of both the regulators and the capacitors nearby by cooling the regulators down a bit.

Since designing the board for this I've learned that I should keep bigger distance between the regulators and the large capacitors because the heat from the regulators can/will speed up the drying out the capacitors that do happen over time anyway...

"Modul" refers to the space between the legs on the ceramic caps. You should be able to see it in the specs for the parts. 1 modul = 2,54 mm = 1/10 of an inch.

 

[goldenGeek]

2x25 is too much I think. That has to do not with the rectifier but the regulators that must bring it down to the 18V rectified. The 2x25 may well be within the regulators' specs, but when 2x25 i rectified it becomes over 2x30V DC and I believe that's more than the regulators can handle.

On that note may I suggest that you put a couple of cooling plates on the regulators. The machine will work fine without but I think we're moving on the edge of what they will take and you can feel safer and probably prolong the life of both the regulators and the capacitors nearby by cooling the regulators down a bit.

Since designing the board for this I've learned that I should keep bigger distance between the regulators and the large capacitors because the heat from the regulators can/will speed up the drying out the capacitors that do happen over time anyway...

"Modul" refers to the space between the legs on the ceramic caps. You should be able to see it in the specs for the parts. 1 modul = 2,54 mm = 1/10 of an inch.

Thanks

I guess I`ll buy a 2x18V then just to be on the safe side.

 

[SIXTYNINER]

hello
I'm working to
try to give some help ,also any help are wellcome....(when bom list info be complete i do a xls or pdf)
someone have parts code from farnell,digikey,mouser ?
about:
1 TOROID TRANSFORMER 2x18V/15VA------FARNELL:9531688 (thanks to goldengeek)
1 RECTIFIER BRIDGE ROUND-----------------FARNELL:7278462 (thanks to goldengeek)
2 DIODE 4003---------------------------------FARNELL:1700910
4 DIODE 1N4148------------------------------FARNELL:9843680
1 ZENER DIODE 10V/0.5W-------------------FARNELL:1467583 (thanks to goldengeek)
3 TL074CP OP-AMP QUAD BIFET LNOI 14P--FARNELL:1105902 ("temporary" wait confirm-by goldengeek)
2 STANDARD RED LED----------------------- ???
2 BD139 NPN TRANSISTOR-------------------FARNELL:1015770
1 BD140 PNP TRANSISTOR--------------------FARNELL:1574351
1 DC REGULATOR 18V/1.0A POS.TO220 ---- FARNELL:9756175 (thanks to goldengeek)
1 DC REGULATOR 18V/ 1A NEG.TO220 ----- FARNELL:1094235 (thanks to goldengeek)
3 RADIAL ELECTROLYTHIC 6.8μF/63V--------FARNELL:
3 RADIAL ELECTROLYTHIC 100μF/25V-------FARNELL:
2 RADIAL ELECTROLYTHIC 1000μF/50V------FARNELL:9451447
3 10 mm H TRIMMER 500 Ω----------------- ???
1 10 mm H TRIMMER 10 KΩ----------------- ???
1 10 mm H TRIMMER 250 KΩ---------------- ???
*
RESITORS : normal metal film ? 500mw (half watt) ?  ,  5% ? , 250volts? .
(as in original la4 skematic?)
3 1% 4.99KΩ RESISTOR----------FARNELL :9468722
4 1% 10.0KΩ RESISTOR----------FARNELL :1099988
*reordered by value:
2 15Ω RESISTOR
2 47Ω RESISTOR
1 330Ω RESISTOR
1 470Ω RESISTOR
1 1.0kΩ RESISTOR
1 2.2kΩ RESISTOR
2 3.3kΩ RESISTOR
3 3.6 KΩ RESISTOR
3 4.7kΩ RESISTOR
1 5.6kΩ RESISTOR
1 8.2kΩ RESISTOR
6 22kΩ RESISTOR
1 30kΩ RESISTOR
3 33kΩ RESISTOR
1 75 KΩ RESISTOR
1 82kΩ RESISTOR
2 100kΩ RESISTOR
2 1.0MΩ RESISTOR
*
*POLY CAP = POLYESTERE ? POLYPROPYLENE ?
4 POLY CAPACITOR 100nF/63V 5mm--------------------- ???
1 POLY CAPACITOR 220nF/63V 7.5mm------------------ ???
1 POLY CAPACITOR 2.2μF/50V 5mm-------------------- ???
*
1 CER. CAPACITOR 4.7 pF 1 MODUL-------------------- FARNELL:1138836 (wait confirm)
1 CER. CAPACITOR 18 pF 1 MODUL--------------------- FARNELL:1138843 (wait confirm)
1 CER. CAPACITOR 22 pF 1 MODUL--------------------- FARNELL:1138845 (wait confirm)
1 CER. CAPACITOR 100 pF 2 MODUL-------------------- FARNELL:1138854 (wait confirm)
2 CER. CAPACITOR 470 pF 2 MODUL---------------------FARNELL:1138863 (wait confirm)
2 POTENTIOMETER 10K LOG----------------------------- ???
2 LORLIN SWITCH 2x6----------------------------------- ???
1 POWER SWITCH---------------------------------------- ???
2 ON-OFF SWITCH (Input Range and Stereo Link)----- ???
1 IEC MAINS POWER INLET FUSED + FUSE (160 mA/Slo Blo is sufficient for dual version)-- ???
1 PHONO JACK FOR STEREO LINKING (Anything will do. Phono jack is used in the original)-- ???
1 XLR PANEL MALE -------------------------- Neutrik gold plated pins-----FARNELL:1390133
1 XLR PANEL FEMALE------------------------ Neutrik gold plated pins-----FARNELL:1390117
2 SILONEX NSL 32. (A standard red LED facing a NSL6910 photoresistor will do the trick)-- ???
1 OEP A262A2E / LUNDAHL LL5402 / CINEMAG CMOQ-2S AUDIO TRANSFORMER------------- ???
1 AL-29 METER OR EQUIVALENT------------------------------------------------------------------ ???
Misc. Knobs, meter light, spacers, nuts, bolts, wire and stuff...
.......

