BA BA2 BA4 BAD Dual99v Build Thread

[Joe Malone]

BA & BAD PCB is designed for easy mounting by it 3 front edge toggle switches like the GO between and GO between plus kits share and are powered direct from one 48v rail supplied usually by our external 48v built MEPS Green SMPS which can run on any mains voltage in the world with out switching. This 48v supplies phantom power and +/-24v for the opamps to run on so makes building may types of transformer input single and dual opamp types of mic pre much easier to build.

What to run the most BA BAD BAN mic pres on the smallest MEPS SMPS power supply please read the Notes and Errata further down this page[/size]



NEW BLACK BA Ver2 PCB

Complete circuit of JLM Baby Animal Ver2 Black PCB here
Note: Build same as old BA PCB except Zpot now has its own 2 pin connector connector and series resistor for Zpot is fitted to Rload on black pcb.
If fixed Z then wire link over 2 pin connector solder pads.

BA PCB

Complete circuit of JLM Baby Animal PCB here
Circuit for Baby Animal Mic Pre with JLM14 & OPA2604 here
Circuit for Baby Animal Mic Pre with JLM14 & JLM99v or Hybrid here

BAD PCB

Complete circuit of JLM Baby Animal Dual PCB here

BAN PCB

See BAN build thread here

The BA & BAD PCB are easy to assemble with all parts with there value marked on the PCB needing to be fitted. Parts marked with * or # and zener diodes are only needed if running on higher than 48v or running opamps that need less then the +/-24v to run on. Parts with a name like Rload, CLoad, Rzobel, CZobel, RPad, RGain need to be selected to match the input transformer and opamp used. Their values for projects like the Dual99v can be found on the overlay sheet for the project.

Original 48 page BA thread on GroupDIY
https://groupdiy.com/index.php?topic=15245.0

Condensed version of The Lab Thread on JLM forum
http://www.jlmaudio.com/forum/viewtopic.php?f=2&t=11

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


Dual99v, BAD Overlay wiring PDF Larger PDF copy here


BA BAD BAN voltage settings


BA Settings (Ratios higher than 1:6.45 below not recommended unless using 50ohm microphones)


Building API 512, API 312 type mic pre on BA PCB
If using JLM25HV or JLM25HV FET NO BD681 is needed & 33v - 39v zener as they can run direct on the +/-24v of the BA PCB.


Cinemag CM-75101APC on BA PCB


Notes & Errata
Note 1. The New 48v 520mA 25w MEPS SMPS external & 48v 315mA 15w internal SMPS power supplies under high capacitive and dc current power up surge can go into hiccup protection mode (power light will flick on and off) more easily than the old non MEPS ones so the below soft start mod is recommended for all new BA BAD BAN builds.

DO NOT DO THIS SOFT START MOD TO ANY NEW BUILDS. If building 3 or more BA kits use our 48v 40W SMPS instead as it can run 8 BA BAD or BAN easy
1. Do the soft start mod shown below. This leaves all parts fitted as normal but one track is cut and wire link added with #BD681 and #10k fitted. This gives 5 second soft start with no direct capacitance across the 48v SMPS and allows for the maximum possible BA BAD BAN combinations on one SMPS power supply. (#Zener is only needed as usual if opamp needs lower than 48v (+/-24v) rail.)
2. As always test each BA BAD BAN module on the 48v power one at a time without opamp fitted and test voltages and then with opamp fitted and test voltages to make sure the module is working properly. If one BA BAD BAN module puts the supply into hiccup mode there is a real fault.
3. While testing measure the voltage across the 10R resistor to see what current the BA BAD BAN module is drawing at idle (mA = V/10). Add up the total mA to check it is less than about 2/3rds of the specified current of the SMPS you are using to leave some headroom fro driving 600ohm loads.
4. Once all BA BAD BAN modules are tested to work correctly turn off and connect all the modules and power supply should powerup smoothly. If you are having problems email me with your exact configuration and which power supply you are using.

(Without mod each BA has 470uF and BAD abd BAN have 1000uF capacitance direct across the 48v rail which causes a short circuit for to long for the new MEPS SMPS)

BA MEPS SMPS Soft start mod (DO NOT DO THIS SOFT START MOD TO ANY NEW BUILDS. If building 3 or more BA kits use our 48v 40W SMPS instead as it can run 8 BA easy)


BAD MEPS SMPS Soft start mod (DO NOT DO THIS SOFT START MOD TO ANY NEW BUILDS. If building 3 or more BAD kits use our 48v 40W SMPS instead as it can run 8 BAD easy)


BAN MEPS SMPS Soft start mod (DO NOT DO THIS SOFT START MOD TO ANY NEW BUILDS. If building 3 or more BAN kits use our 48v 40W SMPS instead as it can run 8 BAN easy)



Some helpful photo's (If there is some detail you need a photo off let me know and I will add it here)

BAD PCB fully assembled except for 2 x 270R for RGain, input transformer and opamps Larger photo here
Notes & Errata#BD681 jumper is wrong in the photo below. Should be E-C. Also Dual99v does not use a Cload cap any more. So leave blank.


