BA BA2 BA4 BAD Dual99v Build Thread

Support for JLM Audio Kits

Moderator: Joe Malone

Osse87
Posts: 2
Joined: Sat Jan 22, 2022 1:18 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Osse87 »

Joe Malone wrote:
Sat Jan 22, 2022 1:14 pm
Osse87 wrote:
Sat Jan 22, 2022 9:37 am
Hello guys, first post here by me, I hope this is the right place for my post. I built a two channel BAD a few years ago and one of the channels have developed a high noise floor since quite some time ago. I think I diagnosed it to one of the OPA2604 that has gone bad as it turns VERY hot within like 10 seconds of powerup. I wonder if there are any direct replacement IC's out there as these seem to not be available anymore? I'm using the small 48v powersupply. I was thinking of the NE5532AP but looks like I'll have to add some zener diode also if going this route.

I'm not totally foreign to converting it into a single IC unit if it's possible to bypass one of the IC sockets either, I rarely need this much gain on tap anyhow. As I've got 3 working OPA2604 I could use one in either unit, and install for a dual in one of them in the few cases where I need the extra gain, is this feasible?

Thanks!

Best,
Ossian
Swap OPA2604 between channels to see if the fault follows the opamp or stays with the channel. If you need a OPA2604 I have some. But do the swap test first and let me know what you find here.
Hello Joe, thanks for your response. The noise follows the OPAMP from one channel to the other so I think it's safe to say that the OPA2604 is the problem.

I have another question aswell, I have the old .375A 18w power supply, would it be possible to also install a pair of GAIN mic pre and hook them up to this PSU for a 4 channel unit? I'm a little confused about the GAIN mic pre unit, as in the store the description says input transformer and that the unit are supplying 48v for phantom power. In the GAIN Mic pre forum thread however there are mentions of an output transformer, no input transformer and that the 48v phantom power is leaved out. I have enough units with phantom power and would ideally only need a unit which does not supply phantom power at all so I can connect it with TRS connectors in the back, it would be simplier to just drill holes for 4 TRS jacks rather than XLR connectors. If it works, what would be a good configuration for the GAIN Mic pre in this situation? Is the GAIN Mic pre provided as a full kit?

Thanks!
Ossian

User avatar
Joe Malone
Site Admin
Posts: 2070
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

Osse87 wrote:
Mon Jan 24, 2022 7:14 am
Joe Malone wrote:
Sat Jan 22, 2022 1:14 pm
Osse87 wrote:
Sat Jan 22, 2022 9:37 am
Hello guys, first post here by me, I hope this is the right place for my post. I built a two channel BAD a few years ago and one of the channels have developed a high noise floor since quite some time ago. I think I diagnosed it to one of the OPA2604 that has gone bad as it turns VERY hot within like 10 seconds of powerup. I wonder if there are any direct replacement IC's out there as these seem to not be available anymore? I'm using the small 48v powersupply. I was thinking of the NE5532AP but looks like I'll have to add some zener diode also if going this route.

I'm not totally foreign to converting it into a single IC unit if it's possible to bypass one of the IC sockets either, I rarely need this much gain on tap anyhow. As I've got 3 working OPA2604 I could use one in either unit, and install for a dual in one of them in the few cases where I need the extra gain, is this feasible?

Thanks!

Best,
Ossian
Swap OPA2604 between channels to see if the fault follows the opamp or stays with the channel. If you need a OPA2604 I have some. But do the swap test first and let me know what you find here.
Hello Joe, thanks for your response. The noise follows the OPAMP from one channel to the other so I think it's safe to say that the OPA2604 is the problem.

I have another question aswell, I have the old .375A 18w power supply, would it be possible to also install a pair of GAIN mic pre and hook them up to this PSU for a 4 channel unit? I'm a little confused about the GAIN mic pre unit, as in the store the description says input transformer and that the unit are supplying 48v for phantom power. In the GAIN Mic pre forum thread however there are mentions of an output transformer, no input transformer and that the 48v phantom power is leaved out. I have enough units with phantom power and would ideally only need a unit which does not supply phantom power at all so I can connect it with TRS connectors in the back, it would be simplier to just drill holes for 4 TRS jacks rather than XLR connectors. If it works, what would be a good configuration for the GAIN Mic pre in this situation? Is the GAIN Mic pre provided as a full kit?

