More Tube Amps

On Saturday I went to Guitar Center to buy a small five-watt tube amp. I went there with one in mind but ended up falling for a Fender Champion 600. It wasn't the killer rock sound that won me over - it doesn't have a killer rock sound. What I liked was that it was designed so simply that there was room for modification. Since then I have perused the Internet and have found many mods available. The YouTube videos of the mods blew me away. I'm glad I chose this amp.

I knew that for the price, this amp was made in China. I assumed (correctly) that the stock tubes were Chinese. The American-made Groove Tubes and the Russian Tung-Sol tubes are rated far above the stock tubes. Just changing them will make an improvement. But I found out more. The only control is for volume. It goes to twelve (take that, Nigel!) and in Fender's opinion, play it at twelve and let the guitar's controls make the settings. The issue at hand is that Fender's optimum tone setting, made with a tone stack between the first and second gain stages, drop the gain too low to drive the output to the sweet spot. I plugged my Ibanez Tube Screamer in and noticed the immediate sound improvement. I will fix the tone stack issue.

Most of the mod websites suggest replacing the speaker. I will not be convinced until I play this amp for a couple of months. Speakers need to be broken in. Also, I will not replace the stock transformers until I'm convinced they are a problem. The tone stack fix is most likely the biggest fix necessary.

The first thing I'm going to do is remove the negative feedback circuit (Resistor R7). After that I will either replace the tone stack midrange resistor (R19) or add a "fat" switch to keep the stock sound available. I am weighing some advice to change the shaping of the guitar signal at the first gain stage with two resistors and a capacitor, as well as a capacitor in the tone stack. The tubes will be replaced next month.

I hope to report that I will be satisfied with these changes. I hope the speaker breaks in well and the transformers won't need replacing. The goal is to be done before Christmas.