Hi I'm working on a 2 channel Marantz amp. I moved the bridge rectifiers and main caps off the board to a discrete power supply, followed by 18ga shielded copper wires back to their original location where extra 2200uF caps are in their place. I've also installed a DAC module.
The amp has two sets of secondaries, one powering the transistors and the other powering everything else.
1. The original configuration has the 0V lines tied together at the main caps by a small wire. Was this an afterthought, or was it intentionally a wire rather than a board trace? Should I leave it there, should I move it to the new power supply (closer to the transformer), or should I remove it now that I've added more capacitance?
Before:
After:
2. I'm worried that I'm drawing too much current from the positive swing of the second secondary. Is this sub-optimal for the op-amps? Will they have too much of a negative bias thereby affecting sound?
I'd love to power the DAC with the negative swing but I would need a negative buck regulator which is rare, and I would also have to isolate the casing of the DAC module because it will still be 12V south of the "grounded" amp casing, creating a short.
Am I being stupid trying to use the amp's transformer and I should just add another switching power supply? The off-the-shelf ones are more noisy than the mini buck regulator I think.
Thanks!
The amp has two sets of secondaries, one powering the transistors and the other powering everything else.
1. The original configuration has the 0V lines tied together at the main caps by a small wire. Was this an afterthought, or was it intentionally a wire rather than a board trace? Should I leave it there, should I move it to the new power supply (closer to the transformer), or should I remove it now that I've added more capacitance?
Before:
After:
2. I'm worried that I'm drawing too much current from the positive swing of the second secondary. Is this sub-optimal for the op-amps? Will they have too much of a negative bias thereby affecting sound?
I'd love to power the DAC with the negative swing but I would need a negative buck regulator which is rare, and I would also have to isolate the casing of the DAC module because it will still be 12V south of the "grounded" amp casing, creating a short.
Am I being stupid trying to use the amp's transformer and I should just add another switching power supply? The off-the-shelf ones are more noisy than the mini buck regulator I think.
Thanks!
Wrong schematics, both, before and after, polarity on bridge rectifier are not correct.
Look at your bridges, plus is on negative pole of your capacitors???
Bridge on protection circuit is wrong oriented.
Look at your bridges, plus is on negative pole of your capacitors???
Bridge on protection circuit is wrong oriented.
Apologies. I shouldn't be making scratch notes so late. Do you have anything else to contribute?
Before:
After:
Before:
An externally hosted image should be here but it was not working when we last tested it.
After:
Last edited:
It would be intentional to avoid ground loops going 'upstream' towards the transformers - ie. the single point of gnd commonality is where the power supplies meet the load circuitry.
Can you elaborate on how you formed that view?
1. Thank you for that insight! Since I have two sets of capacitors now, I've kept the 0v bridge in it's original location which is still where the power supplies meet the load.
Here is the original layout:
...and the modified layout with the PSU extracted. A distribution block is in its place like some kind of Borg implant (Along with the DAC on the far right):
2. We are drawing a ~1A load across both halves of the secondary, +40v to -40v after being rectified. Then we are potentially drawing a second 2A load between 0v and +40v. I know that the secondary winding can probably handle 5A, but this also means that the original load is going to see slightly less current on the positive side of its bridge with respect to the center tap, no? Can I just compensate for that with the main bias adjustment?
Specifically, the original load is a pair of JRC2068DD's
This is the alternative idea I've been working on. A fully end-to-end shielded and pigtailed 12v AC adapter:
Much appreciated.
Here is the original layout:
...and the modified layout with the PSU extracted. A distribution block is in its place like some kind of Borg implant (Along with the DAC on the far right):
2. We are drawing a ~1A load across both halves of the secondary, +40v to -40v after being rectified. Then we are potentially drawing a second 2A load between 0v and +40v. I know that the secondary winding can probably handle 5A, but this also means that the original load is going to see slightly less current on the positive side of its bridge with respect to the center tap, no? Can I just compensate for that with the main bias adjustment?
Specifically, the original load is a pair of JRC2068DD's
This is the alternative idea I've been working on. A fully end-to-end shielded and pigtailed 12v AC adapter:
Much appreciated.