Hi,
I'm trying to step up my PCB game designing a board for Doug Self's EQ/Preamp from LinearAudio Vol. 5. I know, there is a nice "official" board available here. However, I would love to fit this device into a Modushop Galaxy GX247 case. That's about 220mm wide and 170mm deep.
My expirience with designing my own PCB is limited to much smaller endevours. I've done simple home-made single-layer boards but no professionally manufactured boards of this complexity level. But maybe I can still pull this off 🙂
Since building Bonsai's X-Altra Phono Pre made me realize that soldering SMD isn't half as bad as I had imagined it to be, I think I can get the design to fit into the case by using 805 SMD parts where I can.
I tried to follow the best practices that I'm aware of and came up with the following board. Most tracks are .4mm Some are wider, none are smaller. I treid to set up a good star-ground structure and to make the power supply rails clean and staight. I don't know if I should consider any ground-planes. Not sure where that would make sense.
Also, I still need to work out whether I need heat-sinks for the regulators...
It would be great if some of you with more expirience could take a look and point out any glaring oversights, improvements or other tips.
Here is the PCB so far in what I hope is a high enough resolution to make out things...
Here is the GND network highlighted:
And this is the VDC+/- power supply rails
And finally a 3D view...
Would be great to get some insights on what might be missing to make this work...
Cheers!
Lars
I'm trying to step up my PCB game designing a board for Doug Self's EQ/Preamp from LinearAudio Vol. 5. I know, there is a nice "official" board available here. However, I would love to fit this device into a Modushop Galaxy GX247 case. That's about 220mm wide and 170mm deep.
My expirience with designing my own PCB is limited to much smaller endevours. I've done simple home-made single-layer boards but no professionally manufactured boards of this complexity level. But maybe I can still pull this off 🙂
Since building Bonsai's X-Altra Phono Pre made me realize that soldering SMD isn't half as bad as I had imagined it to be, I think I can get the design to fit into the case by using 805 SMD parts where I can.
I tried to follow the best practices that I'm aware of and came up with the following board. Most tracks are .4mm Some are wider, none are smaller. I treid to set up a good star-ground structure and to make the power supply rails clean and staight. I don't know if I should consider any ground-planes. Not sure where that would make sense.
Also, I still need to work out whether I need heat-sinks for the regulators...
It would be great if some of you with more expirience could take a look and point out any glaring oversights, improvements or other tips.
Here is the PCB so far in what I hope is a high enough resolution to make out things...
Here is the GND network highlighted:
And this is the VDC+/- power supply rails
And finally a 3D view...
Would be great to get some insights on what might be missing to make this work...
Cheers!
Lars
I would make a ground plane on the top side of the board, for only the audio circuitry.
Then all ground leads of all parts in the audio circuit go directly to the ground plane.
Use thermal reliefs for the connections. All ground traces in the audio part of the pcb will be gone.
All other traces would be on the bottom of the pcb, so as to not break up the ground plane.
And then the power supply ground connects to the audio ground plane with one wide trace
coming from the regulator grounds.
Then all ground leads of all parts in the audio circuit go directly to the ground plane.
Use thermal reliefs for the connections. All ground traces in the audio part of the pcb will be gone.
All other traces would be on the bottom of the pcb, so as to not break up the ground plane.
And then the power supply ground connects to the audio ground plane with one wide trace
coming from the regulator grounds.
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Don't profess to be an expert, it's only my own experience from having done my first 'serious' audio PCB. On my preamp (volume/tone/mm/mc stages) I'd have struggled to put my ground plane on one side and all the signal traces on the other without them getting long/messy. Maybe I need more practice 🙂 I did all my non-ground routing as tidily as I could using both sides (with minimal vias/swapping of layers) and then flooded both sides with grounded copper. I then stitched the floods on each side together where I could using a zillion vias on a fixed pitch so they looked tidy. I tried to get some grounded copper between all the tracks to minimise crosstalk between the tracks. Like Ryma I took a thick ground track from the regulator ground to the ground floods rather than including the regulator grounds in the ground floods. I'm very happy with the result, so much so I'm tempted to upgrade my DAC to see if I can get more out of my system. I'm yet to try a mc cartridge but the mm stage is very quiet.
It's allowed to use jumper wires on the top side if necessary, or small, short breaks in the ground plane.
Just FYI, the internal width of the GX24x-cases is only 210mm (230mm minus a 10mm panel on either side).
