JLM Baby Animal

[Greg]

Also, I ALWAYS ohm out the rails before powering up anything. If you measure a short then you'll save yourself alot of trouble replacing burnt components.

BTW - nice choice going with the Lundahls. I love those, personally.

 

[craigmorris74]

Also if you are not using the DI kit you should use the black thumb tabs in your kit and as per the voltages pic, fit 2 of them onto the IDC, look at the 2 yellow lines.

I'm not using the DI kit in my BA's. Can I just install jumpers where the yellow lines are?

 

[matta]

I'm not using the DI kit in my BA's. Can I just install jumpers where the yellow lines are?

Yip, I'd solder the IDC connector there first and then use the computer jumpers where you see those 2 lines.

Matt

 

[JLM Audio]

The 0.1 bead...Is it a multilayer ceramic, or a film type cap?

Multilayer ceramic

What parts can I leave out if im going to use the JLM output transformer?

None if you are using a Dual dip IC to drive the output transformer from +out and -out but if you are using a 99v etc you can leave off the the 470uF 50v cap in the centre closest the opamp and the 2 x 10k resistor under the DIP opamp closest to it. As well as the lower 47pF and 51R. Also the 10k above RL can be left off. This removes all the -out and inverting amp parts. So the output transformer connects to +out and 0v wired as 1:2. You will also not need the wire across pin 4 to pin 7 of the DIP IC.

What diameter does the DC jack for the +48v supply need to be?

5.5mm hole 11mm deep with 2.1mm centre pin.

Is the pot for the variable impedance preferrably log or lin?

Log

Also, would there be any idea in implementing a variable impedance for the Beyer transformers? Perhaps someone has tried this?

If you are using a 1:10 Beyer try a 47k in series with 250k or 500k log pot.

I'm doing some testing with a signal generator on BA as I have a case of the hums and I noticed that the output is out of phase with the input unless I flip the phase to phase reverse - is this correct or have I done something wrong?

What transformer and IC are you using? Normal phase is with the toggle on top of the PCB and the switch in the down position.

On both PCBs without the 99V installed I read 0V on
the marked spots where it is said it should be 24V... is this normal?

Yes the 2 positions you marked will only be +24v with the opamp fitted.

Ups, I tried the PCB with 99V installed but the 10R resistor started to burn ....
something isn't right. Then I noticed that I forgot to solder the small jumper
next # zener place. Fixed, but two Opamp pins are still reading 0V.

There should only be a jumper in the BD681. But the other one is across a track so no need to remove it. What voltage power supply are you using ? What voltage rating are the large 470uF caps? Put up a clear shot of the underside of the PCB so I can check for shorts. Also would be good to see the area on top in the shadow clearly.

I'm not using the DI kit in my BA's. Can I just install jumpers where the yellow lines are?

Yep if you just bought the PCB you can just solder in 2 wire jumpers but if you have the kit you might as well fit the IDC and computer jumpers supplied.

 

[Jonkan]

Thank you!

I couldnt find a 500k or 250k log pot at my electronics shop, so ill go with a 470k instead. Im guessing it doesnt matter much.

Looking forward to building these alot!
/Jonas

 

[wiz1der]

OK, almost done with my BA4!! Quick DI question though...

I have seen pics where the mic input is connected to the DI, and the ribbon cable from DI to BA.

I have seen pics where nothing was connected to DI, only ribbon cable.

My question is, Do I hook my ins and outs to the main BA board and just use ribbon cable for DI? Do I need to hook 0v and 48v to DI? Or is this all covered by ribbon cable connection???

So, So confused.

 

[Schmilsson]

It's all covered by the ribbon, no worries

 

[wiz1der]

Thanks eskimo. That made it much easier>>>

NOW I HAVE ANOTHER PROBLEM>

Channel one (OEP + 99V) and channel two (JLM14 + 99V) are working perfectly and sound FANTASTIC!!

Channel 3 (OEP and 2604) and channel 4 (JLM14 + 2604) are giving me a headache! The gain knob is ALL THE WAY DOWN, and i am still passing signal.

