The Amp Garage

Here's some thoughts on this from about 14 years ago. http://www.geofex.com/article_folders/pt-to-pt/pt-to-pt.htm A couple of salient points: - PCBs have tiny parasitic capacitances. So do point to point layouts and tagboard layouts, and every other circuit technique. The devil is in the details of ...

Its the model 1081 R G! Change the 3.3 ohm bias resistors to 12 or 13 ohms nominal. This gets you to about the same "on-ness" that Thomas used for the outputs of the Berkeley 3 or Guardsman silicon outputs. Those are the closest standard values to the value I calculated, 12. 7 ohms. There is a trad...

Sometimes the entire house ground gets high impedance. A loose wire in the main breaker box can do this, as a single point of failure. It's rare, but happens. An even more dangerous situation can happen - a high impedance neutral wire back to the power-pole transformer. When this happens, the two ha...

Thanks for the info R G! Hey, I have a 66 reverb twin and I want to change the outputs to silicon types, are there any value bias resistors you recommend starting off with? What model number? Edit - I should have also noted: There is a fair amount of info on repair/refit/refurbing Thomas Vox at my ...

I'm never going inside another one of these amps. :) That's the received wisdom of nearly everyone who has had to get one running after bending the board up to get at the solder side, breaking off another wire or two. This repair is actually kind of cathartic after that experience. The repair proce...

Yeah, I have something like this in a room of my house that the ground connection isn't actually connected to ground. ACK!! QUICK! CALL AN ELECTRICIAN! That's not an annoyance, it's potentially deadly. Hook up the wrong slightly-defective bit of equipment and grab the wrong thing and you, too, can ...

Is this by chance a two-wire power cord?

Sometimes a two-wire setup or a three-wire with an open/high resistance ground lead will let through RF buzz that mimics hum and changes when a human body touches ground.

I have recently finished testing repair/replacement boards for the preamp of Thomas Vox "big head" amps: the Beatle, Guardsman, Buckingham, and Viscount. These are the original circuits, on a same-size board that fits the original mountings, but with the wiring made sane by placing all the wire conn...