BA BA2 BA4 BAD Dual99v Build Thread

[Joe Malone]

Have you swapped opamps between channels to see if the fault follow the opamp?

Thanks Joe! Have tried swapping opamps and noticed immediately that 99V on second channel have been slightly loose and out from its golden socket legs.
It is likely due to transport of the equipment rack every single night for two weeks for those brass band sessions.
I'm afraid to squeeze these golden sockets to get better grip, maybe its better if I try to tighten it up over "belly" a bit with sort of a belt or something.

Tested for more than hour recording and not a single glitch. Thanks again for the tip! Cheers!

Cool great to hear it was a easy fix. Yes it is a good idea to use a cable tie around each opamp and the PCB to make sure the opamp doesn't come out during transport.

[DavidL]

I've finally been able to get back to the BA2 build! I'm on the home stretch but I have hit a few walls. I am building it with the JLM25HV and JLM14 wired 1:8 and its a 2 channel build.



I'm thoroughly confused about the XLR in/out wiring and how to link the two modules together

BA, BA2, BA4 Overlay wiring PDF Large PDF copy here

here's where I am at so far:

image (1).jpg

OEP/VTX = 10k in series with 100k log pot. (As shown in photo below for Dual99v)
JLM14 = 2k2 in series with 50k log pot (2k2 resistor solders to both pins on the left and red wire solders to all 4 pins on the right)

In my kit I was given a 100K pot. I was also given 1 spare 28k resistor with each BA kit package. How do you recommend i wire the Z pot?

image.jpg

And lastly, I lost a whole bag of these feet thingos:

image (2).jpg

is it possible to buy more of these?

As always thank you very much for the continued support!

Dave

[Joe Malone]

I've finally been able to get back to the BA2 build! I'm on the home stretch but I have hit a few walls. I am building it with the JLM25HV and JLM14 wired 1:8 and its a 2 channel build.

I'm thoroughly confused about the XLR in/out wiring and how to link the two modules together

All input wiring is done these days with the provided 3 head ribbon cable like the Dual99v overlay pdf shows
Plugs into the XLRIO then the DI and then the 10 pin header on the BA pcb. Input wiring done.

Output wiring is still the same +out and 0v to output transformers or +out and -out direct to XLRIO +out and -out without output transformers

OEP/VTX = 10k in series with 100k log pot. (As shown in photo below for Dual99v)
JLM14 = 2k2 in series with 50k log pot (2k2 resistor solders to both pins on the left and red wire solders to all 4 pins on the right)

In my kit I was given a 100K pot. I was also given 1 spare 28k resistor with each BA kit package. How do you recommend i wire the Z pot?

Same as OEP/VTX = 10k in series with 100k log pot. (As shown in photo below for Dual99v)

And lastly, I lost a whole bag of these feet thingos:

They are available on the JLM Audio website at the link below
http://www.jlmaudio.com/shop/6-x-1mm-sockets.html

As always thank you very much for the continued support!

Dave

[Southern]

Hi all. Having some trouble with my BA and BAD. So having read this entire thread first ,I think I may have
A lead. My units were jumpered under the PCB as I wasn't using a DI. Having decided to add one, I build it and put in forgetting about the jumpers. I have read that it's possible to cause a short somewhere when you do this. So, suddenly the units are not passing signal at a proper level. It will pass a extremely small signal if I jack the gain to max and I can get the smallest of signals. The strange thing is,I only plugged the DI into the BA,not the BAD. However the BAD is showing the exact same symptoms which is another mystery. If there was a short of some kind,where would I be looking? All voltages as per the overlay check out ok. Thanks.

[Joe Malone]

Hi all. Having some trouble with my BA and BAD. So having read this entire thread first ,I think I may have
A lead. My units were jumpered under the PCB as I wasn't using a DI. Having decided to add one, I build it and put in forgetting about the jumpers. I have read that it's possible to cause a short somewhere when you do this. So, suddenly the units are not passing signal at a proper level. It will pass a extremely small signal if I jack the gain to max and I can get the smallest of signals. The strange thing is,I only plugged the DI into the BA,not the BAD. However the BAD is showing the exact same symptoms which is another mystery. If there was a short of some kind,where would I be looking? All voltages as per the overlay check out ok. Thanks.

