BA500v2 Mic Pre Amp BUILD THREAD 500/51X

[Joe Malone]

Thanks so much for your prompt response Joe!
I'm using your twenty 5 twenty op amp.
Yes, balanced xlr lead to a balanced input (Metric Halo 2882).
Photos attached.

I cannot see it in the photos but have you jumpered the output transformer ratio as 1:2 or 1:3 (as that is the only extra difference on the 2503 pcb to our JLM111DC version). The 3 pads are next to the output transformer. Add a wire from centre pad to either 1:2 which gives 6db transformer boost or 1:3 which gives 10dB transformer boost and more fat 2nd harmonic

Ah, no I haven't. Sorry, just followed the build map. The ratio is right next to the JLM logo?

Here's a photo of that part of the PCB.
IMG_8593.JPG

Yes correct

BA500v2503 PCB ratio jumpers 800.png

[trispembo]

Thanks so much for your prompt response Joe!
I'm using your twenty 5 twenty op amp.
Yes, balanced xlr lead to a balanced input (Metric Halo 2882).
Photos attached.

I cannot see it in the photos but have you jumpered the output transformer ratio as 1:2 or 1:3 (as that is the only extra difference on the 2503 pcb to our JLM111DC version). The 3 pads are next to the output transformer. Add a wire from centre pad to either 1:2 which gives 6db transformer boost or 1:3 which gives 10dB transformer boost and more fat 2nd harmonic

Ah, no I haven't. Sorry, just followed the build map. The ratio is right next to the JLM logo?

Here's a photo of that part of the PCB.
IMG_8593.JPG

Fab, I found the three pin jumper frame, soldered it in, and added a jumper over 3:1 - all is working! Thanks Joe.

[trispembo]

Hi Joe, first time posting and building one of your (or any) audio kits. Really enjoying the experience so far.

There are two BA500 v2 kits on my bench, with builds completed (or so I thought). I'll focus on unit 1 to begin with before tacking the other one later.

Unit 1 seems to be powering up ok (VU light on, 48v LED comes on, takes signal on XLR & DI with VU meter and gain pot active, pad works) but is not passing any signal to lunchbox output. No noise, nothing. Usual trouble shooting with lunch box confirms slots are working with other gear.

Currently I only have a multimeter for tests, but am happy to procure a signal generator if needed. Any help would be most graciously received!

Great, unit 1 is working.

Now to unit 2. I've added the ratio jumper, so it's now passing audio to my DAW. Yay.

Audio passes from both XLR and DI, pad works, 48v LED comes on and phase switch is working. However, the input transformer is not doing anything - when I turn the gain pot, no change occurs.

I suppose somehow bypassed/shorted the transformer. Is that possible? What do you think I've done wrong?

Photos attached.

IMG_8594.JPG

IMG_8595.JPG

IMG_8596.JPG

[bondo2t]

Hey Joe, hope all is well. I recently built my BA500 and I am unable to get XLR output. I can however get DI. I did not see the schematics anywhere. My Questions is, Does the DI signal pass through the input transformer at all? Anywhere you can think I should look?

[Joe Malone]

Hi Joe, first time posting and building one of your (or any) audio kits. Really enjoying the experience so far.

There are two BA500 v2 kits on my bench, with builds completed (or so I thought). I'll focus on unit 1 to begin with before tacking the other one later.

Unit 1 seems to be powering up ok (VU light on, 48v LED comes on, takes signal on XLR & DI with VU meter and gain pot active, pad works) but is not passing any signal to lunchbox output. No noise, nothing. Usual trouble shooting with lunch box confirms slots are working with other gear.

Currently I only have a multimeter for tests, but am happy to procure a signal generator if needed. Any help would be most graciously received!

Great, unit 1 is working.

Now to unit 2. I've added the ratio jumper, so it's now passing audio to my DAW. Yay.

Audio passes from both XLR and DI, pad works, 48v LED comes on and phase switch is working. However, the input transformer is not doing anything - when I turn the gain pot, no change occurs.

I suppose somehow bypassed/shorted the transformer. Is that possible? What do you think I've done wrong?

Photos attached.

IMG_8594.JPG
IMG_8595.JPG
IMG_8596.JPG

I cannot see the wiring to the gain pot legs to check it is correct.

