Developing the MA100 amplifier

[Sherwood]

Approaching first power / fire / smoke!!

Surely this merits a video and not just pictures!

[Radford Revival]

Surely this merits a video and not just pictures!

The PSU board has proven to work - the active ripple killer circuit works far better than it has any right to. The screen supply is also functioning correctly.

I'm actually fairly certain the amplifier will work - the only question now is dialling in the feedback. Aside from some tweaks that are likely to arise I would tentatively call the design complete.

What remains is correcting the various layout mistakes on the boards (inevitable) and finishing the design of the casework. There may be a few little gremlins in the circuit design but I don't think there's much left hidden - the design has been extensively modelled and the previous version had proved most of the concepts already.

[Radford Revival]

It works! I blew it up a couple of times in the process and have a large list of small errors to correct, but aside from dialling the feedback, everything is now working!

[Radford Revival]

Real prototype pair nearly in existence!

[Radford Revival]

Prototype sneak peak! This is very much a hacked up prototype on a Hammond biscuit tin and doesn't look like much but to get to this point is fairly massive. Most of the amp's "DNA" has now been figured out. Another working copy has been running outside of a case.

It's actually surprising how sparse it looks given the performance of this design. I feared it would end up being overcomplicated but it has ended up pretty simple and elegant. The PCB up top is basically just rectification and smoothing, some extra regulation is done inside. There will be an extra small PCB in that empty space underneath in the final version. Its function will be to configure the output transformer secondaries for 2 4 or 8 ohms.

The chassis only currently has an RCA input but the amplifier natively has a differential input stage, so the real one will have both XLR and RCA inputs.

The real amp won't have wires soldered directly to PCBs - this is a temporary hack as the wire-to-board connector system I originally wanted to use didn't work out so I've just soldered wires for now.

[Swann36]

Looks great and as we are now in 2023 how’s it coming ?

Hoping your both well and I’ve not missed other posts