Hi I've just finished one half of my BA2 2 CH Rack Kit
I'm just doing some testing and all seems well except when I wind up the gain, I'm getting a fair amount of power supply noise, more when the phantom power is engaged. I'm just not sure if I've missed something or my lead dressing is just bad. I've attached a photo.
Thanks
Sam
20210827_141106.jpg
HI Sam
The new black pcbs are supposed to be fully built and should have BD681 and trimpot fitted. We adjust the trimpot so you have about 44v at +v of the opamp as this forms a linear smoothing regulator for each mic pre which I think is the main problem here.
Build looks very neat but you need to keep your gain and impedance wiring as short a possible so I would shorten them down so they only have a bit of slack especially the impedance wiring. Also twist the ribbon cable so it forms a tight tube between the IDC headers.
Hi I've just finished one half of my BA2 2 CH Rack Kit
I'm just doing some testing and all seems well except when I wind up the gain, I'm getting a fair amount of power supply noise, more when the phantom power is engaged. I'm just not sure if I've missed something or my lead dressing is just bad. I've attached a photo.
Thanks
Sam
20210827_141106.jpg
HI Sam
The new black pcbs are supposed to be fully built and should have BD681 and trimpot fitted. We adjust the trimpot so you have about 44v at +v of the opamp as this forms a linear smoothing regulator for each mic pre which I think is the main problem here.
Build looks very neat but you need to keep your gain and impedance wiring as short a possible so I would shorten them down so they only have a bit of slack especially the impedance wiring. Also twist the ribbon cable so it forms a tight tube between the IDC headers.
Hey Joe, thanks for the quick response. Right, I took the wrong approach when referencing the tables at the start of the thread.
Will fit them and make the adjustments and report back.
Hi I've just finished one half of my BA2 2 CH Rack Kit
I'm just doing some testing and all seems well except when I wind up the gain, I'm getting a fair amount of power supply noise, more when the phantom power is engaged. I'm just not sure if I've missed something or my lead dressing is just bad. I've attached a photo.
Thanks
Sam
20210827_141106.jpg
HI Sam
The new black pcbs are supposed to be fully built and should have BD681 and trimpot fitted. We adjust the trimpot so you have about 44v at +v of the opamp as this forms a linear smoothing regulator for each mic pre which I think is the main problem here.
Build looks very neat but you need to keep your gain and impedance wiring as short a possible so I would shorten them down so they only have a bit of slack especially the impedance wiring. Also twist the ribbon cable so it forms a tight tube between the IDC headers.
Hey Joe, thanks for the quick response. Right, I took the wrong approach when referencing the tables at the start of the thread.
Will fit them and make the adjustments and report back.
Thanks!
Fitted and adjustments made. It has made a huge improvement. There's still a little power supply noise when the gain is wound up past 3 o'clock but I'm probably not being too fair to it considering I'm just running to a line in on a basic amp while testing.
20210827_170118.jpg
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The new black pcbs are supposed to be fully built and should have BD681 and trimpot fitted. We adjust the trimpot so you have about 44v at +v of the opamp as this forms a linear smoothing regulator for each mic pre which I think is the main problem here.
Build looks very neat but you need to keep your gain and impedance wiring as short a possible so I would shorten them down so they only have a bit of slack especially the impedance wiring. Also twist the ribbon cable so it forms a tight tube between the IDC headers.
Hey Joe, thanks for the quick response. Right, I took the wrong approach when referencing the tables at the start of the thread.
Will fit them and make the adjustments and report back.
Thanks!
Fitted and adjustments made. It has made a huge improvement. There's still a little power supply noise when the gain is wound up past 3 o'clock but I'm probably not being too fair to it considering I'm just running to a line in on a basic amp while testing.
20210827_170118.jpg
Remember with nothing plugged into the input transformer it will pick up noise. So the best test is with nothing plugged into the input and pad on. Do the second channel and see how they both work with a mic input.
Hey Joe, thanks for the quick response. Right, I took the wrong approach when referencing the tables at the start of the thread.
Will fit them and make the adjustments and report back.
Thanks!
Fitted and adjustments made. It has made a huge improvement. There's still a little power supply noise when the gain is wound up past 3 o'clock but I'm probably not being too fair to it considering I'm just running to a line in on a basic amp while testing.
20210827_170118.jpg
Remember with nothing plugged into the input transformer it will pick up noise. So the best test is with nothing plugged into the input and pad on. Do the second channel and see how they both work with a mic input.
Hey Joe, I had a chance to get back to it today, I finished off the other side, tested and compared. It has a pretty low noise floor, the power supply noise seems to not be an issue so long as the unit is always on and since it's connected via my patchbay, it stays quiet. So I'd say I probably built it OK
I gave it a quick run with some mics and ran a couple tests, the channels seem to be matched well enough for stereo recording straight up and playing bass DI and adjusting the impedance sounds great.
Now that I've got it in my rack, I'll start tracking through it tomorrow. Just out of curiosity, would it be possible to fit an output trim to the BA2? it would be nice to really drive that input transformer! - I could always pad it after the output if I needed to though.
Great kit - simple to build and sounds great! great bang for the buck! Thanks!
Fitted and adjustments made. It has made a huge improvement. There's still a little power supply noise when the gain is wound up past 3 o'clock but I'm probably not being too fair to it considering I'm just running to a line in on a basic amp while testing.
20210827_170118.jpg
Remember with nothing plugged into the input transformer it will pick up noise. So the best test is with nothing plugged into the input and pad on. Do the second channel and see how they both work with a mic input.
Hey Joe, I had a chance to get back to it today, I finished off the other side, tested and compared. It has a pretty low noise floor, the power supply noise seems to not be an issue so long as the unit is always on and since it's connected via my patchbay, it stays quiet. So I'd say I probably built it OK
I gave it a quick run with some mics and ran a couple tests, the channels seem to be matched well enough for stereo recording straight up and playing bass DI and adjusting the impedance sounds great.
Now that I've got it in my rack, I'll start tracking through it tomorrow. Just out of curiosity, would it be possible to fit an output trim to the BA2? it would be nice to really drive that input transformer! - I could always pad it after the output if I needed to though.
Great kit - simple to build and sounds great! great bang for the buck! Thanks!
Sam
Cool great to hear
Adding an output pad only allows you to overdrive the output transformer if you have them fitted which is not as nice as just driving the input without the pad on.
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?
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 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?
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.
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.
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.
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.
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
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.
