Building a Gibson GA-40 clone

Hi. This blog is going to set out the story of my attempt to build a clone of a Gibson GA-40.

To date I have built two amps myself. The first was from a kit supplied by Barry at ampmaker. A lovely 5w single ended amp. Barry's kit and instructions are great. I loved the whole experience. It took about a day to build and at the end of the process I had a very nice sounding amp. I can't recommend amp maker highly enough.

My second amp build was a Marshall JTM45 clone. There are a number of JTM45 kits out there but most base din the US. With the exchange rate, customs duty and postage costs it was just too expensive to order a kit from the US to be sent to me here in London U.K.

Thankfully, George at Metro Amps has placed the instructions for his kit online and available to download for free. I can't thank you enough George. So I sourced the parts from within the UK mostly (although I did get some parts for biasing from Metro Amp because I was feeling guilty!).

I sourced a JTM45 chassis from Valve Power - pre-punch for £20 - thanks Steve!

I sourced the turret board making equipment and materials from Barry at amp maker along with the necessary hardware and wiring

I then spent quite a bit of time trying to find the right transformers online. It is really hard to get hold of tranformers in the UK I think. Eventually I was lucky enough to find Bluebell Audio based in Dundee. Philip there offers what appears to be the entire range of tranformers by the Canadian manufacturer Hammond.

Philip was unbelievably helpful. I ordered by potentienometers form him and he spotted that I had ordered the wrong type of pot for a JTM45 for example. He also sent me the bolts to be able to attach the transformers to the chassis for nothing. What more can you ask for in terms of service?? Philip is a star in my book.

I also got Chris Uff to make a cab for me. You can contact him through the amp maker site. Chris's cabs are just super quality. I can't recommend him highly enough.

After many months of being too busy to be able to do any work on the project I finally got two days and blitzed it. It came together really well. The test measurements were all great. I switched on and hey presto a really fantastic working JTM45.

Well, the amp bug has really got me hooked now. So I have been thinking about what amp to do next. Then I was chatting to a friend who is mad about Ry Cooder and he mentioned that Ry sometimes uses a really old Gibson amp. I was curious to find out more and googled only to learn about the GA-40 for the first time.