If you already have the case you want to use, cut a piece of cardboard to your proposed pcb size,
and see if it fits properly inside. If not, you'll have to reduce the pcb design to fit.
and see if it fits properly inside. If not, you'll have to reduce the pcb design to fit.
when the ground plane gets chopped up quite a bit, wouldn’t there be too much danger of loops being formed? I have read in a few places that a good star ground is no worse if not better for audio frequency work and that ground plane is more for digital and HF - but maybe I just did not look in the right places.
The channels are kept well apart so crosstalk is not my biggest worry.
If you guys have some pointers with regards to ground planes and when and where they are most effective, I‘d be very much interested in those…
oh and about the case. I want the sides of the board to slide into the side panel, like Bonsai did for the X-Altea. So that’s what dictates the width. But you are right. I don’t have 230mm available.
The channels are kept well apart so crosstalk is not my biggest worry.
If you guys have some pointers with regards to ground planes and when and where they are most effective, I‘d be very much interested in those…
oh and about the case. I want the sides of the board to slide into the side panel, like Bonsai did for the X-Altea. So that’s what dictates the width. But you are right. I don’t have 230mm available.
A ground plane will not be a functioning ground plane if it is chopped up. With more complex circuits, that's what
a four layer board is for, and they are often used for audio now.
A ground plane starts being effective above around 1kHz, so it is entirely appropriate for audio.
The conducted low frequency noise can be dealt with by careful component placement and partitioning the planes.
a four layer board is for, and they are often used for audio now.
A ground plane starts being effective above around 1kHz, so it is entirely appropriate for audio.
The conducted low frequency noise can be dealt with by careful component placement and partitioning the planes.
I played around with a ground plane and I think it just gets too Choppy in a 2-layer board for this circuit.
I have a few existing projects (that I did not design myself) that fare very well with a star-ground topology and no ground plane so I think I am confortable with sticking with that kind of topology here too.
I've read up a bit on minimum clearance for the primary side of the power-supply and made sure that there is enough space there. I also had to make some more room at the sides so the approach of slotting into the side-panels of the Modushop case works while leaving enough space to the sides. I also increased the track widths on the power supply and the tracks that connect the two star-grounds together.
This is what it looks like now... any additional notes/pointers/suggestions that you might have a greately appreciated...
I have a few existing projects (that I did not design myself) that fare very well with a star-ground topology and no ground plane so I think I am confortable with sticking with that kind of topology here too.
I've read up a bit on minimum clearance for the primary side of the power-supply and made sure that there is enough space there. I also had to make some more room at the sides so the approach of slotting into the side-panels of the Modushop case works while leaving enough space to the sides. I also increased the track widths on the power supply and the tracks that connect the two star-grounds together.
This is what it looks like now... any additional notes/pointers/suggestions that you might have a greately appreciated...
More experienced designers may agree or disagree but I'm interested in hearing either way. My comments would be that the earth/gnd track running down the side of the transformer is nearer to the mains line or neutral (not sure which) than I'd like myself, at the primary end of the transformer. Also I question taking the ground to the analogue circuit from the feed to the rectifier/ smoothing caps/ regulators, should it come from the ground where the caps are in the bottom left as it will be cleaner here? As I say I'm still learning myself.
Great point and I had similar thoughts/doubts. would be great if someone could add a more expirienced perspective:
Is there a "preferred" place, where the grounds from power supply and the rest of the circuit shouldcome together? Clearly, it needs to be a single point, but does it matter where that point is on the board?
Probably somewhere around the PSU and not far from where the IEC inlet would be as the PE goes to chassis as well on the shortest possible path (and best through a ground breaker). To connect ground to chassis I am using a mounting hole on the PCB where through a metal spacer ground gets connected to chassis without using any hanging wires and the likes.
I just had the first prototypes made and building one up for testing. I want to make sure it works before putting that out there...
Any chance of adding provision for a simple motorized analog pot with IR remote control?
Not having a remote volume is disturbing the listening experience having to get up each time you want to change the volume.
Not having a remote volume is disturbing the listening experience having to get up each time you want to change the volume.
I would try and tighten up the analogue blocks, move the discrete's closer to the IC's,. Using the correct IC footprint a track width of 0.25mm and a spacing of 0.20mm you can easily route a track between the IC pins, allowing more routing on the TOP layer, with the GND plane on the bottom layer. That is how I would do it if restricted to only 2 layers. 4 layers would be far better for the design.
