BA500 Mic Pre Amp BUILD THREAD 500/51X

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Joe Malone »

Warbler wrote:You are so helpful! I really appreciate that.

Image
Build looks good. Start with the below and answer the questions and we should be able to get you going ASAP.

OK check the 10pin plug going into the GO between input as it doesn't look fully plugged in. Sitting out a few mm.

Do you have an extender cable? Y/N

First check you have all 3 power rails +/-16v and 48v at the back edge connector of the BA500? Y/N.
(Pin 13 is 0v for black meter probe, Pin 15 = 48v, Pin 14 = -16v, Pin 12 = +16v.

When you plug a jack into the DI input slowly can you hear the white relay click on and off? Y/N

With nothing plugged into the BA500 input turn up your monitors and see if the output hiss level goes up when you turn up the BA500 gain pot? Y/N

Did you get a dummy plug in your kit (10 pin header with hot melt glue on the back)? Y/N
Joe :-)
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Warbler
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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Warbler »

Thanks Joe. I’ll be able run those checks after the holidays and get back to you.

I do have an extender card.
I did get a dummy plug.
Merry Christmas!

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Warbler »

Ok, back at it.

I have 16+ & 16- & 38v phantom. (This is low for phantom I know. I can adjust that.)
I can hear the relay click when plugging in the DI
When I turn the gain all the way up, there's a funky spot towards the top (just under max) where all of a sudden my gain is there. Bad pot maybe?

Warbler
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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Warbler »

Pot checks out smooth.
And strike that previous comment on the gain being "back". Just makes some noise when the pot is turned past few clicks to max.

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Warbler »

Turns out this mic pre is totally fine. There was a combo of diagnostic stupidities, on my part, leading me astray. My apologies, and thanks for your willingness to help.

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Joe Malone »

Warbler wrote:Turns out this mic pre is totally fine. There was a combo of diagnostic stupidities, on my part, leading me astray. My apologies, and thanks for your willingness to help.
Finally back to work today for start of 2019. Great to to hear the mic pre is working :-)
Joe :-)
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Hynek
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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Hynek »

Hi, Joe--

Just finished the BA500 that arrived a couple of days ago from you. The build was a breeze and everything works great!

I purchased the sweepable HPF mini module along with the BA kit with the intent to integrate it in place of the unused DI. Can you throw me some suggestions as to where the HPF would be best inserted in the circuit? I know you touch upon this subject on the first page of this thread but my situation differs in the fact it is an active LPF circuit rather than just a capacitor.

I already have the HPF powered up so my question is just on
- best insertion point
- any IN and OUT impedance concerns (should I change the Zin of the HPF or is 10k good?)
- the HPF's output is DC blocked, any need to add a cap at the input as well?

Thanks for your help.

PS: What's the deal with the floods we see on the news here? I hope you're staying out of the way!

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Joe Malone »

Hynek wrote:Hi, Joe--

Just finished the BA500 that arrived a couple of days ago from you. The build was a breeze and everything works great!
Cool great to hear :-)
I purchased the sweepable HPF mini module along with the BA kit with the intent to integrate it in place of the unused DI. Can you throw me some suggestions as to where the HPF would be best inserted in the circuit? I know you touch upon this subject on the first page of this thread but my situation differs in the fact it is an active LPF circuit rather than just a capacitor.

I already have the HPF powered up so my question is just on
- best insertion point
- any IN and OUT impedance concerns (should I change the Zin of the HPF or is 10k good?)
- the HPF's output is DC blocked, any need to add a cap at the input as well?
Easy one.

Cut the red wire in the short cable from the GO between 500 pcb to BA500 main pcb as shown in the link below.
http://www.jlmaudio.com/forum/viewtopic ... =188#p2021

Wire HPF input to wire coming from the GO between 500 pcb and HPF output to wire going to the BA500 main pcb

Remove R4 10k or replace with 1MEG otherwise is will overload the variable impedance pot from working properly.

Since the HPF is before the main gain stage you need to use a low noise dual opamp like OPA2134. A NE5532A may even work quieter but may add a bit of variable frequency pot noise while sweeping the frequency.
Thanks for your help.
No Problems. Neat idea :-)
PS: What's the deal with the floods we see on the news here? I hope you're staying out of the way!
All good hear. Flooding above us and fire below us. Seems the wrong way around.
Joe :-)
JLM Audio
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Hynek
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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Hynek »

Glad you're safe and thanks for the guidance!
Will proceed as instructed.

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Mattsoniclab »

Hi Guys.

I had a great time on the weekend building this kit. All up it took me about 5 hours (I'm a pretty slow worker!) But it worked out perfectly, I'm yet to properly put it through its paces though ;)

The only real challenge in the build - and I just wanted to post this here to possibly help someone else out - was fitting the VTX input transformer. It really didn't want to fit between the two header blocks, so these required a fair amount of shaving with a knife and then careful sanding with 120 grit sandpaper to get the transformer between them without causing the PCB to bend.
I'd already soldered them in before I realised how tight the fit would be, so I'd advise people push the header blocks as far to the side as possible when seating them.

oh and it took me a while to realise that there wasn't a ground lift jumper pin in the new design!

