I am considering a push-pull amp for a small combo I want to build. I want to make a tight build, so I mocked some stuff together in Google Sketchup first. So far I think I like the way it might look. This is a small combo amp, only 16" by 16" by 8-1/2" deep. I think it might work with a 10" speaker.
I tried to see if a 12" speaker would work but the cage would be hitting the transformers, or be so tight that heat would be a problem. So, I shrunk the speaker size back to 10" and it looks like there is more than enough room for any buildup of heat and clearance for all components.
I am thinking of using an Eminence Lil'Buddy speaker for this. I think the "bud" part is a joke because the cone is made from hemp. I've heard good things about the Cannabis Rex speaker, but that is a 12" model. Maybe it will be full, clear, and punchy enough. Basically I want something small enough so that I can take it out of the house (in one hand, guitar in the other). I have this delusion that I'll get some kind of invitation and I won't have a simple amp to take without planning and taking apart a head and speaker cab setup.
I used Sketchup for another build, but I didn't go into much detail. But, because I almost ran into an issue on that build with the placement of the transformers, I put some effort into putting most of the components on the chassis that would stick out and interfere with things like the speaker. I haven't built an amp with the chassis in a transverse arrangement like this (tubes facing down), so that would be an interesting challenge.
It seems like everything will be fine except for the heat. Maybe I should put a vent or two on the top. This will be an open-back design, so maybe there will be enough ventilation so that the tubes and transformers don't heat up the cone too much (or warp the cabinet or something). I am really thinking about covering this amp with tweed (even though it is not a Fender Deluxe, I sure like that look). I'm also thinking about using 3/4" pine stock, but routing fluting lines from the inside to shave a few ounces off. I think there would still be more than enough strength.
This will be my first push-pull build. This means there will be to power tubes and a more efficient amplification scheme. I've heard they can be quieter too, especially with negative feedback suppressing extraneous noise. The downside might a loss of the even-order creamy harmonics that single-ended designs can do. I guess I will just have to build one and see, because I don't own any PP amps and I don't spend much time in guitar stores trying amps or guitars out.
--gh