OK remove the DI and replace the links and check you have the 10R carbon resistor on each PCB burnt or best to check they are still 10R?

Do you have 48v between 0v and 48v at each PCB? Encase the 500mA fuse has gone high resistance in the back panel fuse holder.

[Southern]

Turns out I had a short in the mic lead at the mic end! You learn something new every day. I thought a mic lead either worked, or it didnt.

[lynge]

Hey Joe,

Really been enjoying assembling the kit! This is my first DIY and it has been pretty straightforward. I just wanted to double check a few things that are mentioned in the forum, but I wanted to be 100% sure of before I go on.

1) The Rpad should have 51R resistor, right?

2) Rgain 1&2 have 270 R resistors?

3) Does it matter that I already soldered in the terminal blocks on the FET DI? Should I remove them? I didn't realize I would only need the ribbon cable

4) I am a bit confused about the jumper ratio. It looks like you and others recommend starting with the lower ratio. How do I know which two to jumper to give me a lower ratio? Do I just add a jumper cap to the two lower next to the 10 pin header? (lower with respect to the orientation of the PCB). I circled in the image attached in case I am using the wrong terminology.

Thanks for taking a look at my basic questions! I apologize if they have already been answered.

[Joe Malone]

Hey Joe,

Really been enjoying assembling the kit! This is my first DIY and it has been pretty straightforward. I just wanted to double check a few things that are mentioned in the forum, but I wanted to be 100% sure of before I go on.

1) The Rpad should have 51R resistor, right?

Yes correct

2) Rgain 1&2 have 270 R resistors?

Yes correct

3) Does it matter that I already soldered in the terminal blocks on the FET DI? Should I remove them? I didn't realize I would only need the ribbon cable

No doesn't matter at all. Just leave them on the PCB

4) I am a bit confused about the jumper ratio. It looks like you and others recommend starting with the lower ratio. How do I know which two to jumper to give me a lower ratio? Do I just add a jumper cap to the two lower next to the 10 pin header? (lower with respect to the orientation of the PCB). I circled in the image attached in case I am using the wrong terminology.

One jumper joining the centre 2 pins is correct setting for low ratio.

Thanks for taking a look at my basic questions! I apologize if they have already been answered.

Cool no problem. This info is written on the Daul99v overlay PDF in the first post of this thread for others looking for it

[albonardi]

Hi Joe,

I'm in the process of building a 2nd BA unit with JLM 99v,JLM in xformer and opamp di,I have a couple of questions because I noticed some differences among new and old (2009??) pcb and other stuff (I want the 2 channels sound the same possibly)

-in my old BA pcb don't see room for the 10mF 63 v cap,the new pcb I already have (from a friend) has room for it.Is it needed?? I can skip this cap in the new unit??

-the variable impedance thing in my old unit if I detect correctly is made with a 5 kohm pot+4k7 ohm resistor+220pf cap,for the new BA units you suggest in your settings table 50 kohm log pot+2k2 ohm resistor+440pf cap (220+220).Do I need to modify the old channel with these new values to have 2 identical channels?? May I leave the old channel as is because makes no real difference???

-are there in the "new" BA pcb components to add/skip??

-in my old unit at max gain I detect some rf interferences,any suggestions??

best regards
AB

[Joe Malone]

Hi Joe,

I'm in the process of building a 2nd BA unit with JLM 99v,JLM in xformer and opamp di,I have a couple of questions because I noticed some differences among new and old (2009??) pcb and other stuff (I want the 2 channels sound the same possibly)

-in my old BA pcb don't see room for the 10mF 63 v cap,the new pcb I already have (from a friend) has room for it.Is it needed?? I can skip this cap in the new unit??

-the variable impedance thing in my old unit if I detect correctly is made with a 5 kohm pot+4k7 ohm resistor+220pf cap,for the new BA units you suggest in your settings table 50 kohm log pot+2k2 ohm resistor+440pf cap (220+220).Do I need to modify the old channel with these new values to have 2 identical channels?? May I leave the old channel as is because makes no real difference???