The gain knobs are wired exactly like the first two channels, and I do have the jumpers in for no DI on channels 3 and 4. I have also swapped 2604's with the one's from the DI's and the problem still exists. The two leads on the gain that are wired together are defintely going to 0v (checked it with the multimeter). I am kinda new to this and don't know what it could be. All 6 caps near the connector edge are in correctly, and the 330uf is in the proper position.

HELP?

Thanks, I cannot wait to get all 4 channels going so I can post wav files of the different combinations.

 

[JLM Audio]

The gain knob is ALL THE WAY DOWN, and i am still passing signal.

A Gain knob never turns off the audio fully in most mic pres. The minimum gain is transformer gain + 6dB for 99v (12dB if using a 1:2 output transformer) and transformer gain + 12dB for OPA2604. So with JLM14 you get 12dB gain so 18dB minimum gain and with opa2604 you will get 24dB. With the Pad in this become -2dB for 99v and +4dB for OPA2604.

In our built products we rework the RPad value so with minimum gain and pad in the mic pre functions as a 0dB unity gain device which can be inserted over tracks or final mixes to warm them up.

 

[wiz1der]

hey Joe thanks for the quick response, and let me take the time to say that I hav had a very satisfying experience with your company, from the top notch customer service, you and Matt putting in the extra time here at the lab, and above all, FIRST RATE PRODUCTS!

I guess that does make sense. Maybe i should not have wired my oeps for HIGH gain! They are not clipping with the output form my drum machine, but I'm not using the gain as much as i think I should be. Pad is definitely in, maybe I should chage the value of something so I can crank the gain more? or would this make a difference in sound?

To anyone on the fence on this preamp, Make the LEAP! They are NICE!

 

[Purusha]

Hello to all Baby Animal fans :green:

Here is my first BA unit which I put together for my friend. I used my QUAD case and mounted a few extra blue LEDs for a cool look. It was my
first BA DIY and I had some serious problems with one BA board (still do) on which I very likely fried 3 99V Opamps (have to get confirmation
from Joe about it) The last week was horible. Everything went wrong :evil: It must be that the Mercury has striked me very badly.


Anyway here is my first unit

Not as neat as some other BA DIYs but as long as it works I am happy.

Just to confirm, is this wired OK?

 

[Guest]

I'm doing some testing with a signal generator on BA as I have a case of the hums and I noticed that the output is out of phase with the input unless I flip the phase to phase reverse - is this correct or have I done something wrong?

JLM answered :: What transformer and IC are you using? Normal phase is with the toggle on top of the PCB and the switch in the down position.


No transformer and I am using the hybrid Opamp, 48v smp ps.
I've tested with both an oscilliscope and recording into (unbalanced ) inputs on my protools by have two outputs from my signal gen (both outs are in phase checked by recording both in directly to PT first) one going in in directly and the other through my BA and they are out of phase.

Also checked one channel seperatlely buy oscilloscope probing the input xlr and the output xlr at the same time and that gave the same result. checked the wiring to and from pcb to xlrs and thats ok.

Phase switch set to down pos looking at the front of the pcb with the switch on top of pcb - ie opposite position to phantom on. Any ideas?

/Taz

 

[JLM Audio]

I guess that does make sense. Maybe i should not have wired my oeps for HIGH gain! They are not clipping with the output form my drum machine, but I'm not using the gain as much as i think I should be. Pad is definitely in, maybe I should chage the value of something so I can crank the gain more? or would this make a difference in sound?

I prefer the OEP set to low gain is 1:6.45 which is actually still a lot of transformer gain. With the OEP on low gain and OPA2604 you will have about 66dB of gain so you will not need more usually. But make sure you are going straight into a line input on your A/D not a mic or instrument DI input as this is where most people have problems as the BA will overload them with ease even with them turned down so you are not getting full level shown on the software meters. Also most A/D can be set to 2 or 3 in and out levels. Make sure you have your set to the highest pro level settings. Like fireface which you need to set to high and Low gain to get it to work at +19dBM = 0dBFs. If you want to run high ratio on the OEP and still run line level into the BA you will want to make Rpad value smaller to make a larger pad so the BA can get back to unity gain with the pad in.

