Many folks may find this interesting. It is a good place to get started:
The Phase Inverter. Most important tube in your amp?
Moving on: Unlike power/output tubes, which are routinely matched when they are sold (in different ways, some much better than others), preamp tubes are generally tested at best to: (a) make sure they work ? (b) they are not microphonic. In testing, I have found that some suppliers don't seem to test their preamp tubes at all. At times I have even found one side of the triode dead.
|Doing a bit of blueprinting with Carl Verheyen ( www.carlverheyen.com ) on his|
1964 Fender Twin Reverb