-are there in the "new" BA pcb components to add/skip??

-in my old unit at max gain I detect some rf interferences,any suggestions??

best regards
AB

The only change on the BA pcb is the adding of the 10uF for better smoothing if using a BD681 to drop the voltage to 32v. If you have the two BD681 jumpered over because you are running 48v then the 10uF can be left off or fitted it makes no difference, Nothing else has ever changed on the BA pcb.

Impedance parts depend on the input transformer that is fitted? We have never used a 5k pots always 50k or 100k log pot for impedance pots.

RF can be if metal case is not all connected together due to powdercoating under screw heads. Make sure all panels ans screw heads measure 0ohm to each other. Remove some powder coating under the screw head with a drill bit.

Also worth on old builds adding a wire from the DC connector 0v terminal to a bolt on the back panel to make sure case and 0v are connected well.

If you still have noise it will be not be RF but oscillation instead usually because the wrong value for Cload is fitted or no Cload is fitted. Cload value depends on the input transformer and opamp used.

[albonardi]

Hello Joe,

thanks for your reply,I built the second unit and everything seems ok,I checked the values of the variable Z components and the pot was of the correct value.I did the outputs with 2 Carnhill VTB1148 the only trouble that I encountered is that 1 of the 2 channels is out of phase,I checked everything in the input/output wiring several times and connections with transformer and xlr,the 2 channels are wired identical but 1 is out of phase respect to the other.Is there any component wrong placement on the pcb that can cause the problem?? The levels with pad in/out and the sound seem identical.Any suggestions?? Best regards AB.

[Joe Malone]

Hello Joe,

thanks for your reply,I built the second unit and everything seems ok,I checked the values of the variable Z components and the pot was of the correct value.I did the outputs with 2 Carnhill VTB1148 the only trouble that I encountered is that 1 of the 2 channels is out of phase,I checked everything in the input/output wiring several times and connections with transformer and xlr,the 2 channels are wired identical but 1 is out of phase respect to the other.Is there any component wrong placement on the pcb that can cause the problem?? The levels with pad in/out and the sound seem identical.Any suggestions?? Best regards AB.

If the phase switches are both in the same position there is no way the kit can invert the phase. The phase error can only be a transformer or the wiring. We have found lots of transformers with wrongly wired phase internally. Check phase with and without output transformer wired in. Also make sure the in and out XLRs are wired as mirror images as pin 1 is on opposite sides.

[htm]

Hi Joe

I've been happily using my four BA's on drums and guitars for a good while, but I 've noticed that there's something going on with one of them. The gain on one is some 4 dB lower than others and it's not giving out the full 48V phantom power, only 15 or so volts comes out. I checked the wiring, but can't locate the problem there. Is there something on the board, that I should check?

Thanks, Hannu

[Joe Malone]

Hi Joe

I've been happily using my four BA's on drums and guitars for a good while, but I 've noticed that there's something going on with one of them. The gain on one is some 4 dB lower than others and it's not giving out the full 48V phantom power, only 15 or so volts comes out. I checked the wiring, but can't locate the problem there. Is there something on the board, that I should check?

Thanks, Hannu

Check 10R resistor is still 10R ?
Voltage you get on either side of the 10R measured to 0v?
Voltages at opamp pins measured to 0v?
Voltages at +/-in measurted to 0v with phantom on and no mic plugged in?

[htm]

Hi Joe

I've been happily using my four BA's on drums and guitars for a good while, but I 've noticed that there's something going on with one of them. The gain on one is some 4 dB lower than others and it's not giving out the full 48V phantom power, only 15 or so volts comes out. I checked the wiring, but can't locate the problem there. Is there something on the board, that I should check?

Thanks, Hannu

Check 10R resistor is still 10R ?
Voltage you get on either side of the 10R measured to 0v?
Voltages at opamp pins measured to 0v?
Voltages at +/-in measurted to 0v with phantom on and no mic plugged in?

Ok, here goes

10R is 10R
47.3 on the opamp side of 10R and 47.5 on the other side

opamp pins are
+V 47.3
1/2V 23.6
0V 0
out 23.6
both ins 23.6

+/- in are 15.5/15.0