JLM AUDIO

hi guys,

these may be some noob questions, so bear with me.

ive basically built my baby animal pre except I havent attached the input transformer. (I am using the jlm14). What do most people use to mount them off the board? Included in my kit were a couple of plastic washer type looking things which are beige in colour. is this what i use??

Also, the jumpers on the board that go to the transformer with markings of low and high ratio, what exactly does this do for the pre??

Hopefully I'll be able to get this baby up and running over the weekend if i havent blow anything up

What do most people use to mount them off the board? Included in my kit were a couple of plastic washer type looking things which are beige in colour. is this what i use??

Yes use sidecutters or a knife to cut the tube part of them to turn them into flat plastic washers that will sit under the JLM14 to hold it 1mm off the PCB so it doesn't short any tracks.

Also, the jumpers on the board that go to the transformer with markings of low and high ratio, what exactly does this do for the pre??

The JLM14 only has one ratio and does not need any ratio jumper fitted.

Joe Malone wrote:

What do most people use to mount them off the board? Included in my kit were a couple of plastic washer type looking things which are beige in colour. is this what i use??

Yes use sidecutters or a knife to cut the tube part of them to turn them into flat plastic washers that will sit under the JLM14 to hold it 1mm off the PCB so it doesn't short any tracks.

Also, the jumpers on the board that go to the transformer with markings of low and high ratio, what exactly does this do for the pre??

The JLM14 only has one ratio and does not need any ratio jumper fitted.

thanks for the help joe!

I left the washers as they were. Worked fine too.

those plastic washers do a great job .

As im going to be running my BA on 48v I think i need to remove a couple of parts.

I soldered on the *10k and #10k resisters. I take it i need to remove these altogeter and then connect C to E on both BD681 and then also add a connection from pin 4 to 7 on my IC (which is the OPA2604). I think all is ready to go once i sort this part out.

i knew i should have stuck to the dick smith doorbell kit, but the tune it plays would drive me nuts

As im going to be running my BA on 48v I think i need to remove a couple of parts. I soldered on the *10k and #10k resisters. I take it i need to remove these altogeter and then connect C to E on both BD681.

The *10k and #10k can be left on the PCB as they make no difference without the BD681 fitted. So leave them there and just strap C to E on both BD681 positions.

then also add a connection from pin 4 to 7 on my IC (which is the OPA2604). I think all is ready to go once i sort this part out.

If you are using a OPA2604 then you do NOT want the strap between pin 4 and pin 7 as this will kill the OPA opamp because you will be shorting one of its outputs to 0v. The strap between pin 4 and pin 7 is only fitted when using a 99v or other 99* type opamp.

ahh thanks joe..

now i know what i'll need to do when i make more pres with those diff opamps.

wOOHOO!!

It works.

need to put it into its final rack mount chasis and then its time to order more!!

thanks joe!

Welcome to the JLM users club, Paul. Its the all areas access pass to audio niceness.