I thought some folks might like to see some of what goes into designing one of my amps, so I'm posting the early stages of a new amp we are working on. It's so early, we still don't have a name yet. Here is what we're going for in the new design:
- 50 watt power amp (EL34 based)
- DC heaters
- Single channel
- Two footswitchable masters (Regular and Solo), each with 3 way saturation switch
- Series/Parallel switchable Tube buffered EFX Loop with independent Send and Receive pots (can be footswitched in/out of the circuit)
- New 3 way "Bright" switch
- Resonance control instead of Density
- External Bias points and adjustment
- Overall Master (PPIMV)
- No line out (I figure people can use the Suhr Iso Line out box if they need one)?
- Price $2,000-2,200 (TBA, of course!)
The first thing I did was get the schematics done and then it was on to 3D mechanical design. 3D Models of each part are made (Including the new custom 50 watt transformers from Mercury Magnetics) and then the mechanical design can proceed. The pictures above show the current status of the design, however, we are still contemplating some major changes. You can see the new bright switch in the front views well as connections for your multimeter for bias adjustment on the back. In the top view, you can see the black cutouts in the chassis by each power tube socket for the bias adjust pots for each tube. You just put your screwdriver in the hole and the bias pot is right there. The new head shell design will make it easy to take the back panel off to get at these pots. At least you don't have to take the amp out of the chassis!
Now one of the things we wanted to do to reduce cost and simplify the builds was to PCB mount the power tubes (my preamp tubes have always been PCB mounted). Some people complain about PCB mounted tubes, but we think this approach will satisfy everyone. Above are some screenshots I captured from the 3D model to show how these will be done. As you can see, the long leg Belkin socket is soldered to the (green) PCB and there is a hole cut in the PCB on each side of the socket. A 15mm standoff will be screwed to the PCB. When assembling the amp, the standoff comes up to the chassis as well and the standoff is screwed onto the chassis. This way, it is ROCK solid AND we can easily take out the board without having to unsolder the octal sockets. Pretty cool, huh? PCB AND chassis mounted. We'll still be using 1/8" thick boards, so this should work well. We'll use metric screws and spilt washers on this. This design will allow us to use the same pcb to chassis spacing as the Cherry Bomb (same PEMs ~15.956mm). BTW - those long Belkin octal socket legs will, of course, be trimmed after soldering.