Thanks!
Ossian
The GAIN is a BA with no input 48v phase or pad switches and no input transformer. It is made to use large input transformer that are not pcb mount or gain makeup amps for EQ etc. The GAIN is available as pcb parts kit. But needs an input transformer off pcb to give balanced in.

Normally if you just don't need 48v just leave that switch off the BA pcb is usually easier if using pcb mount input transformers.
Joe :-)
JLM Audio
Capturing Audio without Injury

living sounds
Posts: 31
Joined: Tue Jul 17, 2007 6:54 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by living sounds »

Was the phase flipped between BA revisions? I've got two revisions of the BA board. All wiring was done correctly, but the signal is inverted at the trafo input on one channel.

User avatar
Joe Malone
Site Admin
Posts: 2070
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

living sounds wrote:
Sat May 28, 2022 7:07 pm
Was the phase flipped between BA revisions? I've got two revisions of the BA board. All wiring was done correctly, but the signal is inverted at the trafo input on one channel.
Can you let me know or send me a photo of the 2 pcb versions as there are many. And what input transformers are fitted? And if there are output transformer photos of them as well so I can check.
Joe :-)
JLM Audio
Capturing Audio without Injury

living sounds
Posts: 31
Joined: Tue Jul 17, 2007 6:54 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by living sounds »

Joe Malone wrote:
Mon May 30, 2022 8:10 pm
living sounds wrote:
Sat May 28, 2022 7:07 pm
Was the phase flipped between BA revisions? I've got two revisions of the BA board. All wiring was done correctly, but the signal is inverted at the trafo input on one channel.
Can you let me know or send me a photo of the 2 pcb versions as there are many. And what input transformers are fitted? And if there are output transformer photos of them as well so I can check.
I can't make photos at the moment, but one revision is really old (ca 2010) and the other is the latest (black). Both boards have brand new JLM14 fitted. I have measure resistance from the + input to the respective trafo inputs, switches are set identically. Measurements (straight continuity vs the transformers DC resistance) are opposed between the two boards.

User avatar
Joe Malone
Site Admin
Posts: 2070
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

living sounds wrote:
Mon May 30, 2022 9:04 pm
Joe Malone wrote:
Mon May 30, 2022 8:10 pm
living sounds wrote:
Sat May 28, 2022 7:07 pm
Was the phase flipped between BA revisions? I've got two revisions of the BA board. All wiring was done correctly, but the signal is inverted at the trafo input on one channel.
Can you let me know or send me a photo of the 2 pcb versions as there are many. And what input transformers are fitted? And if there are output transformer photos of them as well so I can check.
I can't make photos at the moment, but one revision is really old (ca 2010) and the other is the latest (black). Both boards have brand new JLM14 fitted. I have measure resistance from the + input to the respective trafo inputs, switches are set identically. Measurements (straight continuity vs the transformers DC resistance) are opposed between the two boards.
Ok I cannot see any changes in the front end switch phasing in any of the BA pcbs but we have had several JLM14 that have had red and green wire phasing reversed in the transformer so I think it is most likely this problem which is easily fixed by swapping red and green on the pcb if using 1:4 or red and black if using 1:8. Also check you do not have yellow and blue swapped on one pcb etc
Joe :-)
JLM Audio
Capturing Audio without Injury

living sounds
Posts: 31
Joined: Tue Jul 17, 2007 6:54 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by living sounds »

Thanks Joe, but that wouldn't explain my measurements. The signal is reversed at the primary, at the trafo input. So trafos don't even come into play here.

kolchek
Posts: 3
Joined: Fri Jun 16, 2023 2:22 pm

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by kolchek »

An ignorant question: I’m guessing that if i wanted to pad more than 20db the solution isn’t just increasing the value of rpad? Thanks.