Purusha all the wiring should go direct to the Baby Animal terminals and the only wiring needed to the DI is the ribbon cable. At the moment you have ribbon cable and DI terminals both wired which gives you a very good chance of shorting something out if you get a wire in the wrong place. I would always recommend building the BA and getting it going with the 2 jumpers with no DI and then just pulling the jumpers and plugging in the ribbon cable to add the DI after.

Yes it is wired fine but the 0v should go back to the 0v on each BA PCB. The daisy chain way you have it at the moment can introduce some crosstalk between channels.
Also sent you a email as you have short on the PCB you are having trouble with after the 51R output resistor to 0v from the measurements you sent me.

No transformer and I am using the hybrid Opamp, 48v smp ps.
I've tested with both an oscilliscope and recording into (unbalanced ) inputs on my protools by have two outputs from my signal gen (both outs are in phase checked by recording both in directly to PT first) one going in in directly and the other through my BA and they are out of phase.

Also checked one channel seperatlely buy oscilloscope probing the input xlr and the output xlr at the same time and that gave the same result. checked the wiring to and from pcb to xlrs and thats ok.

Phase switch set to down pos looking at the front of the pcb with the switch on top of pcb - ie opposite position to phantom on. Any ideas?

If there is no input or output audio transformer and the XLR's are wired right there is no chance of the signal being out of phase as the opamp runs in phase with no inversion. How have you wired the BA to the XLR's if you are using no transformers?
Need to see some photo's of your wiring to PCB and XLR's either here or send them to me at my normal email address to work out what is wrong here.

 

[Purusha]

Purusha all the wiring should go direct to the Baby Animal terminals and the only wiring needed to the DI is the ribbon cable. At the moment you have ribbon cable and DI terminals both wired which gives you a very good chance of shorting something out if you get a wire in the wrong place. I would always recommend building the BA and getting it going with the 2 jumpers with no DI and then just pulling the jumpers and plugging in the ribbon cable to add the DI after.

Joe, so I can remove all the wires from the screwed conectors on the DI PCB except the ribbon cable? What about the input from XLR and 48V on the DI?

 

[JLM Audio]

Joe, so I can remove all the wires from the screwed conectors on the DI PCB except the ribbon cable? What about the input from XLR and 48V on the DI?

The input XLR wires to the input on the BA PCB and 48v volts only needs to wire the the BA PCB as Well. The IDC cable takes all these to the DI and back when it is plugged in.

 

[Purusha]

Thank you very much Joe!!! :thumb:

PS, I just saw the post above explaining this

 

[Regis]

Hi to all, this is my first post ,

Im green to electronics and this is my first diy kit experiance ever.
So this is what Joe and all the people on this forum have inspired me to do, an army green BA with variable impedance.

Lazertran was used for the design. The metal box was salvaged from an old crossover, decaped, primed and then painted. The only metal I purchased was a 1 U space filler.

I messed up the knob titles, (lazertran = no white pigments)

Thats a 5K variable resistor (adjusted to 4K7)hanging on the impedance pot. Its all i had going at the time :roll:

This pre will get lots of use recording drums and electric guitar, it has some sweet low mid warmnes going on.
So much better than my presonus pres!

Im addicted... Thanks Joe and mat

Stay tuned i'll be back with more !IRON! :twisted:

 

[Lowfreq]

There's some nice looking units ya'll got there. :thumb: :green: :green: :thumb:

 

[craigmorris74]

Almost finished wiring up 4 BA's. Have a couple of questions.

I think the switch with my kit is DPDT (it has 6 connections in rows of 3). How do I wire this switch using a LED (which side of the LED connects to where). I read earlier descriptions in this thread and the response was to wire the top and bottom connections. This doesn't make sense for the switch I have in my kit. I could be having a brain fart though.

Also what type of wire is recommended for this purpose?

Thanks,

Craig

 

[Regis]

Here is a diagram explaining the dpdt concept

All dpdt switches have their center terminals as the common terminals for both positions. Its pretty much two spdt switches working in parallel.

What i did is wire the incoming 48v to the center left and the outgoing 48v on the top left.
The two adjacent right connectors I have wired to ground.

The LED and 4k7 should also be connected to the top connectors in parallel to your outgoing 48V.

The long leg of the LED is the anod and should be connected to the 48V

I'm realy new to electronics so I hope I got this right :?