For some time now I’ve been contemplating building a tube bass amp, but could never decide on what vintage amp to base it on. Would it be Fender or Ampeg? I have previously built some Fender clone guitar amps successfully so I was confident that I could tackle a bass amp, but which one? In any case which ever I chose, it would be costly, and it would probably be cheaper to buy a used amp, but in my part of the country old tube amps are rare, let alone old bass amps. Anyway there’s more fun doing it yourself. Recently Ampeg have release the B-15 Heritage amp combining the best of their 1964 and 1966 Bass Combo models at a recommended retail price of AU$8600. Whoa! That’s only available to well heeled players, one of which I’m not. The B-15 is of course an iconic amp, one we’ve heard countless times in our youth, even though we didn’t know it at the time, played by the likes of Jamerson and Babbitt. My mind was made up. I can build a clone for a fraction of that price. It may not look like a B-15 Flip top, but it can sound pretty close. So of to Schematic Heaven http://schematicheaven.net for schematic of the B-15 amps and a general search on all things B-15 via Google. This paid off because I found the CtG web site CtG electronics - Home which has published a complete build of what they call the “CtG FCN-51-B custom amplifier (based on the Ampeg B-15-N series)”. The web site has PDFs of the schematics and layout and description of the amp. “The FCN-51-B combines the original circuits of both the B-15NC (1964) as well as the later B-15NF (1965-67). Maintaining these circuits keeps the same gain structure and biasing found in the original B-15N amp designs, helping to preserve their true heritage.” This appears to be close to what Ampeg is offering with the release of their new B-15 Heritage amp. My mind made up, it was time to gather the parts. Parts were sourced from Amplified Parts Amplified Parts in the US, Evatco Electronic Valve & Tube Co. Evatco Pty Ltd | Electronic Valve & Tube Co. and WES Electronics WES AUSTRALIA here in Australia. After an anxious wait, parts began to arrive, and work could begin. First, was deciding a layout for the chassis. I followed the layout suggested in the CtG build, however this proved to be problematical. (If I were to build another I would allow a little more space between the rear of the chassis and the tube sockets). The chassis is a Hammond 1441-26BK3 16 x 8 x 4 inches box from Evatco. The power transformer is also a Hammond 290DEX and output transformer is a Hammond 1650HA Ultra linear also from Evatco. At this stage I won’t be using the ultra linear windings, but may try later, once things are running. The reason for this transformer, is because it was the only one I could find with the correct plate impedance. While waiting on hardware I began to assemble the circuit on a tag board I already had, and from my stock of resistors. When the hardware arrived, this was put aside to work on the chassis. The chassis was duly bashed, and filled with appropriate holes to mount the hardware and wiring began. This is when I found that a little more room at the back would have made for an easier access to components for wiring, but I think it will be ok. Laying out the chassis Chassis with holes Transformers, capacitor and tube sockets mounted Wiring begun Wiring is now to the stage of mounting the volume and tone pots. Stand by for more.