User avatar
Joe Malone
Site Admin
Posts: 2070
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

kolchek wrote:
Tue Jun 20, 2023 8:05 pm
An ignorant question: I’m guessing that if i wanted to pad more than 20db the solution isn’t just increasing the value of rpad? Thanks.
If you want to pad more dB make RPad value smaller. Like in Dual99v on BAD PCB we use RPad = 51R to make 26dB pad.
Joe :-)
JLM Audio
Capturing Audio without Injury

kolchek
Posts: 3
Joined: Fri Jun 16, 2023 2:22 pm

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by kolchek »

Joe Malone wrote:
Wed Jun 21, 2023 10:31 am
kolchek wrote:
Tue Jun 20, 2023 8:05 pm
An ignorant question: I’m guessing that if i wanted to pad more than 20db the solution isn’t just increasing the value of rpad? Thanks.
If you want to pad more dB make RPad value smaller. Like in Dual99v on BAD PCB we use RPad = 51R to make 26dB pad.
Great. Thanks Joe.

pkuchar
Posts: 3
Joined: Tue Jan 23, 2024 1:01 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by pkuchar »

Hi folks, got a question about the 111dc circuit boards, do any of the resisters need to be fitted? I built a BA4 with jlm 14 inputs 99v opamps and 111dc output transformers. with the 48v 25 watt power supply. They are all working but I'm getting a pulsing from the power supply. The leds get dimmer then brighter and I get an audible click. Should I upgrade the power supply to the 40 watt version?
thanks,
Peter Kuchar

User avatar
Joe Malone
Site Admin
Posts: 2070
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

pkuchar wrote:
Sun Feb 18, 2024 1:09 am
Hi folks, got a question about the 111dc circuit boards, do any of the resisters need to be fitted? I built a BA4 with jlm 14 inputs 99v opamps and 111dc output transformers. with the 48v 25 watt power supply. They are all working but I'm getting a pulsing from the power supply. The leds get dimmer then brighter and I get an audible click. Should I upgrade the power supply to the 40 watt version?
thanks,
Peter Kuchar
HI Peter
No resistors need to be fitted to the 111dc pcbs. Only 10 pin header, terminals, transformer, and XLRs

The 25w with modern black BA pcbs should boot up fine and run with a better noise floor than a 40w as long as the BD681 soft start transistor was fitted to each pcb. The hiccup mode is the protection mode for the power supply.

A good idea is to test each BA pcb one at a time on power by removing the 48v wire from the other 3 pcbs. Just to be sure they all power and work fine. Then power a second and then a third and four pcb.

Feel free to put up or email some photos for me to check over
Joe :-)
JLM Audio
Capturing Audio without Injury

pkuchar
Posts: 3
Joined: Tue Jan 23, 2024 1:01 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by pkuchar »

I did fit transistors, trim pot and wired the transformer correct. I'll try to power them one at a time like you suggest.
thanks,
Peter

pkuchar
Posts: 3
Joined: Tue Jan 23, 2024 1:01 am

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by pkuchar »

My voltage was running a bit high. 47.5 volts in and 24.75 out or so on all 4 pres', So I dialed the volts back to about 46.5 in and around 24.33 out and that was enough to get the power supply out of hiccup mode. now all 4 preamps are running smoothly and sounding great! I was going to use them on my 4 toms, now the highs are so smooth they sound great on overheads and guitars. Love the impedence pot, cymbals sound great! One thing is I don't have continuity with zero volts and the case, no noise, should I scratch off some paint where the dc jack connects?
Peter Kuchar

User avatar
Joe Malone
Site Admin
Posts: 2070
Joined: Wed Jan 24, 2007 11:35 pm
Location: Brisbane, Australia
Contact:

Re: BA BA2 BA4 BAD Dual99v Build Thread

Post by Joe Malone »

pkuchar wrote:
Fri Feb 23, 2024 10:56 pm
My voltage was running a bit high. 47.5 volts in and 24.75 out or so on all 4 pres', So I dialed the volts back to about 46.5 in and around 24.33 out and that was enough to get the power supply out of hiccup mode. now all 4 preamps are running smoothly and sounding great! I was going to use them on my 4 toms, now the highs are so smooth they sound great on overheads and guitars. Love the impedence pot, cymbals sound great! One thing is I don't have continuity with zero volts and the case, no noise, should I scratch off some paint where the dc jack connects?
Peter Kuchar
Cool great to hear you got them all going and like them :-)

If you are having trouble with the dc barrel linking the chassis to 0v. We just add a wire from the dc connector 0v to where the side bolts onto the back panel next to it so the 2 screws there link it to the chassis. If the BA4 rack is bolted into a rack frame then it will also get chassis ground from the other gear in the rack so usually it doesn't matter as look as the audio has good quiet noise floor
Joe :-)
JLM Audio
Capturing Audio without Injury

Post Reply