LA3A 500 BUILD

I wouldn't waste my time with stereo link, personally.  ymmv, tho... 

mulletchuck said:

I wouldn't waste my time with stereo link, personally.  ymmv, tho... 

Click to expand...

I use stereo link all the time with mine  ;D

used this for the first time on Thursday on the lead vocals after a Empirical Labs DocDerr, which is a Distressor/1176 style comp - it's just amazing, smooth and consistent... Great clarity and it goes from crunch'y and pump'y to smooth and silk...

I didnt have a chance to use it one its own yet, but I have a feeling it would be great on bass or acoustic instruments...

was a fun build and a great kit - thanks so much Peter - I wish i had bought a pair of them...

KDE said:

mulletchuck said:

I wouldn't waste my time with stereo link, personally.  ymmv, tho... 

Click to expand...

I use stereo link all the time with mine  ;D

Click to expand...

i much prefer dual mono. 

and the Marconi knobs from Classic API fit and look awesome...

Did some testing last nite with the new compressor on my sax channel.

Here is my chain

DIY ELAM251 Microphone
EZ1073 Micpre
LA3A 500
MOTU MKII

into Digital Performer DAW for a touch of eq and verb.

-Scott

http://tiny.cc/1nsdbx

So I was working with the LA3A again tonight using it as a preamp with my DIY elam 251 apex mic.  Anyways I heard this squeal in the upper range when using it and then I unplugged the mic and it was still there.  Here is how I recreate it.

I have the LA3A on with it in COMP mode.  The meter is set to read GR but that doesn't effect the squeal.  I have the Boost up 3/4 of the way but that doesn't effort the squeal either just the volume of it. 

When I turn the squash knob up a little bit past half the squeal start and increases in pitch until the pot stops and sometimes at the point the squeal is gone.  Turn it back down and the squeal's pitch goes down.

Anyone know what it causing this?  Is it a bad pot?  Where should I start looking at?

Not sure how many DB it is but it is definitely in the background but annoying when I am monitoring recording my axe.


Let me know, thanks

Here is a link to a audio recording of it raised up with a limiter plugin just so you can hear it.

https://dl.dropboxusercontent.com/u/30010680/LA3A%20Noise.aif

that sounds like radio interference 
or OpAmp oscillation? 

I never had a problem with radio interference before.  I guess its oscillation,  I have turned R28 CW from fully CCW.  I turned it just a bit CW until the squeal stopped.  Is this the right thing to do?  Don't really know which way this trimmer should be turned.  I think fully CCW is flat which makes me wonder why turning it clocks wise stops the sound when it should be boosting the high end.  Oh well it is gone now and Ill just forget about it. 

I have also notice a bit of noise when I touch the metal knobs i bought,  since the knobs are metal and the pot shafts are metal i guess it picks up some interference / ground from me so I will probably swap out the pots with ones that have plastic shafts.

Hi mulletchuck, and anyone that might be able to clarify

Would be great if you'd be able to help clarify a few things regarding the BOM list and Mulletchuck's Mouser cart 'Customer Part #' order list.


Mouser Cust Part #

- 'R1,3,5,7,9,11,13,15' (10Kohms), are they R11 and R13?

- 'R2,4,6,8,10,12,14,16' (1Kohms), is it R15?

- What is 'PSU R17, 18'?

- With the placement of the 'Unmarked caps' on the PCB. Are they around and under the little PCB boards that we pin on?

- 'ComCat resistor' (820ohms) What's it for and where does it go on the PCB?

- Would it be possible for you to explain the 'Green LED resistor' and the 'Green LED',do they replace the 'RLEDx3' and '1 x LED' on the BOM list?

The BOM list also has 'RG1' which doesn't seem to be on the Mouser order list is it not needed?

david.uulf said:

Hi mulletchuck, and anyone that might be able to clarify

Would be great if you'd be able to help clarify a few things regarding the BOM list and Mulletchuck's Mouser cart 'Customer Part #' order list.


Mouser Cust Part #

- 'R1,3,5,7,9,11,13,15' (10Kohms), are they R11 and R13? Yes thats what I used for both r11 and r13

- 'R2,4,6,8,10,12,14,16' (1Kohms), is it R15? Yes thats what I used r15 only 1kohms

- What is 'PSU R17, 18'? This is for RG1

- With the placement of the 'Unmarked caps' on the PCB. Are they around and under the little PCB boards that we pin on? they are the blank capacitor icons on the PCB

- 'ComCat resistor' (820ohms) What's it for and where does it go on the PCB? I think its the resistor for the relay used

- Would it be possible for you to explain the 'Green LED resistor' and the 'Green LED',do they replace the 'RLEDx3' and '1 x LED' on the BOM list? you need 3 leds, one single color one and 2 two color ones.  Depending on the leds you get will determine what size resistors you need.  There are calculators online to figure that out.