 

[goldenGeek]

Parts at Farnell:

18v regulators 9756175 and 1094235

Power transformer 9531688

Rectifier bridge 7278462

Zener diode 1467583

TL074 1105902 (I think this one should work)

 

[Luny Tune]

Regarding possible replacements for the TL074.

I've tested the MC33079 in the LA-4 and I prefer the TL074. Did a blind test and chose the TL074 over the MC33079 for this comp.

I can hear that the MC33079 is a really good opamp and after testing it in my console, which is full of TL074 chips, I've started to completely replace all TL074 with MC33079 chips in it.

The think is that where the MC33079 gives sort of a better "hole through", I simply like what the TL074 does for the sound when it's in a compressor where I'd like to get a little color and "mojo". I like my console's channels to have more "signal integrity" (don't know if that's the right term, but you know what Imean...) but even there I like what the TL074 does in the master section so I'd leave those in there if I were summing through the console and mixing back into the computer. I'm only monitoring through the master section though, so I've changed the opamps there too because I can trust what I hear better not having the coloration from the TL074 chips.
(It's a Soundtracs MIDI PC 24/8/2 desk.)

Anyways, I find the TL074 perfect for the LA-4.

 

[SIXTYNINER]

Regarding possible replacements for the TL074.
........
I can hear that the MC33079 is a really good opamp and after testing it in my console, which is full of TL074 chips, I've started to completely replace all TL074 with MC33079 chips in it.
.............

hey LUNY
please wich is your console , soundtracs ?
thanks 6T9R

 

[Luny Tune]

(It's a Soundtracs MIDI PC 24/8/2 desk.)

http://www.tunetown.dk/Tune_Town_in_English/Home.html

 

[Luny Tune]

Yeah, it works and sounds great. Can't get the MIDI mute stuff to work though. A may be going about it the wrong way but it doesn't matter too much. I'm just using the channels for inserting them and outboard stuff in Logic. I just monitor through channels 1-2 and the mastersection.

Codes for the parts list... Well, the list on our danish sister site is for a shop here in Denmark but they ship internationally as well so that could maybe be helpful. I'm sure you'd prefer a shop closer to home and it shouldn't be difficult at all to find the parts.

 

[Luny Tune]

Our site is down at the moment but as soon as it's up again (which SHOULD be a matter of hours....maybe tomorrow) I'll notify you.

 

[SIXTYNINER]

OK THANKS

 

[smallbutfine]

Hi Luny,
thanks for the tip on 33079 i your Soundtracs console. I did not try this one out yet, but will check that in my megas mix.. I just disassembed it again two weeks ago. Worth a try.

Nice someone brought the LA 4 back to the board. Seems a much simpler build than many others. I remember Kev built one ages ago and recommended it strongly for diy, I guess he used LED+LDR in a shrink tube...

Kind regards,
Martin