BAD PCB fully assembled as Dual99v (Note 2 links needed between centre pin and E on each BD681 position and 1mm gap under transformer)
Notes & Errata#BD681 jumper is wrong in the photo below. Should be E-C. Also Dual99v does not use a Cload cap any more. So leave blank.


Sit toggle hard against the PCB and solder one front support leg on each toggle to hold in place.


Check toggles level and square to each other and solder all legs and support pins


Dis-guard flat washer and fit the rear nut (should be a few mm gapped from the end of the thread) and washer to all three toggles


Nuts should just screw on an tighten with minimum thread sticking out if the rear nut is set correctly


Nuts and washer order for Power switch


Same again space the rear nut up so the minimum of thread sticks out past front nut.


DC connector and Fuse wiring


All Pot wiring for BAD Dual99v PCB


Gain pot wiring (Photo shows BAD/Dual99v dual pot)
Note BA is the same but only a single pot


Output Pot wiring


Z pot wiring
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)


Output transformer to IOXLR PCB (Note link wire between -2 and +3 is hidden in this photo)


Full Dual99v internal wiring Larger photo here
Errata[/color][/b][/u]#BD681 jumper is wrong in the photo below. Should be E-C. Also Dual99v does not use a Cload cap any more. So leave blank.
[img]http

[tenchijin2]

Hi Joe,

Is there a simple overlay showing the values for fitting the OPA and JLM 14? I'm excited to get to building this when it arrives but I still get dizzy when following a schematic. I've only built a couple very simple projects previous to this ( a treble booster and a mic attenuator).

thanks for all the help you provide,

Aric

[Joe Malone]

Hi Joe,

Is there a simple overlay showing the values for fitting the OPA and JLM 14? I'm excited to get to building this when it arrives but I still get dizzy when following a schematic. I've only built a couple very simple projects previous to this ( a treble booster and a mic attenuator).

thanks for all the help you provide,

Aric

Added the two yellow tables in the first post.

[Paul Maybury]

Hi, I wonder if anyone is having the same problem as me?
I built a Ba4 kit using all jlm parts (no o/p trans), and I am getting hissy noise on most settings of the gain pot.
The hiss goes up in proportion to the gain, up to a point, then , at a certain spot the hiss jumps right up, out of proportion to the gain. If I then turn up the gain one more click, the hiss disappears completely whilst the gain keeps going up right to the end stop. All 4 channels behave the same way, the noisy point is around 3.30 o'clock, then clean, noise free gain from there to max gain.
There were several other spots in the gain range that had hiss noise popping up, out of proportion to gain, but I flushed out all the pots with Clean and Lube (heavy handed I know) and that has reduced the problem to the extent described above.
Could anyone please shed some light on this? I am thinking it must be the pots, sometimes I get odd oscillation type noises when in between clicks on the gain pot.
I love these pre-amps, but I'm not sure I am getting all they are capable of, especially with regard to noise.
Cheers,
Paul Maybury.
Paul Maybury

Joined: 17 Jul 2010, 08:54

[chrisp]

Paul

This should not be happening, its certainly not normal BA operation. Can you post some pics of your gain pot wiring and also the top and bottom of your BA build?

[Paul Maybury]

Thanks for the reply.
I went back through some emails from Joe, and in one he mentioned snipping out the 2x47pf ceramic caps under the op amp.
I did this today and the noise is gone! However, I'm now getting a thump when applying phantom power, and there is dc showing on the gain pot, about 50mV with phantom on and around 10mV
with phantom off. Also getting a little bit of PSU hash on the channel closest to the power switch. It's not much, only discernable with the gain cranked and no input.
I meant to take some photo's of the innerds, but my 4yo dropped the camera again!
Cheers,
Paul Maybury

[Joe Malone]

Hi, I wonder if anyone is having the same problem as me?
I built a Ba4 kit using all jlm parts (no o/p trans), and I am getting hissy noise on most settings of the gain pot.
The hiss goes up in proportion to the gain, up to a point, then , at a certain spot the hiss jumps right up, out of proportion to the gain. If I then turn up the gain one more click, the hiss disappears completely whilst the gain keeps going up right to the end stop. All 4 channels behave the same way, the noisy point is around 3.30 o'clock, then clean, noise free gain from there to max gain.
There were several other spots in the gain range that had hiss noise popping up, out of proportion to gain, but I flushed out all the pots with Clean and Lube (heavy handed I know) and that has reduced the problem to the extent described above.
Could anyone please shed some light on this? I am thinking it must be the pots, sometimes I get odd oscillation type noises when in between clicks on the gain pot.
I love these pre-amps, but I'm not sure I am getting all they are capable of, especially with regard to noise.
Cheers,
Paul Maybury.
Paul Maybury

Joined: 17 Jul 2010, 08:54

I would need to see photo's to see what is wrong but check the below list first. It will not be the pots at fault.

