Help selecting an amp

Hi Guys,

I'm looking for a class A amp to build to power my speakers that i have recently completed.

the spec's on the speaker setups are
120 Watts and sensitivity or 92Db ( this sucks i know )

I looked at something like the A75, but i'm not sure if there is anywhere i can buy the PCB's for that unit.
or would i be better of building some lowr powered but cleaner amps ( zen's ? ) for use with some higher efficiency speakers later.

I would like to build them in a monoblock configuration, with a tube preamp eventually.

I am currently finishing off a 175W mosfet stereo amp ( 4 fets per channel ) for these ( i think its a class B design ) and i would like to improve the sound i am getting ( as well as the fact it would be fun making this amp )

I will eventually get around to building some better speaker boxes with some more efficient drivers in them
Give the A75 a try


I finished the A75 this summer, and I can tell you it is a fine sounding amp, that I'm sure you would be happy with. I really recommend this amp because it is easy to put together, and the documtation will help you learn some of the basic concepts of building an amplifier. You can purchase the pcb's from old colony:

The power supply is $8.95 and the amp with both channels is $14.95. You can check out the details at:

A lot of people have built this amp so their is a lot of help out there, including from Nelson himself. I also recommend reading his article on DIY opamps for a good background in his designs.