Other than that it was a really great kit to build.

thanks Joe and team!

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Joe Malone »

Mattsoniclab wrote:
Thu Jul 02, 2020 5:27 pm
Hi Guys.

I had a great time on the weekend building this kit. All up it took me about 5 hours (I'm a pretty slow worker!) But it worked out perfectly, I'm yet to properly put it through its paces though ;)

The only real challenge in the build - and I just wanted to post this here to possibly help someone else out - was fitting the VTX input transformer. It really didn't want to fit between the two header blocks, so these required a fair amount of shaving with a knife and then careful sanding with 120 grit sandpaper to get the transformer between them without causing the PCB to bend.
I'd already soldered them in before I realised how tight the fit would be, so I'd advise people push the header blocks as far to the side as possible when seating them.

oh and it took me a while to realise that there wasn't a ground lift jumper pin in the new design!

Other than that it was a really great kit to build.

thanks Joe and team!
Hi Matt Great to hear you liked building the kit :-)

Yes the latest batch of VTX transformers have the bottom edge of the mu can flared out a bit. Simply squeezing the Bottom of the mu can in a vice will fix this or fitting the VTX transformer first and add the IDC headers after on a slight angle.

Yes most 500 racks short the pin 1 of the output XLR to 0v so the ground lift is of no use any more.
Joe :-)
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monkeyt
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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by monkeyt »

I hope this is the right spot, if not, I apologize. I built a couple of these BA500 preamps a couple years ago. I've used them a bunch, love them, they sit very nicely with all the other CAPI and AML preamps I've built. Anyway, I guess I've always used dynamic mics on them, because I went to use a phantom powered mic the other day in a session, and I don't have phantom power on either of my BA500 preamps. The LED comes on when I flip it on, but no juice is going out I guess. I tested the slots with other modules and phantom works fine, and I put the BA500 into other slots and still no phantom. Since its both of them, I thought I maybe missed something in the build???? Is there a jumper or something?
I did just notice that with phantom on, if I flip polarity or turn the pad on, a serious POP occurs on the output. Otherwise, they sound great with dynamic mics!!!

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Joe Malone »

monkeyt wrote:
Tue May 31, 2022 7:30 am
I hope this is the right spot, if not, I apologize. I built a couple of these BA500 preamps a couple years ago. I've used them a bunch, love them, they sit very nicely with all the other CAPI and AML preamps I've built. Anyway, I guess I've always used dynamic mics on them, because I went to use a phantom powered mic the other day in a session, and I don't have phantom power on either of my BA500 preamps. The LED comes on when I flip it on, but no juice is going out I guess. I tested the slots with other modules and phantom works fine, and I put the BA500 into other slots and still no phantom. Since its both of them, I thought I maybe missed something in the build???? Is there a jumper or something?
I did just notice that with phantom on, if I flip polarity or turn the pad on, a serious POP occurs on the output. Otherwise, they sound great with dynamic mics!!!
HI What input transformers are in your BA500? If they are JLM14 have you accidentally attached the JLM14 black wire to 0v instead of leaving it disconnected, The black wire should be insulated in heat-shrink and not connected to 0v if you are using the green and red wires for input. The red led coming on means the 48v is there but if you link the black wire to 0v this will hold the balanced input down at 0v so phantom will not work.
Joe :-)
JLM Audio
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monkeyt
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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by monkeyt »

Perfect! That worked, thank you Joe. Fantastic product and fantastic help!
Joe Malone wrote:
Tue May 31, 2022 7:28 pm
monkeyt wrote:
Tue May 31, 2022 7:30 am
I hope this is the right spot, if not, I apologize. I built a couple of these BA500 preamps a couple years ago. I've used them a bunch, love them, they sit very nicely with all the other CAPI and AML preamps I've built. Anyway, I guess I've always used dynamic mics on them, because I went to use a phantom powered mic the other day in a session, and I don't have phantom power on either of my BA500 preamps. The LED comes on when I flip it on, but no juice is going out I guess. I tested the slots with other modules and phantom works fine, and I put the BA500 into other slots and still no phantom. Since its both of them, I thought I maybe missed something in the build???? Is there a jumper or something?
I did just notice that with phantom on, if I flip polarity or turn the pad on, a serious POP occurs on the output. Otherwise, they sound great with dynamic mics!!!
HI What input transformers are in your BA500? If they are JLM14 have you accidentally attached the JLM14 black wire to 0v instead of leaving it disconnected, The black wire should be insulated in heat-shrink and not connected to 0v if you are using the green and red wires for input. The red led coming on means the 48v is there but if you link the black wire to 0v this will hold the balanced input down at 0v so phantom will not work.

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Re: BA500 Mic Pre Amp BUILD THREAD 500/51X

Post by Joe Malone »

monkeyt wrote:
Wed Jun 01, 2022 3:37 am
Perfect! That worked, thank you Joe. Fantastic product and fantastic help!
Great to hear you got it working so quickly :D 8)
Joe :-)
JLM Audio
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