1.Have you got pin 4 to pin 7 wire jumper fitted to the DIP8 socket so quasi balanced out works properly?
2.Rload = 10k Cload = 220pF RGain = 68R?
3.Have you got the output of the BA4 going into a +18dBM to +22dBM pro level balanced input A/D so the noise floor is sitting at the correct level?
4. All wiring short and tightly twisted?

You will always have a small amount of swish noise when moving the gain pot as it is a old school single rail design but this should be very low once the unit has been on for a couple of minutes.

[Paul Maybury]

Hi Joe, thanks for replying. All of the points on your checklist are correct in my build. After taking out the 2 ceramic caps under the op amp, the noise is gone, the only issue now is the thumping noise when switching on phantom power. It's minimal if I have the pad engaged when I switch on phantom, and also some slight psu hash (I think thats what it is) on the channel closest to the power switch. This noise decreases in each channel according to how far they are from the power inlet and switch side of the Ba4.
Cheers,
Paul Maybury.

[Joe Malone]

Hi Joe, thanks for replying. All of the points on your checklist are correct in my build. After taking out the 2 ceramic caps under the op amp, the noise is gone, the only issue now is the thumping noise when switching on phantom power. It's minimal if I have the pad engaged when I switch on phantom, and also some slight psu hash (I think thats what it is) on the channel closest to the power switch. This noise decreases in each channel according to how far they are from the power inlet and switch side of the Ba4.
Cheers,
Paul Maybury.

Phantom power will always thump somewhat when turned on. Do you get 48v at pin 2 and pin 3 of the input XLR when phantom is turned on?

Is the output of the BA plugged into a balanced input pro level A/D +18 to +22dBM ? As this all sounds like a gain structure problem into a -10dbu line input or mic input.

There is no inductive noise from the power switch so it will not radiate noise into anything. So distance to it will not be relevant unless it is to do with power or ground wiring due to wiring length.
.
Did you fit variable impedance to channels 3 & 4 or was in variable pads?

Do yo have different input transformers on some of the BA PCB's as I cannot remember.

But without photo's to see or info on how you are testing it is very hard to know.

[Paul Maybury]

Hi Joe, thanks again for your help.
If the phantom is always going to thump a bit anyway, there's no problem as such. It's no where near as dramatic as the thump my SoundWorkshop console pres make!
My main converters are Motu 24 i/o, RME Fireface and sometimes some MetricHalo's on loan. All are +4 balanced input. I usually do my testing with a small mixer and a pair of Grado headphone's, which are frighteningly revealing. I plug the Ba outputs into the +4 balanced ins of the mixer.
I am getting 48 volts (+/- 0.5 v) at the input xlr's.
I am using JLM input trans, 99v opamps, no output trans. I haven't installed the variable pads that I purchased with the kit in channels 3 and 4, so there are small holes in the front panel for these. I plan to get the variable impedance controls in these channels instead. The first two channels have di's fitted.
Cheers,
Paul

[chrisp]

I'm just finishing up a couple of BAD cards using the VTX 102 003 input transformer, which can be wired low (6.45) or high (12.9) gain. Given the BAD isn't exactly short on gain (we'd be talking 74.5db vs 81db as the choices!), my instinct is to use the low gain jumper. One reason for wiring high might be for tone - is there any difference in the sound by wiring high? Or is there some other reason to wire for high gain?

[Joe Malone]

I'm just finishing up a couple of BAD cards using the VTX 102 003 input transformer, which can be wired low (6.45) or high (12.9) gain. Given the BAD isn't exactly short on gain (we'd be talking 74.5db vs 81db as the choices!), my instinct is to use the low gain jumper. One reason for wiring high might be for tone - is there any difference in the sound by wiring high? Or is there some other reason to wire for high gain?

I only recommend LOW ratio always with the VTX 102 003 / OEP262A3C. Unless you have some 50ohm mics that will work with the 150ohm input impedance when the HIGH ratio is set.

[chrisp]

What, like my matched pair of Reslo ribbons?

Nah, I'm joking - LOW it is. Thanks for the response.

[rpagala]

Is there anyway to incorporate an insert for unbalanced compressor like RNC?

[Joe Malone]

Is there anyway to incorporate an insert for unbalanced compressor like RNC?

The BA PCB is only one gain stage so there is nowhere for a unbalanced insert. Just plug the output of the BA into the RNC.

With the BAD Dual99v there is two gain stages so there is a unbalanced insert point if you cut the O wire going to the output level pot.