Hey guys, I just completed my first ever amp build, a Fairfield County JM Sig by rcolgan. First off, massive thanks to Ryan for everything that he has done to make this a paint-by-numbers project.
The amp sounds okay, is very quiet, but it's definitely not generating the frequency response that I'd expect for this amp. I've attached a recent bode plot that I took. All of the knobs were at 12 o'clock, reverb send and return at zero, and all tone switches in the off position. I'm using a 1 Vpp sine wave input signal and sweeping from 10 Hz to 10 kHz. I've also included my bias voltages for reference.
Hello! Great work! Where are you connecting the output probe to?
For reference, this is measuring at the preamp-out. Ignore the dBm axis. I'm not sure yet if that's accurate but I believe the graph is somewhat normal. This is a comparison I did a while back between two builds helping someone troubleshoot.
I believe the master was down and the gain was noon in these
You do not have the required permissions to view the files attached to this post.
Ryan, thanks for your response. I have a Weber resistive load box with a BNC connector output to scope. My DUT out is coming from the load box. I was comparing to the bode plots from your video comparing your Fairfield with the Two Rock TC.
Here are the plots measured at the effects loop send jack. First one is with tone switches off, second one with tone switches on. The plot with the tone switches engaged is tracking a lot closer to your YT video where you compare the Two Rock TC.
Having the bode plots available to me now has brought me down so many new rabbit holes... like... I swapped out all the tubes and now my overall gain is a bit lower I'm also learning about the tone stack pot values swinging the eq a bit with "noon" controls. Comparing two identical amp builds were different on the plots which is maddening but also I appreciate Dumble understanding this and fine-tuning amps vs someone just slapping together an amp and calling it "good"
I'm also learning about the tone stack pot values swinging the eq a bit with "noon" controls. Comparing two identical amp builds were different on the plots which is maddening but also I appreciate Dumble understanding this and fine-tuning amps vs someone just slapping together an amp and calling it "good"