[Joe Malone]

Hey Joe, hope all is well. I recently built my BA500 and I am unable to get XLR output. I can however get DI. I did not see the schematics anywhere. My Questions is, Does the DI signal pass through the input transformer at all? Anywhere you can think I should look?

The DI input is a active fet di driving into the output transformer so everything is working. Just need to check the relay switches on when jack removed from the Di socket to switch back to the input XLR. If not check you have the BD681 transistor on the di PCB the correct way around and all soldering on the DI pcb is good.

[roninrecording]

Hiya folks

I've just built one of the BA500v2503 with a twenty 5 twenty opamp, a JLM14 on the input and JLM2503 on the output. It powers up ok, phantom LED comes on when switched, but I've got almost zero signal on the output with a 57 plugged in and max gain, just hiss/noise which raises/lowers with gain. High Z pot settings get even more hiss/noise. I've had a crack at some troubleshooting, even using my old pal Chatgpt, and it's telling me to jumper the red wire from the JLM14 to ground. Before I got soldering anything, I figure I should check in with an actual human.

Some pics below...

Anything jump out at anyone? I do believe the DI 10pin socket might be around the wrong way, but there's no DI for this build and I think I caught the snafu and moved the jumpers to the correct place.

[Joe Malone]

Hiya folks

I've just built one of the BA500v2503 with a twenty 5 twenty opamp, a JLM14 on the input and JLM2503 on the output. It powers up ok, phantom LED comes on when switched, but I've got almost zero signal on the output with a 57 plugged in and max gain, just hiss/noise which raises/lowers with gain. High Z pot settings get even more hiss/noise. I've had a crack at some troubleshooting, even using my old pal Chatgpt, and it's telling me to jumper the red wire from the JLM14 to ground. Before I got soldering anything, I figure I should check in with an actual human.

Some pics below...

Anything jump out at anyone? I do believe the DI 10pin socket might be around the wrong way, but there's no DI for this build and I think I caught the snafu and moved the jumpers to the correct place.

Ok if you ever solder the 10 pin headers in backwards it is easy to fix as 2 small screwdrivers will lift the black plastic box up off the pins and it can be turned 180 degrees and slide back down the 10 pins. The only 4 pins needed without a DI is the 2 pairs that are jumpered with jumper shunts. If they are not linked or pcb is damaged then there will be a hole in the audio input to the mic pre which is why you will get no audio but hear the hiss turn up with gain and higher impedance settings.

This hiss means the whole mic pre is working except for the input wiring has a break in it.

Did you manage to remove the 10 pin header at all or just heated it up heaps? As some of the plated holes may have been pulled out if removed. Adding 1 or 2 wire links should be able to fix the GO between if there is a broken track.

Be good to see more photos of the GO between 500 pcb from different angle while still mounted in the BA500 so I can check it over better.

The red wire from the JLM14 never goes to ground.

[roninrecording]

Howdy Joe!

Ahh that's a very cool trick re; the 10pin header, I'll remember that for next time (hopefully there won't be a next time). I didn't bother to remove this header as I figured the only important thing were the jumpers as I'm not fitting this with a DI.

And I did think chatgpt was a little cocky in it's response! The red wire from the xformer is still just going to it's home on the PCB, and the black wire is floating.

I've attached some more pics of the GB500v2 in situ, hopefully they show something.

[bondo2t]

Hey Joe, I want to put a 2623 on a BA500v2503 sub board. If I jumper the output transformer ratio to two, which groupings should I use?

[Flatman]

Hi Joe
Soldered the second BA yesterday, and assembled it this morning. As I was soldering the Main board yesterday, I realised I ordered the 2503 output transformer on the first BA and not the 111. , you’ll notice i’ve ordered a third BA with a Twenty 5 twenty op amp. I was planning on swapping the main boards over between the first BA and the one I have just ordered, and having 2 setup with a JLM14/99/111 config and then the third “api”style, with the JLM14/twenty 5 twenty/2503 config. Hope that will work between what i already have and the parts I have ordered yesterday.

As far as this weekend’s BA build, it went even easier than the first, specially with the added advantage of being able to see the pictures this time.

[Flatman]

I must say, you keep messing with my OCD, by giving us 8 x 10R resistors and a board that only accepts 7.