The BOM list also has 'RG1' which doesn't seem to be on the Mouser order list is it not needed? thats the psu one i wrote about earlier i think

Click to expand...

if you reread this whole thread you will find all the answers, thats all I did and I am still a noob.  I asked a lot of noob questions which will help you through out this thread.

Have fun

Hi saxmonster thanks for the reply i had read the thread several times and had tried to work the answers out my self but was just thrown by some of the custom ref # numbers on the mouser cart and most of it i was ninty % sure of but i did want to just check to make sure i had read it correctly

david.uulf said:

Hi mulletchuck, and anyone that might be able to clarify

Would be great if you'd be able to help clarify a few things regarding the BOM list and Mulletchuck's Mouser cart 'Customer Part #' order list.


Mouser Cust Part #

- 'R1,3,5,7,9,11,13,15' (10Kohms), are they R11 and R13? Yes thats what I used for both r11 and r13
thanks as i said at the top i was 90% sure but was thrown by the Cust part # and was worried i had miss something
- 'R2,4,6,8,10,12,14,16' (1Kohms), is it R15? Yes thats what I used r15 only 1kohms
again just double checking
- What is 'PSU R17, 18'? This is for RG1
thanks that cleared that up
- With the placement of the 'Unmarked caps' on the PCB. Are they around and under the little PCB boards that we pin on? they are the blank capacitor icons on the PCB
thanks i guess this question was unnessasery sorry
- 'ComCat resistor' (820ohms) What's it for and where does it go on the PCB? I think its the resistor for the relay used
i am not sure because there was a resistor for that already RRL? so i was thinking that it had something to do with the common cathode LEDS but i was not able to find referance to it in the BOM or the SCHEM or on the PCB  sorry if it a real noob Qjuestion but this is the one that realy has me stumped.... :-[
- Would it be possible for you to explain the 'Green LED resistor' and the 'Green LED',do they replace the 'RLEDx3' and '1 x LED' on the BOM list? you need 3 leds, one single color one and 2 two color ones.  Depending on the leds you get will determine what size resistors you need.  There are calculators online to figure that out.
the reason this question was in here was that in his cart there was 2x the amount of 1 color LEDS as needed so i was worried that i had missed somethinng some where like there was one in the meter or something stupid like that.

The BOM list also has 'RG1' which doesn't seem to be on the Mouser order list is it not needed? thats the psu one i wrote about earlier i think
thanks again the custom ref threw me abit but that dose make sence

Click to expand...

if you reread this whole thread you will find all the answers, thats all I did and I am still a noob.  I asked a lot of noob questions which will help you through out this thread.

thanks again to you and to mulletchuck for all the help and the answers i do have a little truble with the reading and writing so thanks for you patcence and help

Have fun

I'm sorry comcat is for the common cathode LEDs.  Its the resistor for them. 

RRL is for the relay your right again sorry.

not sure why the 10kohms and the 1kohms have all those other resistors listed but thats what I used for  R11 and R13 are r15.  Maybe chuck can verify why those are listed.

thanks again mate
and i'm assuming that the bit on the board marked RLED corresponds to the LED that it is nearest.

Hey saxmonster did you end up getting the pots that TheJames linked to from mouser (  652-91A1A-B28-D20L)? how are they did you end up having to change them out if so why ? i need to order some and they looked to tick all the boxes but i thought i might check with you seeing as you seemed to have some issues.
thanks dave

I had gotten pots with the metal shafts but the one is making noise already when you turn it and when i touch the metal knobs I have I hear ground interference since the shafts are metal too. 

I just ordered a pair of the ones you linked to, they should be here today so I will let you know how they sound and work.  I would say it should be a go with them.  they have plastic shafts so no ground noise hopefully when I touch them.  This is at very high levels I am talking about and very low decibels also.  Just like my stuff clean as possible.

Go for them.

I used these bournes pots in my first run la3a. They work great. The ones that came with the first round kits were intermittent. I'm not sure if they were faulty or I overheated them, but they would randomly work. Very happy now.

Thanks Duantro and Saxmonstor you guys are the ducks guts will order mine soon
i was rereading the tread last night and came across the post about mounting the stuff that goss under the little amp boards on the the under side of the main board about a hour to late  :'( oh well i guess that is why you make a prototype before the main run. :-[

You might still be able to lay them flat on the pcb to give you some room, i think that is what i did.  Or get one of those solder suckers they work great at removing parts just in case.

Solder suckers are a huge help when this happens. Good luck on the surgery!