JLM Baby Animal

[wolfgang]

What I dont know is:
- where do the red/green/blue/yello cables under OEP go....Seems that they will be going to power supply....will I have any switch or just the one from power supply

The spots with colour markings are for the JLM Input TX which has leads instead of PC-Pins.
So just put the OEP in where it fits and solder it ! Forget the colour holes - you dont need it!

- The CL and 0.1 uF...? do i connect them in the inner holes or the outer? (all photos I've seen are the older PCB's with just one pair of holes)

solder them where the cap fits better! they are connectet together!

- Where does the LED go to? (Is it to show the phantom power is on or not? where does it get attached?)

You have to solder the LED directly to the 48V Switch! I dont know the right legs out of memory but i am sure you will find he information oon the JLM-site!

- I am left with a circular plasitc small bit (size of led light)... where does it go?

This is for the JLM Input TX! you have to screw it and this small washer is to keep distance between the TX and PCB. So to NOT have any short!


I hope this helps!

enjoy the preamps!! they are great!!

regards,
Wolfgang

 

[korni]

It certainly does help!

Thank you very much wolfgang

So the power supply where does it connect to? (is it one from ''0v'' and one from ''+V'' to the PS? )

 

[wolfgang]

So the power supply where does it connect to? (is it one from ''0v'' and one from ''+V'' to the PS? )

yes thats right!! check polarity of the psu before you switch it on!!!

regards,
Wolfgang

 

[korni]

So the power supply where does it connect to? (is it one from ''0v'' and one from ''+V'' to the PS? )

yes thats right!! check polarity of the psu before you switch it on!!!

regards,
Wolfgang

Thank you wolfgang

Edit: I guess I can avoid the polarity check if using a DC socket....

 

[wolfgang]

I always check the opamp-pin polarity before inserting the opamp! i dont want to burn a 40-50 Euro Opamp by accident! 

wolfgang

 

[korni]

Thanks for the advice.
Though I dont even know how to go about it...
I will search it

 

[wolfgang]

Maybe i used the wrong words, my english isnt very well!!

I meant: Measure V at the PCB  Pins where you will put in the opamp.
Measure the V+ Pin and the V- pin! to be sure there are the correct voltages!

wolfgang

 

[korni]

Dont worry. I understood what you meant.

Me too have the same problem + I am a newbie

 

[korni]

Back with my power supply on.

Wolfgang you where so wright.

I get a bunch of voltages as 0 instead of +24V (as shown on the schematic)
I uploaded this image...
where there is a circle I get a 0 reading....
Also there is one reading I dont know wether I should be getting anything or not and circled it....

Any help please? Seems as a mistake carried on but cant find it......

 

[wolfgang]

Hello!

for the markings at the opamp:
take a closer ook to the image of jlm : above the pcb in yellow:""""NOTE.  pins -In and Out  will be 0V with no Opamp fitted.

So this is OK! you can measure again with opamp fitted and you should get the 24V!

For the other spots: it i difficult to see on the picture but one of the caps is connected to the output pin of the single opamp. So it is ok!
one cap is connected to the second output pin of the dual-type opamp( if you use a OPA2604 instead of the JLM Opamp for Example) So this is ok!

the third is connected to the -In pin and RG. which then goes through the Gain-pot to Ground.
so this ok too!!

I think you can insert the opamp and have a test run! Measure again with opamp fitted!
(but do it on your own risk )

Regards,
Wolfgang

 

[korni]

???     

I feel stupid for the OPAMP in and out  ;D .....

Thanks for the help...
I will wait for Joe to give me an answer or something if he finds the time...
If not I will try with the OPAMP in tomorrow...

I am really thrilled I am finishing my first DIY project  ;D

Thanks once again wokfgang
much appreciated

 

[wolfgang]

You are welcome!!

I think your build is on the safe side with your Voltage readings!

JLM BA was my first project to btw!!!
I have 12 channels now!

You will like it!

wolfgang

 

[korni]

hah...

Someone can easily get addicted to it!

Joe said to me that the reading's of voltages are good to continue
and check that there is no dead short (dead short = 0 ohms as he explained)
in between -in and 0v
and out and 0v
to the opamp....

It should be a few hundreds...
BUT
I cant get my hands round that and always get different value.... ???



It is so frustrating when you dont get a fixed value.....
I want black and white....not colours

If it wasnt for you wolfgang and Joe...
I dont know how I would have coped with it....

 

[wolfgang]

Joe said to me that the reading's of voltages are good to continue
and check that there is no dead short (dead short = 0 ohms as he explained)
in between -in and 0v
and out and 0v
to the opamp....

It should be a few hundreds...
BUT
I cant get my hands round that and always get different value....

But you never read 0V??

Is the Ohms value instantly inreasing or decreasing? or is it up and down ? ( if you measure and dont disconnect for a new measuring)

wolfgang

 

[korni]

It just behaves crazy...
Going up and down
at a very small rate...

Anyway,

Apparently as Joe said it must be due to the capacitors and the (low) quality of my meter...
As long as it doesn't give me back a reading of 0Ω then it's ok...

Tomorrow then I will be attaching my final xlr plug
and be testing the Baby Animal.
Cant wait

 

[wolfgang]

I thought also of Capacitors behavior!!
Anyway,  let us here of your tests!!!!

wolfgang

 

[korni]

Ok ,

voltages are ok.
Only that when gain goes more than 70% I get a noise..
(I don't know if this is normal or it is going to disappear if I attach the 0v to the case...but I am not that worried)

Final things is the LED
and a case (plus grounding the pre-amp to it)

It has very nice sound...
Even though I don't have experience with pre-amps I am amazed


Just one question...
if I want to put a power switch to the board
what specks should it have?

As soon as I make a case I will be posting the final pre-amp...

 

[cheu78]

Here's my 8 channel BA modified to put a brazilian DIYed 2520 melville (thanks Fabio).. Cinemag input and output xformers... awesome!!! The preamps sound fat and punchy!!Api should put those cinemag output xformers instead of the profile's, the difference is remarkable...
It's like I wanted it, there's nothing like this on the market.. 1 RU, 8 channel hi quality preamps with input and output transformers..A big THANKS to my friend to Neeno of course, he did a terrific job! and to Cinemag for the great xformers! and of course to JLM for the pcb boards..
I called it the 812a... check it out.. (and for those who might have a doubt there's more than 92db crosstalk separation between the channels..and in the front pic it wasn't finished yet, but it's done now)   ;D
Ciao
Cheu

 

[cheu78]

and here the guts!!!  ;D ;D ;D

Ciao
Cheu

 

[regularjohn]

Does anyone know where to find documentation to build the BAD with a cinemag 75101 input trafo?

It seems there's not a whole lot of info - or really any at all - on the BAD with that trafo.