Hi folks
I built a SE 15w tube amp a while ago, after a number of changes to the circuit to something that I like a lot. Of course things don’t always work 100% first time round:
The circuit config is something like this, based on the AX84 SEL (with a twist in the power stage )
IN-----Stage1-----Vol.1-----Stage2-----Vol.2 ------Stage3------Cathode Follower----Tone Stack -----M.V.-----Power Stage (parallel) -----Out
I battled to keep the induction noises down to acceptable levels, at high gain it picks up a sort of power supply buzz,
Enter the “Audio Probe” - no DIY’er should be without one
This is very simple yet very useful tool for debugging new builds. You need one 1/4″ mono plug, one small 100nF 400v capacitor, alligator clip, some wire, pop rivet and a Bic pen.
When debugging some circuit connect clip to circuit ground and use other end of cap (or wire connected to other end of cap) to follow signal path through circuit. Plug the probe into amp and plug guitar cord to amp input Make someone play guitar while you’re probing circuit and once you find a spot where its noisy or nothing is heard through amp you found a possible problem.
Tip : watch out for connection that have multiple components connected together and have a Chopstick in the other hand to prod components a for bad connections.
If you have a cap small enough you can fit into Bic pen casing with a pop rivet stuck in where the nib used to be . It works very nice and offers protection from nasty shocks, I connected the probe to a set of powered PC speakers
The end result is something like this, these are not my pics I will upload mine tonight:
My Pics
Anyway Enjoy ….. Attila
