VOX AC30 new PCB design

[aaelectronics]

Hi all,
This is Andrea from AAElectronics (https://www.aaelectronicspcb.com/). After a lot of request, I've started design for a PCB for Vox AC30 style amps, with the aim to make it flexible enough to accommodate seevral variants (e.g., EF86 channel, Normal, the AC15 version or additional mods). I'll attach the layout, PCB, and schematic for reference.

Would love to get your input on my design, and whether you'd like to see/add something to the PCB/schematic.
Have a great weekend!
Andrea
AA Electronics

[Merlin]

That will look very cool built up. Semi vintage, semi modern.
Please please please put individual current sense resistors in the EL84 cathodes. The single shared bias resistor in the Vox absolutely sucks and gives you no clue how mismatched the tubes are. I hate modern amps that don't let you easily measure each tube current. Like, it's 2024, throw me a bone!
The use of one dual cap seems a little odd when all the others are singles. Singles throughout would shrink the BOM.
Do not wire the HV CT to the chassis star; it should go straight to C5.
Also, standby switch? Vox never had one.
Since you have the luxury of a PCB, wouldn't it make sense to put the pots on the board too, and eliminate all that wiring?
I probably sound like a d*** now for all that criticism 

[kagliostro]

I'll like it more if you enlarge those component holes on PCB and put Turrets on it (VOX did it)

https://www.voxshowroom.com/uk/amp/ac30h2_2007_hood.html

Franco

p.s.:To my taste I like more the pot to be separated from PCB

[tubeswell]

p.s.:To my taste I like more the pot to be separated from PCB

Me also. But knowing my luck, saying what I prefer means it’ll end up being done the other way.

[shooter]

don't "save-a-buck" on the PCB quality, especially the pads.


A competent Tech should be able to replace components without the trace or pad lifting, ripping because it was cheep, see Fender and Marshall CCP made boards for poorly built, low quality workmanship...But they saved a buck.


nice design!

[pdf64]

The layout doesn't seem to show a connection back to 0V from the tone stack bass lug1.
The HT supply seems wonky, 2 phase winding with CT to 0V, but then a FWB rectifier, also with its negative output to 0V.
Maybe D3&4 are meant to be optional, to be fitted if there's a single phase winding?
The B+2 supply seems to have an additional stage of filtering, compared to any other version I'm aware of. Again, maybe one of them is optional?
C18 cathode bypass V2 can often push the margin of stability too far, such that some settings result in oscillation.
It may be a good idea to mark that as optional.

Well done getting C22 value correct 

[kagliostro]

Me also. But knowing my luck, saying what I prefer means it’ll end up being done the other way

Here we say listen to your father and your mother, then do what you want 

Franco

[aaelectronics]

don't "save-a-buck" on the PCB quality, especially the pads.


A competent Tech should be able to replace components without the trace or pad lifting, ripping because it was cheep, see Fender and Marshall CCP made boards for poorly built, low quality workmanship...But they saved a buck.


nice design!

Absolutely. All my PCBs are 2 mm thick and have 2oz/Cu density... not a fan of flimsy Fender/Marshall style flimsy stuff (which would be at the most 1.5mm and 1oz copper density). Never had a problem with a lifted pad/trace in these :)

[aaelectronics]

I'll like it more if you enlarge those component holes on PCB and put Turrets on it (VOX did it)

https://www.voxshowroom.com/uk/amp/ac30h2_2007_hood.html

Franco

p.s.:To my taste I like more the pot to be separated from PCB

Ciao Franco! Nice to talk to you again, hope Portugal is treating you well :)
I thought about turret holes, but that will substantially enlarge the entire PCB as turret pads require way more real estate. On top of that, even if it is true that you can use a turret pad without a turret, the amount of heat and solder you need to fill such a hole is quite large and impractical imho

[glass54]

Hi Andrea,
Congratulations on your PCB (I know a lot of work went into the project). Can I be a Pain and ask you to post the PCB tracks version. I would love to see the details in terminating pads.
Thank you for the opportunity for all of us to have an input into a great project.
Kind regards
Mirek

[kagliostro]

Portugal ?? I'm Italian and live in north Italy, few Km far from Venice 😉


Franco

[aaelectronics]

Portugal ?? I'm Italian and live in north Italy, few Km far from Venice 😉


Franco

My bad then, I've mistaken you for another Franco!  guitar amp world is small, but apparently not that small 
PS: I'm originally from there as well, close to Resana :)

[kagliostro]

Resana Is not very far from here